| 1. |
- Andersson, John, 1993, et al.
(author)
-
Polymer Brushes on Silica Nanostructures Prepared by Aminopropylsilatrane Click Chemistry: Superior Antifouling and Biofunctionality
- 2023
-
In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 15:7, s. 10228-10239
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Journal article (peer-reviewed)abstract
- In nanobiotechnology, the importance of controlling interactions between biological molecules and surfaces is paramount. In recent years, many devices based on nanostructured silicon materials have been presented, such as nanopores and nanochannels. However, there is still a clear lack of simple, reliable, and efficient protocols for preventing and controlling biomolecule adsorption in such structures. In this work, we show a simple method for passivation or selective biofunctionalization of silica, without the need for polymerization reactions or vapor-phase deposition. The surface is simply exposed stepwise to three different chemicals over the course of ∼1 h. First, the use of aminopropylsilatrane is used to create a monolayer of amines, yielding more uniform layers than conventional silanization protocols. Second, a cross-linker layer and click chemistry are used to make the surface reactive toward thiols. In the third step, thick and dense poly(ethylene glycol) brushes are prepared by a grafting-to approach. The modified surfaces are shown to be superior to existing options for silica modification, exhibiting ultralow fouling (a few ng/cm2) after exposure to crude serum. In addition, by including a fraction of biotinylated polymer end groups, the surface can be functionalized further. We show that avidin can be detected label-free from a serum solution with a selectivity (compared to nonspecific binding) of more than 98% without the need for a reference channel. Furthermore, we show that our method can passivate the interior of 150 nm × 100 nm nanochannels in silica, showing complete elimination of adsorption of a sticky fluorescent protein. Additionally, our method is shown to be compatible with modifications of solid-state nanopores in 20 nm thin silicon nitride membranes and reduces the noise in the ion current. We consider these findings highly important for the broad field of nanobiotechnology, and we believe that our method will be very useful for a great variety of surface-based sensors and analytical devices.
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| 2. |
- Forsvall, Andreas, et al.
(author)
-
Evaluation of the Forsvall biopsy needle in an ex vivo model of transrectal prostate biopsy - a novel needle design with the objective to reduce the risk of post-biopsy infection
- 2021
-
In: Scandinavian Journal of Urology. - : Medical Journals Sweden AB. - 2168-1805 .- 2168-1813. ; 55:3, s. 227-234
-
Journal article (peer-reviewed)abstract
- Background Transrectal prostate biopsy (TRbx) transfers colonic bacteria into prostatic tissue, potentially causing infectious complications, including sepsis. Our objective was to determine whether biopsy needle shape, surface properties and sampling mechanism affect the number of bacteria transferred through the colon wall, and evaluate a novel needle with improved properties. Methods The standard Tru-Cut biopsy needle used today was evaluated for mechanisms of bacterial transfer in a pilot study. A novel Tru-Cut needle (Forsvall needle prototype) was developed. TRbx was simulated using human colons ex-vivo. Four subtypes of the prototype needle were compared with a standard Tru-Cut needle (BARD 18 G). Prototype and standard needles were used to puncture 4 different colon specimens in 10 randomized sites per colon. Needles were submerged into culture media to capture translocated bacteria. The media was cultured on blood agar and then the total amount of transferred bacteria was calculated for each needle. The primary outcome measure was the percent reduction of bacteria translocated by the prototype needles relative to the standard needle. Secondary outcome measures were the effects of tip design and coating on the percent reduction of translocated bacteria. Results Prototype needles reduced the number of translocated bacteria by, on average, 96.0% (95% confidence interval 93.0-97.7%; p < 0.001) relative to the standard needle. This percent reduction was not significantly affected by prototype needle tip style or surface coating. Conclusions The Forsvall needle significantly reduces colonic bacterial translocation, suggesting that it could reduce infectious complications in prostate biopsy. A clinical trial has been initiated.
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| 3. |
- Acimovic, Srdjan, 1982, et al.
(author)
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Antibody−antigen interaction dynamics revealed by analysis of single-molecule equilibrium fluctuations on individual plasmonic nanoparticle biosensors
- 2018
-
In: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 12:10, s. 9958-9965
-
Journal article (peer-reviewed)abstract
- Antibody−antigen interactions are complex events central to immune response, in vivo and in vitro diagnostics, and development of therapeutic substances. We developed an ultrastable single-molecule localized surface plasmon resonance (LSPR) sensing platform optimized for studying antibody−antigen interaction kinetics over very long time scales. The setup allowed us to perform equilibrium fluctuations analysis of the PEG/anti-PEG interaction. By time and frequency domain analysis, we demonstrate that reversible adsorption of monovalently bound anti-PEG antibodies is the dominant factor affecting the LSPR fluctuations. The results suggest that equilibrium fluctuation analysis can be an alternative to established methods for determination of interaction rates. In particular, the methodology is suited to analyze molecular systems whose properties change during the initial interaction phases, for example, due to mass transport limitations or, as demonstrated here, because the effective association rate constant varies with surface concentration of adsorbed molecules.
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| 4. |
- Acimovic, Srdjan, 1982, et al.
(author)
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Superior LSPR substrates based on electromagnetic decoupling for on-a-chip high-throughput label-free biosensing
- 2017
-
In: Light: Science and Applications. - : Springer Science and Business Media LLC. - 2047-7538 .- 2095-5545. ; 6:8, s. e17042-
-
Journal article (peer-reviewed)abstract
- Localized surface plasmon resonance (LSPR) biosensing based on supported metal nanoparticles offers unparalleled possibilities for high-end miniaturization, multiplexing and high-throughput label-free molecular interaction analysis in real time when integrated within an opto-fluidic environment. However, such LSPR-sensing devices typically contain extremely large regions of dielectric materials that are open to molecular adsorption, which must be carefully blocked to avoid compromising the device readings. To address this issue, we made the support essentially invisible to the LSPR by carefully removing the dielectric material overlapping with the localized plasmonic fields through optimized wet-etching. The resulting LSPR substrate, which consists of gold nanodisks centered on narrow SiO2 pillars, exhibits markedly reduced vulnerability to nonspecific substrate adsorption, thus allowing, in an ideal case, the implementation of thicker and more efficient passivation layers. We demonstrate that this approach is effective and fully compatible with state-of-the-art multiplexed real-time biosensing technology and thus represents the ideal substrate design for high-throughput label-free biosensing systems with minimal sample consumption.
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| 5. |
- Andersson, John, 1993, et al.
(author)
-
Control of Polymer Brush Morphology, Rheology, and Protein Repulsion by Hydrogen Bond Complexation
- 2021
-
In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 37:16, s. 4943-4952
-
Journal article (peer-reviewed)abstract
- Polymer brushes are widely used to alter the properties of interfaces. In particular, poly(ethylene glycol) (PEG) and similar polymers can make surfaces inert toward biomolecular adsorption. Neutral hydrophilic brushes are normally considered to have static properties at a given temperature. As an example, PEG is not responsive to pH or ionic strength. Here we show that, by simply introducing a polymeric acid such as poly(methacrylic acid) (PMAA), the highly hydrated brush barrier can change its properties entirely. This is caused by multivalent hydrogen bonds in an extremely pH-sensitive process. Remarkably, it is sufficient to reduce the pH to 5 for complexation to occur at the interface, which is two units higher than in the corresponding bulk systems. Below this critical pH, PMAA starts to bind to PEG in large amounts (comparable to the PEG amount), causing the brush to gradually compact and dehydrate. The brush also undergoes major rheology changes, from viscoelastic to rigid. Furthermore, the protein repelling ability of PEG is lost after reaching a threshold in the amount of PMAA bound. The changes in brush properties are tunable and become more pronounced when more PMAA is bound. The initial brush state is fully recovered when releasing PMAA by returning to physiological pH. Our findings are relevant for many applications involving functional interfaces, such as capture-release of biomolecules.
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| 6. |
- Andersson, John, 1993, et al.
