Antibacterial and osteoconductive polycaprolactone/polylactic acid/nano-hydroxyapatite/Cu@ZIF-8 GBR membrane with asymmetric porous structure.

Repair of periodontal and maxillofacial bone defects is a major challenge in clinical. Guided bone regeneration (GBR) is considered one of the most effective methods. However, the efficacy of currently available GBR membranes for repair is frequently limited by their poor osteogenic potential and lack of antibacterial activity. The first step in this investigation was to construct a zinc-based zeolite-imidazolate framework loaded with copper ions (Cu@ZIF-8). Following that, a novel polycaprolactone/polylactic acid/nano-hydroxyapatite/Cu@ZIF-8 (PCL/PLA/n-HA/Cu@ZIF-8) GBR membrane was developed using a simple porogen with nonsolvent-induced phase separation (NIPS) approach. The produced membrane with asymmetric porous structure (one smooth side and one rough side) possesses hydrophilicity corresponding to the roughness of its two sides. The superior mechanical property, stability of degradation, and ion release capability of the membrane all contribute to the clinical feasibility. Additionally, in vitro biological experiments demonstrated that the PCL/PLA/n-HA/Cu@ZIF-8 membrane had favorable osteogenic and antibacterial properties, which suggests the high potential for application in the GBR procedure.

Flexibility regeneration of silk fibroin in vitro.

Although natural silk fibers have excellent strength and flexibility, the regenerated silk materials generally become brittle in the dry state. How to reconstruct the flexibility for silk fibroin has bewildered scientists for many years. In the present study, the flexible regenerated silk fibroin films were achieved by simulating the natural forming and spinning process. Silk fibroin films composed of silk I structure were first prepared by slow drying process. Then, the silk fibroin films were stretched in the wet state, following the structural transition from silk I to silk II. The difference between the flexible film and different brittle regenerated films was investigated to reveal the critical factors in regulating the flexibility of regenerated silk materials. Compared with the methanol-treated silk films, although having similar silk II structure and water content, the flexible silk films contained more bound water rather than free water, implying the great influence of bound water on the flexibility. Then, further studies revealed that the distribution of bound water was also a critical factor in improving silk flexibility in the dry state, which could be regulated by the nanoassembly of silk fibroin. Importantly, the results further elucidate the relation between mechanical properties and silk fibroin structures, pointing to a new mode of generating new types of silk materials with enhanced mechanical properties in the dry state, which would facilitate the fabrication and application of regenerated silk fibroin materials in different fields.

Silk self-assembly mechanisms and control from thermodynamics to kinetics.

Silkworms and spiders generate fibers that exhibit high strength and extensibility. The underlying mechanisms involved in processing silk proteins into fiber form remain incompletely understood, resulting in the failure to fully recapitulate the remarkable properties of native fibers in vitro from regenerated silk solutions. In the present study, the extensibility and high strength of regenerated silks were achieved by mimicking the natural spinning process. Conformational transitions inside micelles, followed by aggregation of micelles and their stabilization as they relate to the metastable structure of silk are described. Subsequently, the mechanisms to control the formation of nanofibrous structures were elucidated. The results clarify that the self-assembly of silk in aqueous solution is a thermodynamically driven process where kinetics also play a key role. Four key factors, molecular mobility, charge, hydrophilic interactions, and concentration underlie the process. Adjusting these factors can balance nanostructure and conformational composition, and be used to achieve silk-based materials with properties comparable to native fibers. These mechanisms suggest new directions to design silk-based multifunctional materials.

[Forensic pathological analysis on 23 cases of fatal pulmonary thromboembolism].

OBJECTIVE: To analyze the forensic pathological characteristics of sudden death caused by pulmonary thromboembolism and the chronological transformation of thrombus and explore the assessment method of the causal relationship between previous trauma and the following fatal PTE episode. METHODS: All the 23 cases reviewed here were collected from our institute files from the year of 1998 to 2008. RESULTS: Trauma, surgery and braking etc. were all risky factors of PTE. Of these cases, 12 cases were caused by trauma, 21 cases were caused by surgery and 22 cases died in hospitals which were often happened one or two weeks after injury or one week's postoperative time. Of all the cases, 6 cases had single attack of thrombus and the rest 17 cases had the recurrence of thrombus. The number of the leg deep vein to be the embolic source was 16 cases which were often seen in the left leg. CONCLUSION: It is important to confirm the embolic source, trauma, surgery and chronological events in determing the sudden death with PTE.

[Analysis of death caused by postpartum hemorrhage].

OBJECTIVE: To analyze the pathological characteristics and the death reasons due to postpartum hemorrhage, and to help to deal with the obstetrical medical tangles. METHODS: Thirty-two cases of death caused by postpartum hemorrhage encountered in our department since 1995 had been collected and retrospectively analyzed. RESULTS: Death caused by postpartum hemorrhage could be divided into single factor and multi-factor, with 81.25% due to single factor, 12.50% multi-factor, and 6.25% unknown reason. The single factors included uterine atony, retained placenta, placenta increta, laceration of the lower genital tract, and coagulation defects. The multi-factor included a combination of two or more factors mentioned above. CONCLUSION: The causes of death due to postpartum hemorrhage should be analyzed according to the clinical characteristics of the postpartum hemorrhage and the autopsy examination.