| 1. |
- Grandfield, Kathryn, et al.
(författare)
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Characterization of dental interfaces with electron tomography
- 2014
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 9:2, s. 029001-
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the interface between dental materials and tooth is critical in the prevention of secondary caries. Assessing this interface with high-resolution clarity has traditionally been challenging. This work highlights electron tomography, carried out in the transmission electron microscope, as a novel technique to obtain both three-dimensional and nanometer scaled information on dental materials in contact with dentin. In this study, commercial calcium aluminate and glass ionomer based luting agents in contact with human dentin were prepared for electron microscopy via focused ion beam milling. Imaging with high-angle annular dark field provided compositional contrast, and combined with tilting over large angular ranges, enabled the reconstruction of the three-dimensional interface between tissue and cement. The characteristics of the interface were observed with this extra dimensionality and superior resolution, providing evidence for the viability of this technique in interfacial studies of dental materials.
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| 2. |
- Bally, Marta, 1981, et al.
(författare)
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A virus biosensor with single virus-particle sensitivity based on fluorescent vesicle labels and equilibrium fluctuation analysis
- 2013
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Biosensors allowing for the rapid and sensitive detection of viral pathogens in environmental or clinical samples are urgently needed to prevent disease outbreaks and spreading. We present a bioanalytical assay for the detection of whole viral particles with single virus sensitivity. Specifically, we focus on the detection of human norovirus, a highly infectious virus causing gastroenteritis. In our assay configuration, virus-like particles are captured onto a supported lipid bilayer containing a virus-specific glycolipid and detected after recognition by a glycolipid-containing fluorescent vesicle. Read-out is performed after illumination of the vesicle labels by total internal reflection fluorescence microscopy. This allows for visualization of individual vesicles and for recording of their binding kinetics under equilibrium conditions (equilibrium fluctuation analysis), as demonstrated previously. In this work we extend the concept and demonstrate that this simple assay setup can be used as a bioanalytical assay for the detection of virus particles at a limit of detection of 16 fM. Furthermore, we demonstrate how the analysis of the single vesicle-virus-like particle interaction dynamics can contribute to increase the accuracy and sensitivity of the assay by discriminating specific from non-specific binding events. This method is suggested to be generally applicable, provided that these events display different interaction kinetics.
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| 3. |
- Andersson, Olof, et al.
(författare)
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Novel application of imaging surface plasmon resonance for in situ studies of the surface exploration of marine organisms
- 2009
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Ingår i: BIOINTERPHASES. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 4:4, s. 65-68
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Tidskriftsartikel (refereegranskat)abstract
- The surface interactions of exploring cyprids of the barnacle Semibalanus balanoides were studied in situ using imaging surface plasmon resonance. It was demonstrated how the deposition of a proteinaceous adhesive could be followed in real time as the cyprids explored and temporarily attached to a surface. Furthermore, the amount of protein left on the surface when the cyprids moved on could be quantified. Clear differences were demonstrated between an oligo(ethyleneglycol) coated surface and a bare gold substrate. It is anticipated that this technique will be a valuable tool in the development of novel surface chemistries that can prevent biofouling.
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| 4. |
- Angerer, Tina B., 1987, et al.
(författare)
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Optimizing sample preparation for anatomical determination in the hippocampus of rodent brain by ToF-SIMS analysis
- 2016
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- Lipidomics has been an expanding field since researchers began to recognize the signaling functions of lipids and their involvement in disease. Time-of-flight secondary ion mass spectrometry is a valuable tool for studying the distribution of a wide range of lipids in multiple brain regions, but in order to make valuable scientific contributions, one has to be aware of the influence that sample treatment can have on the results. In this article, the authors discuss different sample treatment protocols for rodent brain sections focusing on signal from the hippocampus and surrounding areas. The authors compare frozen hydrated analysis to freeze drying, which is the standard in most research facilities, and reactive vapor exposure (trifluoroacetic acid and NH3). The results show that in order to preserve brain chemistry close to a native state, frozen hydrated analysis is the most suitable, but execution can be difficult. Freeze drying is prone to produce artifacts as cholesterol migrates to surface, masking other signals. This effect can be partially reversed by exposing freeze dried sections to reactive vapor. When analyzing brain sections in negative ion mode, exposing those sections to NH3 vapor can re-establish the diversity in lipid signal found in frozen hydrated analyzed sections. This is accomplished by removing cholesterol and uncovering sulfatide signals, allowing more anatomical regions to be visualized.
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| 5. |
- Asplund, Maria, 1978-, et al.
(författare)
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Composite biomolecule/PEDOT materials for neural electrodes
- 2008
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Ingår i: Biointerphases. - NY : American Institute of Physics. - 1559-4106 .- 1934-8630. ; 3:3, s. 83-93
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Tidskriftsartikel (refereegranskat)abstract
- Electrodes intended for neural communication must be designed to meet boththe electrochemical and biological requirements essential for long term functionality. Metallic electrode materials have been found inadequate to meet theserequirements and therefore conducting polymers for neural electrodes have emergedas a field of interest. One clear advantage with polymerelectrodes is the possibility to tailor the material to haveoptimal biomechanical and chemical properties for certain applications. To identifyand evaluate new materials for neural communication electrodes, three chargedbiomolecules, fibrinogen, hyaluronic acid (HA), and heparin are used ascounterions in the electrochemical polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). The resultingmaterial is evaluated electrochemically and the amount of exposed biomoleculeon the surface is quantified. PEDOT:biomolecule surfaces are also studiedwith static contact angle measurements as well as scanning electronmicroscopy and compared to surfaces of PEDOT electrochemically deposited withsurfactant counterion polystyrene sulphonate (PSS). Electrochemical measurements show that PEDOT:heparinand PEDOT:HA, both have the electrochemical properties required for neuralelectrodes, and PEDOT:heparin also compares well to PEDOT:PSS. PEDOT:fibrinogen isfound less suitable as neural electrode material.
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| 6. |
- Barut, Inci, et al.
(författare)
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Cell and tissue imaging by secondary ion mass spectrometry
- 2023
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Ingår i: Biointerphases. - 1934-8630 .- 1559-4106. ; 18:6
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Tidskriftsartikel (refereegranskat)abstract
- This Tutorial focuses on the use of secondary ion mass spectrometry for the analysis of cellular and tissue samples. The Tutorial aims to cover the considerations in sample preparation analytical set up and some specific aspects of data interpretation associated with such analysis.
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| 7. |
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| 8. |
- Blockhuys, Stephanie, 1983, et al.
(författare)
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Copper distribution in breast cancer cells detected by time-of-flight secondary ion mass spectrometry with delayed extraction methodology
- 2018
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 13:6
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Tidskriftsartikel (refereegranskat)abstract
- Copper (Cu) is an essential transition metal ion that acts as a cofactor in many key enzymes. Cu is also needed for several hallmarks of cancer, and many copper-binding proteins are upregulated in various cancers. However, Cu-dependent cellular mechanisms and molecular pathways involved in cancer progression are not known. Fundamental to a better understanding of such phenomena is the investigation of the Cu subcellular distribution in cancer cells. The authors here show that Time-of-Flight Secondary Ion Mass Spectrometry combined with delayed extraction can be successfully applied to probe Cu localization in fixed MDA-MB-231 breast cancer cells providing subcellular resolution. Interestingly, the authors find Cu to be accumulated at nuclear regions of the cancer cells. Published by the AVS.
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| 9. |
- Carlred, Louise, et al.