(author)
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Pore performance: artificial nanoscale constructs that mimic the biomolecular transport of the nuclear pore complex
- 2022
-
In: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 4:23, s. 4925-4937
-
Research review (peer-reviewed)abstract
- The nuclear pore complex is a nanoscale assembly that achieves shuttle-cargo transport of biomolecules: a certain cargo molecule can only pass the barrier if it is attached to a shuttle molecule. In this review we summarize the most important efforts aiming to reproduce this feature in artificial settings. This can be achieved by solid state nanopores that have been functionalized with the most important proteins found in the biological system. Alternatively, the nanopores are chemically modified with synthetic polymers. However, only a few studies have demonstrated a shuttle-cargo transport mechanism and due to cargo leakage, the selectivity is not comparable to that of the biological system. Other recent approaches are based on DNA origami, though biomolecule transport has not yet been studied with these. The highest selectivity has been achieved with macroscopic gels, but they are yet to be scaled down to nano-dimensions. It is concluded that although several interesting studies exist, we are still far from achieving selective and efficient artificial shuttle-cargo transport of biomolecules. Besides being of fundamental interest, such a system could be potentially useful in bioanalytical devices.
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| 7. |
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| 8. |
- Andersson, John, 1993, et al.
(author)
-
Surface plasmon resonance sensing with thin films of palladium and platinum - quantitative and real-time analysis
- 2022
-
In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 24:7, s. 4588-4594
-
Journal article (peer-reviewed)abstract
- Surface plasmon resonance (SPR) is a highly useful technique in biology and is gradually becoming useful also for materials science. However, measurements to date have been performed almost exclusively on gold, which limits the possibility to probe chemical modifications of other metals. In this work we show that 20 nm Pd and Pt films work "fairly well" for quantitative SPR sensing of organic films despite the high light absorption. In the interval between total reflection and the SPR angle, high intensity changes occur when a film is formed on the surface. Fresnel models accurately describe the full angular spectra and our data analysis provides good resolution of surface coverage in air (a few ng cm(-2)). Overall, the Pd sensors behave quite similarly to 50 nm gold in terms of sensitivity and field extension, although the noise level in real-time measurements is similar to 5 times higher. The Pt sensors exhibit a longer extension of the evanescent field and similar to 10 times higher noise compared to gold. Yet, formation of organic layers a few nm in thickness can still be monitored in real-time. As a model system, we use thiolated poly(ethylene glycol) to make Pd and Pt protein repelling. Our findings show how SPR can be used for studying chemical modifications of two metals that are important in several contexts, for instance within heterogeneous catalysis. We emphasize the advantages of simple sample preparation and accurate quantitative analysis in the planar geometry by Fresnel models.
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| 9. |
- Blake, Jolie, 1986, et al.
(author)
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Scalable Reflective Plasmonic Structural Colors from Nanoparticles and Cavity Resonances – the Cyan-Magenta-Yellow Approach
- 2022
-
In: Advanced Optical Materials. - : Wiley. - 2195-1071 .- 2162-7568. ; 10:13
-
Journal article (peer-reviewed)abstract
- Plasmonic metasurfaces for color generation are emerging as important components for next generation display devices. Fabricating bright plasmonic colors economically and via easily scalable methods, however, remains difficult. Here, the authors demonstrate an efficient and scalable strategy based on colloidal lithography to fabricate silver-based reflective metal–insulator–nanodisk plasmonic cavities that provide a cyan-magenta-yellow (CMY) color palette with high relative luminance. With the same basic structure, they exploit different mechanisms to efficiently produce a complete subtractive color palette. Finite-difference time-domain simulations reveal that these mechanisms include gap surface plasmon modes for thin insulators and hybridized modes between disk plasmons and Fabry–Pérot modes for thicker systems. To produce yellow hues, they take advantage of higher-energy gap surface plasmon modes to allow resonance dips in the blue spectral region for comparably large nanodisks, thereby circumventing difficult fabrication of nanodisks less than 80 nm. It is anticipated that incorporation of these strategies can reduce fabrication constraints, produce bright saturated colors, and expedite large-scale production.
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| 10. |
- Brooke, Robert, 1989-, et al.
(author)
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All-Printed Multilayers and Blends of Poly(dioxythiophene) Derivatives Patterned into Flexible Electrochromic Displays
- 2023
-
In: Macromolecular materials and engineering. - : John Wiley and Sons Inc. - 1438-7492 .- 1439-2054. ; 308:2
-
Journal article (peer-reviewed)abstract
- Low-cost, flexible and thin display technology is becoming an interesting field of research as it can accompany the wide range of sensors being developed. Here, the synthesis of poly(dimethylpropylene-dioxythiophene) (PProDOT-Me2) by combining vapor phase polymerization and screen printing is presented. A multilayer architecture using poly(3,4-ethylenedioxythiophene) (PEDOT) and PProDOT-Me2 to allow for electrochromic switching of PProDOT-Me2, thereby eliminating the need for a supporting transparent conductive (metal oxide) layer is introduced. Furthermore, the technology is adapted to a blended architecture, which removes the additional processing steps and results in improved color contrast (∆E* > 25). This blend architecture is extended to other conductive polymers, such as PEDOT and polypyrrole (PPy), to highlight the ability of the technique to adjust the color of all-printed electrochromic displays. As a result, a green color is obtained when combining the blue and yellow states of PEDOT and PPy, respectively. This technology has the potential to pave the way for all-printed multicolored electrochromic displays for further utilization in printed electronic systems in various Internet of Things applications. © 2022 The Authors.
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| 11. |
- Claudio, Virginia, 1985, et al.
(author)
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Single-Particle Plasmon Sensing of Discrete Molecular Events: Binding Position versus Signal Variations for Different Sensor Geometries
- 2014
-
In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:13, s. 6980-6988
-
Journal article (peer-reviewed)abstract
- The sensitivity of a surface plasmon to the dielectric environment makes it a viable tool in detecting single molecules. To be able to precisely determine sensed molecular concentrations and carry out precise analyses of single-molecule binding/unbinding events in real time it is necessary to quantify rigorously the relation between the number of bound molecules and the spectral response of the plasmonic sensor. However, this is challenging as this relation is subject to an uncertainty which is highly dependent on the spatially varying response of the plasmonic nanosensor of choice. The origin of this uncertainty is little understood, and its effect is often disregarded in quantitative sensing experiments. Here, we employ stochastic diffusion-reaction simulations of biomolecular interactions on a sensor’s surface combined with electromagnetic calculations of the plasmon resonance peak shift of three metal nanosensors (disk, cone, dimer) to clarify the interplay between position-dependent binding probability and inhomogeneous sensitivity distribution in determining the statistical characteristics of the total signal upon molecular binding. This approach is generally applicable regardless of the specific transduction mechanism at the basis of sensing. Here we identify how this interplay affects the feasibility of using certain plasmonic sensors for sensing low concentrations or real-time monitoring of individual binding reactions and how illumination conditions may affect the level of uncertainty of the measured signal upon molecular binding.
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| 12. |
- Conca, Dario Valter, et al.
(author)
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The role of membrane complexity in the early entry stages of SARS-CoV-2 variants
- 2023
-
In: European Biophysics Journal. - 1432-1017 .- 0175-7571. ; 52:SUPPL 1, s. S176-S176
-
Conference paper (other academic/artistic)abstract
- The highest density of mutations in SARS-CoV-2 variants is located on the spike glycoprotein (S), which is responsible for receptor ACE2 engagement. This suggests that SARS-CoV-2 is evolving to optimize viral entry. Several molecular studies report differences in the affinity between isolated S and ACE2 among variants. However, overall ACE2 affinity poorly correlates with the increased infectivity of recent variants. We address this discrepancy by considering the virus interaction with the whole plasma membrane and study the role of avidity and membrane complexity in modulating virus-host binding. To this end, we employ an in-vitro model system combining single-particle tracking and native supported lipid bilayers (nSLBs) made from lung epithelial cells. As virion mimics, we developed S-decorated liposomes that allow for direct comparison between variants and BSL-1 handling. Sliposome interaction with nSLBs showed a significant increase in avidity for Omicron compared to Delta and Wuhan strains. Further, using single-molecule force spectroscopy, we reveal a higher affinity for Omicron and Delta S to sensor immobilise heparan sulfate (HS). Our results indicate a shift in the variants’ attachment strategy towards more efficient use of coreceptors and the role of HS as an initial docking site that facilitates virus accumulation at the membrane and ACE2 engagement.
