Evaluation of three neutral capillary coatings for the determination of analyte-cyclodextrin binding constants by affinity capillary electrophoresis. Application to N , N ⿲-disubstituted piperazine derivatives.

Abstract

The performances of three neutral static coatings (hydroxypropyl cellulose, polyethylene oxide and poly(N,N-dimethylacrylamide) have been evaluated in order to determine the binding constants of the complexes formed between four polycationic compounds (piperazine derivatives) and four cyclodextrins of pharmaceutical interest (β-CD, HP-β-CD, Me-β-CD and sulfobutyl ether-β-CD) by affinity capillary electrophoresis. The physically-adsorbed poly(N,N-dimethylacrylamide) coating proves to be the more efficient to mask the silanol groups of the capillary wall since the lowest electroosmotic flow was measured for this coating. Moreover, it drastically reduces the adsorption of the compounds since it allows a correct repeatability of their migration time, higher efficiencies of the peaks and no baseline shift. Then, it was verified for four complexes that this coating allows a correct determination of the binding constants avoiding the CD adsorption which is responsible of an undervaluation of binding constants. The highest binding constants are obtained using the anionic sulfobutyl ether-β-CD (SBE-β-CD). The structure of the complex formed between the tacrine derivative and the SBE-β-CD was further investigated through 2D ROESY NMR experiments and structure-binding constant relationships. Results suggest that the inclusion in the SBE-β-CD cavity occurs through the aliphatic ring portion of the tacrine moiety.

Capillary coating as an important factor in optimization of the off-line and on-line MEKC assays of the highly hydrophobic enzyme chlorophyllase

“…The broad commercial availability of permanently coated capillaries and reagents for reversible dynamic coating makes the choice not straightforward. Intriguingly, only several systematic comparisons of various capillary modifications can be found in the literature [6–13]. …”

Studying molecular interactions via capillary electrophoresis and microscale thermophoresis: A review

“…The requirement of this method is fast on and off kinetics; therefore, ligand concentrations 1-2 orders of magnitude higher than the analyte are usually used [69,70]. The most studied interactions are systems with cyclodextrins [14,45,[71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90]. They are suitable model systems for the development of new approaches in data evaluation and other theoretical models.…”

Clinical and pharmaceutical applications of affinity ligands in capillary electrophoresis: A review

“…This method has also been utilized to measure various L-amino acids in biological matrices [102]. In addition, CE has been used to determine the binding constants of CDs with solutes such as drugs targeting neurodegenerative diseases or pharmaceuticals that are used to treat obesity [103,104].…”