Cyclopolymerization-based polymeric prodrug system for intracellular delivery and tracking of coumarin-functionalized chlorambucil in cancer cells

Tracking the internalization of non-fluorescent drugs remains a significant challenge in drug delivery systems. Monitoring drug internalization is crucial for enhancing therapeutic efficiency and controlling drug release, minimizing damage to healthy cells. In this study, we synthesized a fluorescent, biocompatible coumarin derivative functionalized with chlorambucil, termed compound <b>5</b>. The 1,6-heptadiyne moiety, known for its ability to cyclopolymerize in the presence of Hoveyda–Grubbs’ second-generation (HG2) catalyst, was modified with monomethyl poly(ethylene glycol) (mPEG-OH) and compound <b>5</b> to create the macromonomer compound <b>8</b>. This macromonomer was polymerized under inert conditions using HG2, yielding the final polymer, compound <b>9</b>, with a molecular weight of 21,300 g/mol. All monomer precursors were thoroughly characterized using various analytical techniques. Dynamic light scattering (DLS) revealed a polymer size of 32 nm, while transmission electron microscopy (TEM) showed spherical morphology in a 1 mg/mL solution in deionized water. Compound <b>9</b> exhibited promising chemotherapeutic activity against HeLa and MCF-7 cell lines. Further internalization studies demonstrated an increase in fluorescence intensity with increasing polymer concentration in both cell lines.