(författare)
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Imaging of amyloid-β in alzheimer’s disease transgenic mouse brains with ToF-SIMS using immunoliposomes
- 2016
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Ingår i: Biointerphases. - : American Institute of Physics (AIP). - 1934-8630 .- 1559-4106. ; 11:2, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been proven to successfully image different kinds of molecules, especially a variety of lipids, in biological samples. Proteins, however, are difficult to detect as specific entities with this method due to extensive fragmentation. To circumvent this issue, the authors present in this work a method developed for detection of proteins using antibody-conjugated liposomes, so called immunoliposomes, which are able to bind to the specific protein of interest. In combination with the capability of ToF-SIMS to detect native lipids in tissue samples, this method opens up the opportunity to analyze many different biomolecules, both lipids and proteins, at the same time, with high spatial resolution. The method has been applied to detect and image the distribution of amyloid-β (Aβ), a biologically relevant peptide in Alzheimer’s disease (AD), in transgenic mouse brain tissue. To ensure specific binding, the immunoliposome binding was verified on a model surface using quartz crystal microbalance with dissipation monitoring. The immunoliposome binding was also investigated on tissue sections with fluorescence microscopy, and compared with conventional immunohistochemistry using primary and secondary antibodies, demonstrating specific binding to Aβ. Using ToF-SIMS imaging, several endogenous lipids, such as cholesterol and sulfatides, were also detected in parallel with the immunoliposome-labeled Aβ deposits, which is an advantage compared to fluorescence microscopy. This method can thus potentially provide further information about lipid–protein interactions, which is important to understand the mechanisms of neurodegeneration in AD.
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| 10. |
- Carlred, Louise M, 1985, et al.
(författare)
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Imaging of Amyloid-β in Alzheimer’s disease transgenic mouse brains with Time-of-Flight Secondary Ion Mass Spectrometry using Immunoliposomes
- 2016
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 11:2, s. 1-11
-
Tidskriftsartikel (refereegranskat)abstract
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been proven to successfully image different kinds of molecules, especially a variety of lipids, in biological samples. Proteins, however, are difficult to detect as specific entities with this method due to extensive fragmentation. To circumvent this issue, the authors present in this work a method developed for detection of proteins using antibody-conjugated liposomes, so called immunoliposomes, which are able to bind to the specific protein of interest. In combination with the capability of ToF-SIMS to detect native lipids in tissue samples, this method opens up the opportunity to analyze many different biomolecules, both lipids and proteins, at the same time, with high spatial resolution. The method has been applied to detect and image the distribution of amyloid-β (Aβ), a biologically relevant peptide in Alzheimer's disease (AD), in transgenic mouse braintissue. To ensure specific binding, the immunoliposome binding was verified on a model surface using quartz crystal microbalance with dissipation monitoring. The immunoliposome binding was also investigated on tissue sections with fluorescence microscopy, and compared with conventional immunohistochemistry using primary and secondary antibodies, demonstrating specific binding to Aβ. Using ToF-SIMS imaging, several endogenous lipids, such as cholesterol and sulfatides, were also detected in parallel with the immunoliposome-labeled Aβ deposits, which is an advantage compared to fluorescence microscopy. This method can thus potentially provide further information about lipid–protein interactions, which is important to understand the mechanisms of neurodegeneration in AD.
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| 11. |
- Diacci, Chiara, et al.
(författare)
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Label-free detection of interleukin-6 using electrolyte gated organic field effect transistors
- 2017
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Ingår i: Biointerphases. - : AMER INST PHYSICS. - 1934-8630 .- 1559-4106. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- Cytokines are small proteins that play fundamental roles in inflammatory processes in the human body. In particular, interleukin (IL)-6 is a multifunctional cytokine, whose increased levels are associated with infection, cancer, and inflammation. The quantification of IL-6 is therefore of primary importance in early stages of inflammation and in chronic diseases, but standard techniques are expensive, time-consuming, and usually rely on fluorescent or radioactive labels. Organic electronic devices and, in particular, organic field-effect transistors (OFETs) have been proposed in the recent years as novel platforms for label-free protein detection, exploiting as sensing unit surface-immobilized antibodies or aptamers. Here, the authors report two electrolyte-gated OFETs biosensors for IL-6 detection, featuring monoclonal antibodies and peptide aptamers adsorbed at the gate. Both strategies yield biosensors that can work on a wide range of IL-6 concentrations and exhibit a remarkable limit of detection of 1 pM. Eventually, electrolyte gated OFETs responses have been used to extract and compare the binding thermodynamics between the sensing moiety, immobilized at the gate electrode, and IL-6. (C) 2017 American Vacuum Society.
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| 12. |
- Dowlatshahi Pour, Masoumeh, 1976, et al.
(författare)
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Mass spectrometric profiling of lipids in intestinal tissue from rats fed cereals processed for medical conditions
- 2016
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 11:2, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used for lipid profiling of intestine tissue sections from rats fed specially processed cereals and rats fed ordinary feed as a control. This cereal is known to increase the activity of antisecretory factor in plasma and the exact mechanism for the activation process at the cellular level is unclear. ToF-SIMS has been used to track food induced changes in lipid content in intestinal tissue sections to gain insight into the possible mechanisms involved. Data from 20 intestine sections belonging to four different rats from each group of control and specially processed cereals-fed rats were obtained using the stage scan macroraster with a lateral resolution of 5 lm. Data were subsequently subjected to orthogonal partial least squares discriminant analysis. The data clearly show that changes of certain lipids are induced by the specially processed cereal feed. Scores plots show a well-defined separation between the two groups. The corresponding loading plots reveal that the groups separate mainly due to changes of vitamin E, phosphocholine, and phosphosphingolipid fragments, and that for the c18:2 fatty acid. The observed changes in lipids might give insight into the working mechanisms of antisecretory factor in the body, and this has been successfully used to understand the working mechanism of specially processed cereal-induced antisecretory factor activation in intestine.
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| 13. |
- Evenbratt, Hanne, 1980, et al.
(författare)
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ToF-SIMS imaging of dual biomolecular monolayer gradients
- 2020
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 15:6
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Tidskriftsartikel (refereegranskat)abstract
- Precise characterization of a monolayer of two different biomolecules in a gradient pattern on a glass surface puts high demand on the method used. Some techniques can detect protein monolayers but not on a glass surface. Others can distinguish between different proteins but not identify a gradient pattern. Here, we used ToF-SIMS to validate the complete surface composition, checking all the necessary boxes. As these types of surfaces can dictate sensitive cell behaviors, the precision on a nanolevel is crucial, and to visualize and determine the molecular distribution become essential. The dual monolayer consisted of laminin 521 and one of three other biomolecules of different sizes, epidermal growth factor, growth differentiation factor 5, or bovine serum albumin, creating opposing gradient patterns. The resulting ToF-SIMS imaging and line scan data provided detailed information on the distribution of the adsorbed proteins.
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| 14. |
- Fletcher, John S.
(författare)
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Latest applications of 3D ToF-SIMS bio-imaging
- 2015
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a rapidly developing technique for the characterization of a wide range of materials. Recently, advances in instrumentation and sample preparation approaches have provided the ability to perform 3D molecular imaging experiments. Polyatomic ion beams, such as C-60, and gas cluster ion beams, often Arn (n = 500-4000), substantially reduce the subsurface damage accumulation associated with continued bombardment of organic samples with atomic beams. In this review, the capabilities of the technique are discussed and examples of the 3D imaging approach for the analysis of model membrane systems, plant single cell, and tissue samples are presented. Ongoing challenges for 3D ToF-SIMS imaging are also discussed along with recent developments that might offer improved 3D imaging prospects in the near future. (C) 2015 Author(s).
