Gold nanoparticle aggregation-based colorimetric assay for β-casein detection in bovine milk samples

• A probe based on mono- (McAb) and polyclonal (PcAb) antibodies modified gold nanoparticle was synthesized.
• The probe showed highly sensitive and selective for the analysis of β-casein.
• A gold nanoparticle aggregation-based colorimetric assay was successfully developed to detect β-casein in bovine milk.
• Application results correlate well with Kjejdahl method.

Traditional Kjeldahl method, used for quality evaluation of bovine milk, has intrinsic defects of time-consuming sample preparation and two analyses to determine the difference between non-protein nitrogen content and total protein nitrogen content. Herein, based upon antibody functionalized gold nanoparticles (AuNPs), we described a colorimetric method for β-casein (β-CN) detection in bovine milk samples. The linear dynamic range and the LOD were 0.08–250 μg mL−1, and 0.03 μg mL−1 respectively. In addition, the real content of β-CN in bovine milk was measured by using the developed assay. The results are closely correlated with those from Kjeldahl method. The advantages of β-CN triggered AuNP aggregation-based colorimetric assay are simple signal generation, the high sensitivity and specificity as well as no need of complicated sample preparation, which make it for on-site detection of β-CN in bovine milk samples.