A dual-mode "signal-on" split-type aptasensor for bisphenol A via target-induced hybridization chain reaction amplification

Digital multimeter-based portable photoelectrochemical immunoassay with enzyme-catalyzed precipitation for screening carbohydrate antigen 125

The degree of the carbohydrate antigen 125 (CA-125) level in serum is positively correlated with the severity of ovarian cancer. In this study, a facile photoelectrochemical (PEC) immunoassay was devised for sensitive detection of CA-125 employing enzyme-catalyzed precipitation to weaken the photocurrent of hollow porous In2O3 nanotubes incorporating CdS nanoparticles. Upon the addition of the target analyte, horseradish peroxidase (HRP) enriches as a result of the formation of the sandwich immunocomplex, which can catalyze the conversion of 4-chloro1-naphthol (4-CN) to benzo-4-chlorohexadienone (4-CD) employing H2O2 as a cofactor. The as-produced insoluble precipitate acts as an obstacle to hinder the absorption of visible light by photoactive materials, thereby resulting in a decrease in photocurrent. Moreover, the weakened signal can be easily read out by a digital multimeter (DMM), advancing the convenience of the detection system. The preliminary analysis data indicate that the PEC immunoassay shows an efficient response to CA-125 levels ranging from 0.1 to 100 U mL-1 with a limit of detection (LOD) as low as 0.046 U mL-1 (S/N = 3). Most importantly, the proposed portable method has shown satisfactory performance in terms of selectivity, reproducibility, stability, and analysis in complex biological matrices.

Signal amplification strategy of DNA self-assembled biosensor and typical applications in pathogenic microorganism detection

Biosensors have emerged as ideal analytical devices for various bio-applications owing to their low cost, convenience, and portability, which offer great potential for improving global healthcare. DNA self-assembly techniques have been enriched with the development of innovative amplification strategies, such as dispersion-to-localization of catalytic hairpin assembly, and dumbbell hybridization chain reaction, which hold great significance for building biosensors capable of realizing sensitive, rapid and multiplexed detection of pathogenic microorganisms. Here, focusing primarily on the signal amplification strategies based on DNA self-assembly, we concisely summarized the strengths and weaknesses of diverse isothermal nucleic acid amplification techniques. Subsequently, both single-layer and cascade amplification strategies based on traditional catalytic hairpin assembly and hybridization chain reaction were critically explored. Furthermore, a comprehensive overview of the recent advances in DNA self-assembled biosensors for the detection of pathogenic microorganisms is presented to summarize methods for biorecognition and signal amplification. Finally, a brief discussion is provided about the current challenges and future directions of DNA self-assembled biosensors.