Ru(phen)32+ doped silica nanoparticle based immunochromatographic strip for rapid quantitative detection of β-agonist residues in swine urine

A Ru(phen)32+ doped silica nanoparticle based immunochromatographic strip was developed for the rapid and quantitative detection of five common β-agonist (salbutamol (SAL), cimbuterol, terbutaline, clenbuterol, and brombuterol) residues in swine urine. The broad spectrum monoclonal antibodies generated by immunizing BALB/c mice with salbutamol conjugated cationic bovine serum albumin. The fluorescence intensities (FIs) of the strip on the test line (FIT) and control line (FIC) were determined using a strip reader. Parameters that influenced the antibody and antigen interaction on the test strip were investigated by recording FIT and FIC values, and the concept of FIT/FIC ratio was used to offset the inherent heterogeneity of the test strips and the effect of the sample matrix. Under optimal conditions, the linear range for the quantitative detection of SAL was 0.6-5.0 ng/ml with a half maximal inhibitory concentration at 1.78 ng/ml. The limit of detection for real swine urine was 0.43 ng/ml. The recovery rates of the intraassay for spiked urine at SAL concentrations of 0.8, 1.5, and 3.5 ng/mL were 88.06%±3.75%, 95.77%±5.33%, and 94.06%±7.43%, whereas those for the interassay were 84.69%±5.0%, 95.06%±9.3%, and 88.34%±7.71%, respectively. The developed quantitative method exhibited excellent agreement with a commercially available competitive enzyme-linked immunosorbent assay kit for SAL-spiked urine samples, with a correlation of coefficient of 0.95 and a slope of 0.99 (n=36). The results indicated that the developed test strip enables sensitive, reproducible, and easily implementable screening for the rapid and quantitative detection of β-agonist residues in swine urine.