Probing the interaction of ciprofol and human serum albumin using multiple spectroscopies

The interaction between ciprofol and human serum albumin (HSA) was studied using spectroscopy-based approaches at different temperatures under simulated physiological conditions in vitro. Quenching of intrinsic Trp fluorescence of HSA with increasing ciprofol concentration is the actuating tool in the analysis. Experimental results proved that ciprofol quenched the intrinsic fluorescence of HSA through a static quenching mechanism. The thermodynamic parameters (ΔG = -2.35 × 10⁴ J·mol⁻¹, ΔS = -131 J·mol⁻¹·K⁻¹, and ΔH = -6.39 × 10⁴ J·mol⁻¹ at 310 K), binding sites (n = 0.83), and binding constant (K_A = 9.12 × 10³ M⁻¹) indicated that hydrogen bond and van der Waals forces played a major role in the HSA-ciprofol association with weak binding force. Furthermore, the circular dichroism, synchronous, and three-dimensional fluorescence spectral results indicated adaptive structural changes of HSA in the presence of ciprofol. In addition, the effect of some common metal ions on the binding between ciprofol and HSA was examined, and Fe³⁺ and Hg²⁺ were proven to help prolong the storage time and improve the drug efficacy. The study provides accurate and full basic data for clarifying the binding mechanisms of ciprofol with HSA and helps understand its effect on protein function during the blood transportation process and activity in vivo.