The method of preparation of highly stable reproducible C₆₀ fullerene aqueous colloid solution is described. The structural organization of C₆₀ fullerenes in aqueous solution was studied and analyzed in detail using various techniques such as chemical analysis, UV/VIS spectroscopy, atomic force and scanning tunneling microscopy, dynamic light scattering, and zeta potential methods.

In the present work we develop a novel approach for quantification of the energetics of C₆₀ fullerene aggregation in aqueous media in terms of equilibrium aggregation constant K_F. In particular, it is shown that the experimental determination of the magnitude of K_F is possible only within the framework of the ‘up-scaled aggregation model’, considering the C₆₀ fullerene water solution as a solution of fullerene clusters. Using dynamic light scattering (DLS) data we report the value, K_F = 56 000 M⁻¹, which is in good agreement with existing theoretical estimates and the results of energetic analyses. It is suggested that the proposed ‘up-scaled model’ may be used in any instances of non-specific aggregation resulting in formation of large spherical particles. The measurement of the translational diffusion coefficient and the dimensions of the light scattering particles using a DLS approach with respect to C₆₀ fullerene aggregates is found to contain significant systematic errors originating from the interaction effect that is well-known for micellar solutions. As a result, corrections to the equations associated with DLS data are proposed.

Background Doxorubicin (Dox) is one of the most potent anticancer drugs, but its successful use is hampered by high toxicity caused mainly by generation of reactive oxygen species. One approach to protect against Dox-dependent chemical insult is combined use of the cytostatic drug with antioxidants. C₆₀ fullerene has a nanostructure with both antioxidant and antitumor potential and may be useful in modulating cell responses to Dox. Objective The aim of this study was to estimate the antitumor effect and antioxidant enzyme activity of combined C₆₀ fullerene and Dox (C₆₀ + Dox) in the liver and heart of mice with Lewis lung carcinoma compared with Dox treatment alone. Methods Highly stable pristine C₆₀ fullerene aqueous colloid solution (concentration 1.0 mg/ml, average hydrodynamic diameter of nanoparticles 50 nm) was used in the study and characterized by means of atomic force microscopy (AFM). The in vivo investigation of C₆₀-Dox action was performed via the standard methods of histological and enzyme activity analyses. Results Dox (total dose 2.5 mg/kg) combined with C₆₀ fullerene (total dose 25 mg/kg) in tumor-bearing animals resulted in tumor growth inhibition, prolongation of life, metastasis inhibition, and increased number of apoptotic tumor cells and was more effective than the corresponding course of Dox treatment alone. C₆₀ fullerene demonstrated a protective effect against superoxide dismutase and glutathione peroxidase inhibition induced by Dox-dependent oxidative insult in the liver and heart. Conclusion Combined treatment with C₆₀ + Dox is considered to be a promising approach for cancer chemotherapy.

We formulated and analyzed a novel nanoformulation of the anticancer drug cisplatin (Cis) with C₆₀ fullerene (C₆₀+Cis complex) and showed its higher toxicity toward tumor cell lines in vitro when compared to Cis alone. The highest toxicity of the complex was observed in HL-60/adr and HL-60/vinc chemotherapy-resistant human leukemia cell sublines (resistant to Adriamycin and Vinculin, respectively). We discovered that the action of the C₆₀+Cis complex is associated with overcoming the drug resistance of the tumor cell lines through observing an increased number of apoptotic cells in the Annexin V/PI assay. Moreover, in vivo assays with Lewis lung carcinoma (LLC) C57BL/6J male mice showed that the C₆₀+Cis complex increases tumor growth inhibition, when compared to Cis or C₆₀ fullerenes alone. Simultaneously, we conducted a molecular docking study and performed an Ames test. Molecular docking specifies the capability of a C₆₀ fullerene to form van der Waals interactions with potential binding sites on P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP-1), and multidrug resistance protein 2 (MRP-2) molecules. The observed phenomenon revealed a possible mechanism to bypass tumor cell drug resistance by the C₆₀+Cis complex. Additionally, the results of the Ames test show that the formation of such a complex diminishes the Cis mutagenic activity and may reduce the probability of secondary neoplasm formation. In conclusion, the C₆₀+Cis complex effectively induced tumor cell death in vitro and inhibited tumor growth in vivo, overcoming drug resistance likely by the potential of the C₆₀ fullerene to interact with P-gp, MRP-1, and MRP-2 molecules. Thus, the C₆₀+Cis complex might be a potential novel chemotherapy modification.