| 1. |
- Barman, Snigdha Roy, et al.
(författare)
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Dendrimer as a multifunctional capping agent for metal nanoparticles for use in bioimaging, drug delivery and sensor applications
- 2018
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Ingår i: Journal of materials chemistry. B. - : ROYAL SOC CHEMISTRY. - 2050-750X .- 2050-7518. ; 6:16, s. 2368-2384
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Forskningsöversikt (refereegranskat)abstract
- Advances in nanoparticle research, particularly in the domain of surface-engineered, function-oriented nanoparticles, have had a profound effect in many areas of scientific research and aided in bringing unprecedented developments forward, particularly in the biomedical field. Surface modifiers/capping agents have a direct bearing on the major properties of metal nanoparticles (MNPs), ranging from their physico-chemical properties to their stability and functional applications. Among the different classes of capping agents, dendrimers have gained traction as effective multifunctional capping agents for MNPs due to their unique structural qualities, dendritic effect and polydentate nature. Dendrimer-coated metal nanoparticles (DC-MNPs) are typically produced by both (i) a one-pot strategy, where metal ions are reduced in the presence of dendrimer molecules and (ii) a multi-pot strategy, where a sequence of reactions involving the reduction of metal ions, activation, conjugation and purification steps are involved. These DC-MNPs have shown remarkable ability to stabilize MNPs by means of electrostatic interactions, coordination chemistry or covalent attachment, due to them entailing a large number of sites at which further molecular moieties can be conjugated. This review article is an attempt to consolidate the on-going work, particularly over the last five years, in the field of the synthesis of dendrimer-coated MNPs and their potential applications in bioimaging, drug delivery and biochemical sensors.
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| 2. |
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| 3. |
- Divagar, M, et al.
(författare)
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Self-assembled polyamidoamine dendrimer on poly (methyl methacrylate) for plasmonic fiber optic sensors
- 2019
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Ingår i: ChemNanoMat. - : John Wiley & Sons. - 2199-692X.
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Tidskriftsartikel (refereegranskat)abstract
- We report a novel one-step polyamidoamine (PAMAM) dendrimer based polymethyl methacrylate (PMMA) surface functionalization strategy for the development of polymeric optical fiber (POF) based plasmonic sensors utilizing gold nanoparticles (AuNP). Simple contact angle measurements over PMMA sheets reveal the ability of the dendrimers to strongly bind to PMMA surface without additional acid/alkali pretreatment, unlike the conventional hexamethylene diamine (HMDA) based surface modification. Subsequently, U-bent POF probes with high evanescent wave absorbance sensitivity were exploited for relative quantification of the surface amine groups using fluorescein isothiocyanate (FITC) binding and efficient chemisorption of gold nanoparticles (AuNP) in order to identify the optimum conditions viz. dendrimer concentration, incubation time and dendrimer generation. While FITC binding showed a proportional increase in amine functional density with PAMAM concentration and time, interestingly the AuNP (40 nm) binding studies revealed the formation of loose PAMAM multilayers and their desorption. PAMAM (G4) concentration as low as 5 mM and incubation time of 24 h provide faster binding rate with densely packed AuNP and the RI sensitivity of ~15 (A546 nm/RIU). This simpler and inexpensive strategy could also be exploited for the development of functional PMMA substrates for various applications including nanotechnology, bio-imaging, drug delivery and analytical separations.
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| 4. |
- Jain, Saumey, et al.
(författare)
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On-Chip Neural Induction Boosts Neural Stem Cell Commitment : Toward a Pipeline for iPSC-Based Therapies
- 2024
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Ingår i: Advanced science (Weinheim, Baden-Wurttemberg, Germany). - : Wiley-VCH Verlagsgesellschaft. - 2198-3844.
