Preparation of silver nanoparticles and riboflavin embedded electrospun polymer nanofibrous scaffolds for in vivo wound dressing application

Biocompatible silver-based nanofibrous frameworks have attracted intensive attention in wound dressing materials ascribed to their greater stability, minimal toxicity, excellent antibacterial activity, and extended therapeutic efficiency. The present investigation delineates a simple approach to synthesize silver nanoparticles (Ag NPs), and riboflavin (RF) decorated polyvinyl alcohol/β-Cyclodextrin (PVA/β-CD) electrospun nanofibrous scaffolds envisioning their application in wound dressings. PVA/β-CD polymer matrix regulates the stabilization of Ag NPs and RF. Also, it promotes the wound healing process and skin regeneration. The morphology, thermal properties, and their structure were also evaluated. Likewise, mechanical properties, biodegradation and drug release profile of the nanofibrous scaffolds were evaluated. In addition Antibacterial studies of the resultant nanofibrous scaffolds showed a strong inhibitory effect against Staphylococcus aureus and Escherichia coli at a considerable level. Moreover, Ag NPs-RF/PVA/β-CD nanofibrous scaffold were studied for its in vitro cytotoxicity using human embryonic kidney cells (HEK-293), and the results suggested that Ag NPs and RF present in the nanofibrous scaffolds exhibited its cytotoxicity. Besides, wound healing efficiency of the Ag NPs-RF decorated nanofibrous scaffolds was assessed using full thickness excision wounds in rat models displayed as an excellent biomaterial for wound dressings.     

Expression and purification of recombinant tristetraprolin that can bind to tumor necrosis factor-alpha mRNA and serve as a substrate for mitogen-activated protein kinases

Tristetraprolin (TTP) is an mRNA-binding protein, but studies of this interaction have been difficult due to problems with the purification of recombinant TTP. In the present study, we expressed human and mouse TTP as glutathione S-transferase and maltose-binding protein (MBP) fusion proteins in Escherichia coli, and purified them by affinity resins and Mono Q chromatography. TTP cleaved from the fusion protein was identified by immunoblotting, MALDI-MS, and protein sequencing, and was further purified to homogeneity by continuous-elution SDS-gel electrophoresis. Purified recombinant TTP bound to the AU-rich element of tumor necrosis factor-alpha (TNFalpha) mRNA and this binding was dependent on Zn(2+). Results from sizing columns suggested that the active species might be in the form of an oligomer of MBP-TTP. Recombinant TTP was phosphorylated by three members of the mitogen-activated protein (MAP) kinase family, p42, p38, and JNK, with half-maximal phosphorylation occurring at approximately 0.5, 0.25, and 0.25 microM protein, respectively. Phosphorylation by these kinases did not appear to affect the ability of TTP to bind to TNFalpha mRNA under the assay conditions. This study describes a procedure for purifying nonfusion protein TTP to homogeneity, demonstrates that TTP's RNA-binding activity is zinc dependent, and that TTP can be phosphorylated by JNK as well as by the other members of the greater MAP kinase family.