Light-induced activation of an inert surface for covalent immobilization of a protein ligand

Immobilization of Active Antibodies at Polymer Melt Surfaces during Injection Molding

We demonstrate the transfer and immobilization of active antibodies from a low surface- energy mold surface to thermoplastic replica surfaces using injection molding, and we investigate the process at molecular scale. The transfer process is highly efficient, as verified by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) of the mold and replica surfaces. AFM analysis reveals partial nanometer-scale embedding of the protein into the polymer matrix as a possible mechanism of permanent immobilization. Replicas with rabbit anti-mouse IgG immobilized as capture antibody at the hot polymer melt surface during injection molding show similar affinity for their antigen (mouse IgG) in sandwich enzyme-linked immunosorbent assay (ELISA) as capture antibodies deposited by passive adsorption onto a bare thermoplastic replica. The transferred antibodies retain their functionality after incubation in serum-containing cell medium for >1 week. A mold coating time of 10 min prior to injection molding is sufficient for producing highly sensitive ELISA assays, thus enabling the short processing cycle times required for mass production of single-use biodevices relying on active immobilized antibodies.

Azido-Functionalized Aromatic Phosphonate Esters in RPOSS-Cage-Supported Lanthanide Ion (Ln = La, Nd, Dy, Er) Coordination

Within this work, a modified preparation of diethyl 4-azidobenzylphosphonate (L1) is presented and the family of 4- or 4'-azido-substituted aromatic phosphonate esters is increased by three new ligand platforms: diisopropyl 4-azidobenzylphosphonate (L2), diisopropyl ((4'-azido-[1,1'-biphenyl]-4-yl)methyl)phosphonate (L3), and diisopropyl 4-azido-2,3,5,6-tetrafluorobenzylphosphonate (L4), which exhibit an anomalous splitting of the N₃ stretching vibrations. Subsequent coordination to the in situ generated ^RPOSS (polyhedral oligomeric silsesquioxane)-cage-supported lanthanide precursors [(Ln{^RPOSS})₂(THF)_m] (P1-P6) (Ln = La, Nd, Dy, Er; R = iBu, Ph; m = 0, 1) yields complexes of the general formula [Ln{^RPOSS}(L1-L4)_n(S1)_x(THF)_m] (1-30) (n = 2, 3; x = 0, 1; m = 0-2) retaining the azide unit for future semiconductor surface immobilization. Because the latter compounds are mostly oils or viscous waxes, preliminary solution-state structure elucidations via DOSY-ECC-MW estimations have been carried out which are in accordance with ¹H NMR integral ratios as well as solid-state structures, where available. Moreover, the optical properties of the Nd, Dy, and Er derivatives of complexes 1-30 are examined in the visible and NIR spectral regions, where applicable.

Ultraminiaturized assay for rapid, low cost detection and quantification of clinical and biochemical samples

Herein, we report a simple, sensitive, rapid and low-cost ultraminiaturized assay technique for quantitative detection of 1 μl of clinical or biochemical sample on a novel ultraminiaturized assay plate (UAP). UAP is prepared by making tiny cavities on a polypropylene sheet. As UAP cannot immobilize a biomolecule through absorption, we have activated the tiny cavities of UAP by 1-fluoro-2-nitro-4-azidobenzene in a photochemical reaction. Activated UAP (AUAP) can covalently immobilize any biomolecule having an active nucleophilic group such as amino group. Efficacy of AUAP is demonstrated by detecting human IgE, antibody of hepatitis C virus core antigen and oligonucleotides. Quantification is performed by capturing the image of the colored assay solution and digitally quantifying the image by color saturation without using costly NanoDrop spectrophotometer. Image - based detection of human IgE and an oligonucleotide shows an excellent correlation with absorbance - based assay (recorded in a NanoDrop spectrophotometer); it is validated by Pearson's product-moment correlation with correlation coefficient of r = 0.9545088 and r = 0.9947444 respectively. AUAP is further checked by detecting hepatitis C virus Ab where strong correlation of color saturation with absorbance with respect to concentration is observed. Ultraminiaturized assay successfully detects target oligonucleotides by perfectly hybridizing with their respective complementary oligonucleotide probes but not with a random oligonucleotide. Ultraminiaturized assay technique has substantially reduced the requirement of reagents by 100 times and assay timing by 50 times making it a potential alternative to conventional method.

