Probing the articaine-human serum albumin interaction and influences of paracetamol and caffeine on the interaction by spectroscopy, voltammetry, and bioinformatics

Interaction between a local anesthetic drug, articaine (ART) and human serum albumin (HSA) was investigated in the absence and presence of paracetamol (PAR) and caffeine (CAF) using spectroscopic, voltammetric, and computational techniques for the first time. The results demonstrated that increasing concentrations of ART in HSA solution led to a decrease in HSA fluorescence signal, indicating the ART-HSA complex formation via the static quenching mechanism. The binding strength of the complex was moderate (binding constant, Ka = 5.87 × 103 M-1 in fluorescence and 6.31 × 103 M-1 in voltammetric at 298 K). Thermodynamic analysis (ΔS = +28.32 J mol-1 K-1; ΔH = -30.17 kJ/mol) of the binding reaction suggested involvement of hydrophobic interactions, van der Waal's forces and hydrogen bonding in stabilizing the ART-HSA complex. Significant microenvironmental alterations near the Trp and Tyr residues of HSA consequent to the ART-HSA complex formation. ART predominantly binds to Sudlow's site I of HSA with more negative binding energy and stronger hydrophobic interactions compared to Site II. The stability of the ART-HSA complex at Site I over a 100 ns timeframe, supported by stable hydrogen bonding and compact HSA structure throughout the molecular dynamics simulations. The effect of PAR and CAF on the binding strength between ART and HSA was also examined, and presence of PAR and CAF in the reaction mixture produced significant reduction in the binding affinity of ART to HSA. These findings underscore the competitive binding between ART, PAR, and CAF, which impacts their pharmacokinetics and efficacy. This study provides valuable insights into the complex interactions between anesthetic drugs and common pharmaceuticals, potentially guiding clinical practices and drug development.