Near Infrared Fluorophores for Optical Biosensors

Although many fluorophores exist which are suitable for labeling biomolecules, most of them have absorbance and fluorescence wavelenghts which overlap with naturally occurring biological fluorescence. This complicates their use with optical bio- sensors. A very limited number of commercially available near-IR fluorophores exist (e.g., Cy-5, Cy-5.5, Cy-7) which contain suitable reactive groups for coupling. How- ever, these fluorophores have relatively small Stokes' shifts and less than optimal photostability. Innovation Associates proposes to develop a new class of near-IR fluorophores which utilize aromatic molecules absorbing in the near-IR to chelate metals in a manner which permits charge transfers from the ligand to the metal. This will give rise to a series of fluorophores which are all excited at the same wavelength but which exhibit fluorescence at various near-IR wavelengths, depending upon the metal. Because ligand-metal charge transfer chelates generally display larger Stokes' shifts and sharper fluorescence bands than purely organic fluorophores, discrimination of a fluorophore's emission from other fluorophore emissions and from the stimulating laser diode will be simplified. Such a series will be ideal for simultaneous meas- urement of several analytes in, biological fluids by means of fluorescence measure- ments at several wavelengths. A family of near-