A POCT colorimetric aptasensor for streptomycin detection using porous silica beads- enzyme linked polymer aptamer probes and exonuclease-assisted target recycling for signal amplification

A point of care testing (POCT) colorimetric aptasensor was developed to detect streptomycin (STR) using porous SiO 2 micro beads (pore size of 200 nm) −enzyme linked polymer (PowerVision™, PV) probes and exonuclease-assisted target recycling for signal amplification. The probe was fabricated by single- stranded DNA binding protein labelled SiO 2 micro particles (P-SiO 2 -SSB) as capture probes and Au NPs & aptamer (Apt) co-immobilized on PV (Apt-Au-PV) as nanotracer. In the presence of STR and exonuclease I (Exo I), the nanotracer would combine with STR to form the complex (STR/Apt-Au-PV). Hereafter, Exo I further digest the aptamer on STR/Apt-Au-PV, then STR was released again to participate new cycling, the approach lead to generate more nanotracers into supernatant to improve the sensitivity. Moreover, the dendrimer PV which contains large quantities of HRPs can efficiently catalyzed H 2 O 2 -TMB (3,3′,5,5′- tetramethylbenzidine) system for color development and the results can observed by the naked eye. Due to the excellent multiple signal amplification effects for porous SiO 2 micro particles to label more nanotracer, PV and exonuclease-assisted target recycling, the aptasensor exhibit a low detection limit with 1 pg mL −1 (S/N = 3). In addition, the developed method might provide a prospect assay for food tests at point of care.