PBS-DLS: A Novel Ultrasensitive Dynamic Light Scattering Immunoassay

Despite significant advances in ultrasensitive detection, current methodologies are often hindered by the need for sophisticated equipment, complex signal amplification processes, and specialized operation. Here, we have developed a novel strategy by universal polyvalent biotin–streptavidin cross-linking aggregation coupled with dynamic light scattering (PBS-DLS) that effectively transduces and amplifies undetected molecular recognition events at low target concentrations, demonstrating its potential application as an ultrasensitive immunoassay. The controllability in the size and quantity of the DLS nanoprobe enables this advanced design to achieve tunable sensitivity down to attomolar levels and a broad detection range spanning six orders of magnitude. By reducing the detection time to approximately 15 min, our PBS-DLS emerges as a promising tool for point-of-care (POC) testing. Moreover, this PBS-DLS immunosensor has been validated through its rapid and ultrasensitive detection of the SARS-CoV-2 nucleocapsid (N) protein (a macromolecular model target) and malachite green (MG, a small molecule model target) in complex sample matrices, outperforming conventional immunoassays and other testing methods. The exceptional sensitivity, simplicity, and speed of this novel approach position it as a highly promising platform for the development of various bioanalytical methods and POC assays.