Anti-Cefalexin polyclonal antibody

In this study, a facile, ultrasensitive and interference-free method to detect cefalexin (CEX) was developed for the first time. This assay was carried out by covalently immobilizing cefalexin-ovalbumin (CEX-OVA) on high specific surface area amorphous nanoparticles of superparamagnetic iron oxide (SPIO). Here, the SPIO-CEX-OVA structure was rich in antibody domains for competitive immunological recognition to anti-CEX antibody and to AlexaFluor 488 labeled goat anti-mouse IgG. Compared with traditional laser induced fluorescence detection, the introduction of SPIO can preconcentrate analytes to reduce the detection limit and greatly shorten the assay time. A pulsed laser with higher peak energy was chosen as the excitation source for generating strong fluorescence signals and to improve sensitivity. The detection limit was 0.34 ng mL(-1) with linearity in the range of 0.5 ng mL(-1) to 50 ng mL(-1), and the IC50 was 1.7 ng mL(-1). The accuracy and reproducibility were determined by using spiked milk samples with three different concentrations of CEX (5, 20 and 50 ng mL(-1)). The recoveries of 85.2-111.4% were obtained with relative standard deviations of 5.3-9.1%, respectively. These results indicate that the method provides a pragmatic platform for convenient detection of small molecular residues due to its high sensitivity, selectivity and short assay time.

Although stir bar sportive extraction was thought to be a highly efficiency and simple pretreatment approach, its wide application was limited by low selectivity, short service life, and relatively high cost. In order to improve the performance of the stir bar, molecular imprinted polymers and magnetic carbon nanotubes were combined in the present study. In addition, two monomers were utilized to intensify the selectivity of molecularly imprinted polymers. Fourier transform infrared spectroscopy, scanning electron microscopy, and selectivity experiments showed that the molecularly imprinted polymeric stir bar was successfully prepared. Then micro-extraction based on the obtained stir bar was coupled with HPLC for determination of trace cefaclor and cefalexin in environmental water. This approach had the advantages of stir bar sportive extraction, high selectivity of molecular imprinted polymers, and high sorption efficiency of carbon nanotubes. To utilize this pretreatment approach, pH, extraction time, stirring speed, elution solvent, and elution time were optimized. The LOD and LOQ of cefaclor were found to be 3.5 ng center dot mL(-1) and 12.0 ng center dot mL(-1), respectively; the LOD and LOQ of cefalexin were found to be 3.0 ng center dot mL(-1) and 10.0 ng center dot mL(-1), respectively. The recoveries of cefaclor and cefalexin were 86.5 similar to 98.6%. The within-run precision and between-run precision were acceptable (relative standard deviation < 7%). Even when utilized in more than 14 cycles, the performance of the stir bar did not decrease dramatically. This demonstrated that the molecularly imprinted polymeric stir bar based micro-extraction was a convenient, efficient, low-cost, and a specific method for enrichment of cefaclor and cefalexin in environmental samples.