Multifarious analytical capabilities of the UV/Vis protein fluorescence in blood plasma.

Autofluorescence of blood plasma has been broadly considered as a prospective disease screening method. However, the assessment of such intrinsic fluorescence is mostly phenomenological, and its origin is still not fully understood, complicating its use in the clinical practice. Here we present the detailed evaluation of analytical capabilities, variability, and formation of blood plasma protein fluorescence based on the open dataset of excitation-emission matrices measured for ∼300 patients with suspected colorectal cancer, and our supporting model experiments. Using high-resolution size-exclusion chromatography coupled with comprehensive spectral analysis, we demonstrate, for the first time, the dominant role of HSA in the formation of blood plasma fluorescence in the visible spectral range (excitation wavelength >350 nm), presumably caused by its oxidative modifications. Furthermore, the diagnostic value of the tryptophan emission, as well as of the tyrosine fluorescence and visible fluorescence of proteins is shown by building a tree-based classification model that uses a small subset of physically interpretable fluorescence features for distinguishing between the control group and cancer patients with >80% accuracy. The obtained results extend current understanding and approaches used for the analysis of blood plasma fluorescence and pave the way for novel autofluorescence-based disease screening methods.