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| 15. |
- Fromell, Karin, et al.
(författare)
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Absence of conformational change in complement factor 3 and factor XII adsorbed to acrylate polymers is related to a high degree of polymer backbone flexibility
- 2017
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- In previous investigations, the authors have examined the adsorption of albumin, immunoglobulin, and fibrinogen to a series of acrylate polymers with different backbone and side-group flexibility. The authors showed that protein adsorption to acrylates with high flexibility, such as poly(lauryl methacrylate) (PLMA), tends to preserve native conformation. In the present study, the authors have continued this work by examining the conformational changes that occur during the binding of complement factor 3 (C3) and coagulation factor XII (FXII). Native C3 adsorbed readily to all solid surfaces tested, including a series of acrylate surfaces of varying backbone flexibility. However, a monoclonal antibody recognizing a "hidden" epitope of C3 (only exposed during C3 activation or denaturation) bound to the C3 on the rigid acrylate surfaces or on polystyrene (also rigid), but not to C3 on the flexible PLMA, indicating that varying degrees of conformational change had occurred with binding to different surfaces. Similarly, FXII was activated only on the rigid poly(butyl methacrylate) surface, as assessed by the formation of FXIIa-antithrombin (AT) complexes; in contrast, it remained in its native form on the flexible PLMA surface. The authors also found that water wettability hysteresis, defined as the difference between the advancing and receding contact angles, was highest for the PLMA surface, indicating that a dynamic change in the interface polymer structure may help protect the adsorbed protein from conformational changes and denaturation. (C) 2017 Author(s).
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| 16. |
- Grininger, Martin, et al.
(författare)
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Electrochemical switching of the flavoprotein dodecin at gold surfaces modified by flavin-DNA hybrid linkers
- 2008
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 3:3, s. 51-58
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Tidskriftsartikel (refereegranskat)abstract
- Dodecin from Halobacterium salinarum is a dodecameric, hollow-spherical protein, which unspecifically adopts flavin molecules. Reduction of flavin dodecin holocomplexes induces dissociation into apododecin and free flavin. Unspecific binding and dissociation upon reduction were used as key properties to construct an electrochemically switchable surface, which was able to bind and release dodecin apoprotein depending on the applied potential. A flavin modified electrode surface (electrode-DNA-flavin) was generated by direct adsorption of double stranded DNA (ds-DNA) equipped with flavin and disulfide modifications at opposite ends. While the disulfide functionality enabled anchoring the ds-DNA at the gold surface, the flavin exposed at the surface served as the redox-active dodecin docking site. The structures of protein and flavin-DNA hybrid ligands were optimized and characterized by x-ray structural analysis of the holocomplexes. By surface plasmon resonance (SPR) spectroscopy, the adsorption of flavin modified DNA as well as the binding and the electrochemically induced release of dodecin apoprotein could be shown. When the surface immobilization protocol was changed from direct immobilization of the modified ds-DNA to a protocol, which included the hybridization of flavin and thiol modified DNA at the surface, the resulting monolayer was electrochemically inactive. A possible explanation for the strong influence of the surface immobilization protocol on addressing dodecin by the applied potential is that electron transfer is rather mediated by defects in the monolayer than modified ds-DNA. (C) 2008 American Vacuum Society. [DOI: 10.1116/1.2965134]
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| 17. |
- Gunnarsson, Stefán Bragi, et al.
(författare)
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Dual topography of laminin corona on gallium arsenide nanowires
- 2020
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 15:5
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Tidskriftsartikel (refereegranskat)abstract
- Nanowires (NWs) are novel nanomaterials with applications in everything from medical implants to solar cells. With increasing number of applications, it is increasingly likely that organisms are exposed to these materials either intentionally or by accident. It is, therefore, important to study their interactions with biological systems and biomolecules. Upon exposure to biological fluids, nanostructure surfaces are quickly covered by a biomolecule corona. The composition of the corona determines the nanostructure's biological fate. Furthermore, upon adsorption, the protein structure can be affected. In order to study the corona morphology, we used two model proteins, laminin of the extracellular matrix and the immune system enzyme myeloperoxidase. We image the protein corona directly by cryo-TEM and enhance resolution by labeling the corona with activated gold nanoparticles. Three-dimensional imaging of the protein corona further increases the resolution and reveals irregularities in corona topography. By doing so, we identified bimodal distribution of spacing between gold nanoparticles and the NW surface for laminin corona at 58 and 85 nm distance from the NWs' surface. The dual topography of the corona is adding a new complexity of the protein corona surface and its interactions with the surrounding biology.
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| 18. |
- Hannestad, Jonas, 1981, et al.
(författare)
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Nanometer-scale molecular organization in lipid membranes studied by time-of-flight secondary ion mass spectrometry
- 2018
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 13:3
-
Tidskriftsartikel (refereegranskat)abstract
- The organization of lipid membranes plays an important role in a wide range of biological processes at different length scales. Herein, the authors present a procedure based on time-of-flight secondary ion mass spectrometry (ToF-SIMS) to characterize the nanometer-scale ordering of lipids in lipid membrane structures on surfaces. While ToF-SIMS is a powerful tool for label-free analysis of lipid-containing samples, its limited spatial resolution prevents in-depth knowledge of how lipid properties affect the molecular assembly of the membrane. The authors overcome this limitation by measuring the formation of lipid dimers, originating in the same nanometer-sized primary ion impact areas. The lipid dimers reflect the local lipid environment and thus allow us to characterize the membrane miscibility on the nanometer level. Using this technique, the authors show that the chemical properties of the constituting lipids are critical for the structure and organization of the membrane on both the nanometer and micrometer length scales. Our results show that even at lipid surface compositions favoring two-phase systems, lipids are still extracted from solid, gel phase, domains into the surrounding fluid supported lipid bilayer surrounding the gel phase domains. The technique offers a means to obtain detailed knowledge of the chemical composition and organization of lipid membranes with potential application in systems where labeling is not possible, such as cell-derived supported lipid bilayers.
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| 19. |
- Hedberg, Yolanda S., et al.
(författare)
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Metal release from stainless steel in biological environments : A review
- 2016
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Ingår i: Biointerphases. - : American Institute of Physics (AIP). - 1934-8630 .- 1559-4106. ; 11:1
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Forskningsöversikt (refereegranskat)abstract
- Due to its beneficial corrosion resistance, stainless steel is widely used in, e.g., biomedical applications, as surfaces in food contact, and for products intended to come into skin contact. Low levels of metals can be released from the stainless steel surface into solution, even for these highly corrosion resistant alloys. This needs to be considered in risk assessment and management. This review aims to compile the different metal release mechanisms that are relevant for stainless steel when used in different biological settings. These mechanisms include corrosion-induced metal release, dissolution of the surface oxide, friction-induced metal release, and their combinations. The influence of important physicochemical surface properties, different organic species and proteins in solution, and of biofilm formation on corrosion-induced metal release is discussed. Chemical and electrochemical dissolution mechanisms of the surface oxides of stainless steel are presented with a focus on protonation, complexation/ligand-induced dissolution, and reductive dissolution by applying a perspective on surface adsorption of complexing or reducing ligands and proteins. The influence of alloy composition, microstructure, route of manufacture, and surface finish on the metal release process is furthermore discussed as well as the chemical speciation of released metals. Typical metal release patterns are summarized.
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| 20. |
- Höök, Fredrik, 1966, et al.
