Hydrogel-reinforced polypyrrole electroactuator.

Robust electroactuators that are lightweight, power-efficient and capable of generating high forces at a low actuation voltage are of great demand in the design of micro-electromechanical systems (MEMS) for biomedical applications. In this work, electroactive composite films of alginate hydrogel and polypyrrole/polyethylene glycol (PPy/PEG) are synthesized and characterized as actuators for driving an implantable insulin micropump. A porous and flexible alginate hydrogel back layer is used to mechanically reinforce the PPy/PEG film by enhancing the actuator's resistance to its generated tension but without increase of its overall rigidness. Scanning electron microscopy (SEM) reveals that the PPy/PEG grows through the alginate hydrogel layer, thus forming a well-integrated composite and eliminating the possibility of delamination in long term applications. Mechanical test proves this alginate-PPy/PEG composite film to be more stretchable than the PPy/PEG film, and electroactuation test in phosphate buffered saline (PBS) demonstrated a large deformation at +2 V in 60 s. Taken together, our work here indicates great promise for this new type of composite actuator to be used in biomedical MEMS.

Effects of D-galactose on ageing of rat mesenchymal stem cells / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the effects of D-galactose (D-gal) on aging of rat marrow mesenchymal stem cells (MSCs) and its mechanism.</p><p><b>METHODS</b>MSCs isolated from young (7 d) SD rats were randomly divided into four groups:control group, 1g/L, 10g/L and 50g/L D-gal treatment groups. In control group MSCs were cultured in DMEM containing 10% FBS for 48 h. In the D-gal treatment groups, MSCs were cultured in DMEM containing 10% FBS with 1g/L, 10g/L or 50g/L D-gal for 48 h. The senescence-associated changes were examined with SA-β-galactosidase (SA-β-gal) staining, the expressions of p53, p21 and p16 were detected by Western blot. The living and apoptotic cells were determined by AO/EB staining. Cell proliferation was detected by MTT assay. SOD activity was measured by xanthine oxidase method, and the MDA content was estimated with thiobarbituric acid (TBA) method.</p><p><b>RESULTS</b>Compared to control group, the number of SA-β-gal positive cells and the expression of p53, p21 and p16 were significantly increased in the 10g/L and 50g/L D-gal treatment groups. The apoptosis rate in 50g/L D-gal group was significantly higher than that in control group (P<0.01). The proliferation of MSCs was decreased in the 10g/L and 50g/L D-gal groups compared to control group (P<0.05). After 10g/L and 50g/L D-gal treatment, SOD activity was significantly decreased (P<0.01), and MDA level was increased (P<0.01).</p><p><b>CONCLUSION</b>The aging of MSCs can be induced by 10g/L and 50g/L D-gal, which may be associated with the elevated levels of oxidative stress.</p>