Control of self-aggregation of fullerenes by connection with calix[4]arene: solvent- and guest-effects to particle size

Water-dispersible fullerene aggregates as a targeted anticancer prodrug with both chemo- and photodynamic therapeutic actions

Prodrug therapy is one strategy to deliver anticancer drugs in a less reactive manner to reduce nonspecific cytotoxicity. A new multifunctional anticancer prodrug system based on water-dispersible fullerene (C60) aggregates is introduced; this prodrug system demonstrates active targeting, pH-responsive chemotherapy, and photodynamic therapeutic (PDT) properties. Incorporating (via a cleavable bond) an anticancer drug, which is doxorubicin (DOX) in this study, and a targeting ligand (folic acid) onto fullerene while maintaining an overall size of approximately 135 nm produces a more specific anticancer prodrug. This prodrug can enter folate receptor (FR)-positive cancer cells and kill the cells via intracellular release of the active drug form. Moreover, the fullerene aggregate carrier exhibits PDT action; the cytotoxicity of the system towards FR-positive cancer cells is increased in response to light irradiation. As the DOX drug molecules are conjugated onto fullerene, the DOX fluorescence is significantly quenched by the strong electron-accepting capability of fullerene. The fluorescence restores upon release from fullerene, so this fluorescence quenching-restoring feature can be used to track intracellular DOX release. The combined effect of chemotherapy and PDT increases the therapeutic efficacy of the DOX-fullerene aggregate prodrug. This study provides useful insights into designing and improving the applicability of fullerene for other targeted cancer prodrug systems.

Absorption spectrophotometric, NMR and theoretical investigations on ground state non-covalent interaction of C₆₀ and C₇₀ with a designed trihomocalix[6]arene in solution

The present paper reports the spectroscopic investigations on non-covalent interaction of fullerenes C(60) and C(70) with a designed trihomocalix[6]arene (2) in toluene. UV-vis studies reveal appreciable ground state interaction between fullerenes and 2. Jobs method of continuous variation establishes 1:1 stoichiometry for fullerene-2 complexes. Binding constant (K) data reveals that 2 binds C(70) more strongly compared to C(60), i.e. K(C60-2)-47,540 dm(3)mol(-1) and K(C70-2)-86,360 dm(3)mol(-1). Proton NMR studies provide very good support in favor of strong binding between C(70) and 2. Estimation of solvent reorganization energy (R(S)) evokes that C(70)-2 complex is stabilized more compared to C(60)-2 complex as R(S(C60-2))- -1.162 eV and R(S(C70-2))- -1.244eV. Semiempirical calculations at third parametric level of theory in vacuo evoke the single projection structures of the fullerene-2 complexes and interpret the stability difference between C(60) and C(70) complexes of 2 in terms of enthalpies of formation values.

Advantages and potential of lipid-membrane-incorporating fullerenes prepared by the fullerene-exchange method

Lipid-membrane-incorporating C(60) and C(70) (LMIC(60) and LMIC(70)) were prepared by the fullerene-exchange reaction from the γ-cyclodextrin cavity to vesicles (we call this method the "exchange method"). An advantage of this method is that the ratios of [C(60)]/[lipids] and [C(70)]/[lipids] can be arbitrarily controlled by adjusting the ratios of the fullerenes and liposome. The maximum ratio (30 mol%) obtained was approximately 14 and 100 times higher than those achieved for LMIC(60) and LMIC(70) , respectively, that were prepared by the classical method, which we call the "premixing method" (dissolving lipids and C(60) or C(70) in chloroform, followed by concentration and extraction with water). Furthermore, the stabilities and photodynamic activities of the LMIC(60) and LMIC(70) solutions prepared by the exchange method were shown to be much higher than those prepared by the premixing method. That is, the exchange method was found to be superior to the premixing method as a preparative method of LMIC(60) and LMIC(70) for applications in photomedical and photomaterials chemistry.