Exploring the flexible chemistry of 4-fluoro-3-nitrophenyl azide for biomolecule immobilization and bioconjugation

Bioconjugation and functionalization of polymer surfaces are two major tasks in materials chemistry which are accomplished using a variety of coupling agents. Immobilization of biomolecules onto polymer surfaces and the construction of bioconjugates are essential requirements of many biochemical assays and chemical syntheses. Different linkers with a variety of functional groups are used for these purposes. Among them, the benzophenones, aryldiazirines, and arylazides represent the most commonly used photolinker to produce the desired chemical linkage upon their photo-irradiation. In this review, we describe the versatile applications of 4-fluoro-3-nitrophenyl azide, one of the oldest photolinkers used for photoaffinity labeling in the late 1960s. Surprisingly, this photolinker, historically known as 1-fluoro-2-nitro-4-azidobenzene (FNAB), has remained unexplored for a long time because of apprehension that FNAB forms ring-expanded dehydroazepine as a major product and hence cannot activate an inert polymer. The first evidence of photochemical activation of an inert surface by FNAB through nitrene insertion reaction was reported in 2001, and the FNAB-activated surface was found to conjugate a biomolecule without any catalyst, reagent, or modification. FNAB has distinct advantages over perfluorophenyl azide derivatives, which are contemporary nitrene-generating photolinkers, because of its simple, single-step preparation and ease of thermochemical and photochemical reactions with versatile polymers and biomolecules. Covering these aspects, the present review highlights the flexible chemistry of FNAB and its applications in the field of surface engineering, immobilization of biomolecules such as antibodies, enzymes, cells, carbohydrates, oligonucleotides, and DNA aptamers, and rapid diagnostics. Graphical Abstract An overview of the FNAB-engineered activated polymer surfaces for covalent ligation of versatile biomolecules.

Microwave non-thermal effect reduces ELISA timing to less than 5 minutes

Microwave-mediated ELISA, which occurs in less than 5 minutes, is due to a microwave non-thermal effect. We postulate that the microwave non-thermal effect is a microwave catalytic effect acting by lowering the activation energy of reactants.

Image-based detection of oligonucleotides--a low cost alternative to spectrophotometric or fluorometric methods

Herein, we report a sensitive and low cost image-based (photocolorimetric) method for the detection of oligonucleotides on an activated polypropylene microtest plate (APPμTP). The assay was developed on the APPμTP by covalently immobilising 20-mer amino-modified oligonucleotides. Biotin-tagged complementary target sequences were then hybridised with the immobilised oligonucleotides. Colour was developed by streptavidin-HRP conjugate and the image of the coloured assay solution was taken by a desktop scanner and analysed using colour saturation. The developed method was analysed for its detection limit, accuracy, sensitivity and interference. The linearity range was found to be 1.7-170 ng mL(-1) while the lower limit of detection and limit of quantification were 1.7 and 5.6 ng mL(-1) respectively. The method showed comparable sensitivity to fluorometric methods, and was found to be correlated to fluorescence (R(2) = 0.8081, p-value < 0.0001) and absorbance (R(2) = 0.9394, p-value < 0.0001)-based quantification. It discriminates mismatched base sequences from perfectly matched sequences efficiently. Validation of the method was carried out by detecting por A DNA of Neisseria meningitidis in bacterial meningitis samples. The por A-specific probe having a 6-carbon spacer at its 5'-NH2 terminus was immobilised covalently to the APPμTP and hybridised with different samples of biotinylated single-stranded por A DNA.

Reversible redox modulation of a lanthanide emissive molecular film

Herein we demonstrate redox switchable emission from a sensitised, europium-ferrocene containing, molecular film assembled by a novel nitrene-based strategy. Electrochemical modulation of europium emission upon switching the ferrocene moiety's redox state is ascribed to the reversible generation of a quenching ferrocenium species.

Screening and identification of a DNA aptamer to concanavalin A and its application in food analysis

Herein, a novel aptamer that targets concanavalin A (Con A), a plant lectin, is isolated using systematic evolution of ligands by an exponential enrichment (SELEX) technique. Nine rounds of SELEX screening over an agarose spin column have resulted in enrichment of eight sequences having high affinity to Con A. The highest affinity sequence was selected as a potent aptamer and characterized it in detail. The evolved Con A aptamer (Con A-aptabody) is a 41 nt ssDNA that binds the Con A specifically with a dissociation constant of 172.7 ± 29.7 nM. In silico analyses predict the Con A-aptabody to form G-quadruplex due to its G-rich sequence (GGAAGGCGGAGGG). A detection method developed using Con A-aptabody is found to have a detection range of 10-750 ng/mL with limits of detection and quantification being 13.22 and 44.09 ng/mL, respectively. The utility of the method is demonstrated by analyzing jack bean (Canavalia ensiformis), kidney bean (Phaseolus vulgaris), wheat (Triticum spp.), mung bean (Vigna radiata), and lentil (Lens culinaris) for their Con A contents. Hence, the developed Con A-aptabody provides a useful substitute to Con A-antibody for food analysis and related applications.