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| 13. |
- Dahlin, Andreas, 1980
(author)
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Biochemical Sensing with Nanoplasmonic Architectures: We Know How but Do We Know Why?
- 2021
-
In: Annual Review of Analytical Chemistry. - : Annual Reviews. - 1936-1327 .- 1936-1335. ; 14, s. 281-297
-
Research review (peer-reviewed)abstract
- Here, the research field of nanoplasmonic sensors is placed under scrutiny, with focus on affinity-based detection using refractive index changes. This review describes how nanostructured plasmonic sensors can deliver unique advantages compared to the established surface plasmon resonance technique, where a planar metal surface is used. At the same time, it shows that these features are actually only useful in quite specific situations. Recent trends in the field are also discussed and some devices that claim extraordinary performance are questioned. It is argued that the most important challenges are related to limited receptor affinity and nonspecific binding rather than instrumental performance. Although some nanoplasmonic sensors may be useful in certain situations, it seems likely that conventional surface plasmon resonance will continue to dominate biomolecular interaction analysis. For detection of analytes in complex samples, plasmonics may be an important tool, but probably not in the form of direct refractometric detection.
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| 14. |
- Dahlin, Andreas, 1980, et al.
(author)
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Electrochemical plasmonic sensors
- 2012
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In: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 402:5, s. 1773-1784
-
Research review (peer-reviewed)abstract
- The enormous progress of nanotechnology during the last decade has made it possible to fabricate a great variety of nanostructures. On the nanoscale, metals exhibit special electrical and optical properties, which can be utilized for novel applications. In particular, plasmonic sensors including both the established technique of surface plasmon resonance and more recent nanoplasmonic sensors, have recently attracted much attention. However, some of the simplest and most successful sensors, such as the glucose biosensor, are based on electrical readout. In this review we describe the implementation of electrochemistry with plasmonic nanostructures for combined electrical and optical signal transduction. We highlight results from different types of metallic nanostructures such as nanoparticles, nanowires, nanoholes or simply films of nanoscale thickness. We briefly give an overview of their optical properties and discuss implementation of electrochemical methods. In particular, we review studies on how electrochemical potentials influence the plasmon resonances in different nanostructures, as this type of fundamental understanding is necessary for successful combination of the methods. Although several combined platforms exist, many are not yet in use as sensors partly because of the complicated effects from electrochemical potentials on plasmon resonances. Yet, there are clearly promising aspects of these sensor combinations and we conclude this review by discussing the advantages of synchronized electrical and optical readout, illustrating the versatility of these technologies.
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| 15. |
- Dahlin, Andreas, 1980, et al.
(author)
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High-Resolution Microspectroscopy of Plasmonic Nanostructures for Miniaturized Biosensing
- 2009
-
In: Analytical Chemistry. - : American Chemical Society. - 0003-2700 .- 1520-6882. ; 81:16, s. 6572-6580
-
Journal article (peer-reviewed)abstract
- In this article, we demonstrate how to perform microscale spectroscopy of plasmonic nanostructures in order to minimize the noise when determining the resonance peak wavelength. This is accomplished using an experimental setup containing standard optical components mounted on an ordinary light microscope. We present a detailed comparison between extinction spectroscopy in transmission mode and scattering spectroscopy under dark field illumination, which shows that extinction measurements provide higher signal-to-noise in almost all situations. Furthermore, it is shown that rational selection of nanostructure, hardware components, and data analysis algorithms enables tracking of the particle plasmon resonance wavelength from a 10 mu m x 50 mu m area with a resolution of 10(-3) nm in transmission mode. We investigate how the temporal resolution, which can be improved down to 17 Ins, affects, the noise characteristics. In addition, we show how data can be acquired from an area as small as 2 mu m x 10 mu m (similar to 240 particles) at the expense of higher noise on longer time scales. In comparison with previous work on macroscopic sensor designs, this represents a sensor miniaturization of 5 orders of magnitude, without any loss in signal-to-noise performance. As a model system, we illustrate biomolecular detection using gold nanodisks prepared by colloidal lithography. The microextinction measurements of nanodisks described here provide detection of protein surface coverages as low as 40 pg/cm(2) (less than0.1% of saturated binding). In fact, the miniaturized system provides a detection limit in terms of surface coverage comparable to state of the art macroscopic sensors, while simultaneously being as close to single protein molecule detection as sensors based on a single nanoparticle.
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| 16. |
- Dahlin, Andreas, 1980, et al.
(author)
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Localized surface plasmon sensing of lipid-membrane-mediated biorecognition events
- 2005
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 127:14, s. 5043-5048
-
Journal article (peer-reviewed)abstract
- Supported phospholipid bilayers (SPBs) have emerged as important model systems for studies of the natural cell membrane and its components, which are essential for the integrity and function of cells in all living organisms, and also constitute common targets for therapeutic drugs and in disease diagnosis. However, the preferential occurrence of spontaneous SPB formation on silicon-based substrates, but not on bare noble-metal surfaces, has so far excluded the use of the localized surface plasmon resonance (LSPR) sensing principle for studies of lipid-membrane-mediated biorecognition reactions. This is because the LSPR phenomenon is associated with, and strongly confined to, the interfacial region of nanometric noble-metal particles. This problem has been overcome in this study by a self-assembly process utilizing localized rupture of phospholipid vesicles on silicon dioxide in the bottom of nanometric holes in a thin gold film. The hole-induced localization of the LSPR field to the voids of the holes is demonstrated to provide an extension of the LSPR sensing concept to studies of reactions confined exclusively to SPB-patches supported on SiO2. In particular, we emphasize the possibility of performing label-free studies of lipid-membrane-mediated reaction kinetics, including the compatibility of the assay with array-based reading (similar to 7 x 7 mu m(2)) and detection of signals originating from bound protein in the zeptomole regime.
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| 17. |
- Dahlin, Andreas, 1980
(author)
-
Nanoplasmonic Biosensors compatible with Artificial Cell Membranes
- 2008
-
Doctoral thesis (other academic/artistic)abstract
- Within life science, there is currently an intense search for novel techniques that enable efficient and reliable analysis of biomolecular interactions. Such methods have future applications within medical diagnostics and drug development, as well as within proteomic research in general. Lately, several concepts have emerged that are based on monitoring molecular binding to surfaces via optical, mechanical or electrical signal transduction. In particular, the plasmons associated with metallic nanoparticles are of interest since they offer a convenient way to monitor biomolecular interactions, also in a miniaturized format, by optical spectroscopy.This thesis describes the development of a biosensor based on the optical properties of nanoscale apertures in continuous metal films. The fabrication and characterization of the nanostructure is described, as well as surface modification protocols based on thiol chemistry for material-specific functionalization. In addition, an experimental setup for spectroscopy is presented together with data analysis algorithms for minimizing noise.It is emphasized that, from an experimental sensing perspective, nanoholes and nanoparticles have essentially the same plasmonic properties. However, the nanoholes offer several advantages because of the fact that the structure is physically different. In particular, it is shown how various artificial cell membranes can be spontaneously formed inside nanoholes. This makes the sensor compatible with studies of processes related to biological membranes. In this context, membrane-bound proteins are of special interest since they constitute a third of our genome and represent the target of half of the most common medical drugs. Potential future applications of the artificial membranes on the plasmonic nanostructures are discussed, with focus on probing transport across the membrane.
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| 18. |
- Dahlin, Andreas, 1980, et al.
(author)
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Nanoplasmonic sensing of metal-halide complex formation and the electric double layer capacitor
- 2012
-
In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 4:7, s. 2339-2351
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Journal article (peer-reviewed)abstract
- Many nanotechnological devices are based on implementing electrochemistry with plasmonic nanostructures, but these systems are challenging to understand. We present a detailed study of the influence of electrochemical potentials on plasmon resonances, in the absence of surface coatings and redox active molecules, by synchronized voltammetry and spectroscopy. The experiments are performed on gold nanodisks and nanohole arrays in thin gold films, which are fabricated by improved methods. New insights are provided by high resolution spectroscopy and variable scan rates. Furthermore, we introduce new analytical models in order to understand the spectral changes quantitatively. In contrast to most previous literature, we find that the plasmonic signal is caused almost entirely by the formation of ionic complexes on the metal surface, most likely gold chloride in this study. The refractometric sensing effect from the ions in the electric double layer can be fully neglected, and the charging of the metal gives a surprisingly small effect for these systems. Our conclusions are consistent for both localized nanoparticle plasmons and propagating surface plasmons. We consider the results in this work especially important in the context of combined electrochemical and optical sensors.
