Thesis (Ph.D.) - Cairo University - National Institute of Laser Enhanced Science - Department of Laser Application in Enviromental Metrology, Photochemistry and Photobiology and Agriculture

Hypericin has gained a great attention as a powerful photosensitizing and fluorescent agent for photodynamic therapy (PDT) and fluorescence diagnosis (FD) of cancer. However, the hydrophobic nature of hypericin and the tendency to form aggregates in aqueous environments constitute the most common obstruction restricting its biological applications.The reported studies about the photophysical properties of hypericin such as fluorescence, extinction coefficient, and quantum yield concluded that hypericin remains photoactive only while it is existing in the monomeric state. Hence, the aqueous formulae of hypericin are not biologically active unless they are chemically modified to remain in the monomeric state. In this thesis, different formulae of hypericin in aqueous media were prepared to improve the water solubility of hypericin for the different biological applications. Hypericin was first encapsulated with polyvinylpyrrolidone (hypericin@PVP) and the absorption and emission characteristics of hypericin@PVP in water were studied at room temperature. Also, the photostability of the prepared hypericin@PVP was studied under visible light irradiation. Upon encapsulation with PVP, hypericin possessed an improved solubility and stability in water as revealed by the relatively enhanced absorption and emission in water.The effect of the molecular weight of the PVP was assessed by adopting PVP with two different molecular weight, namely 10 and 360 KD.

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