Simple, benign, aqueous-based amination of polycarbonate surfaces

Polycarbonate is a desirable material for many applications due to its favorable mechanical and optical properties. Here, we report a simple, safe, environmentally friendly aqueous method that uses diamines to functionalize a polycarbonate surface with amino groups. The use of water as the solvent for the functionalization ensures that solvent induced swelling does not affect the optical or mechanical properties of the polycarbonate. We characterize the efficacy of the surface amination using X-ray photo spectroscopy, Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and contact angle measurements. Furthermore, we demonstrate the ability of this facile method to serve as a foundation upon which other functionalities may be attached, including antifouling coatings and oriented membrane proteins.

Facile photoimmobilization of proteins onto low-binding PEG-coated polymer surfaces

Immobilization of proteins onto polymer surfaces usually requires specific reactive functional groups. Here, we show an easy one-step method to conjugate protein covalently onto almost any polymer surface, including low protein-binding poly(ethylene glycol) (PEG), without the requirement for the presence of specific functional groups. Several types of proteins, including alkaline phosphatase, bovine serum albumin, and polyclonal antibodies, were photoimmobilized onto a PEG-coated polymer surface using a water-soluble benzophenone as photosensitizer. Protein functionality after immobilization was verified for both enzymes and antibodies, and their presence on the surface was confirmed by X-ray photoelectron spectroscopy (XPS) and confocal fluorescence microscopy. Conjugation of capture antibody onto the PEG coating was employed for a simplified ELISA protocol without the need for blocking uncoated surface areas, showing ng/mL sensitivity to a cytokine antigen target. Moreover, spatially patterned attachment of fluorescently labeled protein onto the low-binding PEG-coated surface was achieved with a projection lithography system that enabled the creation of micrometer-sized protein features.

Identification of novel adhesins of M. tuberculosis H37Rv using integrated approach of multiple computational algorithms and experimental analysis

Pathogenic bacteria interacting with eukaryotic host express adhesins on their surface. These adhesins aid in bacterial attachment to the host cell receptors during colonization. A few adhesins such as Heparin binding hemagglutinin adhesin (HBHA), Apa, Malate Synthase of M. tuberculosis have been identified using specific experimental interaction models based on the biological knowledge of the pathogen. In the present work, we carried out computational screening for adhesins of M. tuberculosis. We used an integrated computational approach using SPAAN for predicting adhesins, PSORTb, SubLoc and LocTree for extracellular localization, and BLAST for verifying non-similarity to human proteins. These steps are among the first of reverse vaccinology. Multiple claims and attacks from different algorithms were processed through argumentative approach. Additional filtration criteria included selection for proteins with low molecular weights and absence of literature reports. We examined binding potential of the selected proteins using an image based ELISA. The protein Rv2599 (membrane protein) binds to human fibronectin, laminin and collagen. Rv3717 (N-acetylmuramoyl-L-alanine amidase) and Rv0309 (L,D-transpeptidase) bind to fibronectin and laminin. We report Rv2599 (membrane protein), Rv0309 and Rv3717 as novel adhesins of M. tuberculosis H37Rv. Our results expand the number of known adhesins of M. tuberculosis and suggest their regulated expression in different stages.

Quantitative analysis of the functionalization of gallium phosphide with organic azides

Gallium phosphide (GaP) surfaces were functionalized with two different molecules that contain an azide moiety at their terminus. Compound 4-azidophenacyl bromide (4AB) is an aryl azide with a bromine group at its opposite terminus that provides easy identification of the molecule's presence on the surface with x-ray photoelectron spectroscopy (XPS). O-(2-aminoethyl)-O'-(2-azidoethyl)pentaethylene glycol (AAP) is a small poly(ethylene glycol) molecule with an amine group at its opposite terminus. Atomic force microscopy was used to identify the uniformity of the clean and functionalized GaP surfaces. Water contact angle revealed a more hydrophobic surface with AAP functionalization (33°) and even more hydrophobic (53°) with the 4AB functionalized surface compared to a clean surface (16°). XPS confirmed the presence of each of the organic azides on the surface. XPS was further used to calculate the adlayer thickness of each functionalization. This analysis revealed an adlayer thickness of about 8 Å for the 4AB functionalized surfaces compared to 1 Å for the AAP adlayer, which led to the conclusion that AAP functionalization only provided partial coverage. A stability study using 4AB-functionalized surfaces showed good stability in saline solutions with varying concentrations of hydrogen peroxide. Finally, inductively coupled plasma mass spectrometry was used to evaluate the gallium concentration in the stability solutions. While the functionalization with the organic azides did not provide complete suppression of gallium leaching, both of the azides decreased the leaching by 10-50%.