(författare)
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Supported lipid bilayers, tethered lipid vesicles, and vesicle fusion investigated using gravimetric, plasmonic, and microscopy techniques
- 2007
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:2
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Tidskriftsartikel (refereegranskat)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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| 21. |
- Jonsson, Magnus, 1981, et al.
(författare)
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Nanoplasmonic biosensing with focus on short-range ordered nanoholes in thin metal films
- 2008
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:3, s. FD30-FD40
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Tidskriftsartikel (refereegranskat)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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| 22. |
- Klarström-Engström, Kristin, 1986-, et al.
(författare)
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Toll like receptor 2/1 mediated platelet adhesion and activation on bacterial mimetic surfaces is dependent on src/Syk-signaling and purinergic receptor P2X1 and P2Y12 activation
- 2014
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 9:4, s. 041003-
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Tidskriftsartikel (refereegranskat)abstract
- Platelets are considered to have important functions in inflammatory processes as key players in innate immunity. Toll like receptors (TLRs), expressed on platelets, recognize pathogen associated molecular patterns and trigger immune responses. Pathogens are able to adhere to human tissues and form biofilms which cause a continuous activation of the immune system. The authors aimed to investigate how immobilized Pam(3)CSK(4) (a synthetic TLR2/1 agonist) and IgG, respectively, resembling a bacterial focus, affects adhesion and activation of platelets including release of two cytokines, regulated on activation normal T-cell expressed and secreted (RANTES) and macrophage migration inhibitory factor (MIF). The authors also aim to clarify the signaling downstream of TLR2/1 and Fc gamma RII (IgG receptor) and the role of adenine nucleotides in this process. Biolayers of Pam(3)CSK(4) and IgG, respectively, were confirmed by null-ellipsometry and contact angle measurements. Platelets were preincubated with signaling inhibitors for scr and Syk and antagonists for P2X1 or P2Y1 [adenosine triphosphate (ATP), adenosine diphosphate (ADP) receptors] prior to addition to the surfaces. The authors show that platelets adhere and spread on both Pam(3)CSK(4)- and IgG-coated surfaces and that this process is antagonized by scr and Syc inhibitors as well as P2X1 and P2Y antagonists. This suggests that Pam(3)CSK(4) activated platelets utilize the same pathway as Fc gamma RII. Moreover, the authors show that ATP-ligation of P2X1 is of importance for further platelet activation after TLR2/1-activation, and that P2Y12 is the prominent ADP-receptor involved in adhesion and spreading. RANTES and MIF were secreted over time from platelets adhering to the coated surfaces, but no MIF was released upon stimulation with soluble Pam(3)CSK(4). These results clarify the importance of TLR2/1 and Fc gamma RII in platelet adhesion and activation, and strengthen the role of platelets as an active player in sensing bacterial infections.
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| 23. |
- Klenkar, Goran, et al.
(författare)
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Addressable adsorption of lipid vesicles and subsequent protein interaction studies
- 2008
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:2, s. 29-37
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a convenient chip platform for the addressable immobilization of protein-loaded vesicles on a microarray for parallelized, high-throughput analysis of lipid-protein systems. Self-sorting of the vesicles on the microarray was achieved through DNA bar coding of the vesicles and their hybridization to complementary strands, which are preimmobilized in defined array positions on the chip. Imaging surface plasmon resonance in ellipsometric mode was used to monitor vesicle immobilization, protein tethering, protein-protein interactions, and chip regeneration. The immobilization strategy proved highly specific and stable and presents a mild method for the anchoring of vesicles to predefined areas of a surface, while unspecific adsorption to both noncomplementary regions and background areas is nonexistent or, alternatively, undetectable. Furthermore, histidine-tagged receptors have been stably and functionally immobilized via bis-nitrilotriacetic acid chelators already present in the vesicle membranes. It was discovered though that online loading of proteins to immobilized vesicles leads to cross contamination of previously loaded vesicles and that it was necessary to load the vesicles offline in order to obtain pure protein populations on the vesicles. We have used this cross-binding effect to our benefit by coimmobilizing two receptor subunits in different ratios on the vesicle surface and successfully demonstrated ternary complex formation with their ligand. This approach is suitable for mechanistic studies of complex multicomponent analyses involving membrane-bound systems.
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| 24. |
- Lind, Tania K, et al.
(författare)
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Understanding the formation of supported lipid bilayers via vesicle fusion : a case that exemplifies the need for the complementary method approach
- 2016
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Ingår i: Biointerphases. - : American Institute of Physics (AIP). - 1934-8630 .- 1559-4106. ; 11
-
Forskningsöversikt (refereegranskat)abstract
- In this review, the authors discuss the challenges of studying supported lipid bilayers (SLBs) deposited by vesicle fusion in terms of (1) evaluating SLB formation and quality using quartz crystal microbalance with dissipation and (2) analyzing the composition and asymmetry of SLBs composed by lipid mixtures using complementary surface sensitive techniques. An overview of the literature is presented and the inconsistencies on this topic are discussed with the objective to expand beyond simple lipid compositions and set the basis for forming and analyzing SLBs of complex natural lipid extracts formed via the vesicle fusion method. The authors conclude by providing some guidelines to successfully form SLBs of complex lipid mixtures including natural extracts.
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| 25. |
- Malmberg, Per, 1974, et al.
(författare)
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Formation of hydroxyapatite on titanium implants in vivo precedes bone-formation during healing
- 2017
-
Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 12:4
-
Tidskriftsartikel (refereegranskat)abstract
- The bone material interface has been an area of intense study over many decades, where studies of the healing process ranging from simple mineral deposition in vitro to actual healing in vivo have given important clues to the importance of calcium minerals in the bone/implant interface. Here, the authors use a combination of in vitro cell culture methods and in vivo implantation to study how the role of the spontaneously formed hydroxyapatite layer on Ti-implants for the in vivo-healing into the bone tissue of rat tibia. Initial experiments were made in reduced systems by incubation of TiO2 in cell culture medium and analysis by time of flight secondary ion mass spectrometry (ToF-SIMS) and energy-dispersive x-ray spectroscopy followed by subsequent exposure of human embryological stem cells analyzed by von Kossa staining and environmental scanning electron microsopy. In vivo studies of the bone-material interface was analyzed by ToF-SIMS depth profiling using both C-60(+) ions as well as a gas cluster ion source beam, Ar-1500(+) as sputter source. The low ion yield of the Ar-1500(+) for inorganics allowed the inorganic/organic interface of the implant to be studied avoiding the erosion of the inorganic materials caused by the conventional C-60(+) beam. (C) 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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| 26. |
- Marie, Rodolphe, et al.
(författare)
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A generic surface modification strategy for sensing applications based on Au/SiO2 nanostructures
- 2007
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 2:1, s. 49-55
-
Tidskriftsartikel (refereegranskat)abstract
- A generic protocol for the creation of material-mediated self-assembled patterns of streptavidin, defined solely by patterns of gold and SiO2, is presented. Protein-adsorption resistance of selected regions was obtained by material-specific adsorption of thiol-modified poly(ethylene)glycol (thiol-PEG) on gold followed by adsorption of poly-L-lysine (PLL) modified PEG (PLL-g-PEG) on SiO2. Selective streptavidin binding to either gold or SiO2 (or both) was ensured by introducing biotin-modified thiolated (thiol-biotin) and/or biotin-modified PLL-g-PEG (PLL-g-PEGbiotin) compounds. The introduction of biotin did not influence the protein-adsorption resistance. On the macroscopic scale, the protein-adsorption-resistant properties and the streptavidin-binding capacity were optimized using quartz crystal microbalance with dissipation monitoring. The reproduction of micrometer-scale gold patterns on SiO2 into patterns of streptavidin was verified using fluorescence microscopy, while the compatibility of the material-specific surface-modification strategy with nanoscale features was accomplished by modifying a localized surface plasmon resonance (LSPR) active template, defined by randomly distributed nanoapertures in a thin gold film on SiO2. The demonstrated compatibility of the latter substrate with LSPR-based label-free sensing of biorecognition reactions, combined with the fact that all compounds utilized are commercially available, makes the surface-modification protocol attractive as a generic surface modification solution for a broad range of biorecognition-based assays. (C) 2007 American Vacuum Society.
