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.

Rare Case of Periampullary Duodenal Carcinoma

Periampullary carcinoma is a malignancy that appears around the vatteri ampulla. This malignancy can originate from the pancreas, duodenum, and distal choledochal duct. Duodenal cancer is a very rare case, only about 0.3% of the gastrointestinal malignancies. Reported cases are increasing with the increasing use of esophagogastroduodenoscopy. The most frequently found carcinomas of the duodenum include adenocarcinoma, carcinoid, lymphoma, and leiomyosarcoma. The symptoms of these carcinomas are often not specific so the diagnosis is often late, leading to a poor prognosis. Early diagnosis and proper therapy provide a good prognosis. The case reported here representeda 52-year-old woman presented with hematemesis melena, anemia, jaundice, epigastric mass, right hypochondrial pain, and weight loss. From the esophagogastroduodenoscopy, the mass was found to obstruct half of the duodenum lumen and bleeding, which was easily triggered, was observed in the second part of the duodenum. CT scan revealed a mass in the head of the pancreas with gall bladder hydrops and obstruction of the intra and extra-hepatic billier system. After a Whipple operation Laparotomy, the histology showed papillary adenocarcinoma duodenum. Patients then underwen chemotherapy with 5 fluorouracil regimen. Patient's clinical condition is currently improving and no complaint is conveyed by the patient.