A turn-on fluorescent aptasensor for ampicillin detection based on gold nanoparticles and CdTe QDs

A novel fluorescent aptasensor was proposed for turn-on fluorescent detecting ampicillin (AMP) based on CdTe quantum dots (QDs) as fluorophore and gold nanoparticles (Ag NPs) as the quencher. The 3′end AMP aptamer was modified with Au NPs through Au-S bond. The 5′end of complementary strand (cDNA) of aptamer was modified with CdTe QDs. Due to the complementary hybridize of DNA chain, the fluorescence of QDs was quenched by Au NPs. In the presence of AMP, cDNA modified by QDs were dissociated from the aptamer chain, and then an increase of fluorescence intensity (FL) was observed due to the stronger binding capacity of AMP and aptamer. The developed method showed a good linear range of 0.04–20 μM, and the detection limit of 18 nM for AMP detection. In addition, the proposed analytical method was used to detect AMP in milk samples with the recovery rate of 88.4%-99.0%. The as-prepared aptasensor also can be applied to the analysis of other substances by altering the aptamer.