Coupled Diffusion of Cyclodextrins and Cobalt Chloride in Acidic Aqueous Solutions and Acidic Artificial Saliva: An Experimental Approach

Given the confirmed release of cobalt ions from biomedical alloys in the oral cavity, understanding transport of cobalt chloride in solutions containing cyclodextrins is of prime importance for potential removal treatments. In this study, Taylor dispersion analysis was used to investigate the interaction between Co2+ ions as its chloride and cyclodextrins (α-CD, β-CD, and γ-CD) in both water and artificial saliva at pH 4 at 298.15 K as a strategy to reduce ionic bioavailability. The analysis of the results indicates that there is a formation of 1:1 supramolecular complex between β-CD and γ-CD with Co2+ ions, while no appreciable binding was detected for α-CD. The association constants (Ka) were estimated to be 30.0± 0.6 mol–1 dm3 for β-CD and Ka = 30.0 ± 0.5 mol–1 dm3 for γ-CD, with both systems exhibiting a Gibbs free energy change (ΔG) of −8.4 kJ·mol–1. Similar results were obtained in artificial saliva, with Ka = 30.0 ± 0.6 mol–1 dm3 for β-CD and Ka = 40.0 ± 0.5 mol–1 dm3 for γ-CD, corresponding to ΔG values of −8.4 and −9.1 kJ·mol–1, respectively. Based on these findings, β-CD and γ-CD can be considered promising candidates for reducing the concentration of free Co2+ ions in solution.