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

## TL;DR

This paper introduces a new diagnostic method using quantum sensors to detect disease markers with high sensitivity and speed.

## Contribution

The novel quantum-enabled microfiltration immunoassay (QEMFIA) combines quantum sensing with high-throughput diagnostics.

## Key findings

- Detection limits for C-reactive protein and interleukin-6 are below 100 fM within one hour.
- The method uses fluorescent nanodiamonds with nitrogen-vacancy centers for background-free detection.
- QEMFIA is compatible with standard lab equipment and automation platforms.

## Abstract

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.