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| 19. |
- Dahlin, Andreas, 1980, et al.
(author)
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Performance of nanoplasmonic biosensors
- 2012
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In: Nanoplasmonic Sensors. - New York, NY : Springer New York. - 9781461439332 ; , s. 231-264
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Book chapter (other academic/artistic)abstract
- This chapter aims to give an overview of how to optimize the performance of nanoplasmonic sensors. Specific biosensing challenges beyond the capability of current nanoplasmonic sensors will be discussed. Various methods to improve sensor performance will then be introduced, including solving issues related to surface chemistry. We distinguish the concept of signal enhancement, which is related to the choice of nanostructure and surface functionalization, from the concept of noise minimization, which is related to the spectroscopy techniques employed. The concepts of bulk sensitivity, figure of merit, nanostructure performance, and their relation to detection limit are discussed in detail.
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| 20. |
- Dahlin, Andreas, 1980
(author)
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Plasmonic biosensors: An integrated view of refractometric detection
- 2011
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Book (other academic/artistic)abstract
- The book presents an integrated view of plasmonic biosensors that operate by refractometric detection. This means that analyte binding to the sensor surface induces a local change in refractive index, which alters the far field spectrum, as detected by optical spectroscopy. Other plasmonic biosensors such as those based on coupling between suspended nanoparticles or surface enhanced Raman scattering are not discussed in detail. All aspects of refractometric detection are considered in an integrated view. It is described how efficient surface functionalization becomes critical for specificity in order to reduce nonspecific interactions while preserving high affinity for the analyte. It is also shown how the influence from binding kinetics and mass transport limitations severely affects the applicability of these types of sensors. Some basic optics related to plasmonics is introduced. Nanoparticle plasmons and surface plasmons are described in depth. Plasmons in nanohole arrays as well as near field optics of plasmonic nanostructures are also presented. Throughout the book, analytical formula are given, although no expression is explicitly derived. It is emphasized under which assumptions the formulas hold and their validity is discussed. Numerical methods for plasmonics are not described in detail. Later chapters discuss experimental plasmon spectroscopy and spectral analysis, including the challenge of quantitative interpretation of the response. In particular, it is shown that the refractometric sensing performance of a plasmonic nanostructure is best evaluated in terms of relative intensity changes with liquid refractive index. The extension of the sensitivity into the liquid environment is shown to be another critical factor. Towards the end of the book, the theoretical framework is combined into an integrated view of sensor performance. Among other conclusions, it is suggested that novel nanoplasmonic sensors offer very few advatanges over the established methodology of surface plasmon resonance biosensing. As a final outlook, examples of combinations of plasmonic biosensors with other signal transduction mechanisms are presented.
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| 21. |
- Dahlin, Andreas, 1980, et al.
(author)
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Plasmonic Nanopores in Metal-Insulator-Metal Films
- 2014
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In: Advanced Optical Materials. - : Wiley. - 2195-1071. ; 2:6, s. 556-564
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Journal article (peer-reviewed)abstract
- A novel type of plasmonic nanopore array in a metal-insulator-metal thin film is presented. The optical properties of this structure are described using a generic theoretical framework for surface waves in a coupled multilayer system. The characteristic spacing (short-range order) of the pores enables grating-type coupling to hybridized surface plasmons, with stronger coupling to some modes than others. The nature of the optical resonances and their excitation mechanisms can be conceptually understood from a charge distribution argument. The experimental results are further verified by numerical simulations, which also enable visualization of the near field. This study illustrates the surface plasmon characteristics (sensitive to periodicity) of the extinction maximum in the asymmetric spectral resonance induced by aperture arrays, while the transmission maximum corresponds to a resonance of localized character (sensitive to pore shape). Finally, the use of these nanopores for sensing applications through changes in the refractive index is evaluated.
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| 22. |
- Dahlin, Andreas, 1980, et al.
(author)
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Promises and challenges of nanoplasmonic devices for refractometric biosensing
- 2013
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In: Nanophotonics. - : Walter de Gruyter GmbH. - 2192-8614 .- 2192-8606. ; 2:2, s. 83-101
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Journal article (peer-reviewed)abstract
- Optical biosensors based on surface plasmon resonance (SPR) in metallic thin films are currently standard tools for measuring molecular binding kinetics and affinities - an important task for biophysical studies and pharmaceutical development. Motivated by recent progress in the design and fabrication of metallic nanostructures, such as nanoparticles or nanoholes of various shapes, researchers have been pursuing a new generation of biosensors harnessing tailored plasmonic effects in these engineered nanostructures. Nanoplasmonic devices, while demanding nanofabrication, offer tunability with respect to sensor dimension and physical properties, thereby enabling novel biological interfacing opportunities and extreme miniaturization. Here we provide an integrated overview of refractometric biosensing with nanoplasmonic devices and highlight some recent examples of nanoplasmonic sensors capable of unique functions that are difficult to accomplish with conventional SPR. For example, since the local field strength and spatial distribution can be readily tuned by varying the shape and arrangement of nanostructures, biomolecular interactions can be controlled to occur in regions of high field strength. This may improve signal-to-noise and also enable sensing a small number of molecules. Furthermore, the nanoscale plasmonic sensor elements may, in combination with nanofabrication and materials-selective surface-modifications, make it possible to merge affinity biosensing with nanofluidic liquid handling.
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| 23. |
- Dahlin, Andreas, 1980
(author)
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Sensing applications based on plasmonic nanopores: The hole story
- 2015
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In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 140:14, s. 4748-4759
-
Research review (peer-reviewed)abstract
- A review of sensing applications based on plasmonic nanopores is given. Many new types of plasmonic nanopores have recently been fabricated, including pores penetrating multilayers of thin films, using a great variety of fabrication techniques based on either serial nanolithography or self-assembly. One unique advantage with nanopores compared to other plasmonic sensors is that sample liquids can flow through the surface, which increases the rate of binding and improves the detection limit under certain conditions. Also, by utilizing the continuous metal films, electrical control can be implemented for electrochemistry, dielectrophoresis and resistive heating. Much effort is still spent on trying to improve sensor performance in various ways, but the literature uses inconsistent benchmark parameters. Recently plasmonic nanopores have been used to analyse targets of high clinical or academic interest. Although this is an important step forward, one should probably reflect upon whether the same results could have been achieved with another optical technique. Overall, this critical review suggests that the research field would benefit by focusing on applications where plasmonic nanopores truly can offer unique advantages over similar techniques.
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| 24. |
- Dahlin, Andreas, 1980
(author)
-
Size Matters: Problems and Advantages Associated with Highly Miniaturized Sensors
- 2012
-
In: Sensors. - : MDPI AG. - 1424-8220. ; 12:3, s. 3018-3036
-
Research review (peer-reviewed)abstract
- There is no doubt that the recent advances in nanotechnology have made it possible to realize a great variety of new sensors with signal transduction mechanisms utilizing physical phenomena at the nanoscale. Some examples are conductivity measurements in nanowires, deflection of cantilevers and spectroscopy of plasmonic nanoparticles. The fact that these techniques are based on the special properties of nanostructural entities provides for extreme sensor miniaturization since a single structural unit often can be used as transducer. This review discusses the advantages and problems with such small sensors, with focus on biosensing applications and label-free real-time analysis of liquid samples. Many aspects of sensor design are considered, such as thermodynamic and diffusion aspects on binding kinetics as well as multiplexing and noise issues. Still, all issues discussed are generic in the sense that the conclusions apply to practically all types of surface sensitive techniques. As a counterweight to the current research trend, it is argued that in many real world applications, better performance is achieved if the active sensor is larger than that in typical nanosensors. Although there are certain specific sensing applications where nanoscale transducers are necessary, it is argued herein that this represents a relatively rare situation. Instead, it is suggested that sensing on the microscale often offers a good compromise between utilizing some possible advantages of miniaturization while avoiding the complications. This means that ensemble measurements on multiple nanoscale sensors are preferable instead of utilizing a single transducer entity.
