Electrochemical and associated techniques for the study of the inclusion complexes of thymol and β-cyclodextrin and its interaction with DNA

Thymol, a potent agent for microbial, fungal, and bacterial disease, has low aqueous solubility and it is genotoxic, i.e., is capable of damaging deoxyribonucleic acid (DNA). This possible problem of DNA toxicity needs to be solved to allow the use of different doses of thymol. This study characterized the inclusion compound containing thymol and beta-cyclodextrin (beta-CD) by measuring the interaction between these two components and the ability of thymol to bind DNA in its free and beta-CD complexed form. The encapsulation approach using beta-CD is particularly useful when controlled target release is desired, and a compound is insoluble, unstable, or genotoxic. The interaction between thymol and DNA has been studied using electrochemical quartz crystal microbalance (EQCM), atomic force microscopy (AFM), and differential pulse voltammetry (DPV). The characterization of the inclusion complex of thymol and beta-CD was analyzed by UV-vis spectrophotometry, cyclic voltammetry, and scanning electrochemical microscopy (SECM). Based on the free beta-CD by spectrophotometry method, the association constant of thymol with the beta-CD was estimated to be 2.8 x 10(4) L mol(-1). The AFM images revealed that in the presence of small concentrations of thymol, the dsDNA molecules appeared less knotted and bent on the mica surface, showing significant damage to DNA. The SECM and voltammetry results both demonstrated that the interaction of thymol-beta-CD complex was smaller than the free compound showing that the encapsulation process may be an advantage leading to a reduction of toxic effects and increase of the bioavailability of the drug.