(473f) Polyoxometalate (POM) Nanocluster-Induced Phase Transition in Phospholipid Biomembranes

Polyoxometalate (POM) nanoclusters that are transition metal oxygen clusters with well defined atomic coordination structures have recently emerged as new and functional nanocolloidal materials used as catalysts, anti-cancer medicines, and building blocks for novel functional materials.  However, their implications to human health and environment remain poorly investigated. In this work, we examine the interaction of highly charged anionic and neutral POM nanocluters with phospholipid bilayers as a model cell membrane system.  It is observed that upon the adsorption of highly anionic POMs of 3-5 nm in diameter, lipid dynamics is significantly suppressed and lipid bilayers are disrupted with resultant pore and budding-like structural formation. Direct calorimetric experiment of anionic POM interaction with lipid bilayers of varied lipid compositions confirms the POM-induced fluid-to-gel phase transition in lipid bilayers, due to strong electrostatic interaction between POM nanocluster and lipid head groups. In contrast, for neutral or divalent Zn-S nanocluster of 1-2 nm in diameter, it is revealed that the uptake and insertion of Zn-S nanoclusters into lipid bilayer can induce dynamic supramolecular self-assembly. Additionally, the assembly and disassembly process on lipid bilayer in distinct gel and fluid phases at varied temperature is investigated, suggesting the interfacial assembly critically relies on the phase state of lipid bilayers.