Selecting small molecule DNA aptamers with significant conformational changes for constructing transcriptional switches and biosensors

Small molecule aptamers discovered by traditional selection methods usually lack conformational changes upon target binding.This limits the use of aptamers as molecular probes for small molecule detection and regulatory elements of genetic circuits.Here,we report a new method called capture and in vitro transcription-systematic evolution of ligands by exponential enrichment(CIVT-SELEX)to select DNA aptamers that can not only bind to small molecule ligands but also undergo significant conformational changes.Through this method,we select a structure-switching aptamer of uridine-5′-diphosphate(UDP).Taking advantage of its conformational changes,we first construct a UDP-responsive transcriptional switch by inserting the aptamer in a genetic circuit and demonstrate that it can respond to the addition of UDP and regulate the transcription of downstream genes.We also build a UDP aptamer-based biosensor that can be used for active glycosyltransferase screening.We believe this method can provide a universal platform for selecting small molecule aptamers with conformational changes and expand the use of aptamers in small molecule detection and genetic regulation.

A sandwich structure composite wound dressing with firmly anchored silver nanoparticles for severe burn wound healing in a porcine model

Wounds may remain open for a few weeks in severe burns,which provide an entry point for pathogens and microorganisms invading.Thus,wound dressings with long-term antimicrobial activity are crucial for severe burn wound healing.Here,a sandwich structure composite wound dressing anchored with silver nanoparticles(AgNPs)was developed for severe burn wound healing.AgNPs were in situ synthesized on the fibers of chitosan nonwoven fabric(CSNWF)as the interlayer of wound dressing for sustained release of silver ion.The firmly anchored AgNPs could prevent its entry into the body,thereby eliminating the toxicity of nanomaterials.The outer layer was a polyurethane membrane,which has a nanoporous structure that could maintain free transmission of water vapor.Chitosan/collagen sponge was selected as the inner layer because of its excellent biocompatibility and biodegradability.The presence of AgNPs in the CSNWF was fully characterized,and the high antibacterial activity of CSNWF/AgNPs was confirmed by against Escherichia coli,Pseudomonas aeruginosa and Staphylococcus aureus.The superior wound healing effect on deep dermal burns of presented composite wound dressing was demonstrated in a porcine model.Our finding suggested that the prepared AgNPs doped sandwich structure composite wound dressing has great potential application in severe wound care.