Identification and quantitation of regenerated casein fibers in combination fabric based on lateral flow immunoassay

Regenerated protein fibers with different biogenetic derivations greatly vary in cost. However, finding a proper method for identifying and quantitating regenerated protein fibers is difficult. This study developed a rapid, inexpensive, convenient, and accurate qualitative immunochromatography method to detect regenerated casein fiber (RCF) in textiles. The RCF was characterized by electrospray ionization/time of flight mass spectrometry. Peptide haptens were designed based on an inert, conserved, and immunogenic sequence of regenerated casein. Monoclonal antibodies were prepared from the haptens, and a colloidal gold immunochromatography assay (GICA) was applied for the detection. A limit of detection of 0.1% RCF in textiles was achieved with a total analysis time of only 15 min using an extraction solution of 7 M urea containing 0.1% dithiothreitol and treatment for 10 min in boiling water. Quantitative assay results were obtained by using a GICA reader with the recovery rates of 110 to 130% and relative standard deviations of ≤ 20%.