Development of a highly sensitive lateral flow immunoassay based on receptor-antibody-amorphous carbon nanoparticles to detect 22 β-lactams in milk

[Display omitted] •A new format lateral flow immunoassay (LFIA) based on indirect-labeling was developed.•Monoclonal antibodies against the anti-β-lactam receptors were labeled with amorphous carbon nanoparticles (ACNs).•The receptors were used without any conjugation.•The sensitivity of this LFIA was increased compared with the conventional format. This study aimed to improve the sensitivity of lateral flow immunoassay (LFIA) using two strategies, including using a high sensitivity label and an indirect-labeling format, which were simultaneously applied to develop a highly sensitive LFIA to detect 22 β-lactams. In the new format, β-lactam receptors were used without any labeling, and anti-receptor monoclonal antibodies (mAbs) were labeled with amorphous carbon nanoparticles (ACNs). The new LFIA is based on the following steps: 1) screening mAbs against the receptors for antigen-antibody binding sites away from the active site of the receptors; and 2) detecting immune complexes using receptor-mAb-ACNs. The cut-off values against ampicillin, amoxicillin, benzylpenicillin, dicloxacillin, cloxacillin, oxacillin, nafcillin, cefquinome, cefoperazone, cefapirin, ceftazidime, cephalothin, cefepime, cefoxitin, cefazolin, ceftriaxone, ceftiofur, cefotaxime, cefalexin, imipenem, meropenem, and ertapenem were 1, 2, 2, 10, 10, 10, 10, 3, 3, 3, 5, 10, 10, 20, 20, 20, 30, 30, 100, 10, 15, and 15 ng/mL, respectively, which is significantly lower than that of receptor-mAb-colloidal gold-LFIA using the same immune reagents.