This paper describes the preparation and surface characterization of maleimide-activated silicone elastomer (PDMS(MCC)) followed by covalent functionalization using thiol-terminated DNA sequences (primary oligo). The stability of this attachment chemistry was demonstrated by the retention of the primary oligo through the process of hybridization with a labeled complementary DNA sequence. In these studies, the hybridized labeled DNA oligomers were detected using confocal fluorescence microscopy. We have employed a vapor deposition technique in which a plasma-treated silicone elastomer (PDMS(OH)) was exposed to vapors of 3-(aminopropyl)triethoxysilane (APTS) under vacuum, to yield the amine-functionalized silicone elastomer (PDMS(NH)(2)). PDMS(NH)(2) was further coupled with a heterofunctional cross-linker, sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate to obtain PDMS(MCC). The surface functionalities of the elastomers were characterized using contact angle measurements and X-ray photoelectron spectroscopy. Surface-modified silicone elastomers appear to be promising substrates for use as substrates for disposable microarrays.
The oil-repellent performance of a poly(dimethylsiloxane)-based biomimetic replica (PDMS-replica) was tuned by modifying its surface chemical composition. PDMS-replica possessing a complementary combination of hierarchical roughness and mixed -CF(3) and -SiCH(3) terminal functionality was prepared in the presence of a surface-modifying agent, using nanocasting based on soft lithography. PDMS-replica showed superhydrophobicity and enhanced oil repellency, theta(oil) approximately 86 degrees . PDMS-replica was further modified with silica nanoparticles followed by chemical vapor deposition of (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trichlorosilane. The -CF(3) terminal, silica-modified PDMS-replica (i.e., PDMS-replica(silica/CF(3))) showed both superhydrophobic and high oil-repellent properties (advancing theta(oil) approximately 120 degrees ). During the process of each chemical transformation, the surface pattern present on PDMS-replica was preserved and monitored using scanning electron microscopy. Surface chemical compositions of PDMS-replica and PDMS-replica(silica/CF(3)) were determined using X-ray photoelectron spectroscopy. Understanding the extent of adhesion on a biomimetic replica possessing different surface chemical compositions and roughness would provide fundamental information for various applications.
UCM is feasible for term and late preterm infants who are depressed at birth. A larger clinical trial is needed to evaluate long-term benefits of UCM in neonates with HIE.
Silica-alumina catalysts of varying acidity were used for polymerization of hexamethyl cyclotrisiloxane and octamethyl cyclotetrasiloxane monomers (cyclic trimer and tetramer, respectively). Acidic sites of silica-alumina are responsible for the polymerization and variation in the acidity of the catalyst were shown to influence the polymerization significantly. Mordenite type zeolites with low silica-to-alumina ratio (Ç 5) gave low yields of polymer from tetramer and zeolite ZSM-5 with a much higher silica-to-alumina ratio ( Ç 40) was found to be a very efficient catalyst for polymerization. Studies on the effect of water on the polymerization suggested that the polymerization (rate and yield) depended to some extent on the amount of water present in the system. The products were characterized using FTIR,Si-NMR, and GPC techniques. A plausible mechanism for polymerization of cyclic siloxane monomers on silica-alumina catalysts was proposed.
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