Covalent immobilization of ascorbate oxidase onto polycarbonate strip for L-ascorbic acid detection

Herein, a simple and rapid method is described for detection of L-ascorbic acid by ascorbate oxidase immobilized onto polycarbonate strip pre-activated by 1-fluoro-2-nitro-4-azidobenzene in photochemical reaction. Covalent attachment of ascorbate oxidase was confirmed by XPS studies. The immobilized-ascorbate oxidase shows higher pH, thermal and storage stability in comparison to free enzyme.

Immobilized Candida antarctica lipase B: Hydration, stripping off and application in ring opening polyester synthesis

This work reviews the stripping off, role of water molecules in activity, and flexibility of immobilized Candida antarctica lipase B (CALB). Employment of CALB in ring opening polyester synthesis emphasizing on a polylactide is discussed in detail. Execution of enzymes in place of inorganic catalysts is the most green alternative for sustainable and environment friendly synthesis of products on an industrial scale. Robust immobilization and consequently performance of enzyme is the essential objective of enzyme application in industry. Water bound to the surface of an enzyme (contact class of water molecules) is inevitable for enzyme performance; it controls enzyme dynamics via flexibility changes and has intensive influence on enzyme activity. The value of pH during immobilization of CALB plays a critical role in fixing the active conformation of an enzyme. Comprehensive selection of support and protocol can develop a robust immobilized enzyme thus enhancing its performance. Organic solvents with a log P value higher than four are more suitable for enzymatic catalysis as these solvents tend to strip away very little of the enzyme surface bound water molecules. Alternatively ionic liquid can work as a more promising reaction media. Covalent immobilization is an exclusively reliable technique to circumvent the leaching of enzymes and to enhance stability. Activated polystyrene nanoparticles can prove to be a practical and economical support for chemical immobilization of CALB. In order to reduce the E-factor for the synthesis of biodegradable polymers; enzymatic ring opening polyester synthesis (eROPS) of cyclic monomers is a more sensible route for polyester synthesis. Synergies obtained from ionic liquids and immobilized enzyme can be much effective eROPS.

Pressure: a novel tool for enzyme-linked immunosorbent assay procedure

The enzyme-linked immunosorbent assay (ELISA) technique is the backbone of the diagnostic assay for detection of infectious and allergic diseases. Here, we demonstrate a unique ELISA method for the detection of an antigen or antibody, in which ELISA steps are carried out under pressure instead of conventional thermal incubation. Pressure-mediated ELISA (PELISA), carried out in 1 h shows more than a 2-fold increase in absorbance value than the control experiment carried out at the same time and temperature without applying pressure. Estimation of total IgE by the 1-h PELISA method gives similar absorbance value (1.081±0.031, 823.12 IU) to that obtained by 3-h heat-mediated ELISA on an activated surface (HELISA) (1.165±0.037, 810.96 IU). Since PELISA is sensitive, specific, and reproducible (intra- and interassay CVs were 6.47% and 9.65%, respectively), it could be an excellent alternative to HELISA or conventional ELISA procedures.

Fabrication of substrate-independent protein microarrays using polyelectrolyte scaffolding

While significant advances have been made in regard to protein microarray surface chemistries, the surface modification strategies developed are generally substrate-specific and cannot be interchanged between different materials and platforms. This current lack of substrate-independent surface modification strategies makes it difficult to compare or transfer fabrication methodologies between dissimilar substrates. To address this shortcoming, we have developed an interchangeable surface scaffold, which can be utilized to fabricate protein microarrays on a variety of materials with nearly identical results. The surface scaffold is deposited by alternate electrostatic assembly of the cationic and anionic polyelectrolytes poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate), respectively. Once assembled, the polyelectrolyte scaffold serves to mask the underlying surface properties of different materials and convert them to the surface properties of the scaffold itself. By obtaining common surface properties across different materials, it is possible to eliminate differences in protein surface density, spot diameter, and nonspecific binding of analytes on substrates as diverse as glass, gold, mica, silicon, and polymer. The concept of substrate-independent polyelectrolyte scaffolding described here provides researchers with a powerful new tool that can be utilized to compare, optimize, and transfer useful protein microarray surface chemistries across different materials and platforms.

