C60 in Model Biological Systems. A Visible-UV Absorption Study of Solvent-Dependent Parameters and Solute Aggregation

A study was made of the solubilization of C[sub 60] in various solvents and systems of biological interest, i.e., octanols, micelles, and liposomes, using visible-UV absorption spectroscopy as a diagnostic tool. The state of incorporation of C[sub 60] molecules in micellar and colloidal liposome solutions was monitored using a number of spectroscopic criteria of solute-solvent and solute-solute interactions based on comparison with spectra obtained in alkane and octanol solvents and from thin films of C[sub 60]. Spectral red shifts and intensity modifications of C[sub 60] absorption and C[sub 60] aggregation are discussed in terms of environment-dependent physical parameters. The results indicate that C[sub 60] can be dispersed in micellar solutions of Triton X-100 and Triton X-100 R-S, the fullerene molecules being localized in the inner hydrophobic part of the micelles. C[sub 60] was shown to be incorporated, mainly as aggregates, into phosphatidylcholine liposome colloidal solutions. It is concluded that micellar and liposome solutions can be prepared which could be used to transfer individual C[sub 60] molecules, or groups of molecules, to biological cells. 38 refs., 9 figs., 2 tabs.