Magnetic quantum dots barcodes using Fe3O4/TiO2 with weak spectral absorption in the visible region for high-sensitivity multiplex detection of tumor markers.

Magnetic quantum dot (QD) barcode holds great potential for automatic suspension array and rapid point-of-care detection since it enables simultaneous target encoding, enrichment and separation. However, a serious obstacle to enhancing the encoding capacity of magnetic QD microbeads (MBs) is the fluorescence quenching of magnetic nanoparticles (MNPs) to quantum dots (QDs) in the visible wavelength range due to the broad and strong optical absorption spectrum of MNPs. Here, we report Fe3O4/TiO2 core/shell MNPs and CdSe/ZnS QDs for the construction of dual-function magnetic QD barcodes. Fe3O4/TiO2 MNPs can significantly inhibit fluorescence quenching because the weak absorption of visible light by the TiO2. The two-dimension barcode library of 30 magnetic QD barcodes was constructed based on Fe3O4/TiO2 MNPs and CdSe/ZnS QDs. Moreover, the magnetic QD barcodes showed high sensitivity for the multiplex detection of four tumor markers, cancer antigen 125 (CA125), cancer antigen 199 (CA199), alpha-fetoprotein (AFP), and neuron specific enolase (NSE) with detection limits of 0.89 KU/L, 0.72 KU/L, 0.05 ng/mL, and 0.15 ng/mL, respectively. This bifunctional magnetic QD barcodes are promising for automatic high-sensitivity multiplex bioassay.