Nerve conduit based on HAP/PDLLA/PRGD for peripheral nerve regeneration with sustained release of valproic acid.

The nerve conduits have been developed for nerve defect repair. However, no artificial conduits have obtained comparable results to autografts to bridge the large gaps. A possible reason for this poor performance may be a lack of sustainable neurotrophic support for axonal regrowth. Previous studies suggested nanocomposite conduits can be used as a carrier for valproic acid (VPA), a common drug that can produce effects similar to the neurotrophic factors. Here, we developed the novel bioabsorbable conduits based on hydroxyapatite/poly d-l-lactic acid (PDLLA)/poly{(lactic acid)-co-[(glycolic acid)-alt-(l-lysine)]} with sustained release of VPA. Firstly, the sustained release of VPA in this conduit was examined by high-performance liquid chromatography. Then Schwann cells were treated with the conduit extracts. The cell metabolic activity and proliferation were assayed by 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2-tetrazolium bromide and bromodeoxyuridine staining. A 10-mm segment of rat sciatic nerve was resected and then repaired, respectively, using the VPA conduit (Group A), the PDLLA conduit (Group B), or the autografts (Group C). Nerve conduction velocities (NCVs), compound muscle action potentials (CMAPs), and histological staining were assayed following the surgery. The cell metabolic activity and proliferation were significantly increased (p < .05) by the extracts from VPA-conduit extract compared to others. NCVs and CMAPs were significantly higher in Groups A and C than Group B (p < .05). The nerve density of Groups A and C was higher than Group B. There was no significant difference between Groups A and C. Taken together, this study suggested the sustained-release VPA conduit promoted peripheral nerve regeneration that was comparable to the autografts. It holds potential for future use in nerve regeneration.

Effect and Repair Mechanism of Nano Ag Sponge Dressing Combined with Gelatin-Bletilla Striata Gum/Salvia Miltiorrhiza on Refractory Orthopedic Wounds.

OBJECTIVE: To explore the effect and mechanism of the sponge dressing on the healing of refractory orthopedic wound, and the gelatin-Bletilla striata gum/Salvia miltiorrhiza nano Ag (GBS-Ag) sponge dressing was prepared. METHODS: GBS-Ag sponge dressing was prepared by the freeze-drying method. Twenty male SD rats were randomly divided into the control group (Ctrl group) and GBS-Ag group, with 10 rats in each group, and the rats in the two groups were established a model of back wound infection. The Ctrl group was treated with gauze, while the GBS-Ag group was treated with GBS-Ag sponge dressing. Wound healing rate, blood immune indexes, Ag content in each organ, morphological changes of wound, and expression of transforming growth factor-ß1 (TGF-ß1) in wound transformation were detected in the two groups of rats. RESULTS: The mechanical properties of GBS-Ag sponge dressing were all in line with the standard, and it had good killing effect on the conventional strain after being incubated for 24 hours. Compared with the Ctrl group, the healing rate and lymphocyte percentage in the GBS-Ag group were significantly increased on day 4 and day 10 (P < 0.05), while the total number of white blood cells and the percentage of neutrophils were significantly decreased (P < 0.05). Compared with Ctrl group, the Ag content in liver, spleen, and kidney of rats in the GBS-Ag group was significantly increased (P < 0.05). The histological results showed that the Ctrl group lacked collagen fibers in the dermis, and the angiogenesis was not rich, accompanied by a large number of inflammatory cell infiltration. The epidermal repair of rats in the GBS-Ag group was complete and partially keratinized, the dermis was rich in collagen fibers, with elastic fibers and new blood vessels, inflammatory cells were rare, and new hair follicles and thick-walled blood vessels were also observed. The expression of TGF-ß1 protein in the wounds of rats in the GBS-Ag group was higher than that of the Ctrl group. CONCLUSION: GBS-Ag sponge dressing had multiple effects of sterilization and promoting wound healing, and its mechanism may be related to promoting the TGF-ß1 protein expression.