Browsing by Subject "soluunotto"

The leading causes of vision loss in developed countries are related to the impairment of the posterior segment of the eye. The drug delivery to the posterior segment with topical or systemic methods is challenging due to the protective barriers of the eye. The conventional and effective technique to deliver therapeutic concentrations of drugs to the posterior segment is intravitreal injection. Since naked molecules usually have a rapid vitreal clearance, the invasive injections need repeated administration in chronic conditions, resulting to increased risk of complications and poor patient compliance. The growing field of research of drug delivery systems, such as implants, nano- and microparticles and liposomes emphasizes to answer these challenges by enhancing time-controlled and targeted drug release to retinal and choroidal tissues, enabling less frequent administration and reduced off-target side effects. Liposomal drug delivery systems have potential in delivering therapeutics to posterior eye tissues in sustained and targeted manner. The experimental part of the thesis focused on studying the cell uptake, content release and cytotoxicity of light triggered pH-sensitive gold nanoparticle liposomes in human retinal pigment epithelial (ARPE-19), human umbilical vein endothelial (HUVEC) and monkey choroidal endothelial (RF/6A) cell lines. To enhance the cell differentiation to resemble the in vivo morphology, ARPE-19 cells were also used as a filter-cultured model. HUVEC cells were cultured on an artificial basement membrane matrix and induced with vascular endothelial growth factor (VEGF) to form capillary like tube structures. The liposomes were not cytotoxic during 24-hour incubation. All cells internalized liposomes to some extent, but in HUVEC capillary tubes the uptake seemed to be negligible. The light induced calcein release was variable between the experiments, possibly due to the study setting related factors, such as difficulties in temperature control. The liposomal carrier system has promising attributes to posterior eye drug delivery. Liposome-encapsulation prolongs the half-live of a drug. Light triggered release and pH-sensitivity enables highly targeted intracellular drug release decreasing the off-target side effects. Optimization of the study arrangement and liposome production procedure is needed in order to get more reliable results and further assess the future potential of these liposomes in the treatment of posterior eye diseases.

The major problem in cancer treatment is toxic side effects of the chemotherapy. Typically less than 1 % of the administered free drug reaches target cells while the rest damages non-diseased cells. Toxic side effects often limit dose escalation of anticancer drugs which leads to incomplete tumor response, early disease relapse and possible the development of drug resistance. Liposomes can be targeted in cancer tissue with passive or active targeting. In passive targeting the liposomes accumulate in abnormally formed cancer tissue through the process of extravasation and enhance the concentration of liposomal drug in solid tumor. To further improve the anticancer efficiency of passive targeted liposomes is to couple a targeting ligand to the surface of the drug carrier (i.e. active targeting). The ligand specifically binds to a surface epitope on the target cell leading to the accumulation of the liposomal drug inside the tumor cells. The aim of this study was to investigate the cytotoxicity of targeted immunoliposomes. In experimental part the liposomes were constructed using cetuximab (C225, Erbitux®) antibody and evaluated for specific cellular uptake and cytotoxicity in vitro. Cetuximab antibody is specific and selective inhibitor of HER-1 -protein (ErbB-1, EGFR, epidermal growth factor receptor). HER1 -protein is frequently expressed in high levels in human carcinomas (for example in lung and colorectal cancers, head, neck and breast cancers and in pancreatic, ovarian, prostate and bladder carcinomas). Specific immunoliposome uptake and cytotoxicity were studied in SKOV-3cells (ovarian adenocarsinoma cell line) which overexpress the EGF -receptor. Monkey kidney epithelial cells (CV-1) were used as a control cell line which represents non-diseased cells. Active targeting and cellular uptake of liposomes were investigated in cell uptake studies. Non-targeted pegylated liposomes were used as control liposomes. Specific binding of the cetuximab antibody to EGF -receptor was noticed in competition studies. The in vitro cytotoxicity of doxorubicin containing immunoliposomes was studied with Alamar Blue® cell viability assay. Liposome size was determined at intervals of about two weeks during the experimental part. In conclusions, antibody targeted immunoliposomes showed greater cellular uptake and cytotoxicity in EGFRoverexpressing target cells (SKOV-3) than the corresponding non-targeted liposomal drug. Immunoliposomes showed greater cytotoxicity after five days incubation, which can be a consequence of liposome formulation and slow rate of release of doxorubicin. In contrast, antibody targeted liposomes did not show specific cellular uptake or cytotoxicity in CV-1 control cell line. In clinical cancer therapy actively targeted liposomes could improve the therapeutic effectiveness of the liposomal preparations. Many studies have shown that ligand-bearing liposomes will selectively bind to target cells in vitro, but only few studies have shown the possibility in vivo.