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Biocides are employed to prevent biodeterioration in waterborne paints. In the present study, we used zinc oxide nanoparticles (obtained from spent alkaline batteries) as biocide for indoor waterborne paint at 1.5% of the total solid content in paint. Two different zinc oxides synthesized from spent alkaline batteries, which showed photocatalyst activity, were employed as an antimicrobial agents. After leaching the anode of alkaline batteries, zinc was precipitated from the leachate liquor by introducing oxalic acid (O-ZnO) or sodium carbonate (C-ZnO). The antimicrobial properties of the prepared oxides were tested against Staphylococcus aureus (bacteria), Chaetomium globosum , and Aspergillus fumigatus (fungi) using agar well diffusion method. C-ZnO inhibited the growth of all the strains studied and presented enhanced activity than O-ZnO. The better performance as antimicrobial agent of C-ZnO compared to O-ZnO was attributed to its lower crystallite size, higher amount of oxygen monovacancies, and to its lower band gap energy. The oxide with the best performance in antimicrobial activity, C-ZnO, was employed for the formulation of waterborne acrylic paints. It was observed that 1.5% C-ZnO improved the antifungal properties and antibacterial properties compared to the control sample., Competing Interests: Competing interestsThe authors declare no competing interests., (© Qatar University and Springer Nature Switzerland AG 2022, Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)

We present an easy-to-assemble microfluidic system for synthesizing cell-loaded dextran/alginate (DEX/ALG) hydrogel spheres using an aqueous two-phase system (ATPS) for templated fabrication of multicellular tumor spheroids (MTSs). An audio speaker driven by an amplified output of a waveform generator or smartphone provides acoustic modulation to drive the breakup of an ATPS into MTS template droplets within microcapillary fluidic devices. We apply extensions of Plateau-Rayleigh theory to help define the flow and frequency parameter space necessary for acoustofluidic ATPS droplet formation in these devices. This method provides a simple droplet microfluidic approach using off-the-shelf acoustic components for quickly initiating MTSs and subsequent 3D cell culture.

Context: In the United States, regional poison centers frequently receive calls about toxic workplace exposures. Most poison centers do not share call details routinely with governmental regulatory agencies. Worker health and safety could be enhanced if regulators such as the Occupational Safety and Health Administration (OSHA) had the ability to investigate these events and prevent similar incidents. With this goal in mind, the Georgia Poison Center (GPC) began referring occupational exposures to OSHA in July 2014., Methods: GPC began collecting additional employer details when handling occupational exposure calls. When workers granted permission, GPC forwarded call details to the OSHA Regional Office in Atlanta. These referrals enabled OSHA to initiate several investigations. We also analyzed all occupational exposures reported to GPC during the study period to characterize the events, detect violations of OSHA reporting requirements, and identify hazardous scenarios that could form the basis for future OSHA rulemaking or guidance., Results: GPC was informed about 953 occupational exposures between 1 July, 2014 and 7 January, 2016. Workers were exposed to 217 unique substances, and 70.3% of victims received treatment in a healthcare facility. Hydrogen sulfide was responsible for the largest number of severe clinical effects. GPC obtained permission to refer 89 (9.3%) calls to OSHA. As a result of these referrals, OSHA conducted 39 investigations and cited 15 employers for "serious" violations. OSHA forwarded several other referrals to other regulatory agencies when OSHA did not have jurisdiction. At least one employer failed to comply with OSHA's new rule that mandates reporting of all work-related hospitalizations. This collaboration increased OSHA's awareness of dangerous job tasks including hydrofluoric acid exposure among auto detailers and carbon monoxide poisoning with indoor use of gasoline-powered tools., Conclusions: Collaboration with the GPC generated a useful source of referrals to OSHA. OSHA investigations led to abatement of existing hazards, and OSHA acquired new knowledge of occupational exposure scenarios.

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.

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must be smaller than the incident wavelength of sound and the width of the fluidic channels are typically tens to hundreds of micrometers across, acoustofluidic devices typically use ultrasonic waves generated from a piezoelectric transducer pulsating at high frequencies (in the megahertz range). At characteristic frequencies that depend on the geometry of the device, it is possible to induce the formation of standing waves that can focus particles along desired fluidic streamlines within a bulk flow. Here, we describe a method for the fabrication of acoustophoretic devices from common materials and clean room equipment. We show representative results for the focusing of particles with positive or negative acoustic contrast factors, which move towards the pressure nodes or antinodes of the standing waves, respectively. These devices offer enormous practical utility for precisely positioning large numbers of microscopic entities (e.g., cells) in stationary or flowing fluids for applications ranging from cytometry to assembly.

A dynamically adjustable colloidal assembly technique is presented, which combines magnetic and acoustic fields to produce a wide range of colloidal structures, ranging from discrete colloidal molecules, to polymer networks and crystals. The structures can be stabilized and dried, making them suitable for the fabrication of advanced materials., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A 3D printable and highly stretchable tough hydrogel is developed by combining poly(ethylene glycol) and sodium alginate, which synergize to form a hydrogel tougher than natural cartilage. Encapsulated cells maintain high viability over a 7 d culture period and are highly deformed together with the hydrogel. By adding biocompatible nanoclay, the tough hydrogel is 3D printed in various shapes without requiring support material., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

X. Zhao and co-workers develop on page 4035 a new biocompatible hydrogel system that is extremely tough and stretchable and can be 3D printed into complex structures, such as the multilayer mesh shown. Cells encapsulated in the tough and printable hydrogel maintain high viability. 3D-printed structures of the tough hydrogel can sustain high mechanical loads and deformations., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Clinical management of diabetes must overcome the challenge of in vivo glucose sensors exhibiting lifetimes of only a few days. Limited sensor life originates from compromised enzyme stability of the sensing enzyme. Sensing enzymes degrade in the presence of low molecular weight materials (LMWM) and hydrogen peroxide in vivo. Sensing enzymes could be made to withstand these degradative effects by (1) stabilizing the microenvironment surrounding the sensing enzyme or (2) improving the structural stability of the sensing enzyme genetically. We review the degradative effect of LMWM and hydrogen peroxide on the sensing enzyme glucose oxidase (GOx). In addition, we examine advances in stabilizing GOx against degradation using hybrid silica gels and genetic engineering of GOx. We conclude molecularly engineered GOx combined with silica-based encapsulation provides an avenue for designing long-term in vivo sensor systems., (© 2013 Diabetes Technology Society.)

