Multifunctional Electrospinning Polyhydroxyalkanoate Fibrous Scaffolds with Antibacterial and Angiogenesis Effects for Accelerating Wound Healing.

To treat large-scale wounds or chronic ulcers, it is highly desirable to develop multifunctional wound dressings that integrate antibacterial and angiogenic properties. While many biomaterials have been fabricated as wound dressings for skin regeneration, few reports have addressed the issue of complete skin regeneration due to the lack of vasculature and hair follicles. Herein, an instructive poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) fibrous wound dressing that integrates an antibacterial ciprofloxacin (CIP) and pro-angiogenic dimethyloxalylglycine (DMOG) is successfully prepared via electrospinning. The resultant dressings exhibit suitable flexibility with tensile strength and elongation at break up to 4.08 ± 0.18 MPa and 354.8 ± 18.4%, respectively. The in vitro results revealed that the groups of P34HB/CIP/DMOG dressings presented excellent biocompatibility on cell proliferation and significantly promote the spread and migration of L929 cells in both transwell and scratch assays. Capillary-like tube formation is also significantly enhanced in the P34HB/CIP/DMOG group dressings. Additionally, dressings from the P34HB/CIP and P34HB/CIP/DMOG groups show a broad spectrum of antimicrobial action against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. In vivo studies further demonstrated that the prepared dressings in the P34HB/CIP/DMOG group not only improved wound closure, increased re-epithelialization and collagen formation, as well as reduced inflammatory response but also increased angiogenesis and remodeling, resulting in complete skin regeneration and hair follicles. Collectively, this work provides a simple but efficient approach for the design of a versatile wound dressing with the potential to have a synergistic effect on the rapid stimulation of angiogenesis as well as antibacterial activity in full-thickness skin repair.

Enhanced bone regeneration via PHA scaffolds coated with polydopamine-captured BMP2.

The hierarchical three-dimensional (3D)-printing scaffolds based on microbial polyester poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) were designed and used for bone tissue engineering via surface functionalization on 3D-printed (P34HB) scaffolds using polydopamine (PDA)-mediated recombinant human bone morphogenetic protein-2 (BMP2), leading to enhanced bone formation in a rat model with a calvarial critical-size bone defect. Taking advantage of the adhesive property of PDA under alkaline and aerobic conditions, osteogenic BMP2 was captured on the surface of PHA scaffolds, resulting in their enhanced osteogenic bioactivity, better stem cell adhesion and proliferation, and sustainable release of a bioactive substance over a period of 30 days. These contributed to notable differences in alkaline phosphatase (ALP) activity, mineralization, expressions of osteogenesis-related genes, as well as finally enhanced in vivo bone formation in rats. The functionalized 3D-printed P34HB scaffolds via the PDA-mediated osteogenic activity were developed as a versatile platform for bone tissue regeneration.

Genotypic Characterization of Methicillin-resistant Staphylococcus aureus Isolated from Pigs and Retail Foods in China.

OBJECTIVE: To investigate the genotypic diversity of Methicillin-resistant Staphylococcus aureus (MRSA) isolated from pigs and retail foods from different geographical areas in China and further to study the routes and rates of transmission of this pathogen from animals to food. METHODS: Seventy-one MRSA isolates were obtained from pigs and retail foods and then characterized by multi-locus sequencing typing (MLST), spa typing, multiple-locus variable number of tandem repeat analysis (MLVA), pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility testing. RESULTS: All isolated MRSA exhibited multi-drug resistance (MDR). Greater diversity was found in food-associated MRSA (7 STs, 8 spa types, and 10 MLVA patterns) compared to pig-associated MRSA (3 STs, 1 spa type, and 6 MLVA patterns). PFGE patterns were more diverse for pig-associated MRSA than those of food-associated isolates (40 vs. 11 pulse types). Among the pig-associated isolates, CC9-ST9-t899-MC2236 was the most prevalent clone (96.4%), and CC9-ST9-t437-MC621 (20.0%) was the predominant clone among the food-associated isolates. The CC9-ST9 isolates showed significantly higher antimicrobial resistance than other clones. Interestingly, CC398-ST398-t034 clone was identified from both pig- and food-associated isolates. Of note, some community- and hospital-associated MRSA strains (t030, t172, t1244, and t4549) were also identified as food-associated isolates. CONCLUSION: CC9-ST9-t899-MC2236-MDR was the most predominant clone in pigs, but significant genetic diversity was observed in food-associated MRSA. Our results demonstrate the great need for improved surveillance of MRSA in livestock and food and effective prevention strategies to limit MDR-MRSA infections in China.

Amino acid substitutions of His296 alter the catalytic properties of Zymomonas mobilis 10232 levansucrase.

His296 of Zymomonas mobilis levansucrase (EC 2.4.1.10) is crucial for the catalysis of the transfructosylation reaction. The three-dimensional structures of levansucrases revealed the His296 is involved in the substrate recognition and binding. In this study, nine mutants were created by site-directed mutagenesis, in which His296 was substituted with amino acids of different polarity, charge and length. The substitutions of His296 with Arg or Trp retained partial hydrolysis and transfructosylation activities. The positively charged Lys substitution resulted in a 2.5-fold increase of sucrose hydrolysis. Substitutions with short (Cys or Ser), negatively charged (Glu) or polar (Tyr) amino acids virtually abolished both the activities. Analysis of transfructosylation products indicated that the mutants synthesized different oligosaccharides, suggesting that amino acid substitutions of His296 strongly affected both the enzyme activity and transfructosylation products.