Integrating Experiments and Simulations to Uncover Size-Dependent Bioactivity in Cellular Nanodiscs

Cell membrane-derived nanodiscs or cellular nanodiscs (CNDs) integrate the structural fidelity of biological membranes with the tunability of synthetic nanomaterials, creating a versatile platform for therapeutic and diagnostic applications. Despite growing interest, the relationship between CND size and biological function has not been systematically defined. In this work, we combine experimental and computational approaches to elucidate how CND size governs its performance. Using red blood cell (RBC)-derived CNDs generated with styrene-maleic anhydride copolymers of varying styrene-to-maleic anhydride ratios, we produced three uniform and highly stable CND formulations with diameters of approximately 71, 26, and 15 nm. Functional studies revealed that smaller CNDs exhibited significantly enhanced antibody binding and faster interaction kinetics. Brownian dynamics simulations attributed these improvements to increased diffusion coefficients and higher particle numbers at reduced sizes. In agreement with these predictions, the smallest CNDs demonstrated the most potent α-toxin neutralization in vitro and provided the greatest survival benefit in a mouse intoxication model. Collectively, these findings demonstrate that precise size control is a key determinant of CND bioactivity and offer design principles for optimizing CND formulations towards optimal biological applications.