Detection of Aeromonas hydrophila possessing aerolysin gene using gold nanoparticle probe.

Objective: The aerolysin (aerA) is a virulence indicator used to identify the pathogenicity of the Aeromonas strain. Targeting a pathogen's crucial virulence gene for detection is essential, as it determines the potential threat to the host. This study aimed to develop a gold nanoparticle (AuNP) probe for detecting the gene aerA in Aeromonas hydrophila among field samples. Materials and Methods: Kidney samples among both healthy and sick Nile tilapias in five provinces of Luzon Island were collected for bacterial analysis. Screening using specific primers targeting aerA was conducted in parallel with testing the AuNPs probe on the same sample set. The positive control provided by BFAR-NFLD, confirmed by polymerase chain reaction (PCR) assay, was used as a positive sample containing the target gene. Results: The AuNP probe demonstrated a computed accuracy of 81.32%, sensitivity of 100%, and specificity of 81.26%. Among the 257 reactions, 59 were false positives, while no false negative results were observed. The AuNP probe could detect aerA at levels as low as 30 ng/µl. The low prevalence of the target gene may be attributed to the use of general media instead of specific media like Rimler-Shotts agar. Conclusion: The established colorimetric detection method for A. hydrophila with the aerA gene offers a swift alternative to PCR, negating the requirement for advanced equipment like a thermal cycler.

Gold nanoparticle-based probes for the colorimetric detection of Mycobacterium avium subspecies paratuberculosis DNA.

Gold nanoparticle (AuNP) is considered to be the most stable metal nanoparticle having the ability to be functionalized with biomolecules. Recently, AuNP-based DNA detection methods captured the interest of researchers worldwide. Paratuberculosis or Johne's disease, a chronic gastroenteritis in ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP), was found to have negative effect in the livestock industry. In this study, AuNP-based probes were evaluated for the specific and sensitive detection of MAP DNA. AuNP-based probe was produced by functionalization of AuNPs with thiol-modified oligonucleotide and was confirmed by Fourier-Transform Infrared (FTIR) spectroscopy. UV-Vis spectroscopy and Scanning Electron Microscopy (SEM) were used to characterize AuNPs. DNA detection was done by hybridization of 10 µL of DNA with 5 µL of probe at 63 °C for 10 min and addition of 3 µL salt solution. The method was specific to MAP with detection limit of 103 ng. UV-Vis and SEM showed dispersion and aggregation of the AuNPs for the positive and negative results, respectively, with no observed particle growth. This study therefore reports an AuNP-based probes which can be used for the specific and sensitive detection of MAP DNA.

Green synthesis of gold nanoparticles reduced and stabilized by sodium glutamate and sodium dodecyl sulfate.

The Turkevich method has been used for many years in the synthesis of gold nanoparticles. Lately, the use of plant extracts and amino acids has been reported, which is valuable in the field of biotechnology and biomedicine. The AuNPs was synthesized from the reduction of HAuCl4 3H2O by sodium glutamate and stabilized with sodium dodecyl sulfate. The optimum concentrations for sodium glutamate and sodium dodecyl sulfate in the synthesis process were determined. The characteristics of the synthesized AuNPs was analysed through UV-Vis Spectroscopy and SEM. The AuNPs have spherical shape with a mean diameter of approximately 21.62 ± 4.39 nm and is well dispersed. FTIR analysis of the AuNPs reflected that the sulfate head group of sodium dodecyl sulfate is adsorbed at the surface of the AuNPs. Thus, we report herein the synthesis of AuNPs using sodium glutamate and sodium dodecyl sulfate.