Synthesis, characterization and in vitro activity of a surface-attached antimicrobial cationic peptide

Infection associated with implanted biomaterials is common and costly and such infections are extremely resistant to antibiotics and host defenses. Consequently, there is a need to develop surfaces which resist bacterial adhesion and colonization. The broad spectrum synthetic cationic peptide melimine has been covalently linked to a surface via two azide linkers, 4-azidobenzoic acid (ABA) or 4-fluoro-3-nitrophenyl azide (FNA), and the resulting surfaces characterized by X-ray photoelectron spectroscopy and contact angle measurements. The quantity of bound peptide was estimated by a modified Bradford assay. The antimicrobial efficacy of the two melimine-modified surfaces against Pseudomonas aeruginosa and Staphylococcus aureus was compared by scanning electron microscopy (SEM) and fluorescence microscopy. Attachment of melimine via ABA gave an approximately 4-fold greater quantity of melimine bound to the surface than attachment via FNA. Surfaces melimine-modified by either attachment strategy showed significantly reduced bacterial adhesion for both strains of bacteria. P. aeruginosa exposed to ABA-melimine and FNA-melimine surfaces showed marked changes in cell morphology when observed by SEM and a reduction of approximately 15-fold (p < 0.001) in the numbers of adherent bacteria compared to controls. For the ABA-melimine surface there was a 33% increase in cells showing damaged membranes (p = 0.0016) while for FNA-melimine there was no significant difference. For S. aureus there were reductions in bacterial adhesion of approximately 40-fold (p < 0.0001) and 5-fold (p = 0.008) for surfaces modified with melimine via ABA or FNA, respectively. There was an increase in cells showing damaged membranes on ABA-melimine surfaces of approximately 87% (p = 0.001) compared to controls, while for FNA-melimine there was no significant difference observed. The data presented in this study show that melimine has excellent potential for development as a broad spectrum antimicrobial coating for biomaterial surfaces. Further, it was observed that the efficacy of antimicrobial activity is related to the method of attachment.

Chemical strategies for generating protein biochips

Protein biochips are at the heart of many medical and bioanalytical applications. Increasing interest has been focused on surface activation and subsequent functionalization strategies for immobilizing these biomolecules. Different approaches using covalent and noncovalent chemistry are reviewed; particular emphasis is placed on the chemical specificity of protein attachment and on retention of protein function. Strategies for creating protein patterns (as opposed to protein arrays) are also outlined. An outlook on promising and challenging future directions for protein biochip research and applications is also offered.

Protein Immobilization Strategies for Protein Biochips

In the past few years, protein biochips have emerged as promising proteomic and diagnostic tools for obtaining information about protein functions and interactions. Important technological innovations have been made. However, considerable development is still required, especially regarding protein immobilization, in order to fully realize the potential of protein biochips. In fact, protein immobilization is the key to the success of microarray technology. Proteins need to be immobilized onto surfaces with high density in order to allow the usage of small amount of sample solution. Nonspecific protein adsorption needs to be avoided or at least minimized in order to improve detection performances. Moreover, full retention of protein conformation and activity is a challenging task to be accomplished. Although a large number of review papers on protein biochips have been published in recent years, few have focused on protein immobilization technology. In this review, current protein immobilization strategies, including physical, covalent, and bioaffinity immobilization for the fabrication of protein biochips, are described. Particular consideration has been given to oriented immobilization, also referred to as site-specific immobilization, which is believed will improve homogeneous surface covering and accessibility of the active site.

Functionalization of Poly(ethylene terephthalate) Fibers by Photografting of a Carbohydrate Derivatized with a Phenyl Azide Group

Grafting of a new carbohydrate UV-reactive molecule, an azidophenyl lactamine (AzPhLac), was achieved on fibers of three different diameters: 12, 18, and 32 microm. Adsorption of AzPhLac on fibers was obtained by using the dip-coating method in solution. The effect of the solution concentration on surface density and yield of grafted AzPhLac was investigated. Surface densities in the range 3-67 nmol/cm2 were obtained without marked difference related to the diameter of the fiber. Quantitative grafting was obtained with a surface of fiber of 1 cm2 and the lowest concentration (0.5 mM) of AzPhLac solution. The surface density and grafting yield decreased with the available surface of the fibers. This phenomenon could be attributed to a masking core-shell effect with outer fibers in the shell preventing the UV grafting of the fibers located in the core of the fibers' bundles. Scanning electron (SEM) and atomic force (AFM) microscopic observations suggested that homogeneous grafting might be obtained.

