A Quantum Dots Fluorescence Bioassay For Detecting Perfluorinated Compounds

Objective: The aim of the present study was to develop a bioassay for detecting and monitoring the concentration of perfluorinated compounds(PFCs)in the environmental water, based on the interaction of perfluorooctane sulphonate(PFOS),perfluorooctanoic acid(PFOA)with peroxisome proliferator-activated receptor-α(PPARα) combined with the use of quantum dots (QDs) nanoparticles as a fluorescent marker.Methods: PFOS-BSA was prepared according to the methods as described previously and coated on the 96-microwell plate. Each of the PFOS standards and PPARα-RXRαextract were added to the 96-well plate coated with PFOS-BSA. The supernatants that containing the complex of PPARα-RXRα-PFOS were then transferred to another plate coated with PPARαantibody. Biotin labeled DNA probe was added to each well. The plate was incubated for 1 hr at 37℃to allow the probe to bind with PPARα-RXRα-PFOS. The QDs-SA was diluted in TBS and added to constitute the fluorescent probe through Biotin-Avidin System. At last, we achieved quantitative detection of PFOS by detecting the fluorescence intensity of QDs. And then to make the standard curve by the fluorescence intensity and concentration of PFOS standards,and to detect PFOA using the same method. According to the national standards, we collected water samples and did pretreatment, and then detected the concentration of PFCs by both the bioassay and HPLC/MS, calculated results by the fluorescence intensity and stand curve.Results: In the bioassay, the intensity of fluorescence from each well was linearly related with the PFCs concentrations ranging from 2.5 ng/l to 75 ng/l (PFOS: y = 19.112x-23.995, R~2 = 0.964; PFOA: 17.601x-20.914, R~2 = 0.973). The detection limit of this method was 2.5 ng/L with the mean recovery being 107.8 % and 110.3 %. In comparison, HPLC/MS demonstrated a limit of detection of 1 ng/l and recovery 104.3 % and 105.9%. The concentration range from 2.5 ng/l to 75 ng/l was within its detection linear range(PFOS: y = 2E-05x-26.479, R~2 = 0.996; PFOA: y = 2E-05x-25.023, R~2 = 0.997). To further assess the reliability of the bioassay, water samples collected from the Yangze River in Wuhan, Han River in Wuhan, East lake, waterworks in Wuhan and bottled purified water were detected for PFCs concentration and the results were compared with that determined by HPLC/MS. Detection results of environmental water samples were highly consistent between the bioassay and HPLC/MS.Conclusion: The QDs fluorescence bioassay has outstanding advantages applied in the detection of PFCs in the environmental water samples. It not only has the advantage of immunofluorescence technique, but also improves sensitivity and accuracy compared with the traditional fluorescence method by applying the new fluorescent marker QDs. The bioassay has broad application prospects in screening a large number of environmental water samples in the field.