Laser Induced Fluorescence (LIF) can be used as a diagnostic device in biology and medicine. In general, LIF has difficulties relating the fluorescence spectra to the concentration of the emitters within the tissue, in identifying the various species, and in the possibility of destroying the molecules being probed if the wrong excitation wavelength is used. Many of the problems associated with fluorescence can be eliminated by the use of Raman scattering. Raman techniques allow the measurement of multiple species even in aqueous solutions (not accessible by infra red techniques because of water absorption). However, spontaneous Raman scattering techniques generate very weak signals. Signals can be enhanced through the use of resonance Raman techniques. Both of these methods still suffer from the fact that spatial and to some extent temporal information is lost. Spatial information can be recovered through the use of confocal microscopy. The research in this proposal is intended to investigate a non-invasive, real-time, high resolution device for the measurement of the concentration levels of enzymes, metabolites or other critical molecules. This unique device is based on nonlinear optical methods that can simultaneously measure the concentrations and temporal evolution of several molecular species in individual biological cells.
The method proposed here can be used for the continuous measurement of several molecular concentrations in small samples. Therefore, it may have applications in the medical field, in drug monitoring and manufacturing, and blood gas analysis. Furthermore, it may find applications in environmental monitoring.