We demonstrate a magnetic technique for assembling bidisperse and tridisperse colloidal particle fluids into a variety of complex structures with dimensionality ranging from 0-D (rings) to 1-D (chains) to 2-D (tiles). Compared with prior work on bidisperse particles that are commensurate in size, here we explore the assembly of different sized particles, and we show that due to packing constraints, new particle structures can be realized experimentally. Extending these experiments to a tridisperse system, we demonstrate that at low concentrations the smallest particle does not change the underlying crystal structures of the bidisperse system; however, it can assist in the formation of crystallite structures that were not stable in a bidisperse system. Additionally, we discovered that the smallest particle mimics the role of the ferrofluid, by shifting the locations in phase space where the bidisperse crystal structures can be experimentally obtained. Finally, we demonstrate that 3-particle crystal structures can be tuned by varying the strength of the external field, which is not possible in a 2-particle system.

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.

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/cm(2)) of shear stresses.

The objectives of this study were to examine the feasibility of using glucose oxidase (GOx) dispersed in a silica matrix for glucose monitoring in whole blood, and then to assess whether the flexibility of silica sol-gel chemistry could be exploited to enhance glucose sensor performance and stability. Silica-dispersed GOx was deployed on platinized platinum (Pt) wire to form a Clark-type amperometric glucose sensor. Sensors were calibrated using buffered glucose standard solutions, and then tested against glucose spiked human serum and whole blood. All serum and whole blood measurements met the minimum FDA requirement of falling within the "A+B region" of a Clark Error Grid. To our knowledge this is the first report of using silica-dispersed GOx to measure glucose in whole blood. The effect of condensation pH on sensor performance was assessed by dispersing GOx in silica condensed at pH 3, 7 and 12, and then testing the sensor response against glucose calibration standards. The pH 12 silica sensors had statistically faster response time, and higher sensor sensitivity compared to pH 7, pH 3 silica and glutaraldehyde crosslinked sensors. Membranes of the pH 12 silica had statistically higher glucose diffusion coefficient than did the pH 7 and 3 sensors. GOx dispersed in pH 12 silica also had the longest half life. We hypothesize that the gel-like pH 12 silica gels provided reduced barriers to glucose diffusion, and the more aqueous microenvironment provided greater stability for the enzyme.

The interactions of poly(phenylene ethynylene)- (PPE-) based cationic conjugated polyelectrolytes (CPEs) and oligo(phenylene ethynylene)s (OPEs) with different model lipid membrane systems were investigated to gain insight into the relationship between molecular structure and membrane perturbation ability. The CPE and OPE compounds exhibit broad-spectrum antimicrobial activity, and cell walls and membranes are believed to be their main targets. To better understand how the size, in terms of the number of repeat units, of the CPEs and OPEs affects their membrane disruption activities, a series of PPE-based CPEs and OPEs were synthesized and studied. A number of photophysical techniques were used to investigate the interactions of CPEs and OPEs with model membranes, including unilamellar vesicles and lipid monolayers at the air/water interface. CPE- or OPE-induced dye leakage from vesicles reveals that the CPEs and OPEs selectively perturb model bacterial membranes and that their membrane perturbation abilities are highly dependent on molecular size. Consistent with dye-leakage assay results, the CPEs and OPEs also exhibit chain-length-dependent ability to insert into 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG) monolayers. Our results suggest that, for PPE-based CPE and OPE antimicrobials, chain length can be tuned to optimize their membrane perturbation ability., (© 2011 American Chemical Society)

We demonstrate that interferometric lithography offers a fast, simple route to nanostructured self-assembled monolayers of alkylphosphonates on the native oxide of titanium. Exposure at 244 nm using a Lloyd's mirror interferometer caused the spatially periodic photocatalytic degradation of the adsorbates, yielding nanopatterns that extended over square centimetre areas. Exposed regions were re-functionalised by a second, contrasting alkylphosphonate, and the resulting patterns were used as templates for the assembly of molecular nanostructures; we demonstrate the fabrication of lines of polymer nanoparticles 46 nm wide. Nanopatterned monolayers were also employed as resists for etching of the metal film. Wires were formed with widths that could be varied between 46 and 126 nm simply by changing the exposure time. Square arrays of Ti dots as small as 35 nm (λ/7) were fabricated using two orthogonal exposures followed by wet etching.

