Tailored controllable bifunctional fluorescent-magnetic nanobeads for new generation fast-response immunosensor with dual-signal amplification

Immunosensors based on the fluorescence-linked immunosorbent assay (FLISA) platform are now widely used; however, the long-term response and lower sensitivity limited their development in clinical applications. In this study, we first tailored bifunctional magnetic nanoparticle (MNP)-quantum dot (QD) nanobeads (MQBs) with rapid magnetic response and strong fluorescence intensity for the FLISA platform to construct a fast-response immunosensor. Under optimal conditions, we constructed a dual-signal amplification immunosensor based on an MQB-driven FLISA platform for a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen. We achieved a 29-fold increase in fluorescence intensity over the QD nanobeads (SiO₂/QD/SiO₂, QBs). Compared with the conventional FLISA platform-based QBs, the sensitivity of the developed immunosensor increased 63-fold to 7.50 pg/mL in half the detection time of common FLISA (only 30 min). More important, the test results of this dual-signal amplification immunosensor showed good specificity and accuracy. This novel MQB magnetic-driven FLISA platform with high throughput, as a proof of concept, effectively improved sensitivity and shortened reaction time. As a result, it is expected to have significant potential in the field of point-of-care testing.