In Vitro Efficacy of Paclitaxel-loaded PLGA Nanoformulations for Lung Cancer Treatment Demonstrated by Label-free Multiphoton-Fluorescence Lifetime Imaging Microscopy

Lung cancer remains the leading cause of cancer-related mortality, and despite its limited efficacy, and low specificity, chemotherapy is still commonly used as a first-line treatment. Herein, we prepare and characterize poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) for the use as a non-targeted nanocarrier drug delivery system for the chemotherapeutic drug, paclitaxel (PTX). Drug loading capability, mono-dispersity, zeta potential, morphology, and drug release profile were determined for the PLGA NPs. Furthermore, the IC50 of the loaded nanoparticles was determined to be 20 times lower than the IC50 value of free PTX in cytotoxic studies in A549 lung cancer cells. The time dependent therapeutic efficacy of both free and encapsulated PTX was assess at several time points in A549 monolayers via label-free multiphoton metabolic imaging based on the fluorescence lifetime of the metabolic cofactor NAD(P)H. Specifically, the significant continuous metabolic shift towards oxidative phosphorylation in cells treated with NPs was correlated with the NPs drug release profile, highlighting the sustained and controlled behavior of the drug delivery system. These findings underscore not only the utility of PLGA NPs as a drug delivery system with enhanced efficacy compared to free drug treatments but also the use of label-free multiphoton fluorescence lifetime imaging microscopy for non-invasive imaging, allowing the tracking of metabolic changes on cellular and subcellular level. Additionally, the presented method is extended to include more complex in vitro models allowing for assessing the cellular bioenergetic response of individual cells in 3D models in real time, paving the way for improved therapeutic strategies against lung cancer.