Title: Silica nanoparticle-crosslinked thermosensitive hybrid hydrogels as potential drug-release carriers
Abstract: Thermosensitive hybrid hydrogels were prepared by chemical crosslinking using poly[N-isopropylacrylamide-co-(3-methacryloxypropyltrimethoxysilane)] (pNS) copolymer chains as the backbone and silica nanoparticles (SiP) as crosslinkers. The preparation of these hybrid hydrogels involved mixing a reactive side chain-branched copolymer (pNS) solution with a SiP suspension at 25 °C. During the mixing of these components, caffeine was added as a model drug to form a thermo-responsive drug delivery system. The as-prepared caffeine-loaded hydrogels do not require any further processing. The effects of temperature on the equilibrium swelling ratios and on the release of caffeine from these hybrid hydrogels at different temperatures and with different hydrogel compositions were thoroughly investigated. We found that this novel system provides controllable drug loading and a positive drug-release pattern. More than 90% of the loaded drugs were released at both high and low temperatures, with a faster release rate at higher temperatures. Drug can be loaded into the silica nanoparticle-crosslinked thermosensitive hydrogels while preparing the hydrogels by mixing the silica nanoparticle suspension and copolymer solution at room temperature. These hydrogels can then be used for release study without any other processing like washing, purification, etc., as the copolymer and other chemicals were purified in advance. The simplicity of this preparation method allows a great control of drug loading. Because of the high swelling ratios of these hydrogels, cumulative release is high (more than 90%) in both higher and lower temperature than lower critical solution temperature.