Nanobiotechnology for health-care

Apoptosis induction in human leukemic cells with photoexcited C60 fullerene-doxorubicin conjugate
Anna Grebinyk 1,2,3, Svitlana Prylutska3, Yuriy Prylutskyy3 , Uwe Ritter4, Olga Matyshevska3, Thomas Dandekar2, Marcus Frohme 1
1 Technical University of Applied Sciences Wildau, Hochschulring 1, 15745 Wildau, Germany, E-mail: grebinyk@th-wildau.de
2 Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
3 Taras Shevchenko National University of Kyiv, Volodymyrska 64, 01601 Kyiv, Ukraine
4 Institute of Chemistry and Biotechnology, University of Technology Ilmenau, Weimarer Straße 25 (Curiebau), 98693 Ilmenau, Germany

A carbon nanostructure C60 fullerene (720 kDa, 0.72 nm) exhibits unique physico-chemical properties and biological activity. Due to the extended π-conjugated electron system after visible light irradiation C60 fullerene is able to generate cytotoxic reactive oxygen species (ROS) with 100% efficiency. C60 fullerene also possesses a significant potential to serve as a nanocarrier for efficient drug delivery into cancer cells. 
The main idea of the presented research is to conjugate C60 fullerene with the anticancer drug Doxorubicin (Dox) using C60 both as a nanocarrier for the drug and as a phototoxic anticancer agent. Human leukemic CCRF-CEM cells were incubated for 24 h with C60 fullerene-Dox conjugate, subjected to 10 J/cm2 405nm LEDs light irradiation and intracellular ROS generation, mitochondrial function, caspase 3/7 activity and cell death type were assayed. 
Once cells were incubated with C60-Dox conjugate and irradiated, a 4-fold intensification of ROS generation, significant decay of ATP level and plasma membrane disintegration were found. These data confirm that photoexcited C60-Dox conjugate exhibited mitochondrial toxicity. Photoexcited C60-Dox conjugate induced 5-fold caspase 3/7 activation in leukemic cells. Finally, the level of apoptotic cells was measured upon action of photoexcited complexes, reaching 94% in comparison with 10% of non-illuminated conjugate-containing control. 
The obtained data allow to conclude that toxic effect of C60-Dox conjugate against leukemic cells after photoexcitation was realized through apoptosis induction.