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