p-sulfonated calix[8]arene functionalized graphene as a “turn on” fluorescent sensing platform for aconitine determination

• A novel fluorescent method based on competitive host–guest interaction for aconitine sensing was proposed.
• SCX8-RGO receptor exhibited high quenching performance and excellent supramolecular recognition capability.
• This method showed high selectivity towards aconitine beyond competitive binding analytes.
• The SCX8/aconitine complex was studied by molecular dynamics simulation.
• The binding mode and the driving force between SCX8 and aconitine was clarified.

This work reports a novel method for the determination of aconitine through the competitive host–guest interaction between p-sulfonated calix[8]arene (SCX8) and signal probe/target molecules by using SCX8 functionalized reduced graphene oxide (SCX8-RGO) as a receptor. Three dyes (ST, RhB, BRB) and aconitine were selected as the probe and target molecules, respectively. The formation of SCX8-RGO·ST, SCX8-RGO·RhB, and SCX8-RGO·BRB complexes greatly decreases the fluorescence emission of ST, RhB, and BRB. The aconitine/SCX8 complex possesses a higher binding constant than ST/SCX8, RhB/SCX8, and BRB/SCX8 complexes, thus the dye in the SCX8 cavity can be replaced by aconitine to revert the fluorescence emission of SCX8-RGO·dye, leading to a “switch–on” fluorescence response. The fluorescence intensity of SCX8-RGO·ST, SCX8-RGO·RhB, and SCX8-RGO·BRB complexes increased linearly with increasing concentration of aconitine ranging from 1.0 to 14.0 μM, 2.0–16.0 μM, and 1.0–16.0 μM, respectively. Based on the competitive host–guest interaction, the proposed detection method for aconitine showed detection limits of 0.28 μM, 0.60 μM, and 0.37 μM, respectively, and was successfully applied for the determination of aconitine in human serum samples with good recoveries from 95.1% to 104.8%. The proposed method showed high selectivity for aconitine beyond competitive binding analytes. In addition, the inclusion complex of the SCX8/aconitine was studied by the molecular docking and molecular dynamics simulation, which indicated that the phenyl ester group of the aconitine molecule was included into the SCX8 cavity.