Autofluorescence of blood and its application in biomedical and clinical research

Abstract

Autofluorescence of blood has been explored as a label free approach for detection of cell types, as well as for diagnosis and detection of infection, cancer, and other diseases.Although blood autofluorescence is used to indicate the presence of several physiological abnormalities with high sensitivity, it often lacks disease specificity due to use of a limited number of fluorophores in the detection of several abnormal conditions. In addition, the measurement of autofluorescence is sensitive to the type of sample, sample preparation, and spectroscopy method used for the measurement. Therefore, while current blood autofluorescence detection approaches may not be suitable for primary clinical diagnosis, it certainly has tremendous potential in developing methods for large scale screening that can identify high risk groups for further diagnosis using highly specific diagnostic tests. This review discusses the source of blood autofluorescence, the role of spectroscopy methods, and various applications that have used autofluorescence of blood, to explore the potential of blood autofluorescence in biomedical research and clinical applications.

Biophysical Tools and Concepts Enable Understanding of Asexual Blood Stage Malaria

“…One challenge for live-cell imaging is the long, repeated exposure to light which affects both the fragile parasites and the RBCs. Phototoxicity induces lysis of the acidic food vacuole of the parasites ( Wissing et al., 2002 ) and damages RBC haemoglobin inducing autofluorescence ( Shrirao et al., 2021 ), making it very difficult to follow the parasites during the entire intraerythrocytic cycle. Using DIC and confocal microscopy, Gruring et al ( Grüring et al., 2011 ) were able to visualise the 48-hour development of P. falciparum , elucidating the trafficking mechanism of exported proteins to the host membrane and revealing a fascinating morphology of the parasite at the ring stage.…”

A Pleomorphic Puzzle: Heterogeneous Pulmonary Vascular Occlusions in Patients with COVID-19

“…Various endogenous fluorophores are known to contribute to NEF and, at particular wavelengths, can enable the detection of morphological changes in the vascular structure and indicate physiological abnormalities of blood cells. Several native fluorophores such as reduced NADPH, FAD, tryptophan, collagen, elastin, and hemoglobin in porphyrins are attributed to NEF [ 26 , 27 ]. We found that most occlusions detected at 488/525 nm were positive for hemoglobin and emitted NEF.…”

“…The striking heterogeneous appearance of vascular occlusions in these patients is determined by various levels of NETs-associated proteins, DNA, platelets, fibrinogen, and hemoglobin within the vasculature. Hemoglobin has previously served as a label-free marker for the detection of red blood cells due to its native endogenous fluorescence (NEF) properties [ 25 , 26 ]. Therefore, we could detect most of the vascular occlusions due to the NEF emerging from erythrocytes accumulated in the vasculature without any exogenous-fluorophore labeled antibody.…”

The Mortality Risk and Pulmonary Fibrosis Investigated by Time-Resolved Fluorescence Spectroscopy from Plasma in COVID-19 Patients

“…There is still a great need for easy diagnostic methods that reveal strong predictors of mortality, and those that allow the assessment of the patient’s condition and post-infection fibrosis. Fluorescence spectroscopy of whole blood or its components has been a very convenient tool in the diagnoses of many diseases [ 23 ]. The method enables quick investigations of biological samples, and requires no additional reagents.…”