(79d) Probing Nanoparticle Interaction with Artificial Cell Membranes Via a High-Throughput Fluorescent Liposomal Leakage Assay

Nanomedicines and nanotherapeutics consist of loading biomolecular cargo in or on a nanocarrier, followed by co-incubation or injection into a system of interest, and subsequent integration or uptake past the cell membrane and into a cell. On the scale of the cell membrane, few studies have demonstrated the degree to which qualities of a nanoparticle such as size, functionalization, and coronal surface layer composition fundamentally change the uptake and interaction with the bilayer itself. In this study, we have demonstrated the capability of a high-throughput fluorescence assay to measure how physico-chemical qualities of nanoparticles enable or spurn bilayer interaction. We demonstrate the breadth of this assay by considering a wide variety of nanoparticle compositions and functionalizations. Further, we make preliminary strides to explore the effect of an adsorbed protein corona and thus elucidate the importance of the cellular environment in impacting membrane-nanoparticle interactions.

This fluorescence self-quenching assay relies on (5)6-carboxyfluorescein (CF), a membrane impermeable dye loaded into large unilamellar vesicles (LUV) at a concentration around 40 mM where these tightly packed dye molecules show minimal fluorescence. Release of the CF (as a result of nanoparticle intercalation and disruption at the LUV bilayer) results in an immediate strong fluorescent signal. Comparing the induced dye release over time upon interaction with therapeutically relevant functionalized nanomaterials informs understanding of their compatibility with phospholipid bilayers and exosome-like structures.

A wide range of nanoparticles were considered including (i) 10 nm diameter gold nanospheres functionalized with citrate or an oligonucleotide sequence and (ii) colloidally stabilized single walled carbon nanotubes. We discuss approaches to controls and data processing to account for some inherent nanoparticle light absorption in this fluorescent reporter system. We also incubate select nanoparticles with relevant biological proteins or serum to form an adsorbed protein corona. We then apply our assay to begin elucidation of the degree to which complex biological environments mediate interaction.

Translation of our inferences in nanoparticle-bilayer interaction kinetics to nanomedicine can inform optimal design of targeted delivery agents.