Structural Engineering of <sc>l</sc>-Aspartic Amphiphilic Polyesters for Enzyme-Responsive Drug Delivery and Bioimaging in Cancer Cells

Design and development of amphiphilic polyesters based on bioresources are very important to cater to the ever-growing need for biodegradable polymers in biomedical applications. Here, we report structural engineering of enzyme-responsive amphiphilic polyesters based on l-amino acid bioresources and study their drug delivery aspects in the cancer cell line. For this purpose, an l-aspartic acid-based polyester platform is chosen, and two noncovalent forces such as hydrogen bonding and side-chain hydrophobic interactions are introduced to study their effect on the aqueous self-assembly of nanoparticles. The synthetic strategy involves the development of l-aspartic acid-based dimethyl ester monomers with acetal and stearate side chains and subjecting them to solvent-free melt polycondensation reactions to produce side-chain-functionalized polyesters in the entire composition range. Postpolymerization acid catalyst deprotection of acetal yielded hydroxyl-functionalized polyesters. Amphiphilicity of the polymer is carefully fine-tuned by varying the composition of the stearate and hydroxyl units in the polymer chains to produce self-assembly in water. Various drugs such as camptothecin (CPT), curcumin (CUR), and doxorubicin (DOX) and biomarkers like 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS), rose bengal (RB), and Nile red (NR) are successfully encapsulated in the polymer nanoparticles. Cytotoxicity of biodegradable polymer nanoparticles is tested in normal and breast cancer cell lines. The polymer nanoparticles are found to be highly biocompatible and delivered the anticancer drugs in the intracellular compartments of the cells.