Browsing by Subject "liposome"

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.

Nanolääkkeiden pinnalle elimistössä muodostuva biomolekyylikerros eli proteiinikorona vaikuttaa muun muassa jakautumiseen, toksisuuteen ja soluvuorovaikutuksiin. Koronan ominaisuuksien tuntemus jakautumisen eri vaiheissa on siten edellytys tehokkaampien ja turvallisempien nanolääkkeiden kehittämiselle, mutta kehitystyötä on hidastanut soveltuvien menetelmien puute. Turvallisuuden ja tehon ennakoinnin osalta on korostettu leimavapaiden in vitro -menetelmien tarvetta. Tutkielmassa kehitettiin multiparametriseen pintaplasmoniresonanssilaitteistoon ja laskennalliseen mallinnukseen perustuva menetelmä liposomien koronan tiheyden ja paksuuden määrittämiseen. Toisin kuin koronan tutkimiseen yleisesti käytetyt menetelmät, valoon perustuva kajoamaton ja leimavapaa menetelmä ei vaikuta koronan rakenteeseen. Näin voidaan tutkia myös löyhemmin sitoutuneista proteiineista muodostunutta pintakerrosta, mikä vastaa keskeisimpään kirjallisuuskatsauksessa todettuun menetelmäpuutteeseen. Menetelmää sovellettiin neljän biosensorille immobilisoidun liposomiformulaation pinnalle ihmisen seerumissa muodostuvan koronan tutkimiseen. Sen avulla oli mahdollista määrittää ensimmäistä kertaa tiiviin ja löyhän koronan tiheys ja paksuus laimentamattomassa seerumissa. Tulokset tukevat käsitystä ns. erotteluhypoteesin kuvaamasta erillisestä löyhästä proteiinikerroksesta ja avaavat uusia mahdollisuuksia sen biologisen merkityksen arviointiin. Lisäksi voitiin määrittää ensi kerran opsoniinimolekyylien sitoutumiskinetiikka liposomien pinnalle, minkä avulla voidaan arvioida nanolääkkeiden taipumusta poistua verenkierrosta ja aktivoida sisäsyntyinen immuunipuolustus. Menetelmä soveltuu siten liposomien koostumuksen ja pinta-arkkitehtuurin optimointiin prekliinisessä lääkekehitysvaiheessa.

Liposomes are nano-sized vesicles in which the aqueous phase is surrounded by lipid-derived bilayer. They are excellent drug vehicles for example in ocular drug delivery because they can, among other things, increase the bioavailability and stability of the drug molecules and reduce their toxicity. Liposomes are known to be safe to use, because they degrade within a certain period of time and they are biocompatible with the cells and tissues of the body. Owing to its structure, the surface of liposomes can also be easily modified and functionalized. Light-activated ICG liposomes allow drug release in a controlled manner at a given time and specific site. Their function is based on a small molecule called indocyanine green (ICG) which, after being exposed to laser light, absorbs light energy and thereby locally elevates the temperature of the lipid bilayer. As a result, the drug inside is released into the surroundings. The blood circulation time of liposomes has often been prolonged by coating the liposomes with polyethylene glycol (PEG). Although PEG is generally regarded as a safe and biocompatible polymer, it has been found to increase immunological reactions and PEG-specific antibodies upon repeated dosing. Conversely, hyaluronic acid (HA), is an endogenous polysaccharide, which is present in abundance for instance in vitreous. Thus, it could serve as a stealth coating material which extends the otherwise short half-life of liposomes. One of the main objectives of this thesis was to find out whether HA could be used to coat liposomes instead of PEG. In order to prepare HA-coated liposomes, one of the lipid bilayer phospholipids, DSPE, had to be first conjugated with HA. For the conjugation, potential synthesis protocols were sought from the literature. Ultimately two different reductive amination-based protocols were tested. Consequently, the protocol in which the conjugation was achieved via the aldehyde group of HA, proved to be working. Thereafter, HA-coated liposomes were prepared by thin film hydration from the newly synthesised conjugate as well as DPPC, DSPC and 18:0 Lyso PC. Calcein was encapsulated in the liposomes. HA-covered liposomes were then compared with uncoated and PEGylated liposomes by examining their phase transition temperatures, ICG absorbances, sizes, polydispersities, and both light and heat-induced drug releases. The aforementioned tests were also conducted when the effects of the HA and ICG doubling were examined and the possibility to manufacture HA liposomes with small size was assessed. HA-liposomes showed similar results as PEG-coated liposomes. In addition, successful extrusion of HA-liposomes through a 30 nm membrane was also demonstrated in the results. Doubling of HA did not significantly affect the results. In contrast, increasing the molar amount of ICG by double caused spontaneous calcein leakage even before any heat or light exposure. Based on these findings, HA could work as a coating material instead of PEG, yet further studies are required for ensuring this conclusion. The other key objective was to evaluate the stability of four different formulations, named as AL, AL18, AL16 and AL14, in storage and biological conditions. Based on the differences in the formulation phospholipid composition, the assumption was that AL would be the most stable of the group and that the stability would decrease so that AL18 and AL16 would be the next most stable and eventually AL14 would be the least stable formulation. As in the previous study, the liposomes were prepared by thin film hydration with calcein being encapsulated inside the liposomes. In the storage stability test, liposomes were stored in HEPES buffer at either 4 °C or at room temperature for one month. In the test conducted in physiological conditions, the liposomes were added either to porcine vitreous or fetal bovine serum (FBS) and the samples were incubated at 37 ºC for five days. Regardless of the experiment, phase transition temperatures as well as light and heat-induced drug releases were initially measured. As the test progressed, calcein release, ICG absorbance, size, and polydispersity were measured at each time point. The initial measurements confirmed the hypothesis about the stability differences of tested formulations. In the storage stability test, all formulations, except AL14, appeared to be stable throughout the study and no apparent differences between the formulations or temperatures were observed. On the other hand, the stability of liposomes stored in biological matrices varied so that the liposomes were more stable in vitreous than in FBS and the stability decreased in both media as expected.