Learning from Nature: Bioinspired Chlorin-Based Photosensitizers Immobilized on Carbon Materials for Combined Photodynamic and Photothermal Therapy

Chlorophylls, which are chlorin-type photosensitizers, are known as the key building blocks of nature and are fundamental for solar energy metabolism during the photosynthesis process. In this regard, the utilization of bioinspired chlorin analogs as photosensitizers for photodynamic therapy constitutes an evolutionary topic of research. Moreover, carbon nanomaterials have been widely applied in photodynamic therapy protocols due to their optical characteristics, good biocompatibility, and tunable systematic toxicity. Herein, we review the literature related to the applications of chlorin-based photosensitizers that were functionalized onto carbon nanomaterials for photodynamic and photothermal therapies against cancer. Rather than a comprehensive review, we intended to highlight the most important and illustrative examples over the last 10 years.

Synthesis and properties of novel water-soluble fullerene-glycine derivatives as new materials for cancer therapy

Novel water-soluble fullerene-glycine derivatives were synthesized by means of simple organic chemistry. They are completely soluble in water, yielding a clear brown solution. The products were characterized by fourier transform infrared (FTIR), ultraviolet-visible spectroscopy (UV-Vis), (1)H NMR, (13)C NMR, thermogravimetric analyses (TGA), and scanning electron microscopy (SEM). The assembly behavior of water-soluble fullerene-glycine derivatives was investigated by SEM. The results show that the fullerene-glycine derivatives create morphology that is sphere-like. The cytotoxicity to cancer cell lines of the fullerene-glycine derivatives was evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) and flow cytometry. The results show that fullerene-glycine derivatives exhibit mortality and apoptosis of the cells which increased with the increase of fullerene-glycine derivative concentration. The cytotoxicity mechanism of fullerene-glycine derivatives was investigated for the first time. Novel water-soluble fullerene-glycine derivatives were synthesized by means of simple organic chemistry. The products were characterized by FTIR, UV-Vis, (1)H NMR, (13)C NMR, TGA, and SEM. The bioactivities of fullerene-glycine derivative materials have been tested, and the results show that compared with the fullerene complex, the fullerene-glycine derivative materials exhibit mortality and apoptosis of the cells which increased with the increase of fullerene-glycine derivative concentration. SEM images showed the macrostructure of fullerene-glycine derivative materials was spheres.

Reduction of hydroxylated fullerene (fullerol) in water by zinc: reaction and hemiketal product characterization

Water-soluble, hydroxylated fullerene (fullerol) materials have recently gained increasing attention as they have been identified as the primary product(s) during the exposure of fullerenes (as water stable, nanoscale aggregated C60) to UV light in water. The physical properties and chemical reactivity of resulting fullerols, however, have not been thoroughly studied. In this paper, we identified and characterized the reductive transformation of fullerol (C60(OH)x(ONa)y) by solid zinc metal (Zn(0)) through a series of batch reaction experiments and product characterization, including (13)C NMR, FTIR, XPS, UV-vis, DLS, and TEM. Results indicated the facile formation of water stable, pH sensitive hemiketal functionality as part of a relatively reduced fullerol product. Further, aqueous physical behavior of the product fullerol, as measured by octanol partitioning and surface deposition rates, was observed to significantly differ from the parent material and is consistent with a relative increase in molecular (product) hydrophobicity.

Effects of hydroxyl group distribution on the reactivity, stability and optical properties of fullerenols

We investigate the impact of hydroxyl groups on the properties of C(60)(OH)(n) systems, with n = 1, 2, 3, 4, 8, 10, 16, 18, 24, 32 and 36 by means of first-principles density functional theory calculations. A detailed analysis from the local density of states has shown that adsorbed OH groups can induce dangling bonds in specific carbon atoms around the adsorption site. This increases the tendency to form polyhydroxylated fullerenes (fullerenols). The structural stability is analyzed in terms of the calculated formation enthalpy of each species. Also, a careful examination of the electron density of states for different fullerenols shows the possibility of synthesizing single molecules with tunable optical properties.