Carotenoid:methyl-β-cyclodextrin formulations:: an improved method for supplementation of cultured cells

A physiological, water-soluble complex of carotenoids with methyl-beta-cyclodextrin (M beta CD) was developed for the purpose of cell supplementation. Bioavailability, cytotoxicity and stability of the formulations were compared to carotenoid solutions in organic solvents (THF/DMSO (1:1), THF and ethanol). The stability of the different carotenoid solutions (0.5 mu M) under cell culture conditions was determined by measuring absorbance 1 and 7 days after treatment. To determine the availability of beta-carotene (BC), human skin fibroblasts were incubated for up to 8 days with 5 mu M BC in M beta CD or THF/DMSO and the cellular and medium BC contents were determined by HPLC analysis. Depending on the solubilizer, different orders of stability were found. M beta CD formulation: BC > zeaxanthin > lutein > lycopene. Organic solvents: zeaxanthin > lutein > lycopene > BC. Two days after supplementation with 5 mu M BC in M beta CD, cellular BC levels reached a maximum of 140 +/- 11 pmol/mu g DNA, leveling off to 100 +/- 15 pmol/mu g DNA until day 8. Incubation with BC dissolved in THF/DMSO resulted in a lower BC uptake of 105 +/- 14 pmol/mu g DNA and 64 +/- 20 pmol/mu g DNA respectively. No cytotoxic effects of these formulations were detected. The results show that the M beta CD formulation is an improved method for investigations of carotenoids and other lipophilic compounds in in vitro test systems compared to methods using organic solvents. (C) 2000 Elsevier Science B.V. All rights reserved.