Quantum Spin Detection in Microfiltration Immunoassays for Ultrasensitive and High-Throughput Diagnostics.

This study demonstrates the transformative potential of quantum technologies for healthcare diagnostics by developing a new analytical method, the quantum-enabled microfiltration immunoassay (QEMFIA). QEMFIA integrates the strengths of dot blot and enzyme-linked immunosorbent assays, enabling rapid, sensitive, and quantitative detection of clinically relevant antigens using nanoscale quantum sensors in a high-throughput format. The assay leverages fluorescent nanodiamonds (FNDs) with nitrogen-vacancy centers as reporters, combined with magnetically modulated fluorescence (MMF) for background-free detection of optically addressable spin defects. Additionally, to achieve high-throughput operation, the assays are performed on a 24-well microfiltration manifold, with target antigens captured by antibodies immobilized on a nitrocellulose membrane, followed by detection using antibody-conjugated FNDs. Finally, retained FNDs are directly analyzed on the membrane via MMF under a fluorescence microscope. The limits of detection for disease markers, such as C-reactive protein and interleukin-6, are below 100 fM within 1 h. The method is compatible with standard 96-well plates and conventional lab workflows. It also supports integration with automation platforms for high-throughput analysis across a broad range of target antigens using the FND quantum sensors.