Serotonin and catecholamine metabolites as tumor biomarkers: current advances in instrumental analysis methods

Oncological diseases remain a leading cause of death worldwide. Early cancer diagnosis is crucial for improving patient treatment outcomes. Recently, there has been significant interest in non-invasive detection of tumor biomarkers in biological fluids. These biomarkers range from simple molecules like catecholamines to complex compounds such as proteins, hormones, enzymes, antigens, mRNA, microRNA, and DNA profiles. Catecholamines and their metabolites, particularly vanillylmandelic acid (VMA) and homovanillic acid (HVA), as well as serotonin’s metabolite, 5-hydroxyindoleacetic acid (5-HIAA), are key metabolic biomarkers. Determination of the level of these acids in biological fluids is used for early diagnosis of diseases of the neurogenic tumors, in particular, neuroblastoma, pheochromocytoma, paraganglioma. Determination of 5-HIAA content in daily urine is used in the diagnosis of carcinoid tumors. This review compares methods for detecting tumor biomarkers in human biological fluids. Various instrumental approaches, including spectrophotometry, fluorescence, HPLC, and electrochemical methods of analysis are used for analysis of VMA, HVA, and 5-HIAA. HPLC provides a high sensitivity, though it requires sample preparation, which may significantly increase the cost, complexity, and time of analysis. Electrochemical methods, in particular, sensors based on molecularly imprinted polymers (MIP), are an alternative that does not require complex sample preparation and allows a high accuracy and fast measurement. The inclusion of nanomaterials or MIP in to the recognition layer the sensors increases the sensitivity and selectivity of electrodes, making them promising. The development and improvement of methods for the quantitative analysis of biomarkers open up new opportunities for non-invasive cancer diagnostics, individualizing treatment approaches and monitoring of patients.