Chlorophyll a in cyclodextrin supramolecular complexes as a natural photosensitizer for photodynamic therapy (PDT) applications

• DOI: 10.1016/j.msec.2017.12.012
• Publication Date: 2017-12-15T08:51:55Z
• Authors: Paola Semeraro; Guglielmina Chimi...; Emiliano Altamura; Paola Fini; Vito Rizzi; Pinalysa Cosma
• Keywords: Chlorophyll; HT-29 cell line; Cyclodextrins; Photosensitizing Agents; Cell Death; Chlorophyll a; Chlorophyll A; ROS; Flow Cytometry; 01 natural sciences; Photodynamic therapy; 0104 chemical sciences; 3. Good health; Chlorophyll a; Cyclodextrins; Photodynamic therapy; ROS, HT-29 cell line; Cell Death; Chlorophyll; Chlorophyll A; Cyclodextrins; Flow Cytometry; HT29 Cells; Humans; Photosensitizing Agents; Reactive Oxygen Species; Solubility; Spectrophotometry, Ultraviolet; Subcellular Fractions; Photochemotherapy; Photochemotherapy; Solubility; ROS, HT-29 cell line; Humans; Spectrophotometry, Ultraviolet; Reactive Oxygen Species; HT29 Cells; Subcellular Fractions

Chlorophyll a (Chl a), an amphipathic porphyrin, was employed as natural photosensitizer for photodynamic therapy applications. Due to its lacking solubility in water and high tendency to aggregate, Chl a was included into different modified cyclodextrins (CDs) to form stable water-soluble supramolecular complexes. To achieve this aim, 2-Hydroxypropyl-β-cyclodextrin (2-HP-β-CD), 2-Hydroxypropyl-γ-cyclodextrin (2-HP-γ-CD), Heptakis(2,6-di-o-methyl)-β-cyclodextrin (DIMEB) and Heptakis(2,3,6-tri-o-methyl)-β-cyclodextrin (TRIMEB) were used. The chemical physical properties of Chl a/CD complexes in cellular medium were studied by means of UV-Vis absorption spectroscopy. Results demonstrated the good aptitude of 2-HP-γ-CD, and more particularly of 2-HP-β-CD, to solubilize the Chl a in cell culture medium in monomeric and photoactive form. Then, Chl a/2-HP-β-CD and Chl a/2-HP-γ-CD complexes were evaluated in vitro on human colorectal adenocarcinoma HT-29 cell line, and cytotoxicity and intracellular localization were respectively assessed. Further tests, such as phototoxicity, ROS generation, intracellular localization and mechanism of cell death were then focused exclusively on Chl a/2-HP-β-CD system. This complex exhibited no dark toxicity and a high phototoxicity toward HT-29 cells inducing cell death via necrotic mechanism. Therefore, it is possible to affirm that Chl a/2-HP-β-CD supramolecular complex could be a promising and potential formulation for applications in photodynamic therapy.