POLİKATYONİK AMFİFİLİK SİKLODEKSTRİN NANOPARTİKÜLLERİN ANTİKANSER İLAÇ TAŞIYICI SİSTEM OLARAK ETKİNLİK VE GÜVENLİK AÇISINDAN DEĞERLENDİRİLMESİ
Özet
Nanoparticulate drug delivery systems possess advantages in cancer treatment due to their physicochemical properties. Several polymers have been used to prepare nanoparticles. Cyclodextrins, are natural oligosaccharides. Thanks to their unique structure, they encapsulate hydrophobic drugs in their cavities and provide controlled delivery. They are also frequently preferred in drug formulations due to their biocompatibility. In addition to their use in drug delivery systems, cyclodextrins are used to remove cholesterol from the cell membrane in various studies.
In spite of the numerous studies carried out with nanoparticles, the number of products in the market is limited. The main reason is that, the success achieved by cell culture in laboratory conditions can not be achieved in living systems. Tumor tissue, which is normally interacting with other cells in the biological systems, can not exactly be mimicked by using in vitro cell culture with single cell-type and monolayer. For this purpose, the activities of drug delivery systems are determined in 3-dimensional cell culture studies.
In this thesis, the apoptotic effects of blank amphiphilic cyclodextrins were demonstrated by various mechanistic studies including Caspase-8 activity, lipid peroxidation assay, TUNEL assay, Tali™-based image analysis, cholesterol assay, gene expression studies and survivin assay. Blank nanoparticles exerted cytotoxicity against a variety of cancer cells (MCF-7, HeLa, HepG2, and MB49) but none to healthy cells (L929, G/G). Interestingly, blank 6OCaproβCD and blank PC βCDC6 derivatives were also found to be intrinsically effective on cell number and membrane integrity of MCF-7 cells. In conclusion, blank nanoparticles induced apoptosis through mitochondrial pathway targeted to cholesterol microdomains in cancer cell membrane.
In the second step of the thesis study, paclitaxel:cyclodextrin inclusion complexes were prepared and characterized by differential scanning calorimetry, scanning electron microscopy and fourier transform infrared spectroscopy. As a result of the characterization studies, it was observed that amphiphilic cyclodextrins were successfully complexed with 1:2 molar ratio of paclitaxel. Paclitaxel loaded nanoparticles, prepared from the inclusion complexes and directly from cyclodextrin derivatives, have appropriate particle size distribution and low polydispersity index. The nanoparticles prepared from the inclusion complex have higher drug loading efficiency and prolonged release than the conventionally prepared nanoparticles.
The anticancer activities of drug loaded nanoparticles were evaluated in 2-dimensional cell cultures, co-colture prepared from cancer and healthy cells at different ratios and 3-dimensional multicelluler tumor spheroids. The results of the studies show that, conventional and 3-dimensional cell culture findings are significantly different. In 3-dimensional tumor studies, the drug resistance increased as the proportion of healthy fibroblast cells increased. Paclitaxel-loaded cyclodextrin nanoparticles have been found to have a higher anticancer effect when compared to drug solutions in 2-dimensional and 3-dimensional cell culture. In cellular uptake studies with nile-red loaded nanoparticles, it was observed that amphiphilic cyclodextrins, especially the cationically charged derivative, penetrates into multilayer 3-dimensional tumor.
In conclusion, the mechanism of apoptotic action of blank amphiphilic cyclodextrins is elucidated in this thesis. In this view, effective cancer treatment can be provided with lower dose of active substance. It has been determined that the response and cell morphology of the 3-dimensional tumor are different from those of the 2-dimensional cell culture studies.
