The Promise of Advanced Imaging Techniques for the Detection of Hepatitis C Virus Antigens in the Infected Liver  Benno Wölk, MD, Darius Moradpour, MD  Gastroenterology  Volume 137, Issue 4, Pages 1214-1218 (October 2009) DOI: 10.1053/j.gastro.2009.08.027 Copyright © 2009 AGA Institute Terms and Conditions

Figure 1 Quantum dot (Qdot) staining and 2PE microscopy of HCV antigens in the liver. (A) Liver specimens from HCV-infected patients were obtained during liver surgery for hepatocellular carcinoma or by percutaneous liver biopsy. (B) HCV-specific antigens and dsRNA were immunolabeled with monoclonal antibodies that were directly conjugated with Qdots (illustrated here) or, indirectly, using Qdot-coupled secondary antibodies (not illustrated). (C) Liver tissue was then analyzed by 2PE microscopy. Whereas in conventional 1-photon fluorescence microscopy a single photon (with a wavelength of 510 nm, for example) is able to promote a fluorescent molecule from a ground state (S0) to an excited state (S*), in 2PE microscopy 2 photons (1020 nm) are simultaneously absorbed whose total energy produces the same molecular transition and results in identical emission (530 nm in this example). The effect requires very high excitatory photon densities that are reached only in the focal volume (green) but not in the remaining illumination path (red), thereby eliminating out-of-focus fluorescence. Gastroenterology 2009 137, 1214-1218DOI: (10.1053/j.gastro.2009.08.027) Copyright © 2009 AGA Institute Terms and Conditions