A magnetic bead array-based fluorescence immunoassay platform for robust cancer biomarker analysis in clinical blood samples

The reliable conjugation of antibodies to a solid matrix is crucial for robust immunoassays in microfluidic devices. Various magnetic particles (MPs) have been employed due to their high surface-to-volume ratios and ease of magnetic manipulation, providing a reliable surface for antibody immobilization. However, achieving uniform positioning of MPs across the channel surface has been challenging due to inadequate magnetic forces or magnetic field uniformity. Here, we present the utilization of Halbach magnetic arrays to enable consistent deployment of MPs on the microfluidic surface, thereby facilitating robust immunoassay capabilities. Using finite element method magnetics (FEMM) simulations, we predicted that incorporating Halbach magnetic arrays beneath the microfluidic channels would create more uniform and augmented magnetic flux density gradients over the surface. Subsequently, we applied this platform to assess cancer biomarkers in patients’ blood plasma and achieved statistically reliable results, comparable to those obtained using an FDA-approved device. We detected three cancer biomarkers, including prostate-specific antigen (PSA), alpha-fetoprotein (AFP), and carcinoembryonic antigen (CEA). The limit of detection (LOD) of three biomarkers were < 1 ng/mL, ranging from 0.38–0.95 ng mL⁻¹. This platform provided within-run, between-run, and between-day precisions for the three cancer biomarkers, ranging from 0.37–9.87%. This advancement holds significant promise for improving the accuracy and performance of immunoassays in various microfluidic diagnostic applications.