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| 27. |
- Michelle Grandin, H., et al.
(författare)
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Bioinspired, nanoscale approaches in contemporary bioanalytics (Review)
- 2018
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 13:4
-
Tidskriftsartikel (refereegranskat)abstract
- The genesis for this topical review stems from the interdisciplinary Biointerfaces International conference 2016 (BI 2016) in Zurich, Switzerland, wherein the need for advances in analytical tools was both expressed and addressed. Pushing the limits of detection for characterizing individual components, such as single proteins, single drug-delivery vehicles, or probing single living cells in a more natural environment, will contribute to the understanding of the complex biomolecular systems central to a number of applications including medical diagnostics, tissue engineering, and drug screening and delivery. Accordingly, the authors begin with an overview of single nanoparticle analytics highlighting two emerging techniques and how they compare with existing techniques. The first is based on single particle tracking of nanoparticles tethered to a mobile supported lipid bilayer, enabling the simultaneous characterization of both size and composition of individual nanoparticles. The second technique is based on probing variations in the ionic conduction across nanoscale apertures for detection of not only nanoparticles but also membrane-tethered proteins, thereby allowing a multiparameter characterization of individual nanoscopic objects, addressing their size, shape, charge, and dipole moment. Subsequently, the authors lead into an example of an area of application that stands to benefit from such advances in bioanalytics, namely, the development of biomimetic lipid- and polymer-based assemblies as stimuli-responsive artificial organelles and nanocarriers designed to optimize delivery of next generation high-molecular-weight biological drugs. This in turn motivates the need for additional advanced techniques for investigating the cellular response to drug delivery, and so the review returns again to bioanalytics, in this case single-cell analysis, while highlighting a technique capable of probing and manipulating the content of individual living cells via fluidic force microscopy. In presenting a concerted movement in the field of bioinspired bioanalytics, positioned in the context of drug delivery, while also noting the critical role of surface modifications, it is the authors’ aim to evaluate progress in the field of single component bioanalytics and to emphasize the impact of initiating and maintaining a fruitful dialogue among scientists, together with clinicians and industry, to guide future directions in this area and to steer innovation to successful translation.
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| 28. |
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| 29. |
- Munem, Marwa, et al.
(författare)
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Chemical imaging of aggressive basal cell carcinoma using time-of-flight secondary ion mass spectrometry.
- 2018
-
Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 13:3
-
Tidskriftsartikel (refereegranskat)abstract
- A set of basal cell carcinoma samples, removed by Mohs micrographic surgery and pathologically identified as having an aggressive subtype, have been analyzed using time-of-flight secondary ion mass spectrometry (SIMS). The SIMS analysis employed a gas cluster ion beam (GCIB) to increase the sensitivity of the technique for the detection of intact lipid species. The GCIB also allowed these intact molecular signals to be maintained while surface contamination and delocalized chemicals were removed from the upper tissue surface. Distinct mass spectral signals were detected from different regions of the tissue (epidermis, dermis, hair follicles, sebaceous glands, scar tissue, and cancerous tissue) allowing mass spectral pathology to be performed. The cancerous regions of the tissue showed a particular increase in sphingomyelin signals that were detected in both positive and negative ion mode along with increased specific phosphatidylserine and phosphatidylinositol signals observed in negative ion mode. Samples containing mixed more and less aggressive tumor regions showed increased phosphatidylcholine lipid content in the less aggressive areas similar to a punch biopsy sample of a nonaggressive nodular lesion.
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| 30. |
- Nakano, Shusuke, et al.
(författare)
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Evaluation of biomolecular distributions in rat brain tissues by means of ToF-SIMS using a continuous beam of Ar clusters
- 2016
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 11:2
-
Tidskriftsartikel (refereegranskat)abstract
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) provides detailed chemical structure information and high spatial resolutionimages. Therefore, ToF-SIMS is useful for studying biological phenomena such as ischemia. In this study, in order to evaluate cerebral microinfarction, the distribution of biomolecules generated by ischemia was measured with ToF-SIMS. ToF-SIMS data sets were analyzed by means of multivariate analysis for interpreting complex samples containing unknown information and to obtain biomolecular mapping indicated by fragment ions from the target biomolecules. Using conventional ToF-SIMS (primary ion source: Bi cluster ion), it is difficult to detect secondary ions beyond approximately 1000 u. Moreover, the intensity of secondary ions related to biomolecules is not always high enough for imaging because of low concentration even if the masses are lower than 1000 u. However, for the observation of biomolecular distributions in tissues, it is important to detect low amounts of biological molecules from a particular area of tissue. Rat braintissue samples were measured with ToF-SIMS (J105, Ionoptika, Ltd., Chandlers Ford, UK), using a continuous beam of Ar clusters as a primary ion source. ToF-SIMS with Ar clusters efficiently detects secondary ions related to biomolecules and larger molecules. Molecules detected by ToF-SIMS were examined by analyzing ToF-SIMS data using multivariate analysis. Microspheres (45μm diameter) were injected into the rat unilateral internal carotid artery (MS rat) to cause cerebral microinfarction. The rat brain was sliced and then measured with ToF-SIMS. The brain samples of a normal rat and the MS rat were examined to find specific secondary ions related to important biomolecules, and then the difference between them was investigated. Finally, specific secondary ions were found around vessels incorporating microspheres in the MS rat. The results suggest that important biomolecules related to cerebral microinfarction can be detected by ToF-SIMS.
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| 31. |
- Nie, Heng-Yong, et al.
(författare)
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Detection of gold cysteine thiolate complexes on gold nanoparticles with time-of-flight secondary ion mass spectrometry
- 2021
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Ingår i: Biointerphases. - : AMER INST PHYSICS. - 1934-8630 .- 1559-4106. ; 16:2
-
Tidskriftsartikel (refereegranskat)abstract
- Gold (Au) nanoparticles (NPs) are widely used in nanomedical applications as a carrier for molecules designed for different functionalities. Previous findings suggested that biological molecules, including amino acids, could contribute to the dissolution of Au NPs in physiological environments and that this phenomenon was size-dependent. We, therefore, investigated the interactions of L-cysteine with 5-nm Au NPs by means of time-of-flight secondary ion mass spectrometry (ToF-SIMS). This was achieved by loading Au NPs on a clean aluminum (Al) foil and immersing it in an aqueous solution containing L-cysteine. Upon rinsing off the excessive cysteine molecules, ToF-SIMS confirmed the formation of gold cysteine thiolate via the detection of not only the Au-S bond but also the hydrogenated gold cysteine thiolate molecular ion. The presence of NaCl or a 2-(N-morpholino)ethanesulfonic acid buffer disabled the detection of Au NPs on the Al foil. The detection of larger (50-nm) Au NPs was possible but resulted in weaker cysteine and gold signals, and no detected gold cysteine thiolate signals. Nano-gold specific adsorption of L-cysteine was also demonstrated by cyclic voltammetry using paraffine-impregnated graphite electrodes with deposited Au NPs. We demonstrate that the superior chemical selectivity and surface sensitivity of ToF-SIMS, via detection of elemental and molecular species, provide a unique ability to identify the adsorption of cysteine and formation of gold-cysteine bonds on Au NPs.
