Diagnostic potential of autofluorescence: an explorative study with human urine and stem cells

Most of the biological samples contain molecules, some of which fluoresce when excited by UV/Vis radiation of suitable wavelength (fluorophores). The fluorescence arising from these endogenous fluorophores is an intrinsic property of the sample and is called autofluorescence. In principle, autofluorescence may serve as a useful diagnostic indicator. In the past, autofluorescence has been used to diagnose various diseases including cancer. In this study, I have investigated the autofluorescence of human urine and stem cells, two medically relevant biological materials. With an estimated 150 million instances occurring every year globally and accounting for more than 6 billion dollars in direct health care expenditure, urinary tract infection (UTI) is one of the most common infections in the human population. UTIs can differ in severity, and are treatable if detected early. Left untreated, they can cause lasting damage, chronic kidney disease, and even death from kidney failure. In recent years, several novel approaches have been attempted to diagnose the urinary tract infection. These include immuno-chromatography strips, real time PCR and biosensors. However, they have some limitations. For example, most of the techniques are reagent based, need sample preparation prior to diagnosis, have less sample throughput, are sensitive only to specific bacteria and are expensive. Human urine contains a large number of fluorophores (mostly tryptophan and its metabolites) which can fluoresce under UV excitation. Due to their presence, normal urine has strong fluorescence. Although pathological and physiological changes are known to alter the autofluorescence of urine, there is a shortage of studies investigating autofluorescence as a diagnostic tool for UTIs.