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Alam M.A.,Kumamoto University | Alam M.A.,Noakhali Science and Technology University | Takafuji M.,Kumamoto University | Ihara H.,Kumamoto University | Ihara H.,Kumamoto Institute for PhotoElectro Organics Phoenics
Polymer Journal | Year: 2014

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. © 2014 The Society of Polymer Science, Japan (SPSJ).

Ashraful Alam M.,Kumamoto University | Takafuji M.,Kumamoto University | Ihara H.,Kumamoto University | Ihara H.,Kumamoto Institute for PhotoElectro Organics Phoenics
Journal of Colloid and Interface Science | Year: 2013

A simple methodology for the preparation of thermosensitive organic-inorganic hybrid hydrogels using silica nanoparticle-mediated polymer networks is described. A thermosensitive copolymer poly[N-isopropylacrylamide-co-(3-methacryloxypropyltrimethoxysilane)], (pNS), with reactive side chains (SiOCH3) was first synthesized by free radical polymerization using N-isopropylacrylamide (NIPAAm) and 3-methacryloxypropyltrimethoxysilane (MAPTS). Then, simple mixing of the aqueous solution of this copolymer with silica nanoparticle (SiP) suspensions at room temperature led to the formation of thermosensitive hybrid hydrogels cross-linked with silica nanoparticles (SiP) which did not require any other processing like washing for the removal of unreacted monomers and initiators. The effects of SiP content on gelation abilities, temperature-responsive behaviors, swelling and deswelling kinetics, and mechanical properties of the hydrogels were investigated. The results showed that transparent hybrid hydrogels with adjustable network structures were obtained within a few minutes to a couple of hours depending on the concentration of the copolymers and the silica nanoparticles. The hybrid hydrogels exhibited a lower critical solution temperature (LCST) of around 33°C with no significant deviation from conventional poly(N-isopropylacrylamide) hydrogels; the LCST was not significantly affected by the concentration of silica nanoparticles (which in these systems serve as the cross-linkers). In addition, the hydrogels showed significantly large equilibrium swelling ratios, improved mechanical strength, and suitable deswelling behavior, which can easily be tuned by varying the composition of the hybrid hydrogels. © 2013 Elsevier Inc.

Takafuji M.,Kumamoto University | Takafuji M.,Kumamoto Institute for PhotoElectro Organics Phoenics | Alam M.A.,Kumamoto University | Alam M.A.,Noakhali Science and Technology University | And 3 more authors.
Journal of Colloid and Interface Science | Year: 2015

Spherical hybrid hydrogel microparticles were facilely fabricated by particulation of an aqueous mixture of hydrophilic copolymer with alkoxysilyl side chains and silica nanoparticles in water/silicone oil suspensions. Inside the aqueous phase, the copolymers were webbed with silica nanoparticles to form polymer network through the silane coupling reactions between reactive side chains of copolymer with the silanol groups on silica nanoparticles. An amino-functionalized silane coupling reagent was used to terminate remaining reactive sites at the surface of the hydrogel particles to avoid aggregation. The size of the spherical hydrogel particles was well controlled by the viscosity of the silicone oil, whereas their properties were controlled by composition. The mechanical strength of the microspherical hybrid hydrogel was increased significantly with increasing the concentration of silica nanoparticles. © 2015 Elsevier Inc.

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