In situ one-pot synthesis of chitosan@ P,N-CPDs as a ratiometric scatter up-conversion sensor for α-lipoic acid

Abstract

The rapid sensitive determination of α-lipoic acid (ALA) is essential for monitoring biological functions. Nevertheless, the lack of chromophore and its occurrence in complex biological matrices renders its determination challenging and requires additional treatment steps which lengthen assay procedure and affects method sensitivity. Herein, through the coordination of frequency doubling scatter (FDS) of polysaccharide strands with up-conversion of the embedded in situ formed P, N- carbonized polymer dots (CPDs), a novel ratiometric sensing platform was constructed. One-pot synthesis of chitosan decorated P, N-CPDs (chitosan@ P,N-CPDs) was attempted through microwave-assisted crosslinking-accelerated carbonization, using phosphoric acid as crosslinker and dopant. The constructed platform responded to the presence of α-lipoic acid (ALA) in concentration dependent manner (R2 = 0.995) between 1.65–100 μg/mL, with detection limit of 0.55 μg/mL, good accuracy (%E = 0.52 %) and precision (%RSD < 2 %). Consistent results with comparison method confirmed sensor reliability for determination of ALA in urine, Thiotacid® and Thiotacid compound® tablets, with no interference from the coexisting highly absorbing water-soluble vitamins, thiamine, and cyanocobalamin, or other potential interferents. Thus, the developed high performance sensing platform could be adopted for ALA determination as it is much less prone to spectral interferences and hence more discerning than those operated in single wavelength mode.