title: Performance of the red-shifted fluorescent proteins in deep-tissue molecular imaging applications.
abstract: The discovery of new fluorescent proteins (FPs) that emit in the far-red part of the spectrum, where light absorption from tissue is significantly lower than in the visible, offers the possibility for noninvasive biological interrogation at the entire organ or small animal level in vivo. The performance of FPs in deep-tissue imaging depends not only on their optical characteristics, but also on the wavelength-dependent tissue absorption and the depth of the fluorescence activity. To determine the optimal choice of FP and illumination wavelength, we compared the performance of five of the most promising FPs: tdTomato, mCherry, mRaspberry, mPlum, and Katushka. We experimentally measured the signal strength through mice and employed theoretical predictions to obtain an understanding of the performance of different illumination scenarios, especially as they pertain to tomographic imaging. It was found that the appropriate combination of red-shifted proteins and illumination wavelengths can improve detection sensitivity in small animals by at least two orders of magnitude compared with green FP. It is also shown that the steep attenuation change of the hemoglobin spectrum around the 600-nm range may significantly affect the detection sensitivity and, therefore, necessitates the careful selection of illumination wavelengths for optimal imaging performance.
authors.affiliation: Massachusetts General Hospital and Harvard Medical School, Center for Molecular Imaging Research, Laboratory for Bio-Optics and Molecular Imaging, Charlestown, Massachusetts 02139, USA. ndeliolanis@yahoo.com
authors.forename: Nikolaos C
authors.initials: NC
authors.lastname: Deliolanis
authors.forename: Randa
authors.initials: R
authors.lastname: Kasmieh
authors.forename: Thomas
authors.initials: T
authors.lastname: Wurdinger
authors.forename: Bakhos A
authors.initials: BA
authors.lastname: Tannous
authors.forename: Khalid
authors.initials: K
authors.lastname: Shah
authors.forename: Vasilis
authors.initials: V
authors.lastname: Ntziachristos
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D005910:Glioma / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D008164:Luminescent Proteins / Q000032:analysis / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D008856:Microscopy, Fluorescence / Q000379:methods*; D013050:Spectrometry, Fluorescence / Q000379:methods; D041622:Tomography, Optical / Q000379:methods*
chemical_list: D008164:Luminescent Proteins