Biofilm-based systems, including integrated fixed-film activated sludge and moving bed bioreactors, are becoming increasingly popular for wastewater treatment, often with the goal of improving nitrification through the enrichment of ammonia and nitrite oxidizing bacteria. We have previously demonstrated the utility of self-assembled monolayers (SAMs) as tools for studying the initial attachment of bacteria to substrata systematically varying in physicochemical properties. In this work, we expanded these studies to bacteria of importance in wastewater treatment systems and we demonstrated attachment rates were better correlated with surface energy than with wettability (water contact angle). Toward the long-term goal of improving wastewater treatment performance through the strategic design of attachment substrata, the attachment rates of two autotrophic ammonia-oxidizing bacteria (Nitrosomonas europaea and Nitrosospira multiformis) and a heterotroph (Escherichia coli) were evaluated using SAMs with a range of wettabilities, surface energies, and functional properties (methyl, hydroxyl, carboxyl, trimethylamine, and amine terminated). Cell attachment rates were somewhat correlated with the water contact angles of the SAMs with polar terminal groups (hydroxyl, carboxyl, trimethylamine, and amine). Including all SAM surfaces, a better correlation was found for all bacteria between attachment rates and surface free energy, as determined using the Lewis Acid-Base approach. The ammonia-oxidizers had higher adhesion rates on the SAMs with higher surface energies than did the heterotroph. This work demonstrated the successful application of SAMs to determine the attachment surface preferences of bacteria important to wastewater treatment, and it provides guidance for a new area of research aimed at improving treatment performance through rational attachment surface design.

We demonstrate that interferometric lithography provides a fast, simple approach to the production of patterns in self-assembled monolayers (SAMs) with high resolution over square centimeter areas. As a proof of principle, two-beam interference patterns, formed using light from a frequency-doubled argon ion laser (244 nm), were used to pattern methyl-terminated SAMs on gold, facilitating the introduction of hydroxyl-terminated adsorbates and yielding patterns of surface free energy with a pitch of ca. 200 nm. The photopatterning of SAMs on Pd has been demonstrated for the first time, with interferometric exposure yielding patterns of surface free energy with similar features sizes to those obtained on gold. Gold nanostructures were formed by exposing SAMs to UV interference patterns and then immersing the samples in an ethanolic solution of mercaptoethylamine, which etched the metal substrate in exposed areas while unoxidized thiols acted as a resist and protected the metal from dissolution. Macroscopically extended gold nanowires were fabricated using single exposures and arrays of 66 nm gold dots at 180 nm centers were formed using orthogonal exposures in a fast, simple process. Exposure of oligo(ethylene glycol)-terminated SAMs to UV light caused photodegradation of the protein-resistant tail groups in a substrate-independent process. In contrast to many protein patterning methods, which utilize multiple steps to control surface binding, this single step process introduced aldehyde functional groups to the SAM surface at exposures as low as 0.3 J cm(-2), significantly less than the exposure required for oxidation of the thiol headgroup. Although interferometric methods rely upon a continuous gradient of exposure, it was possible to fabricate well-defined protein nanostructures by the introduction of aldehyde groups and removal of protein resistance in nanoscopic regions. Macroscopically extended, nanostructured assemblies of streptavidin were formed. Retention of functionality in the patterned materials was demonstrated by binding of biotinylated proteins.

Poly(phenylene ethyneylene) (PPE)-based cationic conjugated polyelectrolytes (CPEs) and cationic phenylene ethynylene oligomers (OPEs) exhibit broad-spectrum antimicrobial activity, and their main target is believed to be the cell membrane. To understand better how these antimicrobial molecules interact with membranes, a series of PPE-based CPEs and OPEs with different side chains were studied. Large unilamellar vesicles with lipid compositions mimicking those of mammalian or bacterial membranes were used as model membranes. Among the CPEs and OPEs tested, the anionic CPE, PPE-SO(3)(2-) and the smallest cationic OPE-1 are inactive against all vesicles. Other cationic CPEs and OPEs show significant membrane perturbation ability against bacterial membrane mimics but are inactive against a mammalian cell membrane mimic with the exception of PPE-DABCO and two end-only-functionalized OPEs, which also disrupted a mammalian cell membrane mimic. The results suggest that the phospholipid composition of vesicles dominates the interaction of CPE and OPE with lipid membranes.

Hantaviruses cause two severe diseases in humans: hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). The lack of vaccines or specific drugs to prevent or treat HFRS and HCPS and the requirement for conducting experiments in a biosafety level 3 laboratory (BSL-3) limit the ability to probe the mechanism of infection and disease pathogenesis. In this study, we developed a generalizable spectroscopic assay to quantify saturable fluorophore sites solubilized in envelope membranes of Sin Nombre virus (SNV) particles. We then used flow cytometry and live cell confocal fluorescence microscopy imaging to show that ultraviolet (UV)-killed SNV particles bind to the cognate receptors of live virions, namely, decay accelerating factor (DAF/CD55) expressed on Tanoue B cells and alpha(v)beta(3) integrins expressed on Vero E6 cells. SNV binding to DAF is multivalent and of high affinity (K(d) approximately 26pM). Self-exchange competition binding assays between fluorescently labeled SNV and unlabeled SNV are used to evaluate an infectious unit-to-particle ratio of approximately 1:14,000. We configured the assay for measuring the binding of fluorescently labeled SNV to Tanoue B suspension cells using a high-throughput flow cytometer. In this way, we established a proof-of-principle high-throughput screening (HTS) assay for binding inhibition. This is a first step toward developing HTS format assays for small molecule inhibitors of viral-cell interactions as well as dissecting the mechanism of infection in a BSL-2 environment., (2010 Elsevier Inc. All rights reserved.)

The interactions of antimicrobial cationic conjugated polyelectrolytes (CPEs) with two model membranes, liposomes and lipid monolayers at the air-water interface, have been investigated by fluorescence emission, fluorescence quenching, pressure-area isotherm, and dynamic light scattering measurements. This study continues the evaluation of the antimicrobial mechanism of a cationic poly(phenylene ethynylene) (PPE)-based CPE (polymer 1), which contains a 2,5-thienylene moiety in the repeat unit. To this end, the interactions of polymer 1 with lipids with varying headgroup charge and acyl chain length have been examined. Our results show that the cationic polymer 1 can efficiently associate with and insert into anionic phosphatidylglycerol (PG) membranes. However, polymer 1 does not exhibit any interactions with zwitterionic lipid membranes composed of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) lipids. Polymer 1's selective affinity toward anionic lipids over zwitterionic lipids makes it an attractive antimicrobial agent with low toxicity. The interactions of polymer 1 with lipid membranes of different fluidity were studied by varying the surface pressure of lipid monolayers and by adjusting the temperature of liposomes. We observe that increasing membrane fluidity enhances both the conformational changes of polymer 1 upon associating with lipid membranes and the extent of polymer 1 insertion into lipid monolayers. We also find that the thickness of the lipid bilayers, modulated by acyl chain length, affects the extent of polymer 1 incorporation into the lipid bilayer.

