Fabricating Active Microfibers from Enzyme Responsive Block Copolymers

Enzyme-responsive polymeric fibers and nanoparticles are promising smart materials for applications in the areas of drug delivery, sensing, imaging, diagnostics, and active scaffolds for tissue growth. Due to the overexpression in afflicted tissues, disease-associated enzymes are an effective trigger for the selective release of drugs at the target pathological tissue. The present work reports the design and synthesis of amphiphilic di- and tri-block copolymers and their utilization to form active fibers. Polyethylene glycol (PEG) was chosen as the hydrophilic block and dendrons with enzymatically cleavable lipophilic end-groups as the hydrophobic blocks. The cleavable end-groups were connected to the dendron through ester bonds, which can be cleaved by esterase enzyme. The fabrication of the fibers was carried out using the electrospinning technique. The capability of our fibers to be cleaved by the target enzymes was tested by labeling of the copolymers with a fluorescent marker, and following the enzymatic degradation of fibers by measuring the changes in their fluorescence. This new trackable molecular platform will pave the way to delivery systems capable of releasing drugs in a specific site and reporting the location and degree of the enzymatic activation and of the drug delivery process.