silicon and hydroxyethyl-methacrylate

Silicon rubber has been widely used in the biomedical field due to its excellent mechanical properties and physiological inertia. However, the hydrophobic properties of silicon rubber surfaces limit their further application. Therefore, constructing a silicon rubber coating with hydrophilic and low-friction surface properties would be highly significant. Existing methods to achieve such coatings, including grafting polymer brushes and the deposition of hydrophilic materials, suffer from several deficiencies such as complicated coating processes and insufficient coating firmness. In this paper, we report a hydrophilic polymer poly(hydroxyethyl methacrylate) (PHEMA) coating that can easily coat the surface of silicon rubber to provide low-friction performance. Sample silicon rubber was treated with benzophenone and hydroxyethyl methacrylate monomer solution in turn. The as-prepared coating was characterized by infrared spectroscopy, X-ray photoelectron spectroscopy, white light interference, and MFT-5000 wear test. The results indicated that the PHEMA coating had excellent hydrophilic properties (with a low contact angle of 9.39°) compared to uncoated silicon rubber. As the concentration of glycerol in the monomer solution was increased, the thickness and surface roughness of the as-prepared coating gradually decreased. The coating was firmly adsorbed on the substrate, and it had a zero-class bonding strength. In addition, the as-prepared coating demonstrated good friction-reduced properties, with the coefficient of friction being reduced by 98.0% compared with the uncoated silicon rubber in simulated blood. In summary, a hydrophilic and low-friction coating was successfully prepared using a simple method, and the results reported herein provide valuable insight into the surface design of similar soft materials.

Topics: Friction; Methacrylates; Polyhydroxyethyl Methacrylate; Rubber; Silicon; Surface Properties

Covalently immobilized mixed films of oligonucleotide and oligomer components on glass and silicon surfaces are reported. This work has investigated how such films can improve selectivity for the detection of multiple base-pair mismatches. The intention was to introduce a "matrix isolation" effect on oligonucleotide probe molecules by surrounding the probes with oligomers, thereby reducing oligonucleotide-to-oligonucleotide and/or oligonucleotide-to-surface interactions. Thiol-functionalized oligonucleotide was coupled onto (3-aminopropyl)trimethoxysilane (APTMS) via a heterobifunctional linker, succinimidyl 4-[N-maleimidomethyl]cyclohexane-1-carboxylate (sulfo-SMCC). Using a variety of monomers such as 2-hydroxyethyl methacrylate (HEMA), oligomers were grown by surface-initiated atom transfer radical polymerization (ATRP) from a bromoisobutyryl NHS ester initiator which was immobilized onto APTMS sites that coated glass and oxidized silicon substrates. Various surface modification steps on silicon substrates were characterized by ellipsometry, wettability, atomic force microscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. Polymerized HEMA (PHEMA) in mixture with oligonucleotide probes was evaluated for fluorescence transduction of hybridization. The presence of PHEMA was found to provide a sharper melt curve for hybrids containing both fully complementary and three base-pair mismatched targets, and this surface derivatization also minimized non-selective adsorption. The maximum increase in slope was improvement by a factor of 3-fold. An increase of up to 30% in difference of melting temperatures between fully complementary and 3 base-pair mismatched targets was achieved using PHEMA. The results suggest that the presence of oligomers dispersed among DNA hybrids can improve selectivity through what is believed to be a reduction of dispersity of interactions of probes with targets, and probes within their local environment at a surface.

Topics: Adsorption; Benzaldehydes; Biosensing Techniques; Cross-Linking Reagents; Fluorescence; Glass; Kinetics; Methacrylates; Nucleic Acid Denaturation; Oligonucleotides; Oxidation-Reduction; Polymers; Propylamines; Sensitivity and Specificity; Silanes; Silicon; Surface Properties; Transition Temperature

