Bhagyashree Kulkarni, Bapurao Surnar, Manickam Jayakannan

Multipurpose polymer nano-scaffolds for cellular imaging and delivery of anticancer drug are urgently required for the cancer therapy. The present investigation reports a new polymer drug delivery concept based on biodegradable polycaprolactone (PCL) and highly luminescent -conjugated fluorophore as dual functional nano-carrier for cellular imaging and delivery vehicles for anticancer drug to cancer cells. To accomplish this goal, a new substituted caprolactone monomer was designed and it was subjected to ring opening polymerization using a blue luminescent bishydroxyloligo-phenylenevinylene (OPV) fluorophore as an initiator. A series of A-B-A tri-block copolymer building blocks with a fixed OPV -core and variable chain biodegradable PCL arm length were tailor-made. These tri-blocks self-assembled in organic solvents to produce well defined helical nanofibers whereas in water they produced spherical nanoparticles (size ~ 150 nm) with blue luminescence. The hydrophobic pocket of the polymer nanoparticle was found to be an efficient host for loading water insoluble anticancer drug such as doxorubicin (DOX). The photophysical studies revealed that there was no cross-talking between the OPV and DOX chromophores and their optical purity was retained in the nanoparticle assembly for cellular imaging. In vitro studies revealed that the biodegradable PCL arm was susceptible to enzymatic cleavage at the intracellular lysosomal esterase under physiological conditions to release the loaded drugs. The nascent nanoparticles were found to be non-toxic to cancer cells whereas the DOX loaded nanoparticles accomplished more than 80 % killing in HeLa cells. Confocal microscopic analysis confirmed the cell penetrating ability of the blue luminescent polymer nanoparticles and their accumulation preferably in the cytoplasm. The DOX loaded red luminescent polymer nanoparticles were also taken up by the cells and the drug was found to be accumulated at the peri-nuclear environment. The new nano-carrier approach reported in the present manuscript accomplishes both cellular imaging and delivering drugs to intracellular compartments in a single polymer system. The present investigation is one of the first examples to demonstrate the dual functional biodegradable luminescence nano-carrier concept in the literature and the studies established this proof-of-concept in cellular imaging and drug delivery in cancer cells.