Photoreactive cellulose membrane—A novel matrix for covalent immobilization of biomolecules

We report a simple and mild procedure for the preparation of a photoreactive cellulose membrane capable of forming a covalent bond with a biomolecule in presence of 365 nm UV light. Photoreactive cellulose membrane was prepared by the reaction of fluoro group of 1-fluoro-2-nitro-4-azidobenzene (FNAB) and hydroxyl group of the cellulose in an alkaline medium. X-ray photoelectron spectroscopy (XPS) of the photoreactive cellulose confirmed the incorporation of FNAB moiety. Azido group of the photoreactive membrane on exposure to UV light transforms into highly reactive nitrene which binds with a protein. The efficacy of the activated membrane was checked by immobilizing glucose oxidase (GOD) onto it in presence of light. Immobilized GOD was found to have improved thermal, pH and storage stability. Photoreactive cellulose membrane was successfully used in enzyme-linked immunosorbent assay (ELISA) technique. The antibody immobilized onto such support by UV irradiation in 30 min showed similar ELISA value than the antibody immobilized onto a polystyrene ELISA plate in 12h incubation at 4 degrees C by conventional method.

Light-induced in situ patterning of DNA-tagged biomolecules and nanoparticles

We present an in situ method for the selective manipulation of DNA-tagged nano-objects such as vesicles or gold colloids in aqueous solution, at neutral pH. The method makes use of the photosensitizer concept found in photodynamic therapy. Here, single-stranded DNA is immobilized onto a surface via the biotin/streptavidin linkage. If the streptavidin is fluorescently labeled, reactive species will be created during laser-induced photobleaching of the label. These reactive species can then completely or partly suppress the DNA hybridization and cause the removal of the streptavidin. The technique thereby enables a dynamic on-off control over surface density of immobilized DNA-tagged nano-objects. Furthermore, combining this in situ manipulation of DNA with prepatterning of single-stranded DNA in the micro and later in the nano range provides a means for the dynamic patterning required for applications in biosensing and nanotechnology.

Organic azides: an exploding diversity of a unique class of compounds

Since the discovery of organic azides by Peter Griess more than 140 years ago, numerous syntheses of these energy-rich molecules have been developed. In more recent times in particular, completely new perspectives have been developed for their use in peptide chemistry, combinatorial chemistry, and heterocyclic synthesis. Organic azides have assumed an important position at the interface between chemistry, biology, medicine, and materials science. In this Review, the fundamental characteristics of azide chemistry and current developments are presented. The focus will be placed on cycloadditions (Huisgen reaction), aza ylide chemistry, and the synthesis of heterocycles. Further reactions such as the aza-Wittig reaction, the Sundberg rearrangement, the Staudinger ligation, the Boyer and Boyer-Aubé rearrangements, the Curtius rearrangement, the Schmidt rearrangement, and the Hemetsberger rearrangement bear witness to the versatility of modern azide chemistry.

RGD peptide-conjugated poly(dimethylsiloxane) promotes adhesion, proliferation, and collagen secretion of human fibroblasts

A novel technique for conjugating Arg-Gly-Asp (RGD) peptides to poly(dimethylsiloxane) (PDMS) surfaces as well as its application to cell culture is presented in this paper. This technique performs RGD conjugation to PDMS through photochemical immobilization of functional NHS groups to PDMS surface followed with linking RGD peptide to the surface via coupling reaction with NHS. A bifunctional photolinker, N-sulfosuccinimidyl-6-(4'-azido-2'-nitrophenylamino)hexanoate (sulfo-SANPAH), was used to conjugate RGD peptide to the surface. Compared to existing methods for peptide conjugation to PDMS, this technique is convenient, efficient, and free of organic contamination to PDMS surfaces. It can also be used to conjugate other peptides or proteins to most polymeric materials. In addition, cell culture studies showed that the RGD-conjugated PDMS surfaces promoted the adhesion, proliferation, and collagen production of human skin fibroblasts (HSFs). Finally, the RGD-conjugated PDMS surfaces are resistant to autoclaving and UV irradiation, which enables them to be repeatedly used in cell culture studies.