A magnetite/PMAA nanospheres-targeting SERS aptasensor for tetracycline sensing using mercapto molecules embedded core/shell nanoparticles for signal amplification

Surface-enhanced Raman scattering (SERS) biosensors have promising potential in the field of antibiotics detection because of their ultrahigh detection sensitivity. This paper reports a rapid and sensitive SERS-based magnetic nanospheres-targeting strategy for sensing tetracycline (ITC) using aptamer-conjugated magnetite colloid nanocrystal clusters (MCNCs)-polymethacrylic acid (PMAA) magnetic nanospheres (MNs) as the recognition and the Au/PATP/SiO2 (APS) as the labels. Initially, MNs were fabricated and conjugated with the aptamers through condensation reaction. MNs possessed high saturation magnetization (Ms) value of 71.5 emu/g and excellent biocompatibility, which facilitated the rapid and easy magnetic separation. Then, complementary DNA (cDNA) were loaded on the APS nanocarrier to produce a large amplification factor of Raman signals. The MNs-targeting aptasensor was thus fabricated by immobilizing the APS to the MNs' surfaces via the hybrid reaction between cDNA and aptamers. Sequel, TTC bound successfully to the aptamer upon its addition with the subsequent release of some cDNA-APS into the bulk solution. Under magnet attraction, the nanospheres were deposited together. Consequently, a display of strong SERS signals by supernatants of the resulting mixtures with increasing TTC concentrations was observed. The proposed aptasensor showed excellent performances for TTC detection along with wide linear range of 0.001-100 ng/mL, low detection limit 0.001 ng/mL, high sensitivity, and good selectivity to the general coexisted interferences.