Electrospray based fluorescent nanoparticle synthesis from pyrene butyric acid-functionalized poly (D, L-lactide-co-glycolide) polymer for the efficient delivery of anticancer drug and self-monitoring its effect in the drug-resistant breast cancer cells

A novel approach to synthesize anti-metabolite conjugated and intense blue fluorescence emitting smart polymeric nanoparticles is reported for the efficient delivery anticancer drug and self-monitoring its effect in the drug-resistant metastatic breast cancer cells. To prepare the drug-loaded fluorescent nanoparticle, the FDA approved non-fluorescent poly (D, L-lactide-co-glycolide) (PLGA) polymer was modified into a newly designed fluorescent PLGA polymer molecule by the covalent conjugation of the biocompatible fluorophore, 1-Pyrenebutyiric acid (PBA). The fluorescent PLGA-PBA polymer was then electrosprayed by applying the potential of 8.0 kV to synthesize mono-dispersed spherical fluorescent nanoparticles (PLGA-PBA, size ~40 nm). The surface of PLGA-PBA nanoparticles was conjugated with the potent anti-cancer drug molecule, methotrexate (MTX) through a linker molecule, ethylenediamine (EDA) to kill cancer cells. The fluorescence, FTIR, NMR, and mass spectroscopy results of PLGA-PBA and PLGA-PBA@MTX nanoparticles established the proof of successful synthesis of PBA and MTX conjugated nanoparticles with stable fluorescence for monitoring the in-vitro therapeutic effect. A significant internalization of the PLGA-PBA@MTX nanoparticles was observed inside MTX resistant MDA-MB-231 and MCF7 cells predominantly via micropinocytosis. Since MTX is an analog of folic acid and encourages cell internalization through FRα receptor, a higher population of PLGA-PBA@MTX nanoparticles was observed in MDA-MB-231 cells through the receptors to induced higher cell cytotoxicity than MCF-7 cells. The amide bond, which links the MTX molecules to the surface of the fluorescent PLGA-PBA nanoparticles, was found sensitive to the acidic pH. The controlled release of MTX occurred at pH 6.0 for ~6 days due to the acid-catalyzed amide bond hydrolysis. High MTX loading (36%) with significant conjugation efficiency (91.4%) and the rapid drug release in the acidic medium was justified by the lower IC50 value, than the free MTX molecule and high apoptosis in the nanoparticles treated cells. This study presents the usefulness of an engineered nanoformulation in pH-sensitive drug release and the tracking of the therapeutic response, which may hold the potential benefit in breast cancer treatment.