Rapid Filtration Allows Ultrafast Measurement of Antibody and Nanoparticle Capture in Porous Matrices: Implications...

Capture of biomolecules within porous membranes underpins the performance of lateral flow immunoassays and membrane chromatography, yet direct measurement of binding kinetics on sub-second timescales remains challenging. Here, we introduce an approach based on rapid filtration that enables quantitative measurement of antibody and nanoparticle capture on porous membranes over contact times ranging from 0.25 to 10 s. Using Fusion 5 silica membranes functionalized with protein A, we measured the capture of Alexa Fluor 555-labeled antibodies and antibody-conjugated europium nanoparticles at flow rates between 0.5 and 8 mL s^-1. Antibody capture on protein A surface scaled with contact time rather than flow rate, indicating that binding under these conditions is not transport-limited. Increasing protein A surface density enhanced antibody capture up to ca. 0.42 μg mm ^-2, above which no further increase was observed, suggesting saturation of accessible binding sites. For IgG-conjugated nanoparticles, rapid filtration resolved distinct positive and negative signals within 0.5 s, demonstrating sensitivity on time scales relevant to lateral-flow line formation. This rapid filtration analysis could be widely applied to the study short-time adsorption kinetics in porous matrices and offers quantitative insights for optimizing membrane-based assays and chromatographic separations.