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Despite major advances in biosensing, quick, dependable, and effective on-site detection of bacterial infections remains a serious issue, owing to a lack of acceptable or appropriate diagnostic platforms. To address this gap, we presented a new colorimetric gold NanoZyme aptasensor for rapid sensing of Aeromonas veronii, an infectious bacterial disease in fish. The A. veronii-specific aptamer (AVS01) was developed through Cell-SELEX. The sensing mechanism involves inhibition of AuNPs induced peroxidase-mimic catalytic activity through surface adsorption by AVS01 which in the presence of the A. veronii desorb from the AuNPs allowing recovery of the catalytic activity leading to colorimetric response, whereas the sensor is insesnsitive to other nontarget bacterial cells. This method is very specific and sensitive, allowing for the quick and visible sensing of A. veronii with a detection limit of 1281 CFU mL−1 within 15 min. The method has great potential for rapid diagnosis of bacterial infection in fish caused by A. veronii.

Monolayer tungsten disulfide (1L-WS2) exhibits excellent optical properties due to its direct bandgap. The extraordinary photoluminescence (PL) emission at room temperature from CVD-grown 1L-WS2 was utilized for the first time here as a recognition tool for detecting S. aureus bacteria with high sensitivity and selectivity. The 1L-WS2 possesses sulfur vacancy, which has been utilized for single-standard DNA (ssDNA) aptamer immobilization via the thiol functional group. The small-sized, highly selective ssDNA aptamers identify and selectively interact with targeted S. aureus, enabling selective detection. Interestingly, the PL emission of 1L-WS2 is strongly influenced by external charge doping. The shape of the PL emission peak of 1L-WS2 undergoes significant changes in the presence of targeted S. aureus as a result of charge transfer originating from selective interactions between ssDNA aptamer and S. aureus, while it remains unaffected for non-targeted Escherichia coli. The ratio of the integrated intensities of trion to neutral exciton peak was used as a calibration parameter for the quantification of S. aureus concentrations. The PL analysis of 1L-WS2 with increasing concentration of S. aureus exhibits a linear response over 102 CFU/mL to 107 CFU/ml with a lower detection limit of 2.0 CFU/mL. The proposed sensing system can identify an unknown concentration of S. aureus in human urine with 78% accuracy at a concentration of 105 CFU/mL. These results demonstrate the potential future generation applications of monolayer transition metal dichalcogenides in the optical biosensing of pathogenic species using suitable receptors.

Printed circuit boards, chemical etching, and computer numerical control milling currently dominate industrial processes for manufacturing microwave components. However, these manufacturing methods do not provide the flexibility for customization possible with additive manufacturing. Additive manufacturing (AM) has the potential to fabricate microwave components for desired frequency ranges with less effort in prototyping and fabrication. Relative permittivity (εr) of materials is a critical parameter in microwave component design, yet the value changes during the AM process. This article investigates how relative permittivity for nylon substrates, created with AM, changes with different infill densities and infill patterns. The measurement method and procedure can be used to design AM microwave components like antennas or dielectric-filled waveguides with desired characteristics. The two-microstrip-line method was used and improved for the accurate and convenient measurement of the relative permittivity of AM nylon substrates. Several nylon substrates with different infill patterns, including rectangular, hexagonal, triangular, and solid, were fabricated with AM to demonstrate how the relative permittivity value changes as the infill density increases. A linear relationship between the infill density of the rectangular pattern and the substrate permittivity was found. The permittivity data were applied to the design of a rectangular patch antenna for use in the 2.5-GHz WiMAX band. The fabricated antenna with AM, which was tested using a vector network analyzer, showed good agreement with simulation results. The method and procedure of permittivity measurements are specially designed to be applied in the design of microwave components with AM dielectric substrates.