The ultraviolet light-excitated fluorescence spectra from healthy human blood in vitro have been measured by FLS920 Spectrometer, made in Edinburgh Instruments, exciting light from Xe900 - 450W steady state xenon lamp. The relation between exciting light wavelength and the fluorescence spectral characteristics of blood in the case of certain concentration is provided in this paper. Ultraviolet light excitated healthy human blood fluorescence spectra profiles change in peak intensity and position with exciting light. It may be due to the abruption of large numbers of anisomerous C-C bonds or C-N bonds that absorb the energy by non-resonance on membrane of blood cells, bringing lone-pairs of electrons, forming the new fluorophores and emit fluorescence in the case of later ultraviolet light excitation. It may be why ultraviolet light is able to kill and wound cells. In addition, the fluorescence spectra distributing range is very wide. It is due to contributions of the many fluorophores with large numbers of vibrational energy levels on the ground level in the blood cells. Our understanding of the different wavelength light-induced blood cells fluorescence spectra characteristics may be useful to development of low level laser therapy in vivo and in vitro.
The fluorescent spectra of human blood with different concentration induced by different wavelength LED light are reported in this paper. The phenomenon that fluorescence peaks are apparently red-shifted with the increase of blood concentration is analyzed and the mechanism is given a reasonable explanation. The results indicate that the peak is shifted following the rule of e-exponent with the increase of the blood concentration. The mechanism of different energy transfer with different fluorescent areas is analyzed from the theory of energy transfer. The resonance energy transfer is the primary reason of the fluorescent spectra peaks. The concept of the idea fluorescence and the inner fluorescence is also brought forward in this paper. The research will give refer intrinsic fluorescence diagnostic techniques of organic tissue.
Autofluorescence spectra from whole blood of laboratory rat are measured in this paper. The excitation lights are light emitting diode (LED), Ar+ laser, and He-Ne laser with the wavelength located at 457nm, 457.9nm, and 632.8nm respectively. The three spectral profiles are found to be substantially different, each displaying its own characteristic fluorescence bands. Ar+ laser-induced spectrum has very rich and sharp peaks. The LED-induced one has the strongest and widest fluorescence bands. And the intensity of the spectrum induced by He-Ne laser is much lower than the former two. Comparisons of those three fluorescence spectra indicate that Ar+ laser induced spectrum can show partly fine structure of blood cells. Based on the theoretical analysis, it is presented that the absorption of the fluorophores in blood cells to the wavelength of exciting light has definite selectivity, which depend on energy level structure and state of the fluorophores.
Laser-blood cells interaction was studied by Ar+ laser-induced animal (mouse) blood fluorescence spectra in vitro. The fluorescence spectra of the blood under various irradiated powers of Ar+ laser excitation are shown that there are very rich and sharp spectral peaks from 600 nm to 860 nm. These peaks are located at 616 nm, 666 nm, 708 nm, 739 nm, 752 nm, 766 nm, 800 nm, 812 nm and 844 nm. This may be due to the fact that there are various fluorophores in the blood and the ground electronic state of the fluorophores containing a large number of vibrational levels. In addition, 666 nm peak among them is the most prominent and is a larger change in the intensity under different power of Ar+ lasers excitation. It foretell that laser near a wavelength of 666 nm may be more effective to low lever laser therapy (LLLT). Furthermore, these experiments indicate that when the laser irradiated power density reaches to 30 mW/cm2 the blood cells are still not destroyed. The results may be significative for the choice of irrediation-wavelength in LLLT.