(332f) Enzyme-Triggered Depolymerization of Complex Coacervates for Drug Delivery Applications

A coacervate is a polymer-rich liquid droplet assembled through liquid-liquid phase separation, driven by electrostatic interaction between oppositely charged polymers. Inspired by membraneless organelles (MLOs), which recruit nucleic acids and native proteins, coacervates have been proposed as artificial compartments. They not only mimic the material properties of MLOs but also their function, such as hierarchical organization, compartmentalization, and dynamic exchange of client molecules. These characteristics make coacervates promising for stimuli-responsive drug delivery as they can dynamically assemble and disassemble in response to changes in their environment, such as pH, temperature, and enzymes. Therefore, coacervates have been studied as stimuli-responsive drug carriers for disease treatment. On the other hand, precipitates, another phase form resulting from ionic interaction, are often found to be intractable, but may kinetically trap cargo akin to lyophilization making them an interesting starting point for drug encapsulation. In this study, we explore how carboxymethyl cellulose (CMC) based polyelectrolyte complexes break down when exposed to the cellulase enzyme. We mixed CMC with two polycations, poly(L-lysine) (PLK) and poly(diallyldimethylammonium chloride) (PDADMAC), to form these complexes. At optimal charge ratios, complexation results in the formation of solid-like precipitates in both PLK-CMC and PDADMAC-CMC systems. Upon the introduction of cellulase enzyme to both systems, we observed precipitate transition to coacervate formation in response to cellulase. Cellulase weakens the electrostatic interaction between CMC and the polycations and relaxes the precipitates due to cellulase’s hydrolysis of CMC to glucose, thereby transitioning to coacervate droplets. We confirmed that the two systems undergo phase separation from precipitates to liquid-like droplets over time through brightfield microscopy and determined that higher cellulase concentration accelerates the depolymerization process. Our study has focused on the depolymerization dynamics of coacervates in response to stimuli, particularly enzymes, which could constitute a steppingstone for establishing stimuli-responsive drug carriers.