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Tidskriftsartikel (refereegranskat)abstract
- The clinical translation of induced pluripotent stem cells (iPSCs) holds great potential for personalized therapeutics. However, one of the main obstacles is that the current workflow to generate iPSCs is expensive, time-consuming, and requires standardization. A simplified and cost-effective microfluidic approach is presented for reprogramming fibroblasts into iPSCs and their subsequent differentiation into neural stem cells (NSCs). This method exploits microphysiological technology, providing a 100-fold reduction in reagents for reprogramming and a ninefold reduction in number of input cells. The iPSCs generated from microfluidic reprogramming of fibroblasts show upregulation of pluripotency markers and downregulation of fibroblast markers, on par with those reprogrammed in standard well-conditions. The NSCs differentiated in microfluidic chips show upregulation of neuroectodermal markers (ZIC1, PAX6, SOX1), highlighting their propensity for nervous system development. Cells obtained on conventional well plates and microfluidic chips are compared for reprogramming and neural induction by bulk RNA sequencing. Pathway enrichment analysis of NSCs from chip showed neural stem cell development enrichment and boosted commitment to neural stem cell lineage in initial phases of neural induction, attributed to a confined environment in a microfluidic chip. This method provides a cost-effective pipeline to reprogram and differentiate iPSCs for therapeutics compliant with current good manufacturing practices.
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| 5. |
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| 6. |
- Kipen, Javier, et al.
(författare)
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Efficient Implementation of Robust CUSUM Algorithm to Characterize Nanogaps Measurements with Heavy-Tailed Noise
- 2023
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Ingår i: ICASSP 2023 - 2023 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- Detection of bio-molecules through quantum tunneling currents could lead to the next-generation DNA sequencing methods. In order to analyze the stability of these sensitive devices, it is necessary to characterize their conductance switching statistics. This characterization can be realized by denoising the tunneling current signal and clustering the outcomes. The first step can be done with the CUSUM algorithm, which detects abrupt changes and has been used in similar devices. We found heavy-tailed non-Gaussian noise in the measurement setup of the experimental devices. This paper suggests an approximation in the likelihood ratio step of the CUSUM algorithm that is more robust than the simple Gaussian noise assumption and, at the same time, is computationally more efficient than computing the fitted true likelihoods.
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| 7. |
- Nain, Amit, et al.
(författare)
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Dual mechanism-based sensing of mercury using unmodified, heteroepitaxially synthesized silver nanoparticles
- 2017
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Ingår i: Applied Nanoscience. - : Springer Berlin/Heidelberg. - 2190-5509 .- 2190-5517. ; 7:6, s. 299-307
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Tidskriftsartikel (refereegranskat)abstract
- Mercury and its compounds are widely distributed in the environment and have a significant negative impact on human health. In this paper, we report the development of a rapid and facile method for the detection of mercury ions (Hg2+) using heteroepitaxially synthesized unmodified silver nanoparticle-based smart probes using UV-Vis spectrophotometer and also through the naked eye by means of a paper-based sensor strip. The silver nanoparticles were prepared by heteroepitaxial growth method using gold seed nanoparticle of similar to 2.4 nm size as the template. The silver is grown on the seed particles by reducing the silver-ammonia complex using glucose, which resulted in Glu-AgNPs having an average size of 14.65 +/- 3.53 nm. The sensing of mercury ions was carried out in aqueous solution and the reaction response was monitored by UV-Vis spectrophotometer. The interaction of Hg2+ with Glu-AgNPs resulted in a significant drop in the absorbance at 402 nm along with a prominent color change (from bright yellow to colorless) and wavelength shift (blue shift). The limit of detection (LOD) of this assay was found to be 100 nM (i. e., 20 ppb) with a good linearity in the concentration range of 100-10 mM. To further ease the detection process and make it field deployable, we attempted to develop a paper-based sensor strip by immobilizing Glu-AgNPs on a paper strip. Upon interaction with mercury solution of varying concentrations, the decoloration of the spots could be observed easily through naked eyes, with the limit of detection under sub-optical conditions being 1 mu M.
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| 8. |
- Raja, Shyamprasad Natarajan, et al.
(författare)
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Electromigrated Gold Nanogap Tunnel Junction Arrays: Fabrication and Electrical Behavior in Liquid and Gaseous Media
- 2024
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252.
