Silver nanoparticles-based localized surface plasmon resonance biosensor for Escherichia coli detection

Escherichia coli (E. coli) bacteria with varying solution concentrations have been successfully detected using silver nanoparticles (Ag NPs)-based localized surface plasmon resonance (LSPR) biosensors. The Ag NPs were effectively synthesized by a chemical method using trisodium citrate with L-Histidine (L-His) and deposited on the surface of Au thin film-coated half-cylinder BK-7 prisms. He-Ne laser with a wavelength of 632.8 nm was used to generate LSPR phenomena in Kretschmann configuration with prism/Au thin film/His-Ag NPs/E. coli bacteria/air structure arrangements. The variation of E. coli bacteria concentration was carried out to determine the effect of E. coli bacteria concentration on the LSPR curve characteristics. The characterization results showed that the size of Ag NPs was 18.7 nm, and that of His-Ag NPs was 17.9 nm. Selected area electron diffraction results indicated the formation of diffraction rings with the presence of lattice planes (111), (200), (220), and (311), proving the face-centered cubic crystal structure of silver. The absorbance peak of Ag NPs shifted from a wavelength of 421-414 nm with an increase in band gap energy from 2.94 eV to 2.99 eV, along with a decreased average particle size. The functional groups observed in His-Ag NPs showed wavenumbers at 3320 to 3318 cm-1, 2106 to 2129 cm-1, and 1635 cm-1, showing the OH, CH, and C CO bonds, respectively. The SPR angle of the prism/Au thin film/air structure is 44.80°. Meanwhile, the LSPR angle for the prism/Au thin film/His-Ag NPs/air structure is 44.92°. There is an increase in the LSPR angle by 0.12°. Moreover, the minimum reflectance increases by 0.02. After detecting E. coli bacteria, the LSPR angle shifted by 0.26°, 0.38°, and 0.49° for concentrations of 6.0 × 108 CFU/mL, 6.0 × 107 CFU/mL and 6.0 × 106 CFU/mL respectively. However, the minimum reflectance rose from 0.09° to 0.14°, 0.20°, and 0.22°. Moreover, SPR testing with the structure of the prism/Au thin film/E. coli bacteria/air was carried out to determine the contribution of His-Ag NPs for detecting E. coli bacteria. The results showed that no angular shift occurs. These results indicate that using Ag NPs encapsulated with L-His is essential in amplifying the SPR signal and detecting E. coli bacteria. There was a notable alteration in both the LSPR angle and minimum reflectance indicating that adding His-Ag NPs facilitated the interaction between the E. coli and the sensor surface, thereby enhancing the performance of LSPR-based sensors for E. coli detection for low limit of detection value at 0.47 CFU/mL.

Distribution of glutathione peroxidase 1 in liver tissues of healthy and diabetic rats treated with capsaisin

We investigated the immunohistochemical localization of glutathione peroxidase 1 (GPx 1) and the structural changes that occur in the livers of healthy and diabetic rats that were treated with capsaisin (CAP). Fifty female rats were divided into five groups: group 1, sham; group 2, untreated control; group 3, CAP-treated; group 4, streptozotocin (STZ) diabetic; group 5, STZ diabetic + CAP-treated. STZ was administered to groups 4 and 5; after verifying diabetes, CAP was administered daily for 2 weeks to groups 3 and 5. Diffuse, microvesicular and some macrovesicular fatty degeneration were observed in the cytoplasms of hepatocytes in the livers of the diabetic group. In the CAP-treated diabetic group, fat degeneration in the livers decreased slightly by day 7. Irregularity of the external contours of nuclei of the hepatocytes, swelling of the nuclei, and slight anisocytosis and anisokaryosis were observed in the hepatocytes of the diabetic group. In the CAP-treated diabetic groups, the severity of anisocytosis and anisokaryosis decreased slightly by day 7. In all groups, GPx 1 showed similar immunolocalization, but in the diabetic and diabetic + CAP groups, GPx 1 immunoreactivity was less than in the other groups. GPx 1 immunoreactivity in the CAP-treated diabetic group was weaker than in the diabetic group. In all groups, GPx 1 immunoreactivity was diffusely cytoplasmic in some of the hepatocytes, and diffusely cytoplasmic and diffusely nuclear in other hepatocytes. Also, GPx 1 immunoreactivity in the liver was more intense in the hepatocytes around Kiernan's space. We found that CAP caused a decrease in GPx 1.

Fibroblast growth factor-2 and vascular endothelial growth factor expression in the ileocecal region of quail (Coturnix coturnix japonica)

We undertook this study to immunolocalize in quail vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF-2) in the ileocecal region, which is a significant entry point for intestinal immunity. Diffuse cytoplasmic reaction for FGF-2 and VEGF was observed in the epithelial cells of the distal ileum and proximal cecal mucosa. VEGF immunoreactive cells, which give strong intracytoplasmic immunoreaction, were observed in the lamina propria of both intestinal parts. FGF-2 immunoreactive cells were seen in the lamina propria and germinative centers of lymph follicles in the cecum mucosa. Expressions of FGF-2 and VEGF in healthy quail intestines indicate that these factors have physiological roles in quail.