Simultaneous determination of toltrazuril and its metabolites in chicken and pig skin+fat by UPLC-UV method

Pharmacokinetics of toltrazuril and its metabolites after oral and parenteral administration of novel oil-based suspension based on micro-environmental pH-modifying solid dispersion in rabbits

Toltrazuril (TOL) is a broad-spectrum anticoccidial drug which is widely used in poultry and livestock. A novel oral suspension based on soybean oil-based TOL micro-environmental pH-modifying solid dispersion (micro pHm SD) and a novel injectable suspension based on white oil-based TOL micro pHm SD were developed, showing high physicochemical stability and high drug release in vitro with good histocompatibility. The present study is to evaluate the pharmacokinetic profiles of TOL and its major metabolites, e.g. toltrazuril sulfoxide (TOLSO) and toltrazuril sulfone (TOLSO₂) in rabbits following oral or subcutaneous administration with these two TOL SD suspensions. The plasma concentrations of TOL, TOLSO and TOLSO₂ were determined by high performance liquid chromatography (HPLC). Plasma concentration-time data were analyzed by a non-compartmental model analysis. The soybean oil-based TOL suspension after single oral administration at 20 mg/kg body weight (bw) significantly increased the plasma concentrations of TOL, TOLSO and TOLSO₂ compared with Baycox® 5 % suspension. Following subcutaneous administration of the white oil-based TOL suspension (20 mg/kg bw), TOL was well absorbed and metabolized more slowly to TOLSO and TOLSO₂, compared with oral administration, resulting in the significantly prolonged residence time in rabbits. The two suspensions significantly improved the relative bioavailability of TOL and its two metabolites, showing their potential usage in the control of coccidian in poultry and livestock.

Development of molecularly imprinted electrochemical sensor with reduced graphene oxide and titanium dioxide enhanced performance for the detection of toltrazuril in chicken muscle and egg

A molecularly imprinted electrochemical sensor for toltrazuril (TZR) detection based on molecularly imprinted polymers (MIPs) immobilized on reduced graphene oxide (rGO) and titanium dioxide (TiO₂) modified platinum (Pt) electrode surface was fabricated for the first time. The synergistic fast electron transfer ability, large electroactive surface area and high catalytic activity from rGO and TiO₂ contribute to amplify the electrochemical signal and consequently improve the sensitivity of the sensor. The cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) tests were used to evaluate the performance of the electrochemical sensor. The results showed that the electrochemical sensor possessed high sensitivity, good selectivity and anti-interference ability toward TZR. By using the DPV, the electrochemical sensor displayed a wide linear concentration range from 0.43 to 42.54 μg/L, with a limit of detection of 0.21 μg/L (S/N = 3). Moreover, the recoveries and relative standard deviations (RSD) were 85.0%-97.0% and 3.5%-6.4% at three concentration levels, respectively, implying that the established sensor is promising for the accurate detection of TZR at trace levels in chicken muscle and egg samples.

A colorimetric paper-based sensor for toltrazuril and its metabolites in feed, chicken, and egg samples

In this study, a sensitive monoclonal antibody (mAb) against toltrazuril (Tol) was developed based on a novel hapten. The 50% inhibitory concentrations (IC₅₀) of toltrazuril and its metabolites ranged from 2.19 ng/mL to 4.21 ng/mL. Based on this mAb, a colorimetric paper-based sensor was developed for the rapid screening of Tol and its metabolites in samples. The proposed assay has cutoff values of <20 μg/kg for Tol and 50 μg/kg for Tol sulfone when evaluated with the naked eye, and the results could be obtained in 15 min. Quantitative results were obtained with a strip scan reader, with limits of detection <2.60 μg/kg for Tol and its metabolites in real samples. The sensitivity of both qualitative and quantitative detection meets the European Union requirements. Therefore, this strip assay provides a useful tool for the on-site detection and rapid initial screening of Tol and its derivatives in feed, egg, and chicken samples.