Hydroxypropyl β-cyclodextrin cross-linked multiwalled carbon nanotube-based chiral nanocomposite electrochemical sensors for the discrimination of multichiral drug atorvastatin isomers

Abstract

Drugs having multiple chiral centres pose a greater risk to the human health as their pharmacological effects on human organs, cells and systems due to more number of enantiomers as compared to that of a single enantiomeric drug. To address this challenge, an enantioselective electrochemical sensor was reported for the first time to discriminate atorvastatin isomers (SS-ATS and RR-ATS). A glassy carbon electrode (GCE) was modified with a functionalized multiwalled carbon nanotube (MWCNT) with hydroxypropyl-β-cyclodextrin (HBC), to which each isomer could bind stereoselectively. The preferential recognition of ATS was achieved by adsorptive stripping differential pulse voltammetry (AdSDPV) based on the difference in discernible peak currents rather than peak potentials. Under optimized experimental conditions, the anodic oxidation peak current ratio (I_SS/I_RR) of SS-ATS to RR-ATS was found to be 3.62. AdSDPV experiments revealed changes in the peak current that were compatible with the insertion of ATS isomers in the hydrophobic nanocavities of HBC, forming a 1 : 1 stoichiometric complex. Host–guest enantiorecognition was achieved as the size of ATS isomers (0.79 nm) matched with that of HBC (0.77–0.87 nm). The binding constants for the complexes with RR-ATS (log K = 2.301) and SS-ATS (log K = 1.945) showed the stereoselective nature of HBC. The values of the Gibbs free change (ΔG) calculated for RR-ATS and SS-ATS were found to be −13.12 kJ mol⁻¹ and −11.06 kJ mol⁻¹, respectively, suggesting the complexation process to be exothermic and spontaneous. The developed sensor demonstrated outstanding advantages of chiral nanocomposite-modified electrodes such as (a) excellent enantioselectivity (b) high stereospecificity and (c) good reproducibility.