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  • 1
    Online Resource
    Online Resource
    ARGET–ATRP Synthesis and Characterization of PNIPAAm Brushes for Quantitative Cell Detachment Studies
    American Vacuum Society ; 2012
    In:  Biointerphases Vol. 7, No. 1 ( 2012-12-01)
    Details
    In: Biointerphases, American Vacuum Society, Vol. 7, No. 1 ( 2012-12-01)
    Abstract: Stimuli responsive (or “smart”) polymer brushes represent a non-toxic approach for achieving release of biofouling layers. Thermo-responsive poly(N-isopropylacrylamide) (PNIPAAm) polymer brushes have been shown to modulate bacterial adhesion and release through transition between temperatures above and below the lower critical solution temperature (LCST ~32 °C) of PNIPAAm in water. In this article, we describe a convenient method to synthesize grafted PNIPAAm brushes over large areas for biological studies using a relatively simple and rapid method which allows atom transfer radical polymerization (ATRP) in presence of air using the activator regenerated electron transfer (ARGET) mechanism. PNIPAAm brushes were characterized using X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectroscopy, Fourier transform infrared spectroscopy, ellipsometry, and contact angle measurements. Our studies demonstrate that uniform, high purity PNIPAAm brushes with controlled and high molecular weight can be easily produced over large areas using ARGET–ATRP. We also report the use of a spinning disk apparatus to systematically and quantitatively study the detachment profiles of bacteria from PNIPAAm surfaces under a range (0–400 dyne/cm2) of shear stresses.
    Type of Medium: Online Resource
    ISSN: 1934-8630 , 1559-4106
    URL: Article
    DOI: 10.1007/s13758-012-0032-z
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2012
    detail.hit.zdb_id: 2234510-3
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  • 2
    Online Resource
    Online Resource
    Micrometer and Nanometer Scale Photopatterning of Proteins on Glass Surfaces by Photo-degradation of Films Formed from Oligo(Ethylene Glycol) Terminated Silanes
    American Vacuum Society ; 2012
    In:  Biointerphases Vol. 7, No. 1 ( 2012-12-01)
    Details
    In: Biointerphases, American Vacuum Society, Vol. 7, No. 1 ( 2012-12-01)
    Abstract: Exposure of films formed by the adsorption of oligo(ethylene glycol) (OEG) functionalized trichlorosilanes on glass to UV light from a frequency-doubled argon ion laser (244 nm) causes photodegradation of the OEG chain. Although the rate of degradation is substantially slower than for monolayers of OEG terminated thiolates on gold, it is nevertheless possible to form micrometer-scale patterns by elective adsorption of streptavidin to exposed regions. A low density of aldehyde functional groups is produced, and this enables derivatization with nitrilotriacetic acid via an amine linker. Complexation with nickel enables the site-specific immobilization of histidine-tagged yellow and green fluorescent proteins. Nanometer-scale patterns may be fabricated using a Lloyd’s mirror interferometer, with a sample and mirror set at right angles to each other. At low exposures, partial degradation of the OEG chains does not remove the protein-resistance of the surface, even though friction force microscopy reveals the formation of patterns. At an exposure of ca. 18 J cm−2, the modified regions became adhesive to proteins in a narrow region ca. 30 nm (λ/8) wide. As the exposure is increased further the lines quickly broaden to ca. 90 nm. Adjustment of the angle between the sample and mirror enables the fabrication of lines of His-tagged green fluorescent protein at a period of 340 nm that could be resolved using a confocal microscope.
    Type of Medium: Online Resource
    ISSN: 1934-8630 , 1559-4106
    URL: Article
    DOI: 10.1007/s13758-012-0054-6
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2012
    detail.hit.zdb_id: 2234510-3
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  • 3
    Online Resource
    Online Resource
    Reusable nanoengineered surfaces for bacterial recruitment and decontamination
    American Vacuum Society ; 2016
    In:  Biointerphases Vol. 11, No. 1 ( 2016-03-01)
    Details
    In: Biointerphases, American Vacuum Society, Vol. 11, No. 1 ( 2016-03-01)
    Abstract: Biofouling, or accumulation of unwanted biofilms, on surfaces is a major concern for public health and human industry. Materials either avoiding contamination (fouling resistant) and/or directly killing attached microbes (biocidal) have thus far failed to achieve the goal of eliminating biofouling; fouling resistant surfaces eventually foul and biocidal surfaces accumulate debris that eventually decrease their efficacy. Combined biocidal and fouling release materials offer the potential for both killing and removing debris and are promising candidates for reducing biofouling on manufactured materials. Interference lithography was used to create nanopatterns of initiators, which were then used to initiate atom transfer radical polymerization of the temperature-responsive polymer, poly(N-isopropylacrylamide) (PNIPAAm) as a fouling release component. Biocidal activity was conferred by subsequent layer-by-layer deposition of cationic and anionic poly(phenylene ethynylenes) into the valleys between the PNIPAAm. For both Gram positive and Gram negative model bacteria, dark-regime biocidal activity was observed that did not increase upon exposure to light, suggesting that the mode of antimicrobial activity is due to ionic disruption of the cell wall. Subsequent to killing, bacteria and cellular debris were removed upon a temperature-induced phase transition of the PNIPAAm. These materials exhibited capture, killing, and release activity over multiple cycles of use.
    Type of Medium: Online Resource
    ISSN: 1934-8630 , 1559-4106
    URL: Article
    DOI: 10.1116/1.4939239
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2016
    detail.hit.zdb_id: 2234510-3
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  • 4
    Online Resource
    Online Resource
    Biosensors based on release of compounds upon disruption of lipid bilayers supported on porous microspheres
    American Vacuum Society ; 2008
    In:  Biointerphases Vol. 3, No. 2 ( 2008-06-01), p. 38-49
    Details
    In: Biointerphases, American Vacuum Society, Vol. 3, No. 2 ( 2008-06-01), p. 38-49
    Abstract: The authors describe a biosensing concept based on the release of compounds, which are encapsulated within lipid-coated porous silica microspheres, by detergents and toxins that disrupt supported lipid bilayers SLBs on the microspheres. Suspension and microfluidic based methods have been developed to monitor the release of the encapsulated compounds in response to membrane disruption. The authors established that the SLBs on porous microspheres can endure experimental conditions necessary for their incorporation into packed microchannels while maintaining the bilayer integrity and functionality. Model compounds including a nonionic detergent Triton X-100, a membrane active protein (α-hemolysin, and a membrane lytic antimicrobial peptide melittin were successfully utilized to interact with different formulations of SLBs on porous silica microspheres. The results demonstrate the stability of the SLBs on the microspheres for several weeks, and the feasibility of using this system to detect the release of fluorescent dyes as well as other molecular reporters. The latter were detected by their involvement in subsequent biospecific interactions that were detected by fluorescence. This study exemplifies proof of concept for developing new chemical and biochemical sensors and drug delivery systems based on the disruption of lipid membranes coating porous silica microspheres that encapsulate dyes or bioactive compounds.
    Type of Medium: Online Resource
    ISSN: 1934-8630 , 1559-4106
    URL: Article
    DOI: 10.1116/1.2918743
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2008
    detail.hit.zdb_id: 2234510-3
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  • 5
    Online Resource
    Online Resource
    Creating cellular patterns using genetically engineered, gold- and cell-binding polypeptides
    American Vacuum Society ; 2016
    In:  Biointerphases Vol. 11, No. 2 ( 2016-06-01)
    Details
    In: Biointerphases, American Vacuum Society, Vol. 11, No. 2 ( 2016-06-01)
    Abstract: Patterning cells on material surfaces is an important tool for the study of fundamental cell biology, tissue engineering, and cell-based bioassays. Here, the authors report a simple approach to pattern cells on gold patterned silicon substrates with high precision, fidelity, and stability. Cell patterning is achieved by exploiting adsorbed biopolymer orientation to either enhance (gold regions) or impede (silicon oxide regions) cell adhesion at particular locations on the patterned surface. Genetic incorporation of gold binding domains enables C-terminal chemisorption of polypeptides onto gold regions with enhanced accessibility of N-terminal cell binding domains. In contrast, the orientation of polypeptides adsorbed on the silicon oxide regions limit the accessibility of the cell binding domains. The dissimilar accessibility of cell binding domains on the gold and silicon oxide regions directs the cell adhesion in a spatially controlled manner in serum-free medium, leading to the formation of well-defined cellular patterns. The cells are confined within the polypeptide-modified gold regions and are viable for eight weeks, suggesting that bioactive polypeptide modified surfaces are suitable for long-term maintenance of patterned cells. This study demonstrates an innovative surface-engineering approach for cell patterning by exploiting distinct ligand accessibility on heterogeneous surfaces.
    Type of Medium: Online Resource
    ISSN: 1934-8630 , 1559-4106
    URL: Article
    DOI: 10.1116/1.4952452
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2016
    detail.hit.zdb_id: 2234510-3
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  • 6
    Online Resource
    Online Resource
    Rapid prototyping of active microfluidic components based on magnetically modified elastomeric materials
    American Vacuum Society ; 2001
    In:  Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena Vol. 19, No. 2 ( 2001-03-01), p. 596-599
    Details
    In: Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, American Vacuum Society, Vol. 19, No. 2 ( 2001-03-01), p. 596-599
    Abstract: Replica molding of elastomeric materials has proven to be an extremely useful new technology for the formation of complex microfluidic systems. Recent demonstrations of convenient methods for production of such systems by simple, rapid methods that do not require expensive fabrication facilities have enabled the extensive use of microsystems in research and development into a host of new application fields. This report describes a simple new method for fabricating active elastomeric components in microfluidic systems that is based on deformation of elastic materials that have been impregnated or coated with magnetic materials. Computer controlled miniature electromagnets are used to activate switching valves within microfluidics systems. Similar fabrication techniques can be easily extended to construct complex, and potentially completely integrated, microfluidic systems containing active valves, pumps, injectors, mixers, and flow controllers. Preliminary results indicate fabrication of channels approximately 200 μm in width, with valves approximately 5 mm in size (including both valve chamber and valve actuator). The fabrication cycle time is on the order of one day using readily available benchtop equipment, and the valves seal hermetically against a 1.5 kPa back pressure.
    Type of Medium: Online Resource
    ISSN: 1071-1023 , 1520-8567
    URL: Article
    DOI: 10.1116/1.1350840
    RVK:
    UA 4922
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2001
    detail.hit.zdb_id: 3117331-7
    detail.hit.zdb_id: 3117333-0
    detail.hit.zdb_id: 1475429-0
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  • 7
    Online Resource
    Online Resource
    Thermodynamic analysis of marine bacterial attachment to oligo(ethylene glycol)-terminated self-assembled monolayers
    American Vacuum Society ; 2013
    In:  Biointerphases Vol. 8, No. 1 ( 2013-12-01)
    Details
    In: Biointerphases, American Vacuum Society, Vol. 8, No. 1 ( 2013-12-01)
    Abstract: Colloidal models are frequently used to model the thermodynamics of bacterial attachment to surfaces. The most commonly used of such models is that proposed by van Oss, Chaudhury and Good, which includes both non-polar and polar (including hydrogen bonding) interactions between the attaching bacterium, the attachment substratum and the aqueous environment. We use this model to calculate the free energy of adhesion, ∆Gadh, for attachment of the marine bacterium Cobetia marina to well defined attachment substrata that systematically vary in their chemistry and their ability to attach bacteria, namely a series of oligo(ethylene glycol) (OEG) terminated self-assembled monolayers that vary in the number of OEG moieties. For this system, the values of ∆Gadh calculated using VCG do not correlate with observed attachment profiles. We examine the validity of a number of assumptions inherent in VCG and other colloidal models of adhesion, with special attention paid to those regarding bacterial surfaces.
    Type of Medium: Online Resource
    ISSN: 1934-8630 , 1559-4106
    URL: Article
    DOI: 10.1186/1559-4106-8-24
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2013
    detail.hit.zdb_id: 2234510-3
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  • 8
    Online Resource
    Online Resource
    Robust hybrid thin films that incorporate lamellar phospholipid bilayer assemblies and transmembrane proteins
    American Vacuum Society ; 2006
    In:  Biointerphases Vol. 1, No. 1 ( 2006-03-01), p. 6-10
    Details
    In: Biointerphases, American Vacuum Society, Vol. 1, No. 1 ( 2006-03-01), p. 6-10
    Abstract: This study describes facile methods based on sol-gel processing for the formation of robust thin films that incorporate phospholipid bilayer membranes and transmembrane proteins as multilamellar assemblies in cross-linked silica matrices. Transmission electron microscopy and x-ray diffraction were used to examine the lamellar structure of the hybrid thin films containing 1, 2-dioleyl-sn-glycero-3-phospoethanolamine (DOPE), an unsaturated lipid, and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), a saturated lipid. While the d spacing measured for DOPE containing films varied (from 35 to 48 Å) depending on the amount of DOPE added to the coating solution (10-1 wt %), similar changes were not observed for the films containing saturated lipid, DMPC (d spacing ∼43 Å). Addition of purple membrane containing bacteriorhodopsin to the DOPE/silica coating solution led to the formation of multilamellar vesicle-like structures within the thin films. Mild sonication of these solutions containing the purple membrane prior to coating led to the formation thin films with planar multilamellar structures that exhibit uniform d spacing. The study further investigates the effects of incorporation of gramicidin and sonication on the structure of hybrid films and speculates on the eventual application of thin films prepared in this manner.
    Type of Medium: Online Resource
    ISSN: 1934-8630 , 1559-4106
    URL: Article
    DOI: 10.1116/1.2185654
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2006
    detail.hit.zdb_id: 2234510-3
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