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| 32. |
- Nilsson, Kelly Dimovska, et al.
(författare)
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TOF-SIMS imaging reveals tumor heterogeneity and inflammatory response markers in the microenvironment of basal cell carcinoma
- 2020
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 15:4
-
Tidskriftsartikel (refereegranskat)abstract
- Basal cell carcinoma (BCC) is the most common skin malignancy. In fact, it is as common as the sum of all other skin malignancies combined and the incidence is rising. In this focused and histology-guided study, tissue from a patient diagnosed with aggressive BCC was analyzed by imaging mass spectrometry in order to probe the chemistry of the complex tumor environment. Time-of-flight secondary ion mass spectrometry using a (CO2)(6 k)(+)gas cluster ion beam allowed a wide range of lipid species to be detected. Their distributions were then imaged in the tissue that contained small tumor islands that were histologically classified as more/less aggressive. Maximum autocorrelation factor (MAF) analysis highlighted chemical differences between the tumors and the surrounding stroma. A closer inspection of the distribution of individual ions, selected based on the MAF loadings, showed heterogeneity in signal between different microtumors, suggesting the potential of chemically grading the aggressiveness of each individual tumor island. Sphingomyelin lipids were found to be located in stroma containing inflammatory cells.
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| 33. |
- Nygren, Håkan, 1952, et al.
(författare)
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Mg-corrosion, hydroxyapatite, and bone healing
- 2017
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 12:2
-
Tidskriftsartikel (refereegranskat)abstract
- The different capacities of magnesium in the metallic form (Mg-metal) and magnesium oxide (MgO) to stimulate bone healing are possible clues in the search for products that may promote bone healing. Since both Mg-metal and MgO can be assumed to release comparable amounts of Mg2+ ions during their reactions in the tissue where they have been implanted, it is of some importance to follow this process and analyze the resulting mineral formation in the tissue at the implantation site. Implants of MgO were inserted into rat tibia, and the bone healing was compared with sham-operated controls. Samples were taken after 1 week of healing and analyzed by histology, environmental scanning electron microscopy equipped with an energy dispersive x-ray spectroscopy analyzer, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Callus bone was seen in sham-operated controls after 1 week of healing. Implantation of MgO impaired the callus bone formation by replacing bone with apparently mineralized areas, lacking osteocytes and were denoted, amorphous bodies. Elemental analysis showed increased levels of Ca (7.1%), P (3.7%), and Mg (0.2%) in the bone marrow of MgO-treated animals versus sham-operated controls Ca (2.4%), P (2.3%), and Mg (0.1%). The Ca content of the cortical bone was also significantly increased (Ca, 29% increase) in MgO-treated animals compared to sham-operated controls. The Ca content of the cortical bone of sham-operated animals was also significantly (p < 0.05) higher than the corresponding value of untreated animals, which means that the surgical trauma induces an altered composition of the bone mineral. The Ca/P ratio was 1.26-1.68, which is compatible with that of mineralized bone with different contents of organic materials. Analysis of bone sections using ToF-SIMS showed the presence of hydroxyapatite (HA) and MgCO3 in the bone marrow and in cortical bone. Analysis using x-ray photoelectron spectroscopy of Mg, MgO, and MgCO3 after incubation with cell culture medium (DMEM), in vitro, showed binding of CaPO4 at the Mg and MgO samples. The Ca/P ratio was 0.8, indicating a higher P content than that expected for HA. Exposure of human embryonic stem cells to Mg species preincubated in DMEM resulted in HA production by the cells. Thus, two sources of CaPO4 in the bone marrow of MgO-treated bone were defined, catalytic formation on Mg-species and synthesis from activated stem-cells. The presented data suggest that bone healing near Mg implants is congruent with the fracture healing of bone, boosted by high HA levels in the bone marrow. In this context, the different capacities of Mg-metal and MgO to catalyse the formation of HA can be important clues to their different bone promoting effects. (C) 2017 Author(s).
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| 34. |
- Nylander, Tommy, et al.
(författare)
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Neutron Reflectometry to Investigate the Delivery of Lipids and DNA to Interfaces
- 2008
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:2, s. FB64-FB82
-
Forskningsöversikt (refereegranskat)abstract
- The application of scattering methods in the study of biological and biomedical problems is a field of research that is currently experiencing fast growth. In particular, neutron reflectometry (NR) is a technique that is becoming progressively more widespread, as indicated by the current commissioning of several new reflectometers worldwide. NR is valuable for the characterization of biomolecules at interfaces due to its capability to provide quantitative structural and compositional information on relevant molecular length scales. Recent years have seen an increasing number of applications of NR to problems related to drug and gene delivery. We start our review by summarizing the experimental methodology of the technique with reference to the description of biological liquid interfaces. Various methods for the interpretation of data are then discussed, including a new approach based on the lattice mean-field theory to help characterize stimulus-responsive surfaces relevant to drug delivery function. Recent progress in the subject area is reviewed in terms of NR studies relevant to the delivery of lipids and DNA to surfaces. Lastly, we discuss two case studies to exemplify practical features of NR that are exploited in combination with complementary techniques. The first case concerns the interactions of lipid-based cubic phase nanoparticles with model membranes (a drug delivery application), and the second case concerns DNA compaction at surfaces and in the bulk solution (a gene delivery application).
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| 35. |
- Paul, Alexandra, 1988, et al.
(författare)
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Effect of ambient temperature on respiratory tract cells exposed to SARS-CoV-2 viral mimicking nanospheres - An experimental study
- 2021
-
Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 16:1
-
Tidskriftsartikel (refereegranskat)abstract
- The novel coronavirus caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has reached more than 160 countries and has been declared a pandemic. SARS-CoV-2 infects host cells by binding to the angiotensin-converting enzyme 2 (ACE-2) surface receptor via the spike (S) receptor-binding protein (RBD) on the virus envelope. Global data on a similar infectious disease spread by SARS-CoV-1 in 2002 indicated improved stability of the virus at lower temperatures facilitating its high transmission in the community during colder months (December–February). Seasonal viral transmissions are strongly modulated by temperatures, which can impact viral trafficking into host cells; however, an experimental study of temperature-dependent activity of SARS-CoV-2 is still lacking. We mimicked SARS-CoV-2 with polymer beads coated with the SARS-CoV-2 S protein to study the effect of seasonal temperatures on the binding of virus-mimicking nanospheres to lung epithelia. The presence of the S protein RBD on nanosphere surfaces led to binding by Calu-3 airway epithelial cells via the ACE-2 receptor. Calu-3 and control fibroblast cells with S-RBD-coated nanospheres were incubated at 33 and 37 °C to mimic temperature fluctuations in the host respiratory tract, and we found no temperature dependence in contrast to nonspecific binding of bovine serum ablumin-coated nanospheres. Moreover, the ambient temperature changes from 4 to 40 °C had no effect on S-RBD-ACE-2 ligand-receptor binding and minimal effect on the S-RBD protein structure (up to 40 °C), though protein denaturing occurred at 51 °C. Our results suggest that ambient temperatures from 4 to 40 °C have little effect on the SARS-CoV-2-ACE-2 interaction in agreement with the infection data currently reported.
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| 36. |
- Rosenhahn, Axel, et al.
