A high-quality fluorescence elimination dual-wavelength Raman method for biological detection and its application in...

Raman-based methods offer a promising approach for in vivo biological detection. However, the fluorescence of biological samples will significantly affect Raman measurement accuracy. Moreover, due to the existence of excitation wavelength-dependent fluorescent molecules in biological tissues, especially porphyrin molecules, the fluorescence also exhibits significant wavelength dependence. To achieve high-quality Raman spectra of biological tissue, in this work we proposed a dual-wavelength Raman method. Two lasers with different wavelengths were used to excite optical signals in the same region, and the ordinary fluorescence and additional wavelength-dependent fluorescence in the biological samples could be eliminated by two-step normalization calibration; thus, the accuracy of Raman measurement was significantly enhanced. We applied this method to early cancer diagnosis and identified several molecules and structures worthy of attention in carcinogenesis for esophageal tissue, such as phenylalanine and the CC bonds of porphyrins. Normal, precancerous, and early cancer samples were successfully identified by the changes in biomolecules with associated degrees of malignancy. Thus, the imaging and diagnosis of indefinite tumors were realized, which verified the potential of the dual-wavelength Raman method in biological detection.