Study of photosenzitizers used in photodynamic therapy on nanosystems

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Herényi Levente
SE Biomedical Engineering MSc

Application of porphyrins as photosensitizers (PS) is based on their light-triggered generation of reactive oxygen species (ROS) that may cause oxidative damages and ultimately kill cells. Cellular membranes are the action grounds of many sensitizers due to their amphiphilic character as well as the location of many of the targets attacked by ROS. Hence, the binding ability and location of porphyrins in liposomes as simple models of cellular membranes are of outstanding interest. Here I compare two similar mesoporphyrin (MP) derivatives, namely, MP IX dimethyl ester (MPE) and MP IX dihydrochloride (MPCL). Monocomponent small unilamellar vesicles formed of different saturated and non-saturated phosphatidylcholines with incorporated MPs were investigated. I determined the binding parameters by conventional fluorescence spectroscopy and the inhomogeneous distribution functions (IDFs) by fluorescence line narrowing (FLN) spectroscopy. I found that the binding ability of MPE is considerably higher than that of MPCL. IDFs shows three distinct binding sites. Based on a consistent interpretation at the molecular level the “site I” is between the two lipid layers (for MPE), “site II” is between the hydrocarbon chains (for MPE and MPCL) and “site III” is at the head groups of phosphatidylcholines (for MPCL). I investigated the ROS quantitatively, that was produced by the white light exposed porphyrins.


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