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| 25. |
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| 26. |
- Emilsson, Gustav, 1989, et al.
(author)
-
Gating Protein Transport in Solid State Nanopores by Single Molecule Recognition
- 2018
-
In: ACS Central Science. - : American Chemical Society (ACS). - 2374-7951 .- 2374-7943. ; 4:8, s. 1007-1014
-
Journal article (peer-reviewed)abstract
- Control of molecular translocation through nanoscale apertures is of great interest for DNA sequencing, biomolecular filters, and new platforms for single molecule analysis. However, methods for controlling the permeability of nanopores are very limited. Here, we show how nanopores functionalized with poly(ethylene glycol) brushes, which fully prevent protein translocation, can be reversibly gated to an "open" state by binding of single IgG antibodies that disrupt the macromolecular barrier. On the basis of surface plasmon resonance data we propose a two-state model describing the antibody-polymer interaction kinetics. Reversibly (weakly) bound antibodies decrease the protein exclusion height while irreversibly (strongly) bound antibodies do not. Our results are further supported by fluorescence readout from pore arrays and high-speed atomic force microscopy on single pores. This type of dynamic barrier control on the nanoscale provides new possibilities for biomolecular separation and analysis.
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| 27. |
- Emilsson, Gustav, et al.
(author)
-
Nanoplasmonic Sensor Detects Preferential Binding of IRSp53 to Negative Membrane Curvature
- 2019
-
In: Frontiers in Chemistry. - : Frontiers Media SA. - 2296-2646. ; 7:FEB
-
Journal article (peer-reviewed)abstract
- Biosensors based on plasmonic nanostructures are widely used in various applications and benefit from numerous operational advantages. One type of application where nanostructured sensors provide unique value in comparison with, for instance, conventional surface plasmon resonance, is investigations of the influence of nanoscale geometry on biomolecular binding events. In this study, we show that plasmonic "nanowells" conformally coated with a continuous lipid bilayer can be used to detect the preferential binding of the insulin receptor tyrosine kinase substrate protein (IRSp53) I-BAR domain to regions of negative surface curvature, i.e., the interior of the nanowells. Two different sensor architectures with and without an additional niobium oxide layer are compared for this purpose. In both cases, curvature preferential binding of IRSp53 (at around 0.025 nm(-1) and higher) can be detected qualitatively. The high refractive index niobium oxide influences the near field distribution and makes the signature for bilayer formation less clear, but the contrast for accumulation at regions of negative curvature is slightly higher. This work shows the first example of analyzing preferential binding of an average-sized and biologically important protein to negative membrane curvature in a label-free manner and in real-time, illustrating a unique application for nanoplasmonic sensors.
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| 28. |
- Emilsson, Gustav, 1989, et al.
(author)
-
Polymer brushes in solid-state nanopores form an impenetrable entropic barrier for proteins
- 2018
-
In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 10:10, s. 4663-4669
-
Journal article (peer-reviewed)abstract
- Polymer brushes are widely used to prevent the adsorption of proteins, but the mechanisms by which they operate have remained heavily debated for many decades. We show conclusive evidence that a polymer brush can be a remarkably strong kinetic barrier towards proteins by using poly(ethylene glycol) grafted to the sidewalls of pores in 30 nm thin gold films. Despite consisting of about 90% water, the free coils seal apertures up to 100 nm entirely with respect to serum protein translocation, as monitored label-free through the plasmonic activity of the nanopores. The conclusions are further supported by atomic force microscopy and fluorescence microscopy. A theoretical model indicates that the brush undergoes a morphology transition to a sealing state when the ratio between the extension and the radius of curvature is approximately 0.8. The brush-sealed pores represent a new type of ultrathin filter with potential applications in bioanalytical systems.
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| 29. |
- Emilsson, Gustav, 1989, et al.
(author)
-
Strongly Stretched Protein Resistant Poly(ethylene glycol) Brushes Prepared by Grafting-To
- 2015
-
In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 7:14, s. 7505-7515
-
Journal article (peer-reviewed)abstract
- We present a new grafting-to method for resistant non-fouling poly(ethylene glycol) brushes, which is based on grafting of polymers with reactive end groups in 0.9 M Na2SO4 at room temperature. The grafting process, the resulting brushes, and the resistance toward biomolecular adsorption are investigated by surface plasmon resonance, quartz crystal microbalance, and atomic force microscopy. We determine both grafting density and thickness independently and use narrow molecular weight distributions which result in well-defined brushes. High density (e.g., 0.4 coils per nm(2) for 10 kDa) and thick (40 nm for 20 kDa) brushes are readily achieved that suppress adsorption from complete serum (10x dilution, exposure for 50 min) by up to 99% on gold (down to 4 ng/cm(2) protein coverage). The brushes outperform oligo(ethylene glycol) monolayers prepared on the same surfaces and analyzed in the same manner. The brush heights are in agreement with calculations based on a simple model similar to the de Gennes strongly stretched brush, where the height is proportional to molecular weight. This result has so far generally been considered to be possible only for brushes prepared by grafting-from. Our results are consistent with the theory that the brushes act as kinetic barriers rather than efficient prevention of adsorption at equilibrium. We suggest that the free energy barrier for passing the brush depends on both monomer concentration and thickness. The extraordinary simplicity of the method and good inert properties of the brushes should make our results widely applicable in biointerface science.
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| 30. |
- Emilsson, Gustav, 1989, et al.
(author)
-
Surface plasmon resonance methodology for monitoring polymerization kinetics and morphology changes of brushes-evaluated with poly(N-isopropylacrylamide)
- 2017
-
In: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 396, s. 384-392
-
Journal article (peer-reviewed)abstract
- Polymerization from surfaces and the resulting “brushes” have many uses in the development of novel materials and functional interfaces. However, it is difficult to accurately monitor the polymerization rate, which limits the use of polymer brushes in applications where control of thickness is desirable. We present a new methodology based on angular surface plasmon resonance (SPR) which provides real-time measurements of the thickness evolution during atom transfer radical polymerization, using poly(N-isopropylacrylamide) as an example. Our data analysis shows that the growth is linear with a rate of ?20 nm/min in a water/methanol mixture up to ?100 nm after which chain termination gradually reduces the growth rate. Further, we introduce an improved method in SPR which makes it possible to determine changes in brush height and refractive index during switching of responsive polymers. The ratio between heights in the coil to globule transition at 32 °C in water was found to be almost 5, independent of the initial absolute height up to ?200 nm, in agreement with theory. Complementary quartz crystal microbalance and atomic force microscopy data confirm the accuracy of our results. With the methodology presented here the established SPR technique can be used for quantitative characterization of surface-initiated polymerization and responsive polymer brushes.
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| 31. |
- Fang, Yurui, 1983, et al.
(author)
-
Plasmon Enhanced Internal Photoemission in Antenna-Spacer-Mirror Based Au/TiO2 Nanostructures
- 2015
-
In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 15:6, s. 4059-4065
-
Journal article (peer-reviewed)abstract
- Emission of photoexcited hot electrons from plasmonic metal nanostructures to semiconductors is key to a number of proposed nanophotonics technologies for Solar harvesting, water splitting, photocatalysis, and a variety of optical sensing and photodetector applications. Favorable materials and catalytic properties make systems based on gold and TiO2 particularly interesting, but the internal photo emission efficiency for visible light is low because of the wide bandgap of the semiconductor. We investigated the incident photon-to-electron conversion efficiency of thin TiO2 films decorated with Au nanodisk antennas in an electrochemical circuit and found that incorporation of a Au mirror beneath the semiconductor amplified the photoresponse for light with wavelength lambda = 500-950 nm by a factor 2-10 compared to identical structures lacking the mirror component. Classical electrodynamics simulations showed that the enhancement effect is caused by a favorable interplay between localized surface plasmon excitations and cavity modes that together amplify the light absorption in the Au/TiO2 interface. The experimentally determined internal quantum efficiency for hot electron transfer decreases monotonically with wavelength, similar to the probability for interband excitations with energy higher than the Schottky barrier obtained from a density functional theory band structure simulation of a thin Au/TiO2 slab.
