Nontoxic chemical crosslinked bacterial cellulose-heparin-gelatin composite hydrogel as antibacterial dressing

A hydrogel dressing based on bacterial cellulose(BC),which is grafted with quaternary ammonium func-tional and crosslinked with the gelatin-heparin system,is prepared to provide the features mainly con-cerning softness,high swelling ratio,antibacterial property,and biocompatibility.An innovation of prepa-ration is that the BC is beaten into short-chain scaffolds to improve the efficiency of grafting,which not only simplifies the preparation process but also avoids the biotoxicity caused by the introduction of toxic catalyst such as dimethyl sulfoxide(DMSO)or uncertain toxic side products in long-chain graft-ing.Scanning electron microscopy(SEM)shows that the QBC/Hep/Gel composite hydrogel possesses a three-dimensional mesh structure with high porosity.The hydrogel shows outstanding water manage-ment performance indicated by the swelling ratio of 1476％,water retention ratio of more than 90％at 120 h,and moisture permeability of 3296 g m-2 24 h-1.The antibacterial experiment is implemented with staphylococcus aureus,and the antibacterial effect is represented by an inhibition zone of 3 cm in diameter.In vivo animal experiments suggested that QBC/Hep/Gel could effectively promote epithelial reconstruction,collagen deposition,and angiogenesis in normal wounds,reduce inflammation,and ac-celerate wound healing.All these results indicate that the proposed QBC/Hep/Gel hydrogel is a potential composite for antibacterial dressing.     

脉冲电流-激光复合愈合钛合金深层裂纹微观组织研究

分别借鉴脉冲电流对深层裂纹愈合效果良好及激光对浅层裂纹愈合效果明显的优势,用脉冲电流及激光对钛合金中的深层裂纹进行复合处理。脉冲电流处理过程中,绕流效应使得裂尖处产生了较高的温升并形成了局部压应力。脉冲电流处理结束后,深层裂纹中出现了部分愈合区域,电子探针检测显示愈合区内元素分布均匀,电子背散射衍射检测显示愈合区内主要为细小的针状马氏体。经过脉冲电流与激光复合处理后,钛合金中深层裂纹愈合效果明显。激光重熔使得上部裂纹愈合良好并形成了重熔区-热影响区-基体的结构。在距离重熔区较近位置处,由脉冲电流形成的愈合区呈现出明显的柱状晶结构。