aluminum-tetrasulfophthalocyanine and hypericin

In vitro experiments in plastic receptacles are the basis of characterization of new photosensitizers (PSs) for the photodynamic therapy. We recently reported that lipophilic PSs adhere to cell culture microplates in a kinetic-like manner (Engelhardt et al., 2011). In the current study, we examined the interaction and phototoxic effects of the microplate-adhered PS in cancer cells. Therefore, we preloaded microplates with hypericin, Foscan, PVP-hypericin, or aluminum (III) phthalocyanine tetrasulfonate chloride (AlPCS4) for 24 hours and measured the PS distribution after addition of A431 human carcinoma cells: following another 24 hours up to 68% of hypericin were detected in the cell fraction. The hydrophilic PVP-hypericin and AlPCS4 also diffused into the cells, but the quantities of PS adherence were considerably lower. Microplate-adhered Foscan appeared not to be redistributed. In contrast to the hydrophilic PSs, the cellular phototoxicity of microplate-adhered lipophilic PS was high, independent of whether the PS (i) was pre-loaded onto microplates or (ii) added simultaneously with the cells or (iii) one day after cell seeding. Based on these results, we suggest testing lipophilic PS dyes for their adherence to microplates. Furthermore, the ability of plastic materials to (reversibly) store PSs might represent a new approach for the PS delivery or the development of antimicrobial coatings.

Topics: Anthracenes; Carcinoma; Cell Adhesion; Cell Culture Techniques; Cell Line, Tumor; Cell Membrane; Culture Media; Dermatitis, Phototoxic; Drug Delivery Systems; Humans; Indoles; Mesoporphyrins; Organometallic Compounds; Perylene; Photochemotherapy; Photosensitizing Agents; Plastics

Analysis of photosensitizer (PS) uptake kinetics into tumor cells is a standard cell culture experiment in photodynamic therapy (PDT) - usually performed in plastic microplates or petri dishes. Organic substances such as PS can potentially interact with the plastic surfaces. In this study, we provide a qualitative comparison of three lipophilic PS (hypericin, Foscan® and Photofrin®) and two rather hydrophilic PS formulations (PVP-hypericin and aluminum (III) phthalocyanine tetrasulfonate chloride) regarding their adherence to the surfaces of 96-well microplates obtained from four different manufacturers. For estimation of the relevance of PS adherence for cellular uptake studies we compared the fluorescence signal of the respective PS in microplates containing A431 human epithelial carcinoma cells with microplates incubated with the respective PS under cell-free conditions. We demonstrate that lipophilic PS substances show a strong adherence to microplates - in case of direct lysis and fluorescence measurement resulting in 50% up to 90% of the overall signal to be caused by adherence of the substances to the plastic materials in a cellular uptake experiment. For the hydrophilic compounds, adherence is negligible. Interestingly, adherence of PS agents to microplates takes place in a time-dependent and thus kinetic-like manner, requiring up to several hours to reach a plateau of the fluorescence signal. Furthermore, PS adherence is a function of the PS concentration applied and no saturation effect was observed for the concentrations used in this study. Taken together, this study provides a systematic analysis under which conditions PS adherence to cell culture plates may contribute to the overall fluorescence signal in - for example - PS uptake experiments.

Topics: Anthracenes; Cell Adhesion; Cell Culture Techniques; Cell-Free System; Humans; Hydrophobic and Hydrophilic Interactions; Indoles; Microscopy, Fluorescence; Neoplasms, Glandular and Epithelial; Organometallic Compounds; Perylene; Photochemotherapy; Photosensitizing Agents; Plastics; Polyvinyls; Pyrrolidines; Tumor Cells, Cultured

At present a wide range of photosensitizers are employed in photodynamic therapy (PDT) that have very different characteristics. Although, countless in vitro studies on the attributes of photosensitizers do exist, a direct comparison of these substances on one cell line are rare and may contribute to the choice of the optimal photoactive substance for a specific application. We therefore evaluated the properties of six widespread photosensitizers, namely Foscan, Fospeg, hypericin, aluminum (III) phthalocyanine tetrasulfonate chloride (AlPcS(4)), 5-aminolevulinic acid (ALA), and Photofrin in terms of: (i) cytotoxicity without illumination, (ii) phototoxicity, (iii) cellular uptake and release, and (iv) apoptosis induction in A431 human epidermoid carcinoma cells using comparable illumination regimens. We clearly show that meso-tetrahydroxyphenylchlorin (mTHPC, Foscan) is a very effective photosensitizer inducing high phototoxicity at very low concentrations. Similar in vitro characteristics and phototoxicity were observed for Fospeg, the water-soluble formulation of mTHPC. Hypericin, a photosensitizer extracted from plants of the Hypericum genus, is very effective in inducing apoptosis over a wide range of light fluences. AlPcS(4) absorbs light of 674 nm wavelength providing a higher penetration depth in tissue. Its hydrophilic character allows for application as aqueous solution. ALA can be administered at very high concentrations without producing cytotoxic effects in the dark. The intracellular concentration of protoporphyrin IX rapidly decreases after withdrawal of ALA, thus minimizing the period of light sensitivity post PDT. Among all photosensitizers Photofrin has most clinical approvals and serves as standard.

Topics: Aminolevulinic Acid; Anthracenes; Antineoplastic Agents; Apoptosis; Cell Line, Tumor; Dihematoporphyrin Ether; Humans; Indoles; Mesoporphyrins; Organometallic Compounds; Perylene; Photochemotherapy; Photosensitizing Agents