A Chemiluminescence Enzyme Immunoassay (CLEIA) for the Determination of 19‐Nortestosterone Residues in Aquatic Products

Sensitive and selective simultaneous biosensing of nandrolone and testosterone as two anabolic steroids by a novel biosensor assisted by second-order calibration

Recently, our research group have focused on an interesting project in which a novel dual template molecularly imprinted (DTMIP) biosensor was fabricated and assisted by second-order differential pulse voltammetric (DPV) data for simultaneous determination of nandrolone decanoate (ND) and testosterone decanoate (TS). An indium tin oxide (ITO) was modified with multiwalled carbon nanotubes-graphene-ionic liquid (MWCNT-Gr-IL) and then, the fullerene C₆₀ was casted onto the surface of MWCNT-Gr-IL/ITO and electrochemically reduced. Finally, DTMIPs were electrosynthesized by electropolymerization of 4-aminobenzoic acid (ABA) as monomer with ND and TS as template molecules to obtain the final structure of the biosensor (DTMIP/C₆₀/MWCNT-Gr-IL/ITO). Structure of the biosensor was electrochemically and microscopically characterized. The ND and TS generated two severely overlapped DPVs at the surface of the biosensor which forced us to assist the biosensor with three-way calibration by second-order DPV data to simultaneous determine them. Two second-order algorithms including multivariate curve resolution alternating least squares (MCR-ALS) and parallel factor analysis2 (PARAFAC2) were used to build second-order calibration models and evaluation of their performance in the analysis of synthetic samples showed more superiority of the MCR-ALS than PARAFC2 which motivated us to select PARAFC2 for the analysis of urine samples as real cases. Application of the biosensor assisted by PARAFC2 for the analysis of urine samples towards simultaneous determination of ND and TS was successful.

A competitive chemiluminescence enzyme immunoassay for rapid and sensitive determination of enrofloxacin

With alkaline phosphatase (ALP)-adamantane (AMPPD) system as the chemiluminescence (CL) detection system, a highly sensitive, specific and simple competitive chemiluminescence enzyme immunoassay (CLEIA) was developed for the measurement of enrofloxacin (ENR). The physicochemical parameters, such as the chemiluminescent assay mediums, the dilution buffer of ENR-McAb, the volume of dilution buffer, the monoclonal antibody concentration, the incubation time, and other relevant variables of the immunoassay have been optimized. Under the optimal conditions, the detection linear range of 350-1000 pg/mL and the detection limit of 0.24 ng/mL were provided by the proposed method. The relative standard deviations were less than 15% for both intra and inter-assay precision. This method has been successfully applied to determine ENR in spiked samples with the recovery of 103%-96%. It showed that CLEIA was a good potential method in the analysis of residues of veterinary drugs after treatment of related diseases.

Fullerene-C60-modified electrode as a sensitive voltammetric sensor for detection of nandrolone—An anabolic steroid used in doping

The electrochemical behaviour of nandrolone is investigated by cyclic, differential pulse and square-wave voltammetry in phosphate buffer system at fullerene-C60-modified electrode. The modified electrode shows an excellent electrocatalytic activity towards the oxidation of nandrolone resulting in a marked lowering in the peak potential and considerable improvement of the peak current as compared to the electrochemical activity at the bare glassy carbon electrode. The oxidation process is shown to be irreversible and diffusion-controlled. A linear range of 50 microM to 0.1 nM is obtained along with a detection limit and sensitivity of 0.42 nM and 0.358 nA nM(-1), respectively, in square-wave voltammetric technique. A diffusion coefficient of 4.13x10(-8) cm2 s(-1) was found for nandrolone using chronoamperometry. The effect of interferents, stability and reproducibility of the proposed method were also studied. The described method was successfully employed for the determination of nandrolone in human serum and urine samples. A cross-validation of observed results by GC-MS indicates that the results are in good agreement with each other.

A rapid and sensitive chemiluminescence enzyme-linked immunosorbent assay for the determination of fumonisin B1 in food samples

An enzyme-linked immunosorbent assay (ELISA) based on polyclonal antibody with enhanced chemiluminescent (ECL) detection of fumonisin B1 (FB1) in food samples has been developed. Assay conditions, including concentrations of antibody and enzyme conjugate, competition time and so on, were optimized. The effects of pH and two different organic solvents were investigated. The optimized ECL-ELISA system allowed FB1 determination in a linear working range of 0.14-0.9 microg L(-1) with IC50 value of 0.32 microg L(-1) and a limit of detection of 0.09 microg L(-1). The ECL-ELISA was about 10 times more sensitive and about 30% time less than that of colorimetric ELISA using the same antibody and HRP-conjugate. Good recoveries with spiked food samples were obtained, and the results correlated well with those obtained using conventional direct competition ELISA assay and HPLC method, which indicated that ECL-ELISA was capable of being applied for the specific detection and routine monitoring of FB1 in food samples.