(författare)
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Advanced nanostructures for the control of biofouling : The FP6 EU Integrated Project AMBIO
- 2008
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Ingår i: BIOINTERPHASES. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:1, s. IR1-IR5
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Tidskriftsartikel (refereegranskat)abstract
- The colonization of man made structures by marine or freshwater organisms or "biofouling" is a problem for maritime and aquaculture industries. Increasing restrictions on the use of toxic coatings that prevent biofouling, create a gap in the market that requires new approaches to produce novel nonbiocidal alternatives. This review details the systematic strategy adopted by an FP6 EU Integrated Project "AMBIO" to develop fundamental understanding of key surface properties that influence settlement and adhesion of fouling organisms. By this approach the project contributes to the understanding of fundamental phenomena involved in biofouling, and to the development of environmentally benign solutions by coating manufacturers within the consortium. (c) 2008 American Vacuum Society.
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| 37. |
- Skallberg, Andreas, et al.
(författare)
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Imaging XPS and photoemission electron microscopy; surface chemical mapping and blood cell visualization
- 2017
-
Ingår i: Biointerphases. - : AMER INST PHYSICS. - 1934-8630 .- 1559-4106. ; 12:2
-
Tidskriftsartikel (refereegranskat)abstract
- Combined photoemission electron microscopy (PEEM) and imaging x-ray photoelectron spectroscopy (XPS), i.e., electron spectroscopy for chemical analysis in the nanoregion, has been used for surface characterization of bio-relevant and biological samples. In the first example, the authors prepared a gold patterned silicon substrate, stepwise surface modified by self-assembled monolayers followed by quantum dot (QDot) specific linking and investigated by means of work function mapping and elemental imaging in the submicrometer range. Spatially resolved core level images of C1s, V2p, and Y3d are obtained, which verify the selective thiol adsorption on the gold squares and specific binding of europium doped yttrium vanadate QDots on the self-assembled monolayer. The second example is platelet adhesion to Immunoglobulin G modified silicon surfaces, investigated by means of laterally resolved PEEM. Images of platelets clearly show activated cells with a morphology change including an enlarged surface area and elongated pseudopodia, with a lateral resolution of 140 nm. In the last example, neutrophils were allowed to attach to plain silicon surfaces and investigated by means of PEEM and imaging XPS. Here, the cells show a round shaped morphology, as expected. Threshold imaging with work function contrast is used to localize the area of interest, followed by elemental specific mapping on cells in the submicrometer region. Chemical shifts of C1s in photoemission are used to distinguish vital parts of the cell structure. The strong C1s (C-C) signal is achieved from the region of the cell membrane, i.e., high density of phospholipids, while C1s (C-N) and C1s (C-O) signals are obtained from the core of the cell, in good agreement with the presence of cytoplasm and deoxyribonucleic acid containing cell nucleus. The combination of PEEM and imaging XPS is shown here as a tool to deliver new insight into biological samples, i.e., a rapid sample overview is obtained based on low energy secondary electrons with work function contrast, followed by detailed studies in the narrow mode for elemental compositions based on photoemission. This study illustrates the strength of combined PEEM and XPS in the imaging mode on cell studies. (C) 2017 American Vacuum Society.
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| 38. |
- Sun, Kangdi, et al.
(författare)
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Insight into the assembly of lipid-hyaluronan complexes in osteoarthritic conditions
- 2023
-
Ingår i: Biointerphases. - : American Institute of Physics Inc.. - 1934-8630 .- 1559-4106. ; 18:2
-
Tidskriftsartikel (refereegranskat)abstract
- Interactions between molecules in the synovial fluid and the cartilage surface may play a vital role in the formation of adsorbed films that contribute to the low friction of cartilage boundary lubrication. Osteoarthritis (OA) is the most common degenerative joint disease. Previous studies have shown that in OA-diseased joints, hyaluronan (HA) not only breaks down resulting in a much lower molecular weight (MW), but also its concentration is reduced ten times. Here, we have investigated the structural changes of lipid-HA complexes as a function of HA concentration and MW to simulate the physiologically relevant conditions that exist in healthy and diseased joints. Small angle neutron scattering and dynamic light scattering were used to determine the structure of HA-lipid vesicles in bulk solution, while a combination of atomic force microscopy and quartz crystal microbalance was applied to study their assembly on a gold surface. We infer a significant influence of both MW and HA concentrations on the structure of HA-lipid complexes in bulk and assembled on a gold surface. Our results suggest that low MW HA cannot form an amorphous layer on the gold surface, which is expected to negatively impact the mechanical integrity and longevity of the boundary layer and could contribute to the increased wear of the cartilage that has been reported in joints diseased with OA. © 2023 Author(s).
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| 39. |
- Tymchenko, Nina, 1977, et al.
(författare)
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Reversible Changes in Cell Morphology due to Cytoskeletal Rearrangements Measured in Real-Time by QCM-D
- 2012
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 7:1-4, s. 43-9
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical properties and responses of cells to external stimuli (including drugs) are closely connected to important phenomena such as cell spreading, motility, activity, and potentially even differentiation. Here, reversible changes in the viscoelastic properties of surface-attached fibroblasts were induced by the cytoskeleton-perturbing agent cytochalasin D, and studied in realtime by the quartz crystal microbalance with dissipation (QCM-D) technique. QCM-D is a surface sensitive technique that measures changes in (dynamically coupled) mass and viscoelastic properties close to the sensor surface, within a distance into the cell that is usually only a fraction of its size. In this work, QCM-D was combined with light microscopy to study in situ cell attachment and spreading. Overtone-dependent changes of the QCM-D responses (frequency and dissipation shifts) were first recorded, as fibroblast cells attached to protein-coated sensors in a window equipped flow module. Then, as the cell layer had stabilised, morphological changes were induced in the cells by injecting cytochalasin D. This caused changes in the QCM-D signals that were reversible in the sense that they disappeared upon removal of cytochalasin D. These results are compared to other cell QCM-D studies. Our results stress the combination of QCM-D and light microscopy to help interpret QCM-D results obtained in cell assays and thus suggests a direction to develop the QCM-D technique as an even more useful tool for real-time cell studies.
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| 40. |
- Valiokas, Ramunas, 1970-, et al.
(författare)
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Structural and kinetic properties of laterally stabilized, oligo(ethylene glycol)-containing alkylthiolates on gold : A modular approach
- 2006
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Ingår i: Biointerphases. - : American Institute of Physics (AIP). - 1934-8630 .- 1559-4106. ; 1:1, s. 22-34
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Tidskriftsartikel (refereegranskat)abstract
- The formation of highly ordered self-assembled monolayers (SAMs) on goldfrom an unusually long and linear compound HS(CH2)15CONH(CH2CH2O)6CH2CONH(CH2)15CH3 is investigated by contact angle goniometry, ex situ null ellipsometry, cyclic voltammetry and infrared reflection-absorption spectroscopy. The molecules are found to assemble in an upright position as a complete monolayer within 60 min. The overall structure of the SAM reaches equilibrium within 24 h as evidenced by infrared spectroscopy, although a slight improvement in water contact angles is observed over a period of a few weeks. The resulting SAM is 60 Å thick and it displays an advancing water contact angle of 112° and excellent electrochemicalblocking characteristics with typical current densities about 20 times lower as compared to those observed for HS(CH2)15CH3 SAMs. The dominating crystalline phases of the supporting HS(CH2)15 and terminal (CH2)15CH3 alkyl portions, as well as the sealed oligo(ethylene glycol) (OEG) “core,” appear as unusually sharp features in the infrared spectra at room temperature. For example, the splitting seen for the CH3 stretching and CH2 scissoring peaks is normally only observed for conformationally trapped alkylthiolate SAMs at low temperatures and for highly crystalline polymethylenes. Temperature-programmed infrared spectroscopy in ultrahigh vacuum reveals a significantly improved thermal stability of the SAM under investigation, as compared to two analogous OEG derivatives without the extended alkyl chain. Our study points out the advantages of adopting a “modular approach” in designing novel SAM-forming compounds with precisely positioned in plane stabilizing groups. We demonstrate also the potential of using the above set of compounds in the fabrication of “hydrogel-like” arrays with controlled wetting properties for application in the ever-growing fields of protein and cell analysis, as well as for bioanalytical applications.
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| 41. |
- Werner, Marco, et al.
(författare)
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Nanomaterial interactions with biomembranes: Bridging the gap between soft matter models and biological context
- 2018
-
Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 13:2
-
Tidskriftsartikel (refereegranskat)abstract
- Synthetic polymers, nanoparticles, and carbon-based materials have great potential in applications including drug delivery, gene transfection, in vitro and in vivo imaging, and the alteration of biological function. Nature and humans use different design strategies to create nanomaterials: biological objects have emerged from billions of years of evolution and from adaptation to their environment resulting in high levels of structural complexity; in contrast, synthetic nanomaterials result from minimalistic but controlled design options limited by the authors' current understanding of the biological world. This conceptual mismatch makes it challenging to create synthetic nanomaterials that possess desired functions in biological media. In many biologically relevant applications, nanomaterials must enter the cell interior to perform their functions. An essential transport barrier is the cell-protecting plasma membrane and hence the understanding of its interaction with nanomaterials is a fundamental task in biotechnology. The authors present open questions in the field of nanomaterial interactions with biological membranes, including: how physical mechanisms and molecular forces acting at the nanoscale restrict or inspire design options; which levels of complexity to include next in computational and experimental models to describe how nanomaterials cross barriers via passive or active processes; and how the biological media and protein corona interfere with nanomaterial functionality. In this Perspective, the authors address these questions with the aim of offering guidelines for the development of next-generation nanomaterials that function in biological media.
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| 42. |
- Wigenius, Jens, et al.
(författare)
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Protein biochips patterned by microcontact printing or by adsorption-soft lithography in two modes
- 2008
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Ingår i: Biointerphases. - : American Vacuum Society. - 1934-8630 .- 1559-4106. ; 3:3, s. 75-82
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Tidskriftsartikel (refereegranskat)abstract
- Patterning of proteins is critical to protein biochips. Printing of layers of proteins is well established, as is adsorption of proteins to surfaces properly modified with surface chemical functionalities. The authors show that simple methods based on soft lithography stamps can be used to prepare functional antibody chips through both these routes. Both methods incorporate transfer of the stamp material poly(dimethylsiloxane) (PDMS) to the biochip, whether intended or not intended. The results indicate that microcontact printing of proteins always includes PDMS transfer, thereby creating a possibility of unspecific adsorption to a hydrophobic domain. © 2008 American Vacuum Society.
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| 43. |
- Winkler, Thomas, Ph.D., et al.
(författare)
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Molecular processes in an electrochemical clozapine sensor
- 2017
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Ingår i: Biointerphases. - : American Institute of Physics (AIP). - 1934-8630 .- 1559-4106. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- Selectivity presents a crucial challenge in direct electrochemical sensing. One example is schizophrenia treatment monitoring of the redox-active antipsychotic clozapine. To accurately assess efficacy, differentiation from its metabolite norclozapine-similar in structure and redox potentialis critical. Here, the authors leverage biomaterials integration to study, and effect changes in, diffusion and electron transfer kinetics of these compounds. Specifically, the authors employ a catechol-modified chitosan film, which the authors have previously presented as the first electrochemical detection mechanism capable of quantifying clozapine directly in clinical serum. A key finding in our present work is differing dynamics between clozapine and norclozapine once the authors interface the electrodes with chitosan-based biomaterial films. These additional dimensions of redox information can thus enable selective sensing of largely analogous small molecules.
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| 44. |
- Wogelred, Louise, et al.
(författare)
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Toward multiplexed quantification of biomolecules on surfaces using time-of-flight secondary ion mass spectrometry
- 2018
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 13:3
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Tidskriftsartikel (refereegranskat)abstract
- Accurate detection and quantification of individual molecules is important for the development of improved diagnostic methods as well as biochemical characterization of disease progression and treatments. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a surface analysis technique capable of imaging the distribution of specific molecules on surfaces with a high spatial resolution (<1 mu m) and high sensitivity. ToF-SIMS is particularly suitable for detection of molecules up to similar to 2 kDa, including lipids, whereas larger molecules, such as peptides and proteins, are fragmented during analysis, which makes them difficult to identify. In this study, an approach for extending the molecular detection capability of ToF-SIMS is presented, based on the specific binding of functionalized liposomes to molecular targets on the sample surface and subsequent detection of the liposomes by ToF-SIMS. Furthermore, by using different recognition elements conjugated to liposomes with different lipid compositions, simultaneous detection of different targets was accomplished. This multiplexing capability was investigated for two types of recognition elements (antibodies and cholera toxin) and for target molecules immobilized on surfaces using two frequently applied surface functionalization strategies: a supported lipid bilayer aimed to mimic a cell membrane and a polyethylene glycol modified surface, commonly employed in bioanalytical sensor applications. The efficacy of the conjugation protocols and the specificity of the recognition mechanism were confirmed using quartz crystal microbalance with dissipation monitoring, while fluorescence microscopy was used to validate the ToF-SIMS data and the reliability of the freeze-drying step required for ToF-SIMS analysis. The results demonstrated specific binding of the two types of liposomes to each target and showed a concentration-dependent binding to the targets on the different model surfaces. In particular, the possibility to use the contrasts in the mass spectra of SIMS to identify the concentration dependent coverage of different liposomes opens up new opportunities for multiplexed detection and quantification of molecules at biotechnology relevant interfaces.
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| 45. |
- Zhou, Ye, et al.
(författare)
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Quantitative interpretation of gold nanoparticle-based bioassays designed for detection of immunocomplex formation
- 2007
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Ingår i: BIOINTERPHASES. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- The authors present in this paper how the extended Mie theory can be used to translate not only end-point data but also temporal variations of extinction peak-position changes, Delta lambda(peak)(t), into absolute mass uptake, Gamma(t), upon biomacromolecule binding to localized surface plasmon resonance (SPR) active nanoparticles (NPs). The theoretical analysis is applied on a novel sensor template composed of a three-layer surface architecture based on (i) a self-assembled monolayer of HS(CH2)(15)COOH, (ii) a 1:1 mixture of biotinylated and pure poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), and (iii) NeutrAvidin. Assisted by independent estimations of the thickness of the three-layer architecture using quartz crystal microbalance with dissipation (QCM-D) monitoring, excellent agreement with parallel mass-uptake estimations using planar SPR is obtained. Furthermore, unspecific binding of serum to PLL-g-PEG was shown to be below the detection limit, making the surface architecture ideally suited for label-free detection of immunoreactions. To ensure that the immunocomplex formation occurred within the limited sensing depth (similar to 10 nm) of the NPs, a compact model system composed of a biotinylated human recombinant single-chain antibody fragment (empty set similar to 2 nm) directed against cholera toxin was selected. By tracking changes in the centroid (center of mass) of the extinction peak, rather than the actual peak position, signal-to-noise levels and long-term stability upon cholera toxin detection are demonstrated to be competitive with results obtained using conventional SPR and state-of-the-art QCM-D data. (C) 2007 American Vacuum Society.
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| 46. |
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