Changlong Qu

Simple, rapid and sensitive detection of antibiotics based on the side-by-side assembly of gold nanorod probes

In this work, we report on the application of versatile gold nanorods (GNRs) in optical sensors for the detection of antibiotics. The target analyte, Gentamicin (GM) and ovalbumin (OVA)-antigen-modified GNRs together competed with antibody-modified GNRs, then influenced the formation of side-by-side aggregates of the GNRs by antibody-antigen interactions. Accordingly, the UV-vis absorption intensity of the side-by-side aggregates was changed in the presence of the target analyte. This assay allowed the selective determination of GM in the range of 0.1-20 ng/mL, and the limit of detection (LOD) of GM was 0.05 ng/mL. Furthermore, compared with the traditional plate-based immunoassay, the developed method was easy to perform without washing cycles and the results could be read as soon as the nanoprobe-analyte incubation was complete. Therefore, the developed method could be a promising tool for the detection of antibiotic residues.

Development and application of one-step ELISA for the detection of neomycin in milk

A sensitive enzyme-linked immunosorbent assay (ELISA) for the detection of neomycin (NEO) in milk was developed. Two conjugates were synthesized as the immunogen and coating antigen. Four BALB/c female mice were immunised and the antisera were screened by indirect competitive ELISA (icELISA). The icELISA was further optimised using different coating methods, pH values, ionic strengths of assay buffer and reaction times. After optimised, the indirect competitive ELISA (icELISA) could be finished in 85min with an IC50 value of 0.74±0.05 ng/mL. One-step indirect competitive ELISA (icELISA) exhibited similar sensitivity with an IC50 value of 0.73±0.03 ng/mL, which was sensitive enough for NEO detection and could be finished in 55 min. No cross-reactivity of the antibody was observed with other aminoglycosides based on icELISA, indicating that the antibody is highly specific for neomycin. Milk samples were further analyzed with recovery ranging from 85 to 110% at spiked level of 0.25–10 ng/mL, and the detection limit was 0.08 ng/mL.