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Lactoferrin (LF), a bioactive multifunctional protein of the transferrin family, is found mainly in the secretions of all mammals, especially in milk. In the present study, a hybridoma cell (LF8) secreting IgG against bovine LF was screened, and the purified LF8 mAb showed high specificity and affinity to bovine LF. The linear range of ic-ELISA to detect LF was 9.76 ~ 625 ng/mL, with a limit of detection (LOD) of 0.01 ng/mL. The average recovery of intra- and inter-assay were (104.45 ± 4.12)% and (107.13 ± 4.72)%, respectively. The LOD of colloidal gold- and AuNFs-based strip by naked eye were 9.7 and 2.4 ng/mL, respectively, and the detection time was less than 10 min without any samples pretreatment and expensive equipment. The developed ELISA and lateral flow immunosensors based on specific IgG could be used directly for rapid detection of the bovine LF content in cow milk samples.

The high content of Penicillic acid (PA) in the feed pose threat to human health and cause serious losses to economic wealth through the enrichment effect of the food chain. The reliable and rapidly detection of PA is of significant importance to ensure food safety. In this study, indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and immunochromatographic test strips (ICTS) were established for PA determination based on anti-PA mAb secreted by 4H9 cell line. The linear range of ic-ELISA detection was 0.12–1.95 μg/mL, and the limit of detection (LOD) was 0.03 μg/mL. Then, conventional gold nanospheres (AuNS) with the average diameter of 20 nm were synthetized and AuNS-based strip was developed for rapidly detection of PA. The visual LOD (vLOD) of the AuNS-based strip was 3.9 μg/mL and the assay time of visual evaluation was less than 10 min without any instrument. To enhance the signal sensitivity of the ICTS, the larger size (about 85 nm) of gold nanoflowers (AuNFs) was prepared in our work, and was used as higher signal reporter to establish the AuNF-based strip for PA determination. Fortunately, the vLOD of AuNF-based strip was 0.97 μg/mL, which was approximately 4-fold lower than that of traditional AuNS-based strip. In summary, the rapid and sensitive immunoassays established in this study could be applied to detect and analyze the contamination of PA toxin in real food samples.