Investigating the Intracellular Distribution of Cell-Derived Nanoparticle Complexes, Their Effects on Mitochondrial Dynamics and Mitochondria-ER Contact Sites

Nanomedicine has revolutionised disease treatment and prevention, offering promises for safer and more effective targeted drug delivery. Despite its potential, clinical translation of nanomedicine is often met with disappointment owing to many reasons, including high manufacturing cost, subpar efficacy, and complex regulatory requirements. In terms of understanding their efficacy, endocytosis has been one of the primary focuses in the field. Revealing how nanoparticles are taken up by cells helps to guide the design of nanomedicine with better targeting ability. Evidence on nanoparticle exocytosis on the other hand is relatively underwhelming, as very few studies follow through with their subsequent fates once they have exerted their therapeutic effects in the cells. Here, we describe a cell-derived nanoparticle complex (bionanosome, BNS), excreted by cells after internalising corona nanoparticle. Although biogenesis of BNS remains largely unelucidated, previous studies in our group have uncovered some of their properties unique from their original counterpart, corona. The surface of BNS is decorated with a combination of ribonucleoprotein granules and RNAs, of which we proposed they encode biological information. Our work here aimed to investigate the hypothesis that BNS acts as a delivery machinery for cell-to-cell communication. To achieve this, multiple confocal fluorescence imaging pipelines have been developed, combining with techniques including metabolic assays and flow cytometry. We demonstrated that BNS proteins can separate from their nanoparticle cores and follow a distinct trafficking pathway from their cores. We also illustrated that BNS proteins can evade lysosomal degradation, suggesting effective delivery. Studies on mitochondrial dynamics and mitochondria-ER contact sites have together shown that BNS helps to limit stress response and promote repairing effects in receiving cells. Although it has been reported elsewhere that exocytosis of nanoparticles can help reduce toxicity in the original cell population, to the best of our knowledge, we are the first to reveal their stress mitigating effects in cells on the receiving end of those exocytosed nanoparticles. Our work has shed some light on how cells communicate with each other as a population upon nanoparticle challenges. Such knowledge would serve to supplement the huge body of work in understanding and improving efficacy of nanomedicine.