Hybrid material for enrofloxacin sensing based on aptamer-functionalized magnetic nanoparticle conjugated with upconversion nanoprobes

In this study, aptamer-functionalized magnetic Fe 3 O 4 conjugated with upconversion nanoparticles (UCNPs) were used as hybridization nanoprobes to quantify trace enrofloxacin (ENR) in food samples. Owing to the autofluorescence-free nature of UCNPs, an ENR-responsive aptamer, and the use of magnetic separation to further reduce background signals, our sensing system enabled rapid and highly sensitive detection of trace ENR in real samples. The proposed sensing method was validated in terms of selectivity, linearity, accuracy, precision, and sensitivity; and then was applied to the analysis of four different fish samples. Recoveries between 85.1% and 98.5%, and relative standard deviation (RSD) values in the range of 2.4% to 5.0% and from 3.0% to 4.3%, for intra- and inter-day tests, respectively, were obtained, with the limits of detection and quantification of 0.06 and 0.20   ng/mL, respectively. Therefore, the good validation and application results that we obtained indicate that the sensing method is suitable for the quantification of target ENRs in real samples, and show great potential for wide-ranging application in bioassays by simply changing the type of aptamer.