We report a comprehensive in vitro study of the photo-oxidative stress on different biomolecular and cellular targets generated in the presence of fullerol C-60(OH)(n), a novel, fullerene-based and water-soluble sensitizer of singlet oxygen ((1)Delta(g)). The photodynamic efficiency of fullerol C-60(OH)(n), was checked by using a singlet oxygen scavenger, TMP-OH, and the electron spin resonance (ESR) technique, which was capable of detecting the resulting paramagnetic product, TEMPOL. ESR was also used to monitor the conformation changes occurring in the spin-labelled protein, T4L lysozyme, which Was exposed to the photo-oxidative stress in solutions containing fullerol C-60(OH)(n). Finally, atomic force microscopy (AFM) experiments were performed to monitor changes in the local elastic properties of living and glutaraldehyde-fixed cells (neurons) exposed to the toxic action of (1)Delta(g) generated in the presence of fullerol C-60(OH)(n). Remarkably, the Young's modulus values measured for both living and fixed neurons revealed a pronounced drop as a function of exposure to the toxic action of I Ag. Thus, our ESR and AFM results bring evidence that the multi-hydroxylated fullerene is an efficient (1)Delta(g)-generator in aqueous media and might be implemented as a photosensitizer for performing oxidations in biological systems