Lipid vesicles spontaneously fuse and assemble into a lipid bilayer on planar or spherical silica surfaces and other substrates. The supported lipid bilayers (SLBs) maintain characteristics of biological membranes, and are thus considered to be biomembrane mimetic systems that are stable because of the underlying substrate. Examples of their shared characteristics with biomembranes include lateral fluidity, barrier formation to ions and molecules, and their ability to incorporate membrane proteins into them. Biomimetic silica microspheres consisting of SLBs on solid or porous silica microspheres have been utilized for different biosensing applications. The advantages of such biomimetic microspheres for biosensing include their increased surface area to volume ratio which improves the detection limits of analytes, and their amenability for miniaturization, multiplexing and high throughput screening. This review presents examples and formats of using such biomimetic solid or porous silica microspheres in biosensing.

The use of simple plasma treatments and polymer deposition to tailor the anisotropic wetting properties of one-dimensional (1D) submicrometer-scale grooved surfaces, fabricated using interferometric lithography in photoresist polymer films, is reported. Strongly anisotropic wetting phenomena are observed for as-prepared 1D grooved surfaces for both positive and negative photoresists. Low-pressure plasma treatments with different gas compositions (e.g., CHF(3), CF(4), O(2)) are employed to tailor the anisotropic wetting properties from strongly anisotropic and hydrophobic to hydrophobic with very high contact angle and superhydrophilic with a smaller degree of wetting anisotropy and without changing the structural anisotropy. The change of the surface wetting properties for these 1D patterned surfaces is attributed to a change in surface chemical composition, monitored using XPS. In addition, the initial anisotropic wetting properties on 1D patterned samples could be modified by coating plasma treated samples with a thin layer of polymer. We also demonstrated that the wetting properties of 1D grooved surfaces in a Si substrate could be tuned with similar plasma treatments. The ability to tailor anisotropic wetting on 1D patterned surfaces will find many applications in microfluidic devices, lab-on-a-chip systems, microreactors, and self-cleaning surfaces.

Controlling accumulations of unwanted biofilms requires an understanding of the mechanisms that organisms use to interact with submerged substrata. While the substratum properties influencing biofilm formation are well studied, those that may lead to cellular or biofilm detachment are not. Surface-grafted stimuli-responsive polymers, such as poly (N-isopropylacrylamide) (PNIPAAm) release attached cells upon induction of environmentally-triggered phase changes. Altering the physicochemical characteristics of such polymeric systems for systematically studying release, however, can alter the phase transition. The physico-chemical changes of thin films of PNIPAAm grafted from initiator-modified self-assembled monolayers (SAMs) of omega-substituted alkanethiolates on gold can be altered by changing the composition of the underlying SAM, without affecting the overlying polymer. This work demonstrates that the ability to tune such changes in substratum physico-chemistry allows systematic study of attachment and release of bacteria over a large range of water contact angles. Such surfaces show great promise for studying a variety of interactions at the biointerface. Understanding of the source of this tunability will require further studies into the heterogeneity of such films and further investigation of interactions beyond those of water wettability.

The interactions of antimicrobial poly(phenylene ethynylene) (PPE)-based cationic conjugated polyelectrolytes (CPEs) with lipid membranes were investigated to gain insight into the mechanism of their biocidal activity. Three model membrane systems comprising negatively charged phosphatidylglycerol (PG) lipids were used to mimic the bacterial cell membrane, including unilamellar lipid vesicles in aqueous solution, lipid bilayer coated silica microspheres, and lipid monolayers at the air-water interface. Two PPE CPEs, one containing a thiophene moiety on the PPE repeat unit and the second containing a diazabicyclooctane (DABCO) moiety on the pendant side chain, were chosen, since the former exhibits distinct dark biocidal activity and the latter shows strong light-activated antimicrobial activity but little dark biocidal activity. The interactions of these two PPE polymers with lipid membranes were characterized in detail by CPE fluorescence spectral changes, fluorescence resonance energy transfer (FRET), fluorescence quenching, monolayer insertion, and dynamic light scattering assays. Both PPE polymers exhibit affinity for the anionic lipid membrane systems. Their concomitant association and insertion into the membrane leads to conformational changes of the PPE polymer from an aggregated state to a more extended state, as evidenced by the polymer's enhanced fluorescence and FRET between the polymer and rhodamine incorporated in the lipid membrane. In comparison, the thiophene polymer exhibits stronger interactions with PG lipid membranes than the DABCO-containing polymer. The former induces a larger fluorescence enhancement, shows faster transfer across the lipid membrane, and inserts more readily and to a higher extent into lipid monolayers. The observed differences between the two PPE polymers in their interactions with the lipid membrane may stem from their structural differences, as the DABCO-containing polymer has a much bulkier and larger pendant group on its side chain. The higher degree of membrane interaction and insertion, and subsequent membrane disorganization, of the thiophene polymer may account for its dark biocidal activity.

