The kiwi plant is dioecious, and its sex is generally identified from flower morphology at blossoming, which takes several years. It is quite necessary but challenging to on-spot identify the plant sex in juvenile stage. Here the target DNA was obtained by screening the Friendly boy ( FrBy ) gene which is sex-related for different kiwi plant species. Its complementary sequence was divided into two parts as primer DNA and further attached to different gold nanoparticles (GNPs). The connection between target DNA and primer DNA will promote the formation of plasmonic dimers. Dark field microscopy (DFM) can distinguish particles in different aggregation states. Various conditions were optimized based on the standard of increasing the proportion of dimers while reducing that of large aggregates. Furthermore, two Raman reporters (RR) are separately labeled on the nanoprobes, and the plasmonic dimers lead to a tremendous Raman enhancement of two reporters located at the dimer nanogap. Double-blind tests proved the feasibility of this method on the actual samples of kiwi plant leaves. Our SERS method is sensitive, specific, and reliable for rapid sex identification analysis at the kiwi seeding stage, with great promise for decision-making in field management.
A novel capacitance immunosensor based on DNAzyme concatemer-amplified signal-generation tags was developed for the sensitive detection of interleukin-6 (IL-6) on an interdigitated micro-comb electrode. To construct such an immunosensor, monoclonal mouse anti-human IL-6 antibodies were covalently conjugated onto a bovine serum albumin (BSA)-coated electrode using the glutaraldehyde cross-linker. Gold nanoparticles heavily functionalized with primer DNA (for the subsequent rolling cycle amplification; RCA) and polyclonal rabbit anti-human IL-6 antibodies were used for the development of a sandwich-type immunoassay on the modified interdigitated electrode in the presence of the target IL-6. Thereafter, the attached primer DNA with the immunocomplex triggered the RCA reaction for the formation of numerous DNAzyme concatemers with the assistance of hemins and G-rich DNA probes. DNAzyme concatemers catalyzed 4-chloro-1-naphthol into insoluble benzo-4-chlorohexadienone and were deposited onto the electrode, thus resulting in the local capacitance variation of the interdigitated micro-comb electrode. The performance and external factors affecting the analytical properties were studied in detail. Under optimum conditions, the capacitance variations of the immunosensor were proportional to the IL-6 concentration in the dynamic range of 1.0–1000 pg mL−1 at a detection limit of 0.68 pg mL−1. Good reproducibility, high specificity and acceptable storage stability were acquired for the analysis of the target IL-6. Moreover, the capacitance immunosensor was utilized to determine IL-6 in human serum specimens and gave well-matched analytical results in reference to the human IL-6 ELISA kit.
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