Thermosensitive hybrid hydrogels were prepared by chemical crosslinking using poly [N-isopropylacrylamide-co-(3methacryloxypropyltrimethoxysilane)] (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 1C. 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.

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Hydrogel as a good water absorbent has attracted great research interest. A series of hydrogel based on polyethylene oxide (PEO) and acrylic acid (AAc) was prepared by applying gamma radiation with variation in the concentration of acrylic acid. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) were used to characterize the PEO/ AAc hydrogel. The properties of the prepared hydrogels such as gel content, swelling behavior, tensile strength, and pH sensitivity were evaluated. The formation of the hydrogels was confirmed from FTIR spectra. SEM images showed the inner porous structure of the hydrogels. The dose of gamma radiation was optimized to get a hydrogel with good swelling property and mechanical strength. The swelling ratio and gel content of the hydrogels were increased with increasing acrylic acid content. The pH of the solutions affected the swelling which indicated the pH-responsive property of the prepared hydrogels. Swelling of the prepared hydrogels in sodium chloride salt solutions decreased with increasing the ionic strength.