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| 32. |
- Ferhan, Abdul Rahim, et al.
(author)
-
Nanoplasmonic Sensing Architectures for Decoding Membrane Curvature-Dependent Biomacromolecular Interactions
- 2018
-
In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 90:12, s. 7458-7466
-
Journal article (peer-reviewed)abstract
- Nanoplasmonic sensors have emerged as a promising measurement approach to track biomacromolecular interactions involving lipid membrane interfaces. By taking advantage of nanoscale fabrication capabilities, it is possible to design sensing platforms with various architectural configurations. Such capabilities open the door to fabricating lipid membrane-coated nanoplasmonic sensors with varying degrees of membrane curvature in order to understand how biomacromolecular interaction processes are influenced by membrane curvature. Herein, we employed an indirect nanoplasmonic sensing approach to characterize the fabrication of supported lipid bilayers (SLBs) on silica-coated nanowell and nanodisk sensing platforms and to investigate how membrane curvature influences membrane-peptide interactions by evaluating the corresponding measurement responses from different spectral signatures that are sensitive to specific regions of the sensor geometries. SLBs were prepared by the vesicle fusion method, as monitored in real-time by nanoplasmonic sensing measurements and further characterized by fluorescence recovery after photobleaching (FRAP) experiments. By resolving different spectral signatures in the nanoplasmonic sensing measurements, it was determined that peptide binding induces membrane disruption at positively curved membrane regions, while peptide binding without subsequent disruption was observed at planar and negatively curved regions. These findings are consistent with the peptide's known preference to selectively form pores in positively curved membranes, providing validation to the nanoplasmonic sensing approach and highlighting how the integration of nanoplasmonic sensors with different nanoscale architectures can be utilized to study the influence of membrane curvature on biomacromolecular interaction processes.
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| 33. |
- Ferrand-Drake Del Castillo, Gustav, 1990, et al.
(author)
-
Electrically Switchable Polymer Brushes for Protein Capture and Release in Biological Environments**
- 2022
-
In: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 61:22
-
Journal article (peer-reviewed)abstract
- Interfaces functionalized with polymers are known for providing excellent resistance towards biomolecular adsorption and for their ability to bind high amounts of protein while preserving their structure. However, making an interface that switches between these two states has proven challenging and concepts to date rely on changes in the physiochemical environment, which is static in biological systems. Here we present the first interface that can be electrically switched between a high-capacity (>1 μg cm−2) multilayer protein binding state and a completely non-fouling state (no detectable adsorption). Switching is possible over multiple cycles without any regeneration. Importantly, switching works even when the interface is in direct contact with biological fluids and a buffered environment. The technology offers many applications such as zero fouling on demand, patterning or separation of proteins as well as controlled release of biologics in a physiological environment, showing high potential for future drug delivery in vivo.
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| 34. |
- Ferrand-Drake Del Castillo, Gustav, 1990, et al.
(author)
-
Enzyme Immobilization in Polyelectrolyte Brushes: High Loading and Enhanced Activity Compared to Monolayers
- 2019
-
In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 35:9, s. 3479-3489
-
Journal article (peer-reviewed)abstract
- Catalysis by enzymes on surfaces has many applications. However, strategies for efficient enzyme immobilization with preserved activity are still in need of further development. In this work, we investigate polyelectrolyte brushes prepared by both grafting-to and grafting-from with the aim to achieve high catalytic activity. For comparison, self-assembled monolayers that bind enzymes with the same chemical interactions are included. We use the model enzyme glucose oxidase and two kinds of polymers: anionic poly(acrylic acid) and cationic poly(diethylamino)methyl methacrylate. Surface plasmon resonance and spectroscopic ellipsometry are used for accurate quantification of surface coverage. Besides binding more enzymes, the "3D-like" brush environment enhances the specific activity compared to immobilization on self-assembled monolayers. For grafting-from brushes, multilayers of enzymes were spontaneously and irreversibly immobilized without conjugation chemistry. When the pH was between the pI of the enzyme and the pK a of the polymer, binding was considerable (thousands of ng/cm 2 or up to 50% of the polymer mass), even at physiological ionic strength. However, binding was observed also when the brushes were neutrally charged. For acidic brushes (both grafting-to and grafting-from), the activity was higher for covalent immobilization compared to noncovalent. For grafting-from brushes, a fully preserved specific activity compared to enzymes in the liquid bulk was achieved, both with covalent (acidic brush) and noncovalent (basic brush) immobilization. Catalytic activity of hundreds of pmol cm -2 s -1 was easily obtained for polybasic brushes only tens of nanometers in dry thickness. This study provides new insights for designing functional interfaces based on enzymatic catalysis.
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| 35. |
- Ferrand-Drake Del Castillo, Gustav, 1990, et al.
(author)
-
Generic high-capacity protein capture and release by pH control
- 2020
-
In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 56:44, s. 5889-5892
-
Journal article (peer-reviewed)abstract
- Techniques for immobilization and release of proteins are of general interest but challenging to develop. Here we show a new method for high-capacity (several µg cm-2) immobilization of proteins in polyelectrolyte brushes by multivalent hydrogen bonds. Upon increasing pH, the proteins are fully released with preserved structure and activity.
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| 36. |
- Ferrand-Drake Del Castillo, Gustav, 1990, et al.
(author)
-
Large Changes in Protonation of Weak Polyelectrolyte Brushes with Salt Concentration-Implications for Protein Immobilization
- 2020
-
In: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 11:13, s. 5212-5218
-
Journal article (peer-reviewed)abstract
- We report for the first time that the protonation behavior of weak polyelectrolyte brushes depends very strongly on ionic strength. The pKa changes by one pH step per order of magnitude in salt concentration. For low salt concentrations (∼1 mM), a very high pH is required to deprotonate a polyacidic brush and a very low pH is required to protonate a polybasic brush. This has major consequences for interactions with other macromolecules, as the brushes are actually almost fully neutral when believed to be charged. We propose that many previous studies on electrostatic interactions between polyelectrolytes and proteins have, in fact, looked at other types of intermolecular forces, in particular, hydrophobic interactions and hydrogen bonds.
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| 37. |
- Ferrand-Drake Del Castillo, Gustav, 1990, et al.
(author)
-
Quantitative Analysis of Thickness and pH Actuation of Weak Polyelectrolyte Brushes
- 2018
-
In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 122:48, s. 27516-27527
-
Journal article (peer-reviewed)abstract
- Polymer brushes are widely used as surface coatings for various inert, functional, or responsive interfaces. If the polymer can alter its protonation state (a polyelectrolyte (PE)), the brush can switch between a collapsed and swollen state with pH, which enables applications such as nanoscale actuators. However, changes in brush height as the polymer alters its charge state are not straightforward to measure accurately. Here, we show how surface plasmon resonance can be used to determine the thickness of PE brushes both in their charged and neutral states. We use different methods to measure the heights of brushes consisting of poly(acrylic acid) and the polybasic poly(2-(diethylamino)ethyl methacrylate), both prepared by atom transfer radical polymerization. We find polymers in solution that can act as refractive index probes, which do not interact with the grafted polyelectrolytes, thus providing an "exclusion height" of the brush. Importantly, the angular reflection spectrum can be used to directly identify if a probe is indeed noninteracting. Furthermore, using different noninteracting probes results in small but significant changes (∼10%) in the exclusion height as long as the probe is reasonably large (approximately >2 kg/mol). These differences cannot be attributed to probe charge. Data from multiple brushes show that the relative height increase (at physiological ionic strength), i.e., the "collapse ratio" upon charging due to pH alterations, increases with the absolute brush height. In addition, we show that the plasmonic response to the pH switching of the polyelectrolyte brush is opposite to the response of hydrophilic polymer brushes collapsing at the lower critical solution temperature. This phenomenon is explained by an increase in refractometric constant upon charging. Our study shows that surface plasmon resonance is an excellent tool for characterizing polyelectrolyte brushes and provides useful insights into pH actuation not easily obtained by other methods.
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| 38. |
- Fragasso, Alessio, et al.
