Human epidermal growth factor receptor 2 (HER2) is an important biomarker for detection and treatment of breast cancer. In this study, we developed monoclonal antibodies against the extracellular domain (ECD) of HER2 and established a rapid and accurate lateral flow immunoassay (LFIA) for use in community medical institutions. The gene sequence of human HER2-ECD was obtained from the National Center for Biotechnology Information (NCBI) to construct the expression plasmid. HER2-ECD protein expressed in HEK293F cells was used to immunize BALB/c mice. The monoclonal antibodies were produced in mouse ascites and isolated by hybridoma cell screening. Antibodies were analyzed for purity by SDS-PAGE (sodium dodecyl sulphate-polyacrylamide gel-electrophoresis) and affinity was assessed by enzyme-linked immunosorbent assay (ELISA) while subtypes were detected using the commercial kits. The HER2-ECD test strip was prepared based on the sandwich method and evaluated using a portable detection instrument. The affinity of the paired antibodies, 4D8 and 8D9, both reached 1 × 10⁸ L/mol. Both antibodies specifically recognized the HER2-ECD protein in serum. The limit of detection (LOD) of the gold nanoparticle (AuNP)-based LFIA was 1.7 ng/mL with a detection range of 1.7–400 ng/mL, and the performance of the HER2-ECD strip correlated well with that of a Siemens chemiluminescent immunoassay (CLIA) kit. In conclusion, the paired antibodies were successfully prepared with high affinity and specificity. The AuNP-based LFIA of HER2-ECD provides a fast and accurate method to detect the concentration of HER2-ECD in serum samples for clinical use in community medical institutions, and could contribute to determining the progress of the disease or the effectiveness of treatment.

Anesthetic residues in fish represent a potential risk to human health. Therefore, it is important to develop a sensitive and broad-specific method for the detection of anesthetics. In this study, we developed a colloidal gold-based quadruplex immunochromatographic (Qua-ICS) assay using four highly sensitive monoclonal antibody immunotherapy (mAbs) that simultaneously detected 11 anesthetic residues in fish within 10 min. The colorimetric and cut-off values (COVs) for procaines, eugenols, bupivacaines, and tricaine (TMS) were 0.37–1.1 and 3.3–10, 11–222 and 100–2000, 0.37 and 3.3, and 111 and 10,000 µg/kg, respectively. Quantitative analysis was achieved with a portable strip-reader, and the detection ranges were 0.15–2.6, 6.3–677, 0.13–2.8, and 83–1245 µg/kg for procaines, eugenols, bupivacaines, and tricaine, respectively. Our developed method was reliable and accurate according to the recovery test results and analyses of real samples. Therefore, the strip can be used as an alternative method for the rapid detection of anesthetic residues in fish.

Antibiotic residues, generated by the irrational use of drugs and environmental pollution, have always been a great challenge to aquaculture safety. Therefore, a quick, convenient, and performance-excellent way to detect antibiotic residues in aquaculture fish is urgently required. In this study, a multiplex immunochromatographic strip biosensor based on gold nanoparticles was developed for the simultaneous detection of five classes of antibiotic residues (24 β-lactam antibiotics, 26 sulfonamides, five tetracyclines, 24 quinolones, and four amphenicols) in aquaculture fish within 10 min. The detection ranges of five representative antibiotics, penicillin G, sulfamethazine, tetracycline, enrofloxacin, and chloramphenicol, were 2.33–38.4, 0.688–17.1, 1.4–48.1, 1.45–32.9, and 0.537–9.06 µg/kg, respectively. The accuracy and stability of these measurements were demonstrated by analyzing spiked fish samples, with recovery rates of 87.5%–115.2% and a coefficient of variation < 9.5%. The cross-reaction rates, based on the five representative antibiotics, were 3.77%–202% for β-lactams, 3.95%–137% for sulfonamides, 9.19%–100% for tetracyclines, 4.9%–145% for quinolones, and 3.2%–100% for amphenicols. The excellent testing performance of the biosensor strip to most of antibiotic residues in aquaculture fish ensures they meet the maximum residue limits required by countries or organizations. Therefore, this multiplex immunochromatographic strip biosensor is potentially applicable to the rapidly on-site determination of antibiotic residues in aquaculture fish.

Triazine herbicides have been widely used in agriculture, but their residues can harm the environment and human health. To help monitor these, we have developed an effective immunochromatographic strip test that can simultaneously detect 15 different triazines in grain samples (including ametryn, cyprazine, atraton, prometon, prometryn, atrazine, propazine, terbuthylazine, simetryn, trietazine, secbumeton, simazine, desmetryn, terbumeton and simetone). Based on our optimization procedure, the visual limit of detection (vLOD) for these triazines was found to be 2–10 ng/mL in assay buffer, and 0.02–0.1 mg/kg in grain samples. Four different grain matrices including corn, brown rice, wheat, and sorghum were studied and the test results showed no significant differences between the 15 triazines analyzed using this method. This test is simple, convenient, rapid, and low-cost, and could be an effective tool for primary screening of triazine residues in grain samples.

