Thrombin immobilized polydopamine-diatom biosilica for effective hemorrhage control.

In this study, an efficient composite hemostatic material (DA-diatom-T) was prepared, using a polydopamine layer as a linker to immobilize thrombin on the surface of diatom biosilica. DA-diatom-T retained the porous structure of the diatom with high water absorption capacity, which can absorb 31 times its own weight of water. The thrombin activity of DA-diatom-T was as high as 5.81 U mg-1 that could be maintained at 67% after 30 days at room temperature. DA-diatom-T exhibited non-toxicity to mouse fibroblast cell lines, favorable hemocompatibility and fast procoagulant ability. DA-diatom-T could promote the initiation of the coagulation process and increase platelet activity and blood clot strength to form a physical barrier at the wound. In an in vivo study, DA-diatom-T could significantly reduce the clotting time and reduce the bleeding volume. The above results showed that DA-diatom-T had potential as a new hemostatic material.

The toughness chitosan-PVA double network hydrogel based on alkali solution system and hydrogen bonding for tissue engineering applications.

Biocompatibility and mechanical properties have always been important indicators for the application of hydrogel materials in tissue engineering. In this work, a high strength and toughness chitosan-poly (vinyl alcohol) (PVA) DN (double network) hydrogel based on multiple hydrogen bonding interactions was prepared by applying the simple freezing-heating alternate treatment to the chitosan-PVA alkaline solution. The PVA first network was prepared by freeze crystallization, and the chitosan second network was constructed by raising the chitosan/KOH/urea temperature to 45 °C. The dynamic hydrogen bonding presented in the first PVA network and the second chitosan network given the hydrogel superior compressive (60%-230 KPa), tensile (152 KPa-360%), recoverability (90.77% after 5 cycles) and anti-swelling properties. The results of in vitro cell compatibility and in vivo subcutaneous implantation in rats both indicated that the chitosan-PVA DN hydrogel had the ability to promote cell attachment and wound healing. This DN hydrogel based on hydrogen bonding is expected to be applied in the tissue engineering repair. In addition, the hydrogel preparation process is simple and non-toxic, which provides a reference for the production of green and safe tissue engineering hydrogels.

Mechanically and functionally strengthened tissue adhesive of chitin whisker complexed chitosan/dextran derivatives based hydrogel.

Schiff base reaction crosslinking hydrogels are advantageous by rapid formation and absence of external crosslinkers. However, poor mechanical hindered their broader applications. Here, a mechanically strengthened tissue adhesive was constructed through incorporation of chitin nano-whiskers (CtNWs) with a Schiff base crosslinking hydrogel of carboxymethyl chitosan (CMCS) and dextran dialdehyde (DDA). The optimal formulation of complexed hydrogel exhibited 1.87 folds higher compressive stress than non-complexed and 1.51 time higher adhesive strength on porcine skin. The complexed hydrogel exhibited negligible cytotoxicity, anti-swelling performance in PBS, optimum antibacterial and hemostatic capacities. In vivo implantation studies confirmed the complexed hydrogel was degradable without long-term inflammatory responses. Desirable efficacy of injectable complexed hydrogel as hemostat was demonstrated in rat liver injury model, which could avoid severe postoperative adhesion and necrosis as observed in the treatment with commercial 3 M™ vetbond™ tissue adhesive. The results highlighted that the complexed hydrogel potentiated rapid hemostasis and wound repair applications.

Hydroxybutyl chitosan/diatom-biosilica composite sponge for hemorrhage control.

Effective bleeding control is critical first step in current civilian and military trauma treatment, however commercially available hemostatic materials are difficult to achieve expected effects. In this study, a composite sponge (H-D) based on hydroxybutyl chitosan (HBC) and diatom-biosilica (DB) was designed for hemorrhage control. H-D exhibited hierarchical porous structure, favorable biocompatibility (hemolysis ratio < 5 %, no cytotoxicity), along with high and fast fluid absorbability (11-16 times than that of weight), given effective hemostasis effect (clotting time shortened by 70 % than that of control). In vitro coagulation tests demonstrated that H-D could provide strong interface effect to induce erythrocyte absorption and aggregation, as well as activating the intrinsic coagulation pathway and thus accelerated blood coagulation. These results proved that H-D composite sponge has great potential for hemorrhage control.

Construction of physical-crosslink chitosan/PVA double-network hydrogel with surface mineralization for bone repair.

Weak mechanical properties, lack biocompatibility and relatively bioinert are formidable obstruct in application of bone repair materials. Multifunctional composite materials have been considered as a viable solution to this problem. Here, a new double network (DN) hydrogel was constructed by physical cross-linking of medical grade poly (vinyl alcohol) (PVA) and chitosan in KOH/urea dissolution system. The obtained hydrogel demonstrated excellent tensile strength (0.24 MPa), elongation at break (286%), and high compressive strength (0.11 MPa on the strain of 60%). Our studies showed that the prepared hydrogel had excellent biocompatibility in vitro and the introduction of hydroxyapatite (HAp) by surface mineralization imparted hydrogel the ability to induce rat bone marrow stem cells (rBMSCs) differentiation. The in vivo experiments revealed that the surface mineralized double network hydrogel significantly accelerated simultaneous regeneration of bone defects in a rabbit bone defect model. All the results indicated that this hydrogel has the potential as a bone repair material.