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Porous Silicon in Biosensing Applications
Published in George K. Knopf, Amarjeet S. Bassi, Smart Biosensor Technology, 2018
With regard to the question of molecular size, this was not as straightforward a problem as it might initially appear. While early efforts had demonstrated that high molecular weight DNA sequences (such as lambda bacteriophage) could be efficiently captured, oligonucleotides are inherently flexible and rod-shaped. Therefore, their “molecular size” is not necessarily relevant to the problem of immobilizing and capturing peptides, proteins, and antibodies. Initial experiments in our laboratories with the extracellular domains of intimin and tir, two proteins critical to the infectious mechanism of enteropathogenic and enterohemmorhagic E. coli [24], were characterized by poor reproducibility. This suggested that even these two relatively small proteins (12 and 32 kDa, respectively) had difficulty entering the pores and/or became entrained in smaller channels within the PSi matrix in an inactive conformation. Since increasing the pore diameter was an essential prerequisite of moving forward, we examined the effect of dilute solutions of KOH post etch on the microcavities.
Molecular epidemiology of virulent E. coli among rural small scale dairy herds and shops: Efficacy of selected marine algal extracts and disinfectants
Published in International Journal of Environmental Health Research, 2022
Ahmed S. Ahmed, Hassan M. Diab, Mohammed A. Alkahtani, Mohammed A. Alshehri, Hani Saber, Heba Badr, Mohamed K. Dandrawy, Ahmed A. El-Mansi, Ali A. Shati, Ahmed Ezzat Ahmed
In the present study, virulent E. coli strains harboring eaeA and hly were recovered from 39.1% to 30.4% of milk and milk product samples and 62.5% and 37.5% of water sources commonly used in villages of Qena governorates. In addition, 34.8% and 50% of E. coli identified from milk/milk products and water samples carrying the virulent Stx1 genes which were classified as STEC strains. The intimin gene (eaeA) is a well-known virulence factor, not only for EPEC and EHEC but also for a typical EPEC. It enhances the virulence of STEC showing higher frequency in human strains than those of bovine (Blanco et al. 2004). Intimin, an outer membrane protein encoded by the eaeA gene helping E. coli, was found to intimate the attachment to intestinal epithelial cells, reducing the absorption capacity and stimulating the intestinal secretion (Wilshaw et al. 2000). The alpha-hemolysin (hly) of E. coli is one of the cytolytic pore-forming toxins (PFTs) which lyse the erythrocytes giving strong cytotoxic/cytolytic action against the nucleated cells (Söderström et al. 2017). Shiga toxins (cytotoxins) produced by E. coli are associated with a variety of human illnesses such as bloody or watery diarrhea, thrombotic thrombocytopenic purpura (TTP), hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS) in possible fatal consequences (Zastempowska et al. 2016). Ruminants, especially cattle, are the main reservoir of STEC and outbreaks associated with the consumption of milk and dairy products as reported worldwide (Vendramin et al. 2014).