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A label-free electrochemical strategy is proposed combining equivalent substitution effect with AuNPs-assisted signal amplification. According to the differences of S1 protein in various infectious bronchitis virus (IBV) strains, a target DNA sequence that can specifically recognize H120 RNA forming a DNA-RNA hybridized double-strand structure has been designed. Then, the residual single-stranded target DNA is hydrolyzed by S1 nuclease. Therefore, the content of target DNA becomes equal to the content of virus RNA. After equivalent coronavirus, the target DNA is separated from DNA-RNA hybridized double strand by heating, which can partly hybridize with probe 2 modified on the electrode surface and probe 1 on AuNPs’ surface. Thus, AuNPs are pulled to the surface of the electrode and the abundant DNA on AuNPs’ surface could adsorb a large amount of hexaammineruthenium (III) chloride (RuHex) molecules, which produce a remarkably amplified electrochemical response. The voltammetric signal of RuHex with a peak near − 0.28 V vs. Ag/AgCl is used as the signal output. The proposed method shows a detection range of 1.56e−9 to 1.56e−6 μM with the detection limit of 2.96e−10 μM for IBV H120 strain selective quantification detection, exhibiting good accuracy, stability, and simplicity, which shows a great potential for IBV detection in vaccine research and avian infectious bronchitis diagnosis. Graphical abstract Electronic supplementary material The online version of this article (10.1007/s00604-020-04582-3) contains supplementary material, which is available to authorized users.

An aptamer based assay is presented for the determination of the antibiotics oxytetracycline (OTC) and kanamycin (KAN). Magnetic beads were applied for separation, and gold nanoparticles (AuNPs) for signal amplification. DNA aptamers against OTC and KAN were firstly designed. After specific recognition events, the aptamer sequences were released from the surface of magnetic beads and the remaining DNA probes captured horseradish peroxidase (HRP) modified AuNPs. Subsequently, 3,3′,5,5′-tetramethylbenzidine and o-phenylenediamine are catalytically oxidized by HRP, and the generated colorimetric responses can reflect the concentrations of OTC (at 370 nm) and KAN (at 450 nm), respectively. Experimental results demonstrate that the method is highly sensitive with the detection limit as low as 1 ag mL−1 for OTC and KAN. An extremely wide linear range (over 11 orders of magnitude) is achieved. The high selectivity is attributed to the high affinity between aptamer and the substrate. The results of real sample tests also verify that the method is promising for antibiotics analysis in the applications of food monitoring and clinical diagnosis.

Taurine (Tau) is reported to have a key role in the regulation of the innate immune response and thus reduce tissue damage induced by bacterial infection. In this study, the effects of Tau on a rat model of mastitis induced by Streptococcus uberis (S. uberis) and the changes of T regulatory cells (Tregs) were assessed. Starting on gestation day 14 and continuing until parturition, 100 mg/kg of taurine (group TS) or an equal volume of physiological saline (group CS) was administered daily, per os. Seventy-two hours after parturition, rats were infused with approximately 100 cfu of S. uberis into each of two mammary glands. The results showed that the resultant inflammation, evidenced by swelling, secretory epithelial cell degeneration, increased adipose tissue and neutrophil (PMN) infiltration were evident in mammary tissue following injection with S. uberis. Pre-treatment with Tau attenuated these morphologic changes, the expression of interleukin (IL)-2, interferon (INF)-γ mRNA, myeloperoxidase (MPO) activity and N-acetyl-β-D-glucosaminidase (NAGase) in mammary tissue. The percentages of Foxp3+CD25+CD4+/lymphocytes (Tregs) were dramatically increased after the S. uberis challenge. Significant differences (P