Direct detection of unamplified hepatitis C virus RNA using unmodified gold nanoparticles

BackgroundGold 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.ObjectiveThis work aims to develop a rapid, simple and cheap assay for direct detection of unamplified HCV RNA extracted from clinical samples using unmodified AuNPs.MethodsSerum 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.ResultsSalt, 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.ConclusionsTo 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.