Competitive fluorescent immunoassay for the ultrasensitive determination of amyloid beta peptide1-42 based on Ag@SiO2@N, S-GQD nanocomposites.

A competitive fluorescent immunoassay is described for the ultrasensitive determination of amyloid beta peptide1-42 (Aß1-42), a biomarker for early diagnosis of Alzheimer's disease. N, S-doped graphene quantum dots (N, S-GQDs) were freely assembled on the surface of Ag@SiO2 nanoparticles to obtain a composite (Ag@SiO2@N, S-GQD nanocomposite), which was successfully prepared and characterized. By theoretical study, the optical properties of nanocomposites are improved compared with GQDs, due to the advantages of combining N, S co-doping and metal-enhanced fluorescence (MEF) effect of Ag NPs. In addition, Aß1-42 was modified by Ag@SiO2@N, S-GQDs to prepare a probe with high photoluminescence properties (Ag@SiO2@N, S-GQDs-Aß1-42). In the presence of Aß1-42, a competitive reaction towards anti-Aß1-42 fixed on the ELISA plate was proceeded between Aß1-42 and Ag@SiO2@N, S-GQDs-Aß1-42 by specific capture of antigen-antibody. The emission peak of Ag@SiO2@N, S-GQDs-Aß1-42 (400 nm emission) was used for the quantitative determination of Aß1-42. Under the optimal conditions, the fluorescent immunoassay exhibited a linear range of 0.32 pg·mL-1-5 ng·mL-1 with a detection limit of 0.098 pg·mL-1. The results show that the immunoassay has good analytical ability and can provide a new method for the clinical determination of Aß1-42.

Simplification of the Acidithiobacillus ferrooxidans Culture Process for Expanding the Field of Biomachining.

Biomachining is an eco-friendly metal processing method with broad application potential. Nevertheless, the bacterial culture methods that are currently involved in biomachining require the intensive use of chemical reagents, especially FeSO4, specialized equipment, and professional-level skills in the field of biology. Herein, the differences between two cultures with and without sterilization were evaluated. Acidithiobacillus ferrooxidans was cultured with iron instead of FeSO4 in the culture medium. The chemical and biochemical parameters of the culture were analyzed by studying the area of exposed iron and continuously regulating the pH. Eliminating the sterilization and sterile inoculation of the medium is feasible for culturing A. ferrooxidans. The key to achieving a high bacterial density in culture with iron was to maintain the solution pH. The possibility of mass culturing A. ferrooxidans with steel cuttings was evaluated in a custom bioreactor, and the bacterial concentration reached 9 × 107 cells/mL.

An ultrasensitive unlabeled electrochemical immunosensor for the detection of cardiac troponin I based on Pt/Au-B,S,N-rGO as the signal amplification platform.

In this study, an ultrasensitive unlabeled electrochemical immunosensor for the detection of cardiac troponin I (cTnI) was developed based on Pt/Au modified B,S,N co-doped reduced graphene oxide (Pt/Au-B,S,N-rGO) as a signal amplification platform. First-principles calculations were employed to analyze the electron density of states of Pt/Au-B,S,N-rGO, revealing an increase in the electron density of the graphene oxide (GO) states. Furthermore, scanning electron microscopy (SEM), X-ray photoelectron diffraction spectroscopy (XPS), and electrochemical detection were used to successfully construct and analyze Pt/Au-B,S,N-rGO. The results showed that B,S,N-rGO exhibited good electrochemical activity, and the Au/Pt NPs demonstrated excellent catalytic properties, which provided a strong foundation for achieving high-sensitivity detection. Moreover, the constructed unlabeled electrochemical immunosensor had an ideal linear range (0.1 pg/mL∼50 ng/mL) and detection limit (0.082 pg/mL). In human serum detection, the results of this immunosensor were essentially similar to the ELISA results for the same samples, which suggested that the immunosensor had a promising clinical application prospect for the detection of cTnI.

A label-free electrochemical immunosensor based on Au-BSN-rGO for highly-sensitive detection of ß-amyloid 1-42.

A label-free electrochemical immunosensor for high-sensitive detection of ß-amyloid 1-42 (Aß 1-42) was constructed based on Au-modified B, S, and N co-doped reduced graphene oxide (Au-BSN-rGO). The electronic structure of Au-BSN-rGO was investigated by first-principles calculations, which showed that the band gap of graphene was opened, thus improving its electrical conductivity. Moreover, Au-BSN-rGO was successfully prepared and characterized, and the obtained results discovered that it could be used as a signal amplifier for immunosensors due to the advantages of the good electrochemical characteristics and enormous surface area of BSN-rGO and the accelerated electron transfer ability of Au NPs. Furthermore, the label-free electrochemical immunosensor had a linear detection range of 0.1 pg mL-1-10 ng mL-1 and a detection limit of 0.072 pg mL-1, and it had good specificity, stability, and reproducibility. Also, this immunosensor showed recoveries of 89%-109% with an RSD of 2.61%-4.19% for detecting Aß 1-42 in actual sample analysis. Therefore, the label-free electrochemical immunosensor based on Au-BSN-rGO should have a promising clinical application prospect for detecting Aß 1-42.

A sensitive ratiometric biosensor for determination cardiac troponin I of myocardial infarction markers based on N, Zn-GQDs.

A sensitive unlabeled ratiometric biosensor was developed to the detection of cardiac troponin I (cTnI). This biosensor was established by using the glassy carbon electrode coated with graphene oxide to form a platform bonded with N, Zn co-doped graphene quantum dots (N, Zn-GQDs). The N, Zn-GQDs was successfully prepared as the raw materials of graphite powder and characterized. Antibodies of cTnI were bonded to the surface of N, Zn-GQDs as the nanoprobe by amide bonds. The signals of electrochemiluminescence (ECL) and differential pulse voltammetry (DPV) were exposed to decrease in the presence of cTnI, which caused the signal substance to move farther away from the electrode. It was found that the immune complex layer attenuated the intensity of ECL and DPV which could be used as the good overall signal for determining concentration of cTnI. The ratiometric biosensor had a good response to cTnI with the detection limit is 4.59 pg L-1 in the concentration range of 10-106 pg L-1. The developed method was evaluated for the detection of cTnI in human serum, and the obtained results were consistent compared to the reference values obtained by hospital standard enzyme linked immunoassay (ELISA) with 9.09%-11.1% of RSD. Our findings suggested that this ratiometric biosensor could be used to the detection of cTnI in human serum with lower cost and higher sensitivity, it also might be better potential application prospect based on N, Zn-GQDs to detect other biomarkers.