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In order to improve bioactivity of hydroxyapatite (HA), the surface of HA was modified with calcium or magnesium ion irradiation. Calcium ion irradiation improved bioactivity of HA up to ion dose 1014 ions/cm2, whereas magnesium ion irradiation did not affect bone-like apatite formation. It is found that this different phenomena were attributed to surface electrical potential. Ion irradiation generally induces surface nano-scopic damage, however the strength of HA was not significantly affected by ion irradiation. From cell proliferation, no toxicity of HA irradiated with calcium ions was confirmed. From these results, the effectiveness of calcium ion irradiation on the treatment of bone defect using HA is confirmed.

We investigated the temperature-responsive gelation of collagen/genipin solutions using pepsin-solubilized collagen (PSC) and acid-solubilized collagen (ASC) as substrates. Gelation occurred in the PSC/genipin solutions at genipin concentrations 0–2 mM under moderate change in temperature from 25 to 37°C. The PSC/genipin solutions exhibited fluidity at room temperature for at least 30 min, whereas the ASC/genipin solutions rapidly reached gel points. In specific cases PSC would be preferred over ASC as an injectable gel system. The temperature-responsive gelation of PSC/genipin solutions was due to temperature responses to genipin crosslinking and collagen fibril formation. The elastic modulus of the 0.5% PSC/genipin gel system could be adjusted in a range of 2.5 to 50 kPa by the PSC and genipin concentrations, suggesting that a PSC/genipin solution is a potential injectable gel system for drug and cell carriers, with mechanical properties matching those of living tissues.

Manual pipette methods are conventionally used to determine the viscosity (η) of gelatin solutions. The purpose of this study is to demonstrate the accuracy and precision of viscosity measurements of gelatin solutions using a rotational rheometer. Seven gelatin samples with different molecular weights were tested. The 2 × standard deviations of the obtained η were within ± 2.4 % of the mean values in triplicate measurements, suggesting the evident precision of the viscosity measurements. Accuracy was demonstrated by the triplicate measurements of the standard liquids for a viscometer. The sample volume required by the rheometer was only 0.6 mL, whereas gelatin solutions of approximately 100 mL are usually required for pipette methods. We propose viscosity measurement using a rheometer as an alternative method to the pipette ones. [ABSTRACT FROM AUTHOR]

AbstractProgress in stem cell research has prioritized the refinement of cell-labeling techniques for in vitroand in vivobasic and therapeutic studies. Although quantum dots, because of their optical properties, are emerging as favorable nanoparticles for bioimaging, substantial refinements or modifications that would improve their biocompatibility are still required. We report here that internalizing quantum dots (i-QDs) generated by their conjugation with an internalizing antibody against a heat shock protein-70 family stress chaperone, mortalin, offered an efficient, genetically noninvasive, nontoxic, and functionally inert way to label mesenchymal stem cells (MSCs). The i-QD-labeled MSCs underwent normal adipocyte, osteocyte, and chondrocyte differentiation in vitroand in vivo, suggesting the potential application of i-QDs in in vivodiagnostics, regenerative and therapeutic medicine. [ABSTRACT FROM AUTHOR]