Speaker
Description
Quantitative analysis of blood plasma metabolites is an important tool for assessing metabolic alterations associated with various pathological conditions [1]. In particular, the analysis of free amino acids can provide valuable information for the diagnosis and monitoring of cancer [2]. However, comprehensive amino acid profiling typically requires sophisticated analytical instrumentation and costly reagents, limiting its application in routine clinical practice. Owing to its intrinsic fluorescence, tryptophan can be quantified using relatively simple spectrofluorimetric methods, making it a promising analyte for the spectroscopic assessment of biological fluids.
In this study, blood plasma samples were analyzed from 17 patients with oropharyngeal cancer who had previously had COVID-19. Plasma was separated by centrifugation at 4000 rpm for 20 min. A pooled plasma sample obtained from three healthy individuals served as the control.
High-molecular-weight proteins and peptides were precipitated by adding an equal volume of 10% perchloric acid, followed by centrifugation. The resulting supernatant was diluted with phosphate buffer to a final pH of 7.5. Fluorescence spectra were recorded using an Edinburgh Instruments FS5 spectrofluorometer over the wavelength range of 280–550 nm. Upon excitation at 280 nm, a characteristic fluorescence emission maximum was observed at approximately 347 nm. Tryptophan concentrations in the plasma samples were determined using a calibration curve constructed from fluorescence intensity measurements of tryptophan solutions of known concentrations prepared in a matrix similar to that used for sample preparation.
The results revealed a noticeable difference in the content in free tryptophan levels among patients with oropharyngeal cancer compared with the pooled control sample. The measured concentrations were both higher and lower than the control value, with no consistent trend across the patient group. This variability may reflect the combined effects of multiple pathological processes. On the one hand, enhanced tissue catabolism associated with oncological disease alters the composition of circulating amino acids. On the other hand, previous studies indicate that both COVID-19 and oncological pathology may lead to decreased tryptophan levels in the bloodstream.
These findings support the potential use of spectrofluorimetric analysis for monitoring free tryptophan levels in the blood plasma of patients with oropharyngeal cancer, particularly those with a history of COVID-19 or other viral infections. Further studies involving larger patient cohorts and appropriate control groups are needed to clarify the relationship between tryptophan levels, cancer-associated metabolic alterations, and previous viral infections.
References
[1] C. A. Kraft et al., Quantitative Analysis of Protein-Lipid Interactions Using Tryptophan Fluorescence. Sci. Signal. 2, pl4-pl4 (2009). https://doi.org/10.1126/scisignal.299pl4
[2] Liu M, Wang X, Wang L, Ma X, Gong Z, Zhang S, Li Y. Targeting the IDO1 pathway in cancer: from bench to bedside. J Hematol Oncol. 11(1), 100 (2018). https://doi.org/10.1186/s13045-018-0644-y