Finger-actuated Microfluidic Chip Integrated with Visual Immunoassay for Ultrasensitive Detection of PSA in Whole Blood

Cumbersome preprocessing and specialized manual operations in clinical blood samples remain a significant challenge for achieving high sensitivity and accurate quantification in point-of-care testing. In this paper, a finger-driven integrated microfluidic chip based on visualization of single nanoparticle scattering was proposed for the detection of prostate-specific antigen (PSA) in the whole blood. To control on-chip fluid, a finger-driven module based on a Tesla valve was designed to unidirectionally regulate fluid mixing and separation in the microchannel. In addition, a membrane separation unit was designed to efficiently separate blood cells and serum, reducing interference from blood cells in the detection process. For quantitative PSA concentration detection, a Multi-functional core-satellite magnetic probe was constructed by using the principle of complementary base pairing of ligands on the surface of gold nanoparticles and magnetic beads. In the presence of target PSA, the constructed core-satellite nanostructure was decomposed, producing a characteristic fluorescence signal and releasing gold nanoparticles with green scattering spots under dark-field microscopy. By correlating the concentration with the number of green scattering spots, cancer risk levels were displayed intuitively using a traffic light system. This biosensor achieves an ultra-low detection limit of 0.5 pg/mL for PSA. Due to the ultra-sensitive ability in detection, the monitoring of PSA concentrations for patients during treatment was also demonstrated. Compared with other methods, this proposed microfluidic assay technology has the advantages of small sample volume, minimal operation, high sensitivity and accuracy. Overall, this biosensor provides a new approach for cancer recurrence monitoring and early diagnosis.