BSA-Incorporated Sulphur and Nitrogen Doped Carbon dots (BSA-S,N-CDs) Based Platform for turn-on Fluorescence Detection of Histidine in Presence of Cu2+ ion

Measuring of histidine levels can be used as an indication of the onset of diseases such as chronic kidney disease (CKD), anaemia, and cancer, etc. Due to its abnormal level in human diseases, histidine (His) monitoring has received a lot of interest. Here a feasible, sulphur and nitrogen-doped carbon dots-based (BSA-S,N-CDs) fluorescent switch-off-on nano sensor has been developed for the detection of histidine in an aqueous solution. The BSA-S,N-CDs was synthesized via microwave-assisted method from citric acid, urea, and bovine serum albumin (BSA). The blue fluorescence of BSA-S,N-CDs ( λ_em: 444 nm) was quenched in the presence of Cu²⁺ ion by static quenching and the quenched probe (BSA-S,N-CDs@Cu²⁺ ) was used for the detection of histidine in the linear range from 0.29 to 2.33 mM. The limit of detection (LOD) and quantification (LOQ) of the probe was obtained as 34.55 µM and 115.18 µM respectively. The sensor exhibits good selectivity and less interference toward various biomolecules and ions. The BSA-S,N-CDs@Cu²⁺ probe was used to detect histidine in spiked human serum and urine samples. Additionally, a paper strip-based sensor was developed to validate its practical applicability.