Synthesis and surface characterization of nanosized Y 2 O 3 :Eu and YAG:Eu luminescent phosphors which are useful in photodynamic therapy of cancer

A series of finely dispersed Y 2 O 3 :Eu and YAG:Eu phosphors useful for the enhancement of photodynamic therapy (PDT) of cancer were prepared using the Pechini method and self-propagating high temperature synthesis (SHS). The obtained phosphors can be used in cancer therapy drugs in combination with a photosensitizer which accumulates selectively in tumor tissues. Upon excitation with X-ray irradiation which easily penetrates the organism such phosphors are activated to radiate the visible light with wavelengths required to stimulate the photosensitizer yielding active singlet oxygen which destroys cancer cells. Thus the developed phosphors provide an extension of PDT in the treatment of internal tumors which are inaccessible for activating light from the outside. A detailed characterization of the obtained phosphors was performed to define various types of adsorption centers and the functional groups on their surface, including hydroxyls with different acid-base characteristics and an admixture hydrated carbonate layer which may help in linking with other drugs (photosensitizer and pluronic binder) and is important in respect of biocompatibility. A model describing the composition of acid-base centers with various pK a values on the surface of the studied materials is suggested on the basis of the obtained results as an approach to study the adjustable modification of various compounds in respect of the compatibility between their ingredients as well as their overall biocompatibility. Y 2 O 3 :Eu phosphor prepared via the SHS method was successfully tested for biological (therapeutic) activity which provided an effective destruction of fibroblast cell cultures of Chinese hamster V-79 in combination with a photosensitizer upon X-ray irradiation.