We have used a very large scale integration process to generate well-defined patterns of polymerized 2-hydroxyethyl methacrylate (HEMA) on patterned Si(100) surfaces. An atom transfer radical polymerization initiator covalently bonded to the patterned surface was employed for the graft polymerization of HEMA to prepare the poly(2-hydroxyethyl methacrylate) (PHEMA) brushes. After immersing wafers presenting lines of these polymers in water and cyclohexane, we observed brush- and mushroom-like regions, respectively, for the PHEMA brushes, with various pattern resolutions. The PHEMA brushes behaved as "tentacles" that captured ferritin complexes from aqueous solution through entanglement between the brushes and the ferritin proteins, whose ferritins were trapped due to the collapsing of the PHEMA. Using high-resolution scanning electron microscopy, we observed patterned ferritin iron cores on the Si surface after thermal removal of the patterned PHEMA brushes and ferritin protein sheaths.

Topics: Adsorption; Cyclohexanes; Ferritins; Methacrylates; Microscopy, Electron, Scanning; Models, Chemical; Proteins; Silicon; Solvents; Surface Properties; Time Factors; Water

To investigate the in vitro dehydration process of conventional hydrogel and silicone-hydrogel contact lens materials.. Eight conventional hydrogel and five silicone-hydrogel contact lenses were dehydrated under controlled environmental conditions on an analytical balance. Data were taken at 1-min intervals and dehydration curves of cumulative dehydration (CD), valid dehydration (VD), and dehydration rate (DR) were obtained. Several quantitative descriptors of the dehydration process were obtained by further processing of the information.. Duration of phase I (r(2) = 0.921), CD at end of phase I (r(2) = 0.971), time to achieve a DR of -1%/min (r(2) = 0.946) were strongly correlated with equilibrium water content (EWC) of the materials. For each individual sample, the VD at different time intervals can be accurately determined using a 2nd order regression equation (r(2) > 0.99 for all samples). The first 5 min of the dehydration process show a relatively uniform average CD of about -1.5%/min. After that, there was a trend towards higher average CD for the following 15 min as the EWC of the material increases (r(2) = 0.701). As a consequence, average VD for the first 5 min displayed a negative correlation with EWC (r(2) = 0.835), and a trend towards uniformization among CL materials for the following periods (r(2) = 0.014). Overall, silicone-hydrogel materials display a lower dehydration, but this seems to be primarily due to their lower EWC.. DR curves under the conditions of the present study can be described as a three-phase process. Phase I consists of a relatively uniform DR with a duration that ranges from 10 to almost 60 min and is strongly correlated with the EWC of the polymer as it is the CD during this phase. Overall, HEMA-based hydrogels dehydrate to a greater extent and faster than silicone-hydrogel materials. There are differences in water retention between lenses of similar water content and thickness that should be further investigated.

Topics: Contact Lenses, Hydrophilic; Dehydration; Hydrogels; Methacrylates; Silicon

The in vitro uptake and release behaviour of cromolyn sodium, ketotifen fumarate, ketorolac tromethamine and dexamethasone sodium phosphate with silicon-containing (lotrafilcon and balafilcon) and p-HEMA-containing (etafilcon, alphafilcon, polymacon, vifilcon and omafilcon) hydrogel contact lenses indicated that both drug and material affected the uptake and release behaviour. Rapid uptake and release (within 50 min) was observed for all drugs except ketotifen fumarate which was more gradual taking approximately 5h. Furthermore, the maximum uptake differed significantly between drugs and materials. The highest average uptake (7879+/-684 microg/lens) was cromolyn sodium and the lowest average uptake (67+/-13 microg/lens) was dexamethasone sodium phosphate. Partial release of the drug taken up was observed for all drugs except dexamethasone sodium phosphate where no release was detected. Sustained release was demonstrated only by ketotifen fumarate. Drug uptake/release appeared to be a function of lens material ionicity, water and silicon content. The silicon-containing materials released less drug than the p-HEMA-containing materials. The lotrafilcon material demonstrated less interactions with the drugs than the balafilcon material which can be explained by their different bulk composition and surface treatment.

Topics: Adsorption; Contact Lenses, Hydrophilic; Hydrogel, Polyethylene Glycol Dimethacrylate; Methacrylates; Silicon; Solubility