Microfluidic diffusional sizing in bioanalysis and biosensing

Microfluidic diffusional sizing (MDS) has emerged as a versatile lab-on-a-chip technology for quantitative analysis of biomolecules in solution, particularly for determining particle sizes and characterizing biomolecular interactions. By measuring the diffusive behavior of molecules under laminar flow in a microfluidic chip, MDS enables the precise determination of hydrodynamic radii and binding affinities, even in complex biological samples, while requiring only minute sample volumes. As a result, MDS is establishing itself as a key tool in the life sciences. This review summarizes recent advances and applications of MDS in the context of bioanalysis and biosensing. We outline the fundamental principles of MDS and highlight its wide range of applications, including studies of protein aggregation, antibody affinity profiling, protein-lipid interactions, and nanoparticle sizing. We further discuss recent technological developments, such as single-molecule detection, label-free strategies, and multidimensional analysis, that have significantly expanded the scope, sensitivity, and utility of MDS. We conclude with an outlook on the anticipated impact of MDS on biomedical research, diagnostics, and therapeutic development.