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Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS–Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe2.85O4and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe2O3and hydroxyapatite.

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As one of important biomaterials for localized drug delivery system, chitosan hydrogel still suffer several challenges, including poor mechanical properties, passive drug release behavior and lack of remote stimuli response. To address these challenges, a facile in situ hybridization method was reported for fabricate tough magnetic chitosan hydrogel (MCH), which remotely switched drug release from passive release to pulsatile release under a low frequency alternating magnetic field (LAMF). The in situ hybridization method avoided the aggregation of magnetic nanoparticles (MNPs) in hydrogel, which simultaneously brings 416% and 265% increase in strength and elastic modulus, respectively. The mechanical property enhancement was contributed by the physical crosslinking of in situ synthesized MNPs. When a LAMF with 15 min ON-15 min OFF cycles was applied to MCH, the fraction release showed zigzag shape and pulsatile release behavior with quick response. The cumulative release and fraction release of drug from MCH were improved by 67.2% and 31.9%, respectively. MTT results and cell morphology indicated that the MCH have excellent biocompatibility and no acute adverse effect on MG-63 cells. The developed tough MCH system holds great potential for applications in smart drug release system with noninvasive characteristics and magnetic field stimulated drug release behavior.

The aim of this study was to investigate the healing characteristics and the underlying signalling pathway of human dermal fibroblasts under the influence of pulsed electrical stimulation (PES). Primary human dermal fibroblasts were seeded on polypyrrole-coated polyester fabrics and subjected to four different PES protocols. The parameters of the rectangular pulse included potential intensity (50 and 100 mV/mm) and stimulation time (pulse width 300 s within a period of 600 s, and pulse width 10 s within a period of 1200 s). Our study revealed that PES moderately improved the ability of the cells to migrate in association with a statistically significant (p < 0.05) increase of FGF2 secretion by the PES-exposed fibroblasts. These exposed fibroblasts were able to contract collagen gel matrix up to 48 h and this collagen gel contraction paralleled an increase in α-SMA mRNA expression and protein production from the PES-exposed fibroblasts. Interestingly, the effect of PES on the human fibroblasts involved the Smad signalling pathway, as we observed higher levels of phosphorylated Smad2 and Smad3 in the stimulated groups compared to the control groups. Overall, this study demonstrated that PES modulates fibroblast activities through the Smad signalling pathway, thus providing new mechanistic insights related to the use of PES to promote wound healing in humans. Copyright © 2015 John Wiley & Sons, Ltd.