Carotenoid : methyl-beta-cyclodextrin formulations: an improved method forsupplementation of cultured cells

A physiological, water-soluble complex of carotenoids with methyl-beta-cycl odextrin (M beta CD) was developed for the purpose of cell supplementation. Bioavailability, cytotoxicity and stability of the formulations were compa red to carotenoid solutions in organic solvents (THF/DMSO (1:1), THF and et hanol). The stability of the different carotenoid solutions (0.5 mu M) unde r cell culture conditions was determined by measuring absorbance 1 and 7 da ys after treatment. To determine the availability of beta-carotene (BC), hu man skin fibroblasts were incubated for up to 8 days with 5 mu M BC in M be ta CD or THF/DMSO and the cellular and medium BC contents were determined b y HPLC analysis. Depending on the solubilizer, different orders of stabilit y were found. M beta CD formulation: BC > zeaxanthin > lutein > lycopene. O rganic solvents: zeaxanthin > lutein > lycopene > BC. Two days after supple mentation 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 unti l day 8. Incubation with BC dissolved in THF/DMSO resulted in a lower BC up take 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 compare d to methods using organic solvents. (C) 2000 Elsevier Science B.V. All rig hts reserved.