Silk-protein-based gradient hydrogels with multimode reprogrammable shape changes for biointegrated devices.

Biocompatible and morphable hydrogels capable of multimode reprogrammable, and adaptive shape changes are potentially useful for diverse biomedical applications. However, existing morphable systems often rely on complicated structural designs involving cumbersome and energy-intensive fabrication processes. Here, we report a simple electric-field-activated protein network migration strategy to reversibly program silk-protein hydrogels with controllable and reprogrammable complex shape transformations. The application of a low electric field enables the convergence of net negatively charged protein cross-linking networks toward the anode (isoelectric point plane) due to the pH gradient generated in the process, facilitating the formation of a gradient network structure and systems suitable for three-dimensional shape change. These tunable protein networks can be reprogrammed or permanently fixed by control of the polymorphic transitions. We show that these morphing hydrogels are capable of conformally interfacing with biological tissues by programming the shape changes and a bimorph structure consisting of aligned carbon nanotube multilayers and the silk hydrogels was assembled to illustrate utility as an implantable bioelectronic device for localized low-voltage electrical stimulation of the sciatic nerve in a rabbit.

In-situ fermentation with gellan gum adding to produce bacterial cellulose from traditional Chinese medicinal herb residues hydrolysate.

In this study, bacterial cellulose was synthesized by Taonella mepensis from traditional Chinese medicinal herb residues hydrolysate. To overcome the inhibitory effect of fermentation environment, in-situ fermentation with gellan gum adding was carried out for the first time. After 10 days' static fermentation, both high-acyl gellan gum and low-acyl gellan gum adding showed certain beneficial effects for bacterial cellulose production that the highest bacterial cellulose yield (0.866 and 0.798 g/L, respectively) was 59% and 47% higher than that (0.543 g/L) without gellan gum adding. Besides, gellan gum based bacterial cellulose showed some better texture characteristics. Gellan gum was loaded in the nano network of bacterial cellulose, and gellan gum adding had some influence on the crystal structure and thermal degradation behaviors of bacterial cellulose but affected little on its functional groups. Overall, this in-situ fermentation technology is attractive for bacterial cellulose production from low-cost but inhibitory substrates.

Tissue-engineered esophagus: recellular esophageal extracellular matrix based on perfusion-decellularized technique and mesenchymal stem cells.

Perfusion-decellularization was an interesting technique to generate a natural extracellular matrix (ECM) with the complete three-dimensional anatomical structure and vascular system. In this study, the esophageal ECM (E-ECM) scaffold was successfully constructed by perfusion-decellularized technique through the vascular system for the first time. And the physicochemical and biological properties of the E-ECM scaffolds were evaluated. The bone marrow mesenchymal stem cells (BMSCs) were induced to differentiate into myocytesin vitro. E-ECM scaffolds reseeded with myocytes were implanted into the greater omenta to obtain recellular esophageal ECM (RE-ECM), a tissue-engineered esophagus. The results showed that the cells of the esophagi were completely and uniformly removed after perfusion. E-ECM scaffolds retained the original four-layer organizational structure and vascular system with excellent biocompatibility. And the E-ECM scaffolds had no significant difference in mechanical properties comparing with fresh esophagi,p> 0.05. Immunocytochemistry showed positive expression ofα-sarcomeric actin, suggesting that BMSCs had successfully differentiated into myocytes. Most importantly, we found that in the RE-ECM muscularis, the myocytes regenerated linearly and continuously and migrated to the deep, and the tissue vascularization was obvious. The cell survival rates at 1 week and 2 weeks were 98.5 ± 3.0% and 96.4 ± 4.6%, respectively. It was demonstrated that myocytes maintained the ability for proliferation and differentiation for at least 2 weeks, and the cell activity was satisfactory in the RE-ECM. It follows that the tissue-engineered esophagus based on perfusion-decellularized technique and mesenchymal stem cells has great potential in esophageal repair. It is proposed as a promising alternative for reconstruction of esophageal defects in the future.

A microfluidic refractometric sensor based on gratings in optical fibre microwires.

In this paper we investigate a novel method to manufacture gratings in optical fiber microwires and discuss their application to sensing. Gratings can be manufactured by wrapping an optical fiber microwire on a microstructured rod. This method avoids post-processing the thin optical fiber microwire and it has great flexibility: chirping can be realized by designing the air hole size and position in the microstructured rod. By exploiting the large evanescent field in an inner channel, microfluidic refractometric sensors with sensitivity > 10(3) nm/RIU can be achieved.