Construction Of A Novel Antitumor Drug System Based On Aptamer - Specific Recognition

Cancer is a growing health problem around the world, particularly with the steady rise in life expectancy, increasing urbanization, and the subsequent changes in environmental conditions and lifestyle. Although the mortality has decreased in the past few years with the improvement of diagnostic equipments and therapeutic technology, chemotherapy, alone or combined with radiotherapy, often kills healthy cells and thus shows significant toxicity and unavoidable side effects due to that traditional anticancer drugs cannot discern between diseased and healthy cells. Moreover, the drug dose within cancerous cells is always limited due to the non-specific, non-targeted nature of most of the anticancer drugs and their inadequate delivery to tumor tissues. To improve the therapeutic index of drugs, researchers have been made much effort to develop drug carriers for tumor-targeted delivery. Such as gold nanoparticles, porous silica materials, laponite nanodisks, carbonaceous materials and quantum dots etc. This work reports a novel anticancer drug loading and cell-specific delivery system based on cell-type-specific aptamer-functionalized graphene oxide (GO) using decitabine (DAC) and A549cell as anticancer drug and target cell model, respectively. On the basis of this, we also through hydrothermal route prepared oxidation of graphene quantum dots, and we have been carried on the preliminary characterization and cell imaging experiments. Aptamers are short, single stranded DNA or RNA that could form unique3-dimensional structures that specifically recognize a wide variety of targets from small organic molecules, proteins, cells to complex living organisms with high affinity. The aim results are as follows:1. We conjugated GO with aptamer Al (a45-base oligonucleotide binds to A549cell with high specificity and affinity) and then loaded DAC onto surface of GO (A1-GO/DAC complexes). The loading capacity of DAC on GO surface is pH-and DAC initial concentration-dependent, the saturated loading capacity, as high as～3.0mg DAC/mg GO (corresponding to the loading efficiency of～64%), is attained at physiological condition (pH7.4) and DAC initial concentration of higher than0.7mg/mL. The release of DAC from the complexes is also pH-dependent, and DAC is released at a quicker rate at acidic pH condition (pH5.5) than at physiological pH condition.2. The complexes (Al-GO/DAC) can specifically recognize A549cells from other types of cancer cells and subtypes of lung cancer cells due to the specific binding of the aptamer with the cells. Importantly, cell viability assay results reveal that the complex displays a much higher therapeutic efficacy in inhibiting the growth of the cancer cells by inducing the cell membrane damage than free DAC drug. The high DAC payload and antitumor efficacy render our developed system promising for different biomedical applications. Moreover, with aptamer being available for any kind of target, the developed approach here may become a general route for delivery of various anticancer drugs for a range of cancer therapy.3. We through hydrothermal route prepared grapheme oxide quantum dots (GQDs) whose particles size about of5-8nm. The GQDs have been carried some preliminary characterization, including TEM、HRTEM、UV-vis and FTIR. At the same time, we also use GQDs for cell imaging experiments. The laser confocal images of HeLa and A549cells shown that GQDs could enter these these two kinds of cell membrance and cytoplasm in cancer cells and couldn’t change the morphology of cells. Those data is not enough, so we will characterizing the GQDs with XPS, XRD, Raman and FTIR. On the basis of former experiment system, we suppose that the aptamer which have specific selection function by chemical bonds conjugate with the oxygen-containing functional groups on the surface of GQDs. That’s to say, GQDs was functionalized and have specific selectivity. Then we load anti-cancer drug doxorubicin (DOX) on the aptamer-GQDs surface deploy this combined drug transport system aptamer-GQDs/DOX in the treatment of cancer.