Polystyrene Nanodiscs via Seeded Dispersion Polymerization for Enhanced Sensitivity in Turbidimetric Immunoassays

Abstract Particle shape plays a critical yet underexplored role in aggregation-based biosensing, particularly at the nanoscale, where quantitative detection is required. In this study, we demonstrate a simple strategy for engineering nonspherical polymer nanoparticles that substantially enhance the sensitivity of turbidimetric immunoassays. Polystyrene (PS) nanospheres with diameters of a few hundred nanometers, suitable for quantitative turbidimetric detection, were synthesized via dispersion polymerization under unconventional conditions. The nanospheres were subsequently deformed into disc-shaped nanoparticles (∼300 nm) through seeded dispersion polymerization coupled with phase separation and selective extraction. The resultant PS nanodiscs exhibited markedly enhanced aggregation behavior upon antigen–antibody interactions, forming larger anisotropic aggregates via face-to-face stacking than their spherical counterparts. Consequently, the nanodiscs achieved an approximately four-fold improvement in detection sensitivity, while providing a wider quantitative detection range. These findings demonstrate a direct link between the shape of polymer nanoparticles and biosensing performance and may provide a versatile platform for designing next-generation high-sensitivity immunoassay systems based on shape-engineered polymer nanoparticles.