Salmonella typhimurium detection and ablation using OmpD specific aptamer with non-magnetic and magnetic graphene oxide.

Foodborne diseases have increased in the last few years due to the increased consumption of packaged and contaminated food. Major foodborne bacteria cause diseases such as diarrhea, vomiting, and sometimes death. So, there is a need for early detection of foodborne bacteria as pre-existing detection techniques are time-taking and tedious. Aptamer has gained interest due to its high stability, specificity, and sensitivity. Here, aptamer has been developed against Salmonella Typhimurium through the Cell-Selex method, and to further find the reason for specificity and sensitivity, OmpD protein was isolated, and binding studies were done. Single molecular FRET experiment using aptamer and graphene oxide studies has also been done to understand the mechanism of FRET and subsequently used for target bacterial detection. Using this assay, Salmonella Typhimurium can be detected up to 10 CFU/mL. Further, Magnetic Graphene oxide was used to develop an assay to separate and ablate bacteria using 808 nm NIR where temperature increase was more than 60 °C within 30 s and has been shown by plating as well as a confocal live dead assay. Thus, using various techniques, bacteria can be detected and ablated using specific aptamer and Graphene oxide.

Influence of Fe(III) on the Fluorescence of Lysozyme: a Facile and Direct Method for Sensitive and Selective Sensing of Fe(III).

Lysozyme is widely used for the synthesis of nanomaterials (e.g., gold nanoparticle) to fluorescently sense metal ions. However, the effect of metal ions on the fluorescence of lysozyme is not studied yet. Herein, we have explored the interactions of lysozyme with different metal ions to develop a direct sensing platform for Fe(III). It has been observed that the fluorescence of lysozyme was slightly decreased in the presence of Cu(II), Hg(II), As(V), Co(II), Cd(II), Cr(II), Fe(II), Mn(II), Pb(II), and Zn(II), while a significant decrease in the lysozyme fluorescence was observed for Fe(III). The effect of thermal stability on the fluorescence quenching was also studied from 25 to 60 °C. In the present study, the lysozyme sensing probe was able to selectively and accurately detect 0.5-50 ppm of Fe(III) with a LOD of 0.1 ppm (1.8 µM) at 25 °C.

Experimental and Computational Study on the Selective Interaction of Functionalized Gold Nanoparticles with Metal Ions: Sensing Prospects.

Herein, we have developed citrate-, glutathione-, and ascorbate-functionalized gold nanoparticles (AuNPs) to examine their interactions with diverse heavy metal ions, such as Cd, Mn, Cr, Fe, Co, Pb, Hg, Zn, and Ti. These interactions are crucial in defining the final outcome of AuNP-based sensing/removal of heavy metals. We have evaluated these interactions by analyzing the variations in the color and spectroscopic signals of functionalized AuNPs. Additionally, the obtained results were also compared and validated with the computational studies. It has been observed that citrate-AuNPs and GSH-AuNPs displayed high selectivity toward Cr and Mn with Eforce values of -23.4 and -14.0 kJ/mol, respectively. Likewise, the ascorbate-AuNPs displayed sensitivity for multiple ions, for example, Cd, Fe, and Mn, with an Eforce value of -19.6 kJ/mol. A detailed analysis focusing on the electrostatic charges, ionic sizes, and interaction energy values has been provided to show specific interactions between functionalized AuNPs and heavy metal ions. The respective mechanisms of interaction between heavy metal ions and functionalized AuNPs have been explored with the help of experimental and computational outcomes.