Tough Magnetic Chitosan Hydrogel Nanocomposites for Remotely Stimulated Drug Release

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 <i>in situ</i> 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 <i>in situ</i> 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 <i>in situ</i> 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

Synergistic Effects of Surface Chemistry and Topologic Structure from Modified Microarc Oxidation Coatings on Ti Implants for Improving Osseointegration

Microarc oxidation (MAO) coating containing Ca, P, Si, and Na elements on a titanium (Ti) implant has been steam-hydrothermally treated and further mediated by post-heat treatment to overcome the compromised bone-implant integration. The bone regeneration, bone-implant contact, and biomechanical push-out force of the modified Ti implants are discussed thoroughly in this work. The best <i>in vivo</i> performances for the steam-hydrothermally treated one is attributed to the synergistic effects of surface chemistry and topologic structure. Through post-heat treatment, we can decouple the effects of surface chemistry and the nanoscale topologic structure easily. Attributed to the excellent <i>in vivo</i> performance of the surface-modified Ti implant, the steam-hydrothermal treatment could be a promising strategy to improve the osseointegration of the MAO coating covered Ti implant

Structure, MC3T3-E1 Cell Response, and Osseointegration of Macroporous Titanium Implants Covered by a Bioactive Microarc Oxidation Coating with Microporous Structure

Macroporous Ti with macropores of 50–400 μm size is prepared by sintering Ti microbeads with different diameters of 100, 200, 400, and 600 μm. Bioactive microarc oxidation (MAO) coatings with micropores of 2–5 μm size are prepared on the macroporous Ti. The MAO coatings are composed of a few TiO₂ nanocrystals and lots of amorphous phases with Si, Ca, Ti, Na, and O elements. Compared to compact Ti, the MC3T3-E1 cell attachment is prolonged on macroporous Ti without and with MAO coatings; however, the cell proliferation number increases. These results are contributed to the effects of the space structure of macroporous Ti and the surface chemical feature and element dissolution of the MAO coatings during the cell culture. Macroporous Ti both without and with MAO coatings does not cause any adverse effects in vivo. The new bone grows well into the macropores and micropores of macroporous Ti with MAO coatings, showing good mechanical properties in vivo compared to Ti, MAO-treated Ti, and macroporous Ti because of its excellent osseointegration. Moreover, the MAO coatings not only show a high interface bonding strength with new bones but also connect well with macroporous Ti. Furthermore, the pushing out force for macroporous Ti with MAO coatings increases significantly with increasing microbead diameter