We designed and synthesized novel haptens to produce monoclonal antibodies (mAb) against vitamin B₆ (VB₆). A group-specific mAb (2F9) that recognized pyridoxine (PN), pyridoxamine (PM), and pyridoxal (PL) was prepared using a homologous strategy with 50% maximal inhibitory concentration (IC₅₀) values of 106.60, 250.57, and 400.11 ng/mL, respectively. Based on this, a gold nanoparticles (AuNPs)-based immunochromatographic strip (ICS) test was established for the detection of VB₆ in energy drinks and B-vitamin complex tablets. The developed ICS test results could be semi-quantitatively evaluated by the naked eye within 10 min, and displayed the visual limit of detection (vLOD) values of 250, 500, and 1,000 ng/mL for PN, PM, and PL, respectively. For quantitative analysis, the results obtained by strip reader, with calculated LOD values for PN, PM, and PL were 14.10, 55.58, and 56.25 ng/mL, respectively. Commercial energy drinks and B-vitamin complex tablet samples were detected by the strips and the results were confirmed with high-performance liquid chromatography. Overall, the developed AuNPs-based immunochromatographic sensor was suitable and promising for the group-specific recognition and rapid detection of VB₆ in fortified foods and dietary supplements.

A gold immunochromatographic sensor (GICS) was developed for the rapid detection of 26 sulfonamides in honey samples. The sensor was based on a group-specific monoclonal antibody (mAb) that can recognize all 26 sulfonamides. Three haptens (hapten 1 with a thiazole ring, hapten 2 with a benzene ring, and hapten 3 with a straight carbon chain) were used for antigen preparation. With hybridoma technology, a group-specific mAb was screened with a 50% maximal inhibitory concentration (IC₅₀) against sulfathizole (STZ) and the other 25 analogues ranging from 0.08 to 90.18 ng/mL. Mono-dispersed gold nanoparticles were conjugated with the mAb to develop the lateral immunochromatographic strip. A labeled antibody concentration of 0.1 μg/mL and a coating antigen concentration of 0.2 μg/mL in the test line were chosen for strip preparation. Under optimized conditions, the visual limits of detection (vLOD) for the concentrations of STZ, sulfamethoxazole, sulfamethizole, sulfadiazine, sulfamerazine, sulfadimethoxine, sulfamonomethoxine, sulfameter, sulfamethoxypyridazine, and sulfachloropyridazine were 5, 0.25, 0.25, 10, 5, 10, 25, 2.5, 5, 0.25, and 10 μg/kg, respectively. Scanner analysis in honey samples revealed good performance for detection of the 26 sulfonamides. Commercial honey samples were tested with the sensor and positive results were confirmed with high-performance liquid chromatography. The proposed strip sensor provides a convenient method for the rapid and reliable determination of sulfonamides pollutants in honey samples.

For rapid and simultaneous detection of (fluoro)quinolones, a broadly specific monoclonal antibody (mAb) that recognizes 32 (fluoro)quinolone antibiotics was prepared using a mixture of a norfloxacin derivative and a sarfloxacin derivative as the hapten. An immunochromatographic strip based on gold nanoparticles (AuNPs) was then assembled with goat anti-mouse antibody and antigen (sarfloxacin coupled to ovalbumin), used to form the C line and T line, respectively. This antigen competes with the (fluoro)quinolones in a sample incubated with mAbs labeled with AuNPs. The strip can detect 32 (fluoro)quinolones including oxolinic acid, nalidixic acid, miloxacin, pipemidic acid, piromidic acid, rosoxacin, cinoxacin, norfloxacin, pefloxacin, lomfloxacin, enofloxacin, fleroxacin, ciprofloxacin, enrofloxacin, dafloxacin, orbifloxacin, sparfloxacin, gemifloxacin, besifloxacin, balofloxacin, gatifloxacin, moxifloxacin, nadifloxacin, ofloxacin, marbofloxacin, flumequine, pazufloxacin, prulifloxacin, sarafloxacin, difloxacin, trovafloxacin, and tosufloxacin in milk within 10 min with the naked eye. The cut-off values of the strip range from 1 to 100 ng/mL and the limits of detection are 0.1-10 ng/mL. The strip does not cross-react with antibiotics including tetracycline, sulfamethazine, ampicillin, erythromycin, aflatoxin B1, or gentamicin. In short, this immunochromatographic strip is a very useful tool for the primary screening of (fluoro)quinolones in milk.