In this work, we examine the interaction between thin films composed of terminally anchored poly(N-isopropyl acrylamide) (PNIPAAm) immersed in water and test surfaces. Understanding this force of interaction can be important when using PNIPAAm surfaces in biotechnological applications such as biological cell cultures. The two novel contributions that are presented here are (1) the use of a recently developed self-consistent field (SCF) theory to predict the force-vs-distance profiles, and (2) the use of a modified polymer scaling theory to estimate the wet film thickness from experimental force-vs-distance profiles. SCF theory was employed to model the equilibrium structure of the uncompressed PNIPAAm chains, and the force between a compressed polymer film and a test surface as a function of wall separation distance. The parameters that were varied include temperature, polymer molecular weight, and surface coverage. The force-vs-distance profiles obtained at low and high temperatures with the SCF theory were in qualitative agreement with the experimentally measured profiles reported in the literature. We also compared the results of our SCF theory to the Alexander de Gennes scaling theory and found agreement at large separation distance. We also propose a method to estimate the wet polymer film thickness from a force-vs-distance profile obtained from an atomic force microscope measurement. The main novelties of this approach are that we employed a density functional theory corrected version of scaling theory proposed by McCoy et al. [McCoy, J. D.; Curro, J. G. J. Chem. Phys. 2005, 122, 164905], and we provide equations to account for various geometries of AFM tips.

In this paper we report a study of cationic poly(arylene ethynylene) conjugated polyelectrolytes. The objective of the study was to compare the behavior of a polymer where a thiophene has replaced a phenyl ring in poly(phenylene ethynylene) polycations (PPE) previously investigated. Properties of solution phase and physisorbed suspensions of the polymer on microspheres were investigated. The photophysical properties of the polymer are evaluated and used to understand the striking differences in biocidal activity compared to the PPE polymers previously examined. The principal findings are that the thiophene polymer has remarkable dark biocidal activity against Pseudomonas aeruginosa strain PAO1 but very little light-activated activity. The low light-activated biocidal activity of the thiophene polymer is attributed to a highly aggregated state of the polymer in aqueous solutions and on microspheres as a physisorbed coating. This results in low triplet yields and a very poor sensitization of singlet oxygen and other reactive oxygen intermediates. The highly effective dark biocidal activity of the thiophene-containing polymers is attributed to its high lipophilicity and the presence of accessible quaternary ammonium groups. The difference in behavior among the polymers compared provides insights into the mechanism of the dark process and indicates that aggregation of polymer can reduce light activated biocidal activity by suppressing singlet oxygen generation.

The interactions between charged molecules and channel surfaces are expected to significantly influence the electrokinetic transport of molecules and their separations in nanochannels. This study reports the effect of wall-molecule interactions on flow control of negatively charged Alexa 488 and positively charged Rhodamine B dye molecules in an array of nanochannels (100 nm wx 500 nm dx 14 mm l) embedded in fluidic field effect transistors (FETs). For FET flow control, a third electrical potential, known as a gate bias, is applied to the channel walls to manipulate their zeta-potential. Electroosmotic flow of charged dye molecules is accelerated or reversed according to the polarity and magnitude of the gate bias. During FET flow control, we monitor how the electrostatic interaction between charged dye molecules and channel walls affects the apparent velocity of molecules, using laser-scanning confocal fluorescence microscopy. We observe that the changes in flow speed and direction of negatively charged Alexa 488 is much more pronounced than that of positively charged Rhodamine B in response to the gate bias that causes either repulsive or attractive electrostatic interactions. This observation is supported by calculations of concentration-weighted velocity profiles of the two dye molecules during FET flow control. The velocity profile of negatively charged Alexa 488 is much more pronounced at the center of each nanochannel than near its walls since Alexa 488 molecules are repelled from negatively charged channel walls. This pronounced center velocity further responds to the gate bias, increasing the average velocity by as much as 23% when -30 V is applied to the gate (zeta-potential = -80.6 mV). In contrast, the velocity profile of positively charged Rhodamine B is dispersed over the entire channel width due to dye-wall attraction and adsorption. Our experimental observations and calculations support the hypothesis that valence-charge-dependent electrostatic interaction and its manipulation by the gate bias would enhance molecular separations of differentially charged molecules in nanofluidic FETs.

The current system employed electrochemical sensor technology for the measurement of autoantibodies in human sera. Anti-chromatin antibodies are an early and sensitive indicator of systemic lupus erythematosus (SLE) and are typically quantified using enzyme-linked immunosorbent assays (ELISA). Electrochemical detection compared favorably with ELISA using a sample of 30 SLE sera (r=0.9), and non-specific binding by normal serum immunoglobulin was undetectable. The electrochemical sensor assay required <20min processing time and utilized a hand-held apparatus with a disposable electrode. These results demonstrate the applicability of this technology to the rapid measurement of a clinically relevant analyte with an apparatus of potential simplicity and low cost.

We have studied and modeled the morphology and dynamics of fluid planar lipid bilayer membranes supported on a textured silicon substrate. The substrate is fabricated to have channels on its surface that are a few hundred nanometers across, with a channel depth of a few hundred nanometers perpendicular to the plane of observation. Using atomic force microscopy and quantitative fluorescence microscopy, we have shown that the bilayer assemblies conform to the underlying nanostructured substrate. As far as dynamics is concerned, when observed over length scales exceeding the dimensions of the nanostructured features, the macroscopic diffusion is anisotropic. However, the macroscopic anisotropy is well simulated using models of diffusion on the nanostructured surface that consider the lipids to diffuse homogeneously and isotropically on the supporting substrate. Consistent with previous observations on less well characterized or less periodic nanostructures, we find that the nanostructured substrate produces an effective anisotropy in macroscopic diffusion of the conformal membrane. More importantly, we demonstrate how quantitative analysis of dynamics probed by larger-scale fluorescence imaging can yield information on nanoscale thin-film morphology.

