Hydrophobic ring substitution on 9-O position of berberine act as a selective fluorescent sensor for the recognition of bovine serum albumin

Abstract

Current research on the detection of serum albumin (SA) by fluorescence-based sensing probe has earned massive interest due to its various proficiencies. In this belief, we report a cost-effective fluorescence probe BRDR4 from well-known medicinal herb berberine for distinguishing BSA from HSA selectively. The probe itself has very weak fluorescence intensity which was increased ~269 fold with the addition of 47 μM of BSA (detection limit 5.9 nM). Interestingly under the same condition, HSA remains silent towards the studied probe. To establish the sensing mechanism and the fluorometric sensing potency we further compare characteristics of the interaction with structurally comparable four more berberine derivatives (BRDR1, BRDR2, BDRD3 and BRDR5) with BSA. Furthermore, to reveal the mechanistic insight of BSA sensing a systematic binding investigation was performed on all BRDR series using various spectroscopic techniques. The binding affinity of all BRDR with BSA was evaluated using absorbance and fluorescence spectroscopy. The calculated binding constants and quenching constants suggests highest binding affinity of BRDR4 towards BSA. On the other hand, fluorescence anisotropy, FT-IR spectroscopic study and 3D fluorometric analysis indicates the change of hydrophobic environment and α-helix content of BSA during the interaction. The fluorescence lifetime and FRET theory recommended that the stable ground state complex formation phenomenon was only responsible for BSA sensing. All the approached experimental evidences successfully assessed that the probe BRDR4 sufficiently altered the native structure of BSA which helps it to become a delicate BSA sensor.