Dual Enzymatic Activation of Polymeric Micelles

Synthetic self-assembled nano structures and their interactions with enzymes have been drawing increased attention as part of the growing interest in biocompatible and biodegradable stimuli-responsive polymeric platforms. Utilization of enzymes as triggers that can modify the structural properties of polymeric assemblies can be highly relevant for biological applications such as controlled drug delivery, tissue engineering, etc. The key factors that grant enzymes the potential to act as stimuli are their catalytic efficiency, high selectivity towards their substrates and vast natural abundance in biological tissues. Furthermore, many disease states are frequently associated with a unique enzymatic over-expression, which could be exploited to stimulate cleverly designed platforms in order to induce a site specific-response. Our research group recently developed a simple synthetic approach for preparation of enzyme-responsive PEG-dendron hybrids. Our molecular design included PEG as the hydrophilic backbone, while the enzyme-responsive functionalities were attached to the terminal positions of a dendron unit. These amphiphilic hybrids were shown to self-assemble in aqueous media into nano-sized polymeric micelles and to disassemble in response to the designed enzymatic stimulus. In this work, we wished to expand the enzymatic trigger from a single enzyme into two activating enzymes by attaching two different kinds of dendrons to the block copolymer junction. Each dendron unit was functionalized with different substrates and activation by either one of the enzymes was shown to cause the micelles to disassemble and release their encapsulated molecular cargo. In addition, simultaneous activation with both enzymes caused the micelles to disassemble even faster, granting a much wider range of activation rates.