Ultrasensitive quantitation of Paraquat based on a small molecule-induced dual-cycle amplification strategy.

Paraquat (PQ) is a typical biotoxic small molecule. Knowledge of how to directly introduce it into cyclic amplification rather than transform it into a secondary target is lacking in current analytical methods. Considering the urgent need for trace pesticide residue detection and the inherent defects of small molecule analysis, a CRISPR/Cas12a-driven small molecule-induced dual-cycle strategy was developed based on the immune competition method. The key to signal amplification is the mutual activation and acceleration between Cycle 1 triggered by the small molecule and Cycle 2 driven by CRISPR/Cas12a. Impressively, small molecules have been successfully incorporated into the dual-cycle strategy, which achieves a low detection limit (3.1 pg/mL) and a wide linear range (from 10 pg/mL to 50 µg/mL). Moreover, the designed biosensor was successfully employed to evaluate the PQ residual level in real samples and showed effective implementation for the bioanalysis of small molecule targets and pesticide residue-related food safety.

Ultrasensitive electrochemical strategy for NT-proBNP detection with gold nanochains and horseradish peroxidase complex amplification.

A novel electrochemical immunosensor for sensitive detection of cardiac biomarker N-terminal pro-B-type natriuretic peptide (NT-proBNP) is fabricated based on the nanostructural gold and carbon nanotubes composite as desirable platform for the capture antibodies immobilization and gold nanochains (AuNCs) and horseradish peroxidase (HRP) complex labeled secondary antibodies (AuNCs-HRP-Ab(2)) for signal amplification. The gold nanochains were prepared by the employment of L-ascorbic acid (AA) as a mediator and template. With the surface area enhancement by nanostructural gold functionalized carbon nanotubes composite, the amount of immobilized primary antibodies (Ab(1)) can be enhanced. More importantly, enhanced sensitivity can be achieved by introducing the multibioconjugates of AuNCs-HRP-Ab(2) onto the electrode surface through "sandwich" immunoreactions. The linear range extended from 0.02 to 100 ng/mL with a correlation coefficient of R=0.997 and a limit of detection reaching 6 pg/mL at a signal-to-noise ratio of 3:1, which is well below the commonly accepted concentration threshold (0.1 ng/mL) used in clinical diagnosis. The specificity, regeneration and stability test demonstrated the feasibility of the developed immunoassay, which gives the attractive characteristics to be a candidate for the detection of NT-proBNP and other proteins of interest in both fundamental and applied research.

[Preparation and characterization of rabbit anti-human apurinic/apyrimidinic endonuclease(APE1) polyclonal antibody].

AIM: To prepare a rabbit anti-human apurinic/apyrimidinic endonuclease polyclonal antibody and then have its characterization analyzed. METHODS: A rabbit polyclonal antibody was prepared through a modified rapid immune procedure and then it was purified using a specific avidity column. The efficacy of this antibody was detected by ELISA, Western blot and immunohistochemistry. RESULTS: The titer of the antiserum determined by ELISA was up to 1:128,000. The kaff value of the antibody was 8.96 x 10(-6) mol/L. Western blot analysis showed the antibody was of high specificity. The final purified antibody was highly specific to native form of APE1 protein in mice and rats. CONCLUSION: The rabbit anti-human APE1 polyclonal antibody with high titer and specificity has been successfully prepared. It can be used not only to elucidate the roles of APE1 protein in many important cellular procedures, but also to detect the expression of the APE1 protein in mice and rats.