Nanoplasmonic biosensing of specific LC3 autophagy markers enabling drug discovery of autophagy modulators

Autophagy is a fundamental intracellular catabolic process that degrades cytoplasmic constituents to maintain cellular homeostasis. Since autophagy-targeting cancer therapies are gaining attention for their association with cancer progression and drug resistance, the need to develop rapid and precise autophagic flux measurement to evaluate the efficacy of chemotherapies is critical. Here, we present a localized surface plasmon resonance (LSPR) based two-step sensing platform, enabling microtubule-associated proteins 1 A/1B light chain 3 (LC3) turnover assay, measuring LC3-I conversion to LC3-II, which indicates autophagic flux. This work represents an improvement made to our previous total LC3 detecting sensor by measuring specific LC3 ratios within a wide dynamic concentration range from 10² to 10⁶ fM with the treatment of phosphatidylethanolamine binding protein 1 (PEBP1). Furthermore, it enables autophagic flux measurement without any limitation in LC3 compositions of clinical samples, compared to the sensor of our previous study. The sensor successfully analyzed the drug efficacy with high sensitivity under clinical conditions where autophagy-targeted drugs were treated to human cancer cell lines. Our results suggest that this sensor, capable of quantifying individual LC3 forms in a single platform, can be utilized as a rapid, convenient, and cost-effective drug discovery tool in relevance with autophagy-targeted chemotherapies.