title: Direct detection of unamplified hepatitis C virus RNA using unmodified gold nanoparticles.
abstract: BACKGROUND
  Gold nanoparticles (AuNPs) exhibit a unique phenomenon known as Surface Plasmon Resonance, which is responsible for their intense red color. This color changes to blue upon aggregation of AuNPs.
  
  
  OBJECTIVE
  This work aims to develop a rapid, simple and cheap assay for direct detection of unamplified HCV RNA extracted from clinical samples using unmodified AuNPs.
  
  
  METHODS
  Serum samples were collected from healthy volunteers (n=45) and chronic HCV patients (n=30). Extracted RNA, hybridization buffer containing PBS, and a primer targeting the 5'UTR of HCV were mixed. The mixture was denatured, annealed, and then cooled to room temperature for 10 min followed by addition of AuNPs.
  
  
  RESULTS
  Salt, primer, AuNPs concentrations and annealing temperature and time were all optimized. In HCV positive specimens, the color of the solution changed from red to blue within 1 min. The assay has a sensitivity of 92%, a specificity of 88.9%, and a detection limit of 50 copies/reaction.
  
  
  CONCLUSIONS
  To our knowledge, this is the first assay that allows the detection of unamplified HCV RNA in clinical specimens using unmodified AuNPs. The developed assay is highly sensitive, has a turnaround time of 30 min, and eliminates the need for thermal cycling and detection instruments.
authors.affiliation: Department of Chemistry & Yousef Jameel Science & Technology Research Center, the American University in Cairo, PO Box 74 New Cairo 11835, Egypt.
authors.forename: Sherif M
authors.initials: SM
authors.lastname: Shawky
authors.forename: Dirk
authors.initials: D
authors.lastname: Bald
authors.forename: Hassan M E
authors.initials: HM
authors.lastname: Azzazy
mesh_terms: D016022:Case-Control Studies; D003124:Colorimetry; D006046:Gold; D016174:Hepacivirus / Q000235:genetics / Q000302:isolation & purification*; D006526:Hepatitis C / Q000175:diagnosis; D006801:Humans; D057230:Limit of Detection; D053768:Metal Nanoparticles; D012367:RNA, Viral / Q000032:analysis* / Q000302:isolation & purification; D012680:Sensitivity and Specificity
chemical_list: D012367:RNA, Viral; D006046:Gold