(author)
-
A designer FG-Nup that reconstitutes the selective transport barrier of the nuclear pore complex
- 2021
-
In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1, s. 2010-
-
Journal article (peer-reviewed)abstract
- Nuclear Pore Complexes (NPCs) regulate bidirectional transport between the nucleus and the cytoplasm. Intrinsically disordered FG-Nups line the NPC lumen and form a selective barrier, where transport of most proteins is inhibited whereas specific transporter proteins freely pass. The mechanism underlying selective transport through the NPC is still debated. Here, we reconstitute the selective behaviour of the NPC bottom-up by introducing a rationally designed artificial FG-Nup that mimics natural Nups. Using QCM-D, we measure selective binding of the artificial FG-Nup brushes to the transport receptor Kap95 over cytosolic proteins such as BSA. Solid-state nanopores with the artificial FG-Nups lining their inner walls support fast translocation of Kap95 while blocking BSA, thus demonstrating selectivity. Coarse-grained molecular dynamics simulations highlight the formation of a selective meshwork with densities comparable to native NPCs. Our findings show that simple design rules can recapitulate the selective behaviour of native FG-Nups and demonstrate that no specific spacer sequence nor a spatial segregation of different FG-motif types are needed to create selective NPCs.
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| 39. |
- Gugole, Marika, 1993, et al.
(author)
-
Comparison of Electrodeposited and Sputtered Tungsten Trioxide Films for Inorganic Electrochromic Nanostructures
- 2023
-
In: ACS Applied Optical Materials. - : American Chemical Society (ACS). - 2771-9855 .- 2574-0962. ; 1:2, s. 558-568
-
Journal article (peer-reviewed)abstract
- Electrochromic materials and their implementation with structural colors are currently being intensely researched because of their promising applications as non-emissive display devices utilizing ambient light. In particular, several fully inorganic devices that rely on electrochromic tungsten trioxide (WO3) have been presented. For preparing nanoscale films of this material, sputtering is the most established technique, but electrodeposition has recently been shown to be capable of achieving exceptionally high electro-optical modulation contrast without the need for expensive equipment. In this work, we investigate the possibilities of electrodeposited WO3 and present a systematic comparison with sputtered WO3 with respect to performance in electrochromic devices. Importantly, we show that “ultralarge” electro-optical modulation (∼95% change in transmission) is possible for both types of films. However, it is only the sputtered films that enable such high contrast in a stable electrolyte such as LiClO4 in propylene carbonate. The electrodeposited films are less uniform and difficult to make thicker than ∼500 nm. We find no evidence that the electrochromic properties of the electrodeposited WO3 are intrinsically better than those of sputtered WO3. However, the electrodeposited films are much rougher and/or porous on the nanoscale, which increases the switching speed considerably. We conclude that electrodeposited WO3 is mainly useful in applications in which high contrast is not essential while switching speed is. As an example, we present the first electrodeposited WO3 integrated with structural colors by sandwiching the material between two metal films. By electrical control, the reflective colors can then be tuned at least one order of magnitude faster (a few seconds) than previously reported while having fair color quality and without any loss of brightness.
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| 40. |
- Gugole, Marika, 1993, et al.
(author)
-
Electrochromic Inorganic Nanostructures with High Chromaticity and Superior Brightness
- 2021
-
In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 21:10, s. 4343-4350
-
Journal article (peer-reviewed)abstract
- The possibility of actively controlling structural colors has recently attracted a lot of attention, in particular for new types of reflective displays (electronic paper). However, it has proven challenging to achieve good image quality in such devices, mainly because many subpixels are necessary and the semitransparent counter electrodes lower the total reflectance. Here we present an inorganic electrochromic nanostructure based on tungsten trioxide, gold, and a thin platinum mirror. The platinum reflector provides a wide color range and makes it possible to "reverse"the device design so that electrolyte and counter electrode can be placed behind the nanostructures with respect to the viewer. Importantly, this makes it possible to maintain high reflectance regardless of how the electrochemical cell is constructed. We show that our nanostructures clearly outperform the latest commercial color e-reader in terms of both color range and brightness.
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| 41. |
- Gugole, Marika, 1993, et al.
(author)
-
High-Contrast Switching of Plasmonic Structural Colors: Inorganic versus Organic Electrochromism
- 2020
-
In: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 7:7, s. 1762-1772
-
Journal article (peer-reviewed)abstract
- Plasmonic structural colors have recently received a lot of attention. For many applications there is a need to actively tune the colors after preparing the nanostructures, preferably with as strong changes in the optical response as possible. However, to date, there is a lack of systematic investigations on how to enhance contrast in electrically induced color modulation. In this work we implement electrochromic films with plasmonic metasurfaces and compare systematically organic and inorganic materials, with the primary aim to maximize brightness and contrast in a reflective color display. We show nanostructures with good chromaticity and high polarization-insensitive reflectivity (-90%) that are electrochemically stable in a nonaqueous solvent. Methods are evaluated for reliable and uniform electropolymerization of the conductive polymer dimethylpropylenedioxythiophene (PProDOTMe2) on gold. The resulting organic films are well-described by Lambert-Beer formalism, and the highest achievable contrast is easily determined in transmission mode. The optical properties of the inorganic option (WO3) require full Fresnel models due to thin film interference, and the film thickness must be carefully selected in order to maintain the chromaticity of the metasurfaces. Still, the optimized fully inorganic device reaches the highest contrast of approximately 60% reflectivity change for all primary colors. The switching time is about an order of magnitude faster for the organic films (hundreds of ms). The bistability is very long (hours) for the inorganic devices and comparable for the polymers, which makes the power consumption essentially zero for maintaining the same state. Finally, we show that switching of the primary colors in optimized devices (both organic and inorganic) provides almost twice as high brightness and contrast compared to existing reflective display technologies with RGB subpixels created by color filters.
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| 42. |
- Gugole, Marika, 1993, et al.
(author)
-
Optimizing electrochromism for plasmonic electronic paper: Inorganic vs organic
- 2019
-
In: International Conference on Metamaterials, Photonic Crystals and Plasmonics. - 2429-1390. ; , s. 760-761
-
Conference paper (peer-reviewed)abstract
- The combination of plasmonic nanostructures and electrochromic materials for dynamic color generation has been of interest in recent years due to the possibility to make reflective displays in full color with extremely low power consumption compared to emissive displays. We show a comparison between two electrochromic materials, tungsten trioxide (inorganic) and PProDOTMe2 (organic), for electrical modulation of the resonantly reflected light from plasmonic nanostructures. The comparison focuses on achievable contrast, switching speed, coloration memory and power consumption.
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| 43. |
- Gugole, Marika, 1993, et al.
(author)
-
Plasmonic Electronic Paper
- 2021
-
In: International Conference on Metamaterials, Photonic Crystals and Plasmonics. - 2429-1390.
-
Conference paper (peer-reviewed)abstract
- We work on developing reflective displays (electronic paper) in color by combining plasmonic nanostructures and electrochromic materials. The main motivation is to save energy in comparison with emissive displays.
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| 44. |
- Höök, Fredrik, 1966, et al.
(author)
-
Supported lipid bilayers, tethered lipid vesicles, and vesicle fusion investigated using gravimetric, plasmonic, and microscopy techniques
- 2007
-
In: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:2
-
Journal article (peer-reviewed)abstract
- This article summarizes our most recent contributions to the rapidly growing field of supported lipid assemblies with emphasis on current studies addressing both fundamental and applied aspects of supported lipid bilayer (SLB) and tethered lipid vesicles (TLVs) to be utilized in sensing applications. The new insights obtained from combining the quartz crystal microbalance with dissipation monitoring technique with surface plasmon resonance are described, and we also present recent studies in which nanoplasmonic sensing has been used in studies of SLBs and TLVs. To gain full control over the spatial arrangement of TLVs in both two and three dimensions, we have developed a method for site-selective and sequence-specific sorting of DNA-tagged vesicles to surfaces modified with complementary DNA. The combination of this method with nanoplasmonic sensing formats is covered as well as the possibility of using DNA-modified vesicles for the detection of unlabeled DNA targets on the single-molecule level. Finally, a new method for membrane fusion induced by hybridization of vesicle-anchored DNA is demonstrated, including new results on content mixing obtained with vesicle populations encapsulating short, complementary DNA strands.
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| 45. |
- Ikenoya, Y., et al.
