A Label-Free Fluorescence Polarization for Protein Detection Based on Albumin Nanoparticles

Human serum albumin (HSA), an endogenous protein, was employed in the synthesis of nanoparticles. The treatment of an HSA solution with ethanol and glutaraldehyde resulted in the formation of human serum albumin nanoparticles (HSA NPs), which exhibited a weak fluorescence emission peak at 515 nm upon excitation at 360 nm. Importantly, these synthesized HSA NPs displayed a pronounced fluorescence polarization (FP) signal under identical excitation and emission conditions. Furthermore, incubation of the HSA NPs with specific DNA aptamers targeting lysozyme and thrombin led to a significant decrease in the FP values. This reduction in FP was effectively reversed upon the addition of lysozyme and thrombin. Based on these observations, a label-free fluorescence polarization-based detection platform for lysozyme and thrombin was developed utilizing HSA NPs and a DNA aptamer system.