Development of Water-Insoluble Vehicle Comprising Natural Cyclodextrin-Vitamin E Complex

Abstract

Development of a novel antioxidant-delivery vehicle exerting biosafety has been attracting a great deal of interest. In this study, a vehicle comprising a natural composite consisting of vitamin E (α-tocopherol; Toc) and cyclodextrin (CD) additives was developed, directed toward aqua-related biological applications. Not only β-CD, but also γ-CD, tended to form a water-insoluble aggregate with Toc in aqueous media. The aggregated vehicle, in particular the γ-CD-added system, showed a remarkable sustained effect because of slow dynamics. Furthermore, a prominent cytoprotective effect by the γ-CD-Toc vehicle under the oxidative stress condition was confirmed. Thus, the novel vitamin E vehicle motif using γ-CD as a stabilizer was proposed, widening the usability of Toc for biological applications.

Keywords: cell viability; oxidative stress; radical scavenging; vehicle; vitamin E; γ-cyclodextrin.

Figure 1

Molecular structures of (blue) a vitamin E (α-Tocopherol; Toc), a water-soluble artificial Toc analogue, 2,2,5,7,8-pentamethyl-6-chromanol (PMC), and (pink) natural cyclodextrin (CD) compounds used in this study.

Figure 2

Photographs for I and for a sample diluted from 30 mM to 10 mM of γ-CD, respectively.

Figure 3

Contained vitamin E (Toc) concentration in I as the function of (a) initial γ-cyclodextrin (CD) concentrations and (b) added total amount of Toc. For (a), the added amount of Toc was 1.2 times mole of γ-CD. For (b), the γ-CD concentration was constant at 30 mM.

Figure 4

Results of the ABTS radical scavenging test for sample I. (a) Time dependence measurement and (b) radical scavenging ability (RSA) after 12 h and 30 min for the γ-cyclodextrin (CD)-added systems. The β-CD and γ-CD concentrations were diluted from 10 mM and 30 mM for the test, respectively, and the measurement was performed for the CD concentrations below 0.8 mM.

Figure 5

Cytoprotective impact of the γ-cyclodextrin (CD)-vitamin E (Toc) complex in the presence of a cytotoxic oxidative stressor. (a) Viability of COS-7 cells cultured for 30 min in the presence or absence of γ-CD or γ-CD-Toc before exposure to 0, 50, 100, or 200 µM tert-butyl hydroperoxide (TBHP) for 18 h. Cell viability was measured using a Cell Counting Kit-8 (Dojindo Laboratories) (* p < 0.05). (b) Phase-contrast photomicrographs of COS-7 cells cultured for 30 min in the presence or absence of γ-CD or γ-CD-Toc before exposure to 0, 100, or 200 µM TBHP for 18 h. The red arrowhead indicates a dead cell.