(author)
-
Optical Resonances in Short-Range Ordered Nanoholes in Ultrathin Aluminum/Aluminum Nitride Multilayers
- 2013
-
In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:12, s. 6373-6382
-
Journal article (peer-reviewed)abstract
- Nanoholes with short-range ordering were fabricated in ultrathin aluminum/aluminum nitride multilayer films where each layer is as thin as a few nanometers. Optical resonances of the trilayer system with a single metallic layer and five-layer system with two metallic layers were successfully tuned in the visible-near-infrared (vis/NIR) range. The resonance wavelength as well as the width can be predicted and designed by solving the dispersion relation and comparing with the lateral dimension of the short-range ordering. To solve the dispersion relation, we developed a general formulation for multilayer systems. The thermal stability of the fabricated nanoholes in ultrathin multilayers was also tested by vacuum annealing the samples up to 400 degrees C. While no structural change of the nanohole or the multilayer surface has been observed, the optical property showed almost no change in the resonance confirming no structural change but emergence of the interband transition!
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| 46. |
- Jonsson, Magnus, 1981, et al.
(author)
-
Locally Functionalized Short-Range Ordered Nanoplasmonic Pores for Bioanalytical Sensing
- 2010
-
In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 82:5, s. 2087-2094
-
Journal article (peer-reviewed)abstract
- Nanoplasmonic sensors based on short-range ordered nano-holes in thin metal films and discrete metal nanoparticles are known to provide similar sensing performance. However, a perforated metal film is unique in the sense that the holes can be designed to penetrate through the substrate, thereby also fulfilling the role of nanofluidic channels. This paper presents a bioanalytical sensing concept based on short-range ordered nanoplasmonic pores (diameter 150 nm) penetrating through a thin (around 250 nm) multilayer membrane composed of gold and silicon nitride (SiN) that is Supported on a Si wafer. Also, a fabrication scheme that enables parallel production of multiple (more than 50) separate sensor chips or more than 1000 separate nanoplasmonic membranes on it single wafer is presented. Together with the localization of the sensitivity to within such short-range ordered nanoholes, the structure provides it two-dimensional nanofluidic network, sized in the order of 100 x 100 mu m(2), with nanoplasmon active regions localized to each individual nanochannel. A material-specific surface-modification scheme was developed to promote specific binding of target molecules on the optically active gold regions only, while suppressing nonspecific adsorption on SiN. Using this protocol, and by monitoring the temporal variation in the plasmon resonance of the structure, we demonstrate flow-through nanoplasmonic sensing of specific biorecognition reactions with a signal-to-noise ratio of around 50 at a temporal resolution below 190 ms. With flow, the uptake was demonstrated to be at least 1 order of magnitude faster than under stagnant conditions, while still keeping the sample consumption at a minimum.
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| 47. |
- Jonsson, Magnus, 1981, et al.
(author)
-
Nanoplasmonic biosensing with focus on short-range ordered nanoholes in thin metal films
- 2008
-
In: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:3, s. FD30-FD40
-
Journal article (peer-reviewed)abstract
- The resonance conditions for excitation of propagating surface plasmons at planar metal/dielectric interfaces and localized surface plasmons associated with metal nanostructures are both sensitive to changes in the interfacial refractive index. This has made these phenomena increasingly popular as transducer principles in label-free sensing of biomolecular recognition reactions. In this article, the authors review the recent progress in the field of nanoplasmonic bioanalytical sensing in general, but set particular focus on certain unique possibilities provided by short-range ordered nanoholes in thin metal films. Although the latter structures are formed in continuous metal films, while nanoparticles are discrete entities, these two systems display striking similarities with respect to sensing capabilities, including bulk sensitivities, and the localization of the electromagnetic fields. In contrast, periodic arrays of nanoholes formed in metal films, most known for their ability to provide wavelength-tuned enhanced transmission, show more similarities with conventional propagating surface plasmon resonance. However, common for both short-range ordered and periodic nanoholes formed in metal films is that the substrate is electrically conductive. Some of the possibilities that emerge from sensor templates that are both electrically conductive and plasmon active are discussed and illustrated using recent results on synchronized nanoplasmonic and quartz crystal microbalance with dissipation monitoring of supported lipid bilayer formation and subsequent biomolecular recognition reactions. Besides the fact that this combination of techniques provides an independent measure of biomolecular structural changes, it is also shown to contribute with a general means to quantify the response from nanoplasmonic sensors in terms of bound molecular mass. c 2008 American Vacuum Society.
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| 48. |
- Jonsson, Magnus, 1981, et al.
(author)
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Nanoplasmonic sensing combined with artificial cell membranes
- 2012
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In: Nanoplasmonic Sensors. - New York, NY : Springer New York. - 9781461439332 ; , s. 59-82
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Book chapter (other academic/artistic)abstract
- This chapter is dedicated to nanoplasmonic sensing systems made compatible with studies of artificial cell membranes. After a short motivation to the opportunity of sensors designed for such studies to fill an existing technological gap, we introduce basic features of cell membranes and common mimics of the cell membrane that have been proven useful in various bioanalytical sensing applications. With suitable examples from the literature, subsequent sections exemplify how nanoplasmonics can be used to study different reactions that are associated with cell membranes. In particular, focus is on unique possibilities provided by different types of nanoplasmonic structures. For example, while discrete nanoplasmonic particles can be used as mobile probes attached to cell membranes, conductive nanoplasmonic hole structures can be used for combined optical and electrical transduction. Examples on how the latter possibility has enabled cell membrane-related reactions to be investigated with nanoplasmonic sensing combined with quartz crystal microbalance with dissipation monitoring are presented. Another key aspect of nanoplasmonic structures is that the plasmonic field (and hence the refractive index sensitivity) is strongest at the sensor surface and decays rapidly away from the surface. We describe how this feature provides a means to monitor structural changes of molecules on the surface, such as the spontaneous rupture of lipid vesicles into a supported lipid bilayer on silicon oxide-coated nanoplasmonic holes.
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| 49. |
- Junesch, Juliane, 1987, et al.
(author)
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Location-specific nanoplasmonic sensing of biomolecular binding to lipid membranes with negative curvature
- 2015
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In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:37, s. 15080-15085
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Journal article (peer-reviewed)abstract
- The biochemical processes of cell membranes are sensitive to the geometry of the lipid bilayer. We show how plasmonic "nanowells" provide label-free real-time analysis of molecules on membranes with detection of preferential binding at negative curvature. It is demonstrated that norovirus accumulate in invaginations due to multivalent interactions with glycosphingolipids.
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| 50. |
- Junesch, Juliane, 1987, et al.
(author)
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Optical Properties of Nanohole Arrays in Metal-Dielectric Double Films Prepared by Mask-on-Metal Colloidal Lithography
- 2012
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In: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 6:11, s. 10405-10415
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Journal article (peer-reviewed)abstract
- We present the fabrication and optical characterization of plasmonic nanostructures consisting of nanohole arrays in two thin films, a metal and a dielectric. A novel method called mask-on-metal colloidal lithography is used to prepare high aspect ratio holes, providing efficient mass fabrication of stable structures with close to vertical walls and without the need for an adhesion layer under the metal. Our approach for understanding the transmission properties is based on solving the dispersions of. the guided modes supported by the two films and calculating the Influence from interference. The methodology is generic and can be extended to multilayered films. In particular, the influence from coupling to waveguide modes is discussed. We show that by rational design of structural dimensions It Is possible to study only bonding surface plasmons and the associated hole transmission maximum. Further, numerical simulations with the multiple multipole program provide good agreement with experimental data and enable visualization of the asymmetric near field distribution in the nanohole arrays, which is focused to the interior of the "nanowells". The refractometric sensitivity Is evaluated-experimentally both by liquid bulk changes and surface adsorption. We demonstrate how the localized mode provides reasonably good sensitivity in terms of resonance shift to molecular binding inside-the voids. Importantly, high resolution sensing can be accomplished also for the surface plasmon mode, despite its extremely low figure of merit. This is accomplished by monitoring the coupling efficiency of light to plasmons instead of conventional sensing which is based on changes in plasmon energy We suggest that these nanohole structures can be used for studying molecular transport through nanopores and the behavior of molecules confined in volumes of approximately one attoliter.
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