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Tidskriftsartikel (refereegranskat)abstract
- Tunnel junctions have been suggested as high-throughput electronic single molecule sensors in liquids with several seminal experiments conducted using break junctions with reconfigurable gaps. For practical single molecule sensing applications, arrays of on-chip integrated fixed-gap tunnel junctions that can be built into compact systems are preferable. Fabricating nanogaps by electromigration is one of the most promising approaches to realize on-chip integrated tunnel junction sensors. However, the electrical behavior of fixed-gap tunnel junctions immersed in liquid media has not been systematically studied to date, and the formation of electromigrated nanogap tunnel junctions in liquid media has not yet been demonstrated. In this work, we perform a comparative study of the formation and electrical behavior of arrays of gold nanogap tunnel junctions made by feedback-controlled electromigration immersed in various liquid and gaseous media (deionized water, mesitylene, ethanol, nitrogen, and air). We demonstrate that tunnel junctions can be obtained from microfabricated gold nanoconstrictions inside liquid media. Electromigration of junctions in air produces the highest yield (61–67%), electromigration in deionized water and mesitylene results in a lower yield than in air (44–48%), whereas electromigration in ethanol fails to produce viable tunnel junctions due to interfering electrochemical processes. We map out the stability of the conductance characteristics of the resulting tunnel junctions and identify medium-specific operational conditions that have an impact on the yield of forming stable junctions. Furthermore, we highlight the unique challenges associated with working with arrays of large numbers of tunnel junctions in batches. Our findings will inform future efforts to build single molecule sensors using on-chip integrated tunnel junctions.
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| 9. |
- Raja, Shyamprasad Natarajan, et al.
(författare)
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High-bandwidth low-current measurement system for automated and scalable probing of tunnel junctions in liquids
- 2024
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 95:7
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Tidskriftsartikel (refereegranskat)abstract
- Tunnel junctions have long been used to immobilize and study the electronic transport properties of single molecules. The sensitivity of tunneling currents to entities in the tunneling gap has generated interest in developing electronic biosensors with single molecule resolution. Tunnel junctions can, for example, be used for sensing bound or unbound DNA, RNA, amino acids, and proteins in liquids. However, manufacturing technologies for on-chip integrated arrays of tunnel junction sensors are still in their infancy, and scalable measurement strategies that allow the measurement of large numbers of tunneling junctions are required to facilitate progress. Here, we describe an experimental setup to perform scalable, high-bandwidth (>10 kHz) measurements of low currents (pA–nA) in arrays of on-chip integrated tunnel junctions immersed in various liquid media. Leveraging a commercially available compact 100 kHz bandwidth low-current measurement instrument, we developed a custom two-terminal probe on which the amplifier is directly mounted to decrease parasitic probe capacitances to sub-pF levels. We also integrated a motorized three-axis stage, which could be powered down using software control, inside the Faraday cage of the setup. This enabled automated data acquisition on arrays of tunnel junctions without worsening the noise floor despite being inside the Faraday cage. A deliberately positioned air gap in the fluidic path ensured liquid perfusion to the chip from outside the Faraday cage without coupling in additional noise. We demonstrate the performance of our setup using rapid current switching observed in electromigrated gold tunnel junctions immersed in deionized water.
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| 10. |
- Sangeeta, K., et al.
(författare)
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Investigation of bimetallic hollow nanoparticles for colorimetric detection of mercury
- 2018
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Ingår i: Nanophotonics VII 2018. - : SPIE. - 9781510618701
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Konferensbidrag (refereegranskat)abstract
- In this study, we have investigated the potential of bimetallic hollow nanostructures (BHNS) consisting of silver and gold metals for the detection of mercury in an aqueous medium. The BHNS of varying compositions of gold and silver were prepared by galvanic etching of the template silver nanoparticles (AgNPs) using gold(III) salt solution. The BHNS of varying composition were prepared by modulating the molar ratio, of gold to silver, ranging from 0.13 to 2.0, in the reaction mixture. The resultant nanostructures were characterized using UV-Vis spectroscopy and transmission electron microscopy. The absorption maxima of the BHNS batches were found to be increased from 463 ± 9 nm to 611 ± 12 nm as a function of gold to silver molar ratio. An increase in the nanoparticles size was observed from 54 ± 6 (molar ratio = 0.25) to 75 ± 10 (molar ratio = 2.0) with an increase in gold to silver molar ratio. The interaction of different volumes of mercury solution (ranging from 0.1 to 0.4 mL) with all types of BHNS was studied. A considerable change in color of the solution was observed and consequently, a change in the absorbance intensity and a shift in the peak plasmonic wavelength was also noticed. Among the different BHNS batches investigated, the highest change in the intensity and peak wavelength was observed for BHNS0.13, with higher silver and lower gold content. This suggests that the reaction between silver and mercury is more favored compared to that between mercury and gold.
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| 11. |
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| 12. |
- Yadav, Sangeeta, et al.
(författare)
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Bimetallic Hollow Nanostructures for Colorimetric Detection of Picomolar Level of Mercury.
- 2020
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Ingår i: Journal of Nanoscience and Nanotechnology. - : Ingenta. - 1533-4880 .- 1533-4899. ; 20:2, s. 991-998
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report the use of bimetallic hollow nanostructures (BHNS), consisting of gold and silver metals, for colorimetric detection of mercury. The sodium dodecyl sulphate (SDS)-capped BHNS were prepared by galvanic etching of silver nanoparticles (AgNPs) using gold chloride resulting in a partially hollow AgNPs with the gold layer at its surface. These BHNS were interacted with an aqueous solution of mercury ions (Hg2+) in the concentration range of 10 pM-10 mM. Interestingly, at higher concentration range (10 μM-10 mM), a noticeable change in the solution color was observed with a prominent decrease in the absorption intensity and blue-shift in the peak plasmonic wavelength. This could be attributed to (i) complexation reaction between the anionic BHNS (due to the negatively charged SDS capping) and cationic Hg2+ and (ii) oxidative etching of silver from BHNS causing its depletion and resulting into Ag-Hg amalgam and/or aggregation of the nanostructures. In contrast, at lower concentration range (i.e., 10 pM-10 nM), an increase in the absorption intensity was observed, which was possibly due to the oxidative etching of silver from BHNS without aggregation of the nanostructures. The low amount of Hg2+ was not sufficient enough to interact with SDS capping layer present on the BHNS surface, unlike the higher concentrations of mercury and therefore, did not cause any aggregation. The developed colorimetric sensor showed high sensitivity and selectivity towards Hg2+ detection with a limit of detection of 10 pM and good linearity (R² = 0.97) in the concentration range of 10 pM-10 nM.
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| 13. |
- Zeglio, Erica, 1987-, et al.
(författare)
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Mixing Insulating Commodity Polymers with Semiconducting n-type Polymers Enables High-Performance Electrochemical Transistors
- 2024
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Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095.
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Tidskriftsartikel (refereegranskat)abstract
- Diluting organic semiconductors with a host insulating polymer is used to increase the electronic mobility in organic electronic devices, such as thin film transistors, while considerably reducing material costs. In contrast to organic electronics, bioelectronic devices such as the organic electrochemical transistor (OECT) rely on both electronic and ionic mobility for efficient operation, making it challenging to integrate hydrophobic polymers as the predominant blend component. This work shows that diluting the n-type conjugated polymer p(N-T) with high molecular weight polystyrene (10 KDa) leads to OECTs with over three times better mobility-volumetric capacitance product (µC*) with respect to the pristine p(N-T) (from 4.3 to 13.4 F V−1 cm−1 s−1) while drastically decreasing the amount of conjugated polymer (six times less). This improvement in µC* is due to a dramatic increase in electronic mobility by two orders of magnitude, from 0.059 to 1.3 cm2 V−1 s−1 for p(N-T):Polystyrene 10 KDa 1:6. Moreover, devices made with this polymer blend show better stability, retaining 77% of the initial drain current after 60 minutes operation in contrast to 12% for pristine p(N-T). These results open a new generation of low-cost organic mixed ionic-electronic conductors where the bulk of the film is made by a commodity polymer.
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