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This study introduces the utilization of self-powered microbial fuel cell (MFC)-based biosensors for the detection of biotoxicity in wastewater. Current MFC-based biosensors lack specificity in distinguishing between different pollutants. To address this limitation, a novel approach is introduced, capitalizing on the adaptive capabilities of anodic biofilms. By acclimating these biofilms to specific pollutants, an enhancement in the selectivity of MFC biosensors is achieved. Notably, electrochemically active bacteria (EAB) were cultivated on 3D porous carbon felt with and without a model toxicant (target analyte), resulting in the development of toxicant-resistant anodic biofilms. The model toxicants, Pb2+ ions and the antibiotic neomycin sulfate (NS), were deployed at a concentration of 1 mg L−1 during MFC operation. The influence of toxicity on biofilm growth and power production was investigated through polarization and power density curves. Concurrently, the electrochemical activity of both non-adapted and toxicity-adapted biofilms was investigated using cyclic voltammetry. Upon maturation and attainment of peak powers, the MFC reactors were evaluated individually as self-powered biosensors for pollutant detection in fresh wastewater, employing the external resistor (ER) mode. The selected ER, corresponding to the maximum power output, was positioned between the cathode and anode of each MFC, enabling output signal tracking through a data logging system. Subsequent exposure of mature biofilm-based MFC biosensors to various concentrations of the targeted toxicants revealed that non-adapted mature biofilms generated similar current–time profiles for both toxicity models, whereas toxicity-adapted biofilms produced distinctive current–time profiles. Accordingly, these results suggested that merely by adapting the anodic biofilm to the targeted toxicity, distinct and identifiable current–time profiles can be created. Furthermore, these toxicity-adapted and non-adapted biofilms can be employed to selectively detect the pollutant via the differential measurement of electrical signals. This differentiation offers a promising avenue for selective pollutant detection. To the best of our current knowledge, this approach, which harnesses the natural adaptability of biofilms for enhanced sensor selectivity, represents a pioneering effort in the realm of MFC-based biosensing. [ABSTRACT FROM AUTHOR]

In this work, we reported a new strategy based on DNA strands hydrolysis in combination with the employment of functionalized carbon black modified screen‐printed electrode (f‐CB/SPE) for guanine detection. Using glass microbeads as a solid substrate of ssDNA probe fixation, and under appropriate conditions of temperature, time, and hydrochloric acid concentration, DNA hydrolysis has been successfully used to release the guanine, allowing its oxidation at f‐CB/SPE using differential pulse voltammetry. The selectivity was successfully tested with a non‐complementary sequence, and a detection limit of 0.7 nM of the target DNA has been reached. [ABSTRACT FROM AUTHOR]

Here a new colorimetric assay and electrochemical biosensor for microRNA detection based on magnetic bead separation and enzyme amplification are reported. MicroRNA-155 was selected as a model because of its involvement in breast and lung cancer. A novel platform was developed for label-free microRNA detection based on a sandwich assembly using streptavidin magnetic beads coupled with a biotinylated capture probe that hybridized only a portion of the microRNA, the remainder hybridized with biotinylated detection probe linked to streptavidin-alkaline phosphatase. After appropriate reaction with the substrate, the enzymatic product was evaluated with colorimetric and electrochemical detection. The electrochemical method showed high sensitivity, allowing microRNA detection at 29 pmol L−1, which correspond to 1.4 fmole in 50 μL with a linear range from 81 pmol L−1to 1.2 nmol L−1. This simple and efficient biosensor may have application in clinical molecular diagnostics and biomedical research. [ABSTRACT FROM PUBLISHER]

A novel and highly sensitive colorimetric DNA sensor for determination of miRNA-155 at attomolar levelsis presented that combines the peroxidase-like activity of copper nanoparticles (CuNPs) with the hybridization chain reaction (HCR) . The utilization of CuNPs offers advantages such as strong interaction with double-stranded DNA, excellent molecular recognition, and mimic catalytic activity. Herein, a capture probe DNA (P 1 ) was immobilized on carboxylated magnetic beads (MBs), allowing for amplified immobilization due to the 3D surface. Subsequently, the presence of the target microRNA-155 led to the formation of a sandwich structure (P 2 /microRNA-155/P 1 /MBs) when P 2 was introduced to the modified P 1 /MBs. The HCR reaction was then triggered by adding H 1 and H 2 to create a super sandwich (H 1 /H 2 ) n . Following this, Cu 2+ ions were attracted to the negatively charged phosphate groups of the (H 1 /H 2 ) n and reduced by ascorbic acid, resulting in the formation of CuNPs, which were embedded into the grooves of the (H 1 /H 2 ) n . The peroxidase-like activity of CuNPs catalyzed the oxidation reaction of 3,3',5,5'-Tetramethylbenzidine (TMB), resulting in a distinct blue color measured at 630 nm. Under optimal conditions, the colorimetric biosensor exhibited a linear response to microRNA-155 concentrations ranging from 80 to 500 aM, with a detection limit of 22 aM, and discriminate against other microRNAs. It was also successfully applied to the determination of microRNA-155 levels in spiked human serum., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)