Mineralized Collagen/Polylactic Acid Composite Scaffolds for Load-Bearing Bone Regeneration in a Developmental Model

Repairing load-bearing bone defects in children remains a big clinical challenge. Mineralized collagen (MC) can effectively simulate natural bone composition and hierarchical structure and has a good biocompatibility and bone conductivity. Polylactic acid (PLA) is regarded as a gold material because of its mechanical properties and degradability. In this study, we prepare MC/PLA composite scaffolds via in situ mineralization and freeze-drying. Cell, characterization, and animal experiments compare and evaluate the biomimetic properties and repair effects of the MC/PLA scaffolds. Phalloidin and DAPI staining results show that the MC/PLA scaffolds are not cytotoxic. CCK-8 and scratch experiments prove that the scaffolds are superior to MC and hydroxyapatite (HA)/PLA scaffolds in promoting cell proliferation and migration. The surface and interior of the MC/PLA scaffolds exhibit rich interconnected pore structures with a porosity of ≥70%. The XRD patterns are typical HA waveforms. X-ray, micro-CT, and H&E staining reveal that the defect boundary disappears, new bone tissue grows into MC/PLA scaffolds in a large area, and the scaffolds are degraded after six months of implantation. The MC/PLA composite scaffold has a pore structure and composition similar to cancellous bone, with a good biocompatibility and bone regeneration ability.

[Application and clinical efficacy of ultrasound debridement method in residual burn wounds]

Objective: To investigate the application and clinical efficacy of ultrasound debridement method in residual burn wounds. Methods: A retrospective cohort study was conducted. From August 2017 to August 2021, 64 patients with residual burn wounds who met the inclusion criteria were admitted to the 980th Hospital of the Joint Logistic Support Force of PLA. According to the debridement method adopted for the residual wounds, the patients were divided into ultrasound debridement group (34 cases, 22 males and 12 females, aged (31±13) years) and traditional debridement group (30 cases, 19 males and 11 females, aged (32±13) years). After the corresponding debridement, the wounds of patients in the two groups were selected for stamp skin grafting or large skin grafting according to the wound site and skin donor status. For unhealed wounds after stage Ⅰ surgery, secondary debridement and skin grafting were be performed, with the wound debridement methods in the 2 groups being the same as those of stage Ⅰ, respectively. On postoperative day 3, drug-sensitive test was used to detect the bacteria in the wound and the positive rate of bacteria was calculate. On postoperative day 7, the survival rate of skin slices in wound and the incidence of subcutaneous hematoma were calculated. At discharge, wound healing time and debridement times of patients were counted, and the secondary debridement rate was calculated. Data were statistically analyzed with independent sample t test or chi-square test. Results: On postoperative day 3, the wounds in ultrasound debridement group were infected with Staphylococcus aureus in 2 cases and Pseudomonas aeruginosa in 2 cases, and the wounds in traditional debridement group were infected with Staphylococcus aureus in 5 cases, Pseudomonas aeruginosa in 3 cases, Acinetobacter baumannii in 1 cases, Klebsiella pneumoniae in 1 cases, and Enterobacter cloacae in 1 cases. The positive rate of bacteria of wound in ultrasound debridement group was significantly lower than that in traditional debridement group (χ2=5.51, P<0.05). On postoperative day 7, the survival rate of skin grafts in ultrasound debridement group was (92±5) %, which was significantly higher than (84±10) % in traditional debridement group (χ2=6.78, P<0.01); the incidence of subcutaneous hematoma in ultrasound debridement group was 17.6% (6/34), which was significantly lower than 40.0%( 12/30) in traditional debridement group, χ2=3.94, P<0.05. At discharge, the wound healing time in ultrasound debridement group was (11.0±2.0) d, which was significantly shorter than (13.0±3.1) d in traditional debridement group (t=3.81, P<0.01); the secondary debridement rate of wounds in ultrasound debridement group was 2.9% (1/34), which was significantly lower than 20.0% (6/30) in traditional debridement group (χ2=4.76, P<0.05). Conclusions: Ultrasound debridement method can significantly reduce the bacterial load of residual burn wounds, reduce postoperative hematoma formation, and promote the survival of skin grafts to shorten the course of disease of patients.