A pair of cationic phenylene ethynylene oligomers (OPEs) have been synthesized, and their optical properties have been studied in solution with and without added scaffold materials, including carboxymethylcellulose, carboxymethylamylose, and Laponite. The OPEs are strongly fluorescent in methanol solution, but in water, the fluorescence yield is suppressed. The addition of scaffolds to aqueous solutions of OPEs leads to a red shift in the absorption and in most cases a significant increase in the fluorescence quantum yield. The effects most likely arise because of template-induced formation of linear J-dimers or possibly because of planarization, which give rise to an effective increase in the conjugation length of OPEs.

A fluorescence based assay for human serum-derived phospholipase activity has been developed in which cationic conjugated polyelectrolytes are supported on silica microspheres. The polymer-coated beads are overcoated with an anionic phospholipid (1,2-dimyristoyl-sn-glycero-3-[phospho- rac-(1-glycerol)) (DMPG) to provide "lipobeads" that serve as a sensor for PLA2. The lipid serves a dual role as a substrate for PLA2 and an agent to attenuate quenching of the polymer fluorescence by the external electron transfer quencher 9,10-anthraquinone-2,6-disulfonic acid (AQS). In this case quenching of the polymer fluorescence by AQS increases as the PLA2 digests the lipid. The lipid can also be used itself as a quencher and substrate by employing a small amount of energy transfer quencher substituted lipid in the DMPG. In this case the fluorescence of the polymer is quenched when the lipid layer is intact; as the enzyme digests the lipid, the fluorescence of the polymer is restored. The sensing of PLA2 activity has been studied both by monitoring fluorescence changes in a multiwell plate reader and by flow cytometry. The assay exhibits good sensitivity with EC50 values in the nanomolar range.

A series of water soluble, cationic conjugated polyelectrolytes (CPEs) with backbones based on a poly(phenylene ethynylene) repeat unit structure and tetraakylammonium side groups exhibit a profound light-induced biocidal effect. The present study examines the biocidal activity of the CPEs, correlating this activity with the photophysical properties of the polymers. The photophysical properties of the CPEs are studied in solution, and the results demonstrate that direct excitation produces a triplet excited-state in moderate yield, and the triplet is shown to be effective at sensitizing the production of singlet oxygen. Using the polymers in a format where they are physisorbed or covalently grafted to the surface of colloidal silica particles (5 and 30 microm diameter), we demonstrate that they exhibit light-activated biocidal activity, effectively killing Cobetia marina and Pseudomonas aeruginosa. The light-induced biocidal activity is also correlated with a requirement for oxygen suggesting that interfacial generation of singlet oxygen is the crucial step in the light-induced biocidal activity.

This article presents an analysis of the electric field distribution and current transport in fluidic nanochannels fabricated by etching of a silicon chip. The channels were overcoated by a SiO2 layer. The analysis accounts for the current leaks across the SiO2 layer into the channel walls. Suitable voltage biasing of the Si substrate allows eliminating of the leaks or using them to modify the potential distribution of the fluid. Shaping the potential in the fluid can be utilized for solute focusing and separations in fluidic nanochannels.

We report a simple approach to the formation of 3D colloidal nanoparticle structures incorporating enclosed mesoscopic structures through a simple process of spin-coating-driven directed self-assembly onto lithographically defined polymer templates. Removal of the buried polymer patterns by high temperature calcination results in the formation of hierarchically enclosed channels, continuous networks, isolated cavities, and multilayered structures with high stability and environmental resistance. These channels are used to investigate the transport of DNA molecules in constrained geometries.

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 (alpha-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.

Assays for biointeractions of molecules with supported lipid bilayers using fluorescence superquenching are described. A conjugated cationic polymer was adsorbed on to silica microspheres, which were then coated with an anionic lipid bilayer. The lipid bilayer attenuated superquenching by acting as a barrier between the conjugated polymer and its quencher. Biointeractions of the lipid bilayer with a membrane lytic peptide, melittin, were detected and quantitated by superquenching of the conjugated polyelectrolyte in flow cytometric and microfluidic bioassays. A higher sensitivity for detecting melittin lysis of the lipid bilayer at lower concentrations and shorter times for melittin action was found using flow cytometry in this study in comparison to other existing methods. This study combined the sensitivity of superquenching and flow cytometry to detect biointeractions with a lipid bilayer, which serves as a platform for developing functional assays for sensor applications, lipid enzymology, and investigations of molecular interactions. In addition, this study demonstrated proof-of-concept for using superquenching detected as a result of lipid bilayer disruption in a microfluidic format.

Using Si as the substrate, we have fabricated multiple internal reflection infrared waveguides embedded with a parallel array of nanofluidic channels. The channel width is maintained substantially below the mid-infrared wavelength to minimize infrared scattering from the channel structure and to ensure total internal reflection at the channel bottom. A Pyrex slide is anodically bonded to the top of the waveguide to seal the nanochannels, while simultaneously enabling optical access in the visible range from the top. The Si channel bottom and sidewalls are thermally oxidized to provide an electrically insulating barrier, and the Si substrate surrounding the insulating SiO(2) layer is selectively doped to function as a gate. For fluidic field effect transistor (FET) control, a DC potential is applied to the gate to manipulate the surface charge on SiO(2) channel bottom and sidewalls and therefore their zeta-potential. Depending on the polarity and magnitude, the gate potential can accelerate, decelerate, or reverse the flow. Here, we demonstrate that this nanofluidic infrared waveguide can be used to monitor the FET flow control of charged, fluorescent dye molecules during electroosmosis by multiple internal reflection Fourier transform infrared spectroscopy. Laser scanning confocal fluorescence microscopy is simultaneously used to provide a comparison and verification of the IR analysis. Using the infrared technique, we probe the vibrational modes of dye molecules, as well as those of the solvent. The observed infrared absorbance accounts for the amount of dye molecules advancing or retracting in the nanochannels, as well as adsorbing to and desorbing from the channel bottom and sidewalls.

We have used rapid-mix flow cytometry to analyze the early subsecond dynamics of the disassembly of ternary complexes of G protein-coupled receptors (GPCRs) immobilized on beads to examine individual steps associated with guanine nucleotide activation. Our earlier studies suggested that the slow dissociation of Galpha and Gbetagamma subunits was unlikely to be an essential component of cell activation. However, these studies did not have adequate time resolution to define precisely the disassembly kinetics. Ternary complexes were assembled using three formyl peptide receptor constructs (wild type, formyl peptide receptor-Galpha(i2) fusion, and formyl peptide receptor-green fluorescent protein fusion) and two isotypes of the alpha subunit (alpha(i2) and alpha(i3)) and betagamma dimer (beta(1)gamma(2) and beta(4)gamma(2)). At saturating nucleotide levels, the disassembly of a significant fraction of ternary complexes occurred on a subsecond time frame for alpha(i2) complexes and tau(1/2)< or =4s for alpha(i3) complexes, time scales that are compatible with cell activation. beta(1)gamma(2) isotype complexes were generally more stable than beta(4)gamma(2)-associated complexes. The comparison of the three constructs, however, proved that the fast step was associated with the separation of receptor and G protein and that the dissociation of the ligand or of the alpha and betagamma subunits was slower. These results are compatible with a cell activation model involving G protein conformational changes rather than disassembly of Galphabetagamma heterotrimer.

The spectroscopic properties of quantum dots can be strongly influenced by the conditions of their synthesis. In this work, we have characterized several spectroscopic properties of commercial, streptavidin functionalized quantum dots (QD525, lot 1005-0045, and QD585, lot 0905-0031, from Invitrogen). This is the first step in the development of calibration beads to be used in a generalizable quantification scheme of multiple fluorescent tags in flow cytometry or microscopy applications. We used light absorption, photoexcitation, and emission spectra, together with excited state lifetime measurements, to characterize their spectroscopic behavior, concentrating on the 400- to 500-nm wavelength ranges that are important in biological applications. Our data show an anomalous dependence of emission spectrum, lifetimes, and quantum yield (QY) on excitation wavelength that is particularly pronounced in the QD525. For QD525, QY values ranged from 0.2 at 480 nm excitation up to 0.4 at 450 nm and down again to 0.15 at 350 nm. For QD585, QY values were constant at 0.2 between 500 and 400 nm, but they dropped to 0.1 at 350 nm. We attribute the wavelength dependencies to heterogeneity in size and surface defects in the QD525, consistent with characteristics described previously in the chemistry literature. The results are discussed in the context of bridging the gap between what is currently known in the physical chemistry literature of quantum dots and the quantitative needs of assay development in biological applications.

The use of fluorescence calibration beads has been the hallmark of quantitative flow cytometry. It has enabled the direct comparison of interlaboratory data as well as quality control in clinical flow cytometry. In this article, we describe a simple method for producing color-generalizable calibration beads based on streptavidin functionalized quantum dots. Based on their broad absorption spectra and relatively narrow emission, which is tunable on the basis of dot size, quantum dot calibration beads can be made for any fluorophore that matches their emission color. In an earlier publication, we characterized the spectroscopic properties of commercial streptavidin functionalized dots (Invitrogen). Here we describe the molecular assembly of these dots on biotinylated beads. The law of mass action is used to readily define the site densities of the dots on the beads. The applicability of these beads is tested against the industry standard, namely commercial fluorescein calibration beads. The utility of the calibration beads is also extended to the characterization surface densities of dot-labeled epidermal growth factor ligands as well as quantitative indicators of the binding of dot-labeled virus particles to cells.

A direct method for preparation of conjugated polymer-grafted silica particles is reported. Silica particles (0.3 and 5 mum diameter) are treated with a 3-(trimethoxysilyl)propylamine derivative that is functionalized with an aryl iodide unit. A solution step-growth polymerization reaction is performed in solution that contains a dispersion of the aryl iodide-functionalized particles. The reaction is a Pd(0)-catalyzed (Sonogashira) A-B-type polymerization of an oligo(ethylene glycol)-fuctionalized diiodobenzene and a bis(propyloxy)sulfonate-substituted diethynylbenzene. The overall process affords silica particles that feature a surface graft layer of an anionic poly(phenylene ethynylene)-type conjugated polyelectrolyte. The particle surface modification process was monitored by infrared (FTIR) spectroscopy, and the polymer-grafted silica particles were characterized by thermogravimetric analysis, scanning and transmission electron microscopy, confocal fluorescence microscopy, and absorption and fluorescence spectroscopy. The conjugated polyelectrolyte-grafted silica particles are highly fluorescent, and a Stern-Volmer quenching study of the particles' fluorescence with electron-transfer- and energy-transfer-type quenchers shows that the quenching response depends on the type of quenching mechanism.

The introduction of functional transmembrane proteins into supported bilayer-based biomimetic systems presents a significant challenge for biophysics. Among the various methods for producing supported bilayers, liposomal fusion offers a versatile method for the introduction of membrane proteins into supported bilayers on a variety of substrates. In this study, the properties of protein containing unilamellar phosphocholine lipid bilayers on nanoporous silica microspheres are investigated. The effects of the silica substrate, pore structure, and the substrate curvature on the stability of the membrane and the functionality of the membrane protein are determined. Supported bilayers on porous silica microspheres show a significant increase in surface area on surfaces with structures in excess of 10 nm as well as an overall decrease in stability resulting from increasing pore size and curvature. Comparison of the liposomal and detergent-mediated introduction of purified bacteriorhodopsin (bR) and the human type 3 serotonin receptor (5HT3R) are investigated focusing on the resulting protein function, diffusion, orientation, and incorporation efficiency. In both cases, functional proteins are observed; however, the reconstitution efficiency and orientation selectivity are significantly enhanced through detergent-mediated protein reconstitution. The results of these experiments provide a basis for bulk ionic and fluorescent dye-based compartmentalization assays as well as single-molecule optical and single-channel electrochemical interrogation of transmembrane proteins in a biomimetic platform.

This article presents a summary of theory, experimental studies, and results for the electrokinetic transport in small fluidic nanochannels. The main focus is on the effect of the electric double layer on the EOF, electric current, and electrophoresis of charged analytes. The double layer thickness can be of the same order as the width of the nanochannels, which has an impact on the transport by shaping the fluid velocity profile, local distributions of the electrolytes, and charged analytes. Our theoretical consideration is limited to continuum analysis where the equations of classical hydrodynamics and electrodynamics still apply. We show that small channels may lead to qualitatively new effects like selective ionic transport based on charge number as well as different modes for molecular separation. These new possibilities together with the rapid development of nanofabrication capabilities lead to an extensive experimental effort to utilize nanochannels for a variety of applications, which are also discussed and analyzed in this review.

Thermosensitive inorganic-organic hybrid polymers and gels can be used for controlled molecular transport in a variety of applications that require robust, mechanically stable materials. Silica and poly(N-isopropylacrylamide) (PNIPAAm) precursors were copolymerized in the presence of surfactant supramolecular assemblies to form hybrid gels with ordered nanostructure. This method was less complicated and results in enhanced reversible transport properties compared to previous approaches noted herein. In this study, the thermoresponsive polymer, PNIPAAm, was incorporated into polymerizing silica networks using the coupling agent 3-methacryloxypropyltrimethoxysilane. The hydration transition of PNIPAAm associated with its lower critical solution temperature (LCST) in aqueous solution was retained in the hydrated silica matrices and was used to control the permeability of membranes and molecular release behavior of particles. This report presents new methods for formation of hybrid silica/PNIPAAm membranes and particles, characterization of these materials, and documentation of reversible molecular transport properties of these new hybrid materials.

We describe the development of an optical sensing system for the high-throughput screening (HTS) of a broad range of biological molecules, whole cells, organisms and pathogens, and illustrate the technology applications by a hyaluronidase enzyme activity assay as a specific example. At the core of the technology described in this paper, is the exciton concept that is relevant to molecular aggregation. J-aggregates of cyanine dyes have a narrower, red-shifted absorption band compared to monomer. We demonstrate that self-assembly may be driven by the helicogenic nature of the cyanine dye, converting the linear polymers of hyaluronic acid or carboxymethyl cellulose into supramolecular helical assemblies. This self-assembly is accompanied by an intense, sharp, red-shifted J-aggregate fluorescence. We utilized this property to develop an assay for the enzyme hyaluronidase, based upon the concept of "scaffold destruction," whereby the disruption/destruction of the hyaluronic acid polymer by hyaluronidase is accompanied by an attenuation of light emission from the J-aggregate. The extent of light attenuation provides an index of hyaluronidase activity. Other polymers of carbohydrates, proteins, nucleic acids and chemical polymers (such as the carbon nanotube) might provide a similar scaffold for helicogenic dyes upon which molecular aggregation can occur. A key feature of these assays is that they are label-free.

Bicellar mixtures, planar lipid bilayer assemblies comprising long- and short-chain phosphatidylcholine lipids in suspension, were used to form supported lipid bilayers on flat silicon substrate and on nanotextured silicon substrates containing arrays of parallel troughs (170 nm wide, 380 nm deep, and 300 nm apart). Confocal fluorescence and atomic force microscopies were used to characterize the resulting lipid bilayer. Formation of a continuous biphasic undulating lipid bilayer membrane, where the crests and troughs corresponded to supported and suspended lipid bilayer regions, is demonstrated. The use of interferometric lithography to fabricate nanotexured substrates provides an advantage over other nanotextured substrates such as nanoporous alumina by offering flexibility in designing different geometries for suspending lipid bilayers.

Background: Fluorescent conjugated polymers display high fluorescence quantum yields and enhanced sensitivity to quenching (superquenching) by oppositely charged quenchers through energy or electron transfer. Fluorescent polymers and their quenchers are used in bead-based biosensor applications where the polymers are coated on particles. In this work, we investigate a detection method that utilizes superquenching on microspheres, which can be used for flow cytometric assays., Methods: Microspheres were coated with the fluorescent cationic polyelectrolyte poly(p-phenylene-ethynylene) (PPE), and its superquenching by 9,10-anthraquinone-2,6-disulfonic acid (AQS) was examined by fluorometric methods in presence and in absence of a barrier to superquenching in the form of an anionic lipid bilayer., Results: Flow cytometry detected superquenching of PPE on microspheres (MS-PPE) by AQS where high levels of reduction in fluorescence were observed. Adding different concentrations of AQS to MS-PPE yielded a Stern-Volmer quenching constant of 0.8x10(6) M-1. While forming an anionic lipid bilayer around the MS-PPE acted as a barrier to superquenching by AQS, disrupting the lipid bilayer allowed superquenching to take place., Conclusions: The sensitivity of flow cytometry in detecting fluorescence of microspheres and the amplified quenching sensitivity of fluorescent conjugated polymers both offer advantages over other fluorometric methods and conventional quenching detection. This study used superquenching of fluorescent polymers as a new tool in flow cytometry, thus combining the advantages offered by both method and detector. In addition, we employed the formation and the disruption of a supported lipid bilayer in mediating superquenching to offer new biosensing applications., (Copyright (c) 2006 International Society for Analytical Cytology.)