Electrochemical Quartz Crystal Microbalance Study of Accumulating Properties of the β-Cyclodextrin and Carboxymethylated β-Cyclodextrin Polymer Films with Respect to the Azepine and Phenothiazine Type Antidepressive Drugs

Accumulating properties of thin films of condensation polymers of β-cyclodextrin (β-CDP) and carboxymethylated β-cyclodextrin (β-CDPA) were compared with respect to the selected azepine and phenothiazine type antidepressive drugs by using simultaneous measurements of cyclic voltammetry and piezoelectric microgravimetry at an electrochemical quartz crystal microbalance. At pH 7.4, the drug accumulation by the film of β-CDPA in its anionic, i.e., cation-exchange, form is much higher than that of the β-CDP nonionic film. This favorable property of the β-CDPA film is due to concurrent effects of the supramolecular complex formation between the β-CD inclusion sites of the polymer and drug molecules as well as ion exchange of cationic drugs at the carboxymethyl deprotonated groups. For both polymers, sorption plots were described by the Langmuir-type isotherms and values of the apparent sorption equilibrium constant, βpol, as well as the free energy of sorption, Δpol0 determined. For the β-CDP film, mutual differences in the βpol, and Δpol0 parameters determined for all drugs were consistent with the differences in the stability constants of respective supramolecular complexes in solutions reported in literature.