We chose the organic dyes DEAC, TAMRA, and CF633 to label the three target peptides because their absorption peaks were close to the excitation wavelengths of the three laser sources. However, there are other dyes available at each wavelength, and we considered other important parameters, including fluorophore solubility, synthesis feasibility, fluorescence at neutral pH, biodistribution, clearance, and potential toxicity for future clinical use, before making our final decision. Moreover, the covalent conjugation of these dyes to the peptide must not affect the binding activity of the targeting moiety. While no clinical data have been reported for use of these dyes, there is reason to believe that each of these fluorophores will be safe for human use, in particular with topical application. Coumarin derivatives have been shown to be safe in a number of preclinical studies.34,35 TAMRA is structurally similar to fluorescein, an imaging agent that is FDA-approved for human use. The red-shift in fluorescence with increased concentration from the TAMRA-labeled peptide likely results from a quenching effect, which occurs when more of the shorter wavelengths of fluorescence becomes absorbed with a reduced average distance between dye molecules.36 We do not expect this shift to introduce crosstalk in the multispectral images because the peptides bind at low concentration. In addition, CF633 belongs to the carbocyanine family along with indocyanine green, another FDA-approved dye.