Enyzme-responsive polymeric assemblies hold great potential for biomedical applications due to the over-expression of disease-associated enzymes, which can be utilized to activate such systems only in afflicted tissues. Herein we demonstrate that the overall molecular weight of polymeric amphiphiles, which have the same hydrophilic/hydrophobic ratio, can be tuned to create polymeric micelles with an extreme range of degradation rates. This approach expands the available set of molecular parameters that can be adjusted to tune the degradation rate of polymeric assemblies, paving new possibilities for rational design of polymeric systems with controlled degradation rates.

Taking advantage of the high fidelity of thiol-ene and thiol-yne chemistries, we used mixtures of thiols to prepare degradable PEG-dendron amphiphiles functionalized with two different types of enzymatically cleavable end groups. By tuning the feed ratios of the two thiols, we achieved mixtures of hybrids with statistically different ratios of end groups. Studies of the disassembly of statistically mixed hybrids showed that these amphiphiles have higher degrees of response when incubated with each of the activating enzymes, whereas a greater degree of selectivity was observed for a control mixture of two distinct amphiphiles, which required the presence of both types of enzyme to undergo complete disassembly. The potential to introduce different end groups by using a mixture of thiols in an efficient single thiol-ene or thiol-yne step opens the way for simple modification of various ene- or yne-containing polymers and tailoring of their structural and functional properties.