FRET-assisted selective detection of flavins via cationic conjugated polyelectrolyte under physiological conditions

Flavins viz. riboflavin (RF, vitamin B₂), flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) represent an important class of biomolecules ubiquitously found in living systems that are vital for numerous cellular activities inside the body. The fluorescence amplified detection of these flavins at ppb levels is achieved for the first time using water soluble cationic conjugated polymer PMI under physiological conditions. The substantial FRET, variable binding abilities of flavins with PMI via Columbic interaction and the subsequent displacement of FMN/FAD by simple chelating agent like Cu²⁺ affords a simple and consistent method to detect and discriminate them even in the presence of most common interfering analytes usually found in biosystems. This new strategy based on FRET provides more precise measurement using two different emission bands and hence, eliminates the environmental effects unlike in classical or direct fluorescence method. Furthermore, the determination of flavins in human blood serum using cationic conjugated polyelectrolyte PMI signifies the potential of this protocol in studying the metabolic processes and clinical assessment of diseases related to flavins.