Surface plasma enhanced fluorescence combined aptamer sensor based on silica modified silver nanoparticles for signal amplification detection of cholic acid

Cholic acid (CA), as an important gut bacterial metabolite in humans, would cause DNA damage when its level increases. Determination of CA is extremely significant and necessary in human because of its importance in medical and clinical diagnose. Herein, aptamer-modified fluorescence sensor combined surface plasmon resonance (SPR) enhanced fluorescence for signal amplification detection of CA was firstly developed. Silica-coated silver nanoparticles (Ag@SiO2) as SPR materials were decorated with CdTe quantum dots (QDs) to obtain enhancement of fluorescent signal. Then CA aptamer was modified to the surface of the CdTe QDs (Ag@SiO2@QDs-Apt) through the covalent binding for specific recognition of CA. The maximum fluorescent enhancement was obtained with 36 nm of Ag nanoparticle. Compared with aptamer-modified QDs (QDs-Apt), Ag@SiO2@QDs-Apt showed super sensitivity with the linear range of 0.1-500 mu M. Finally, the as-prepared nanosensor was applied to the detection of CA in human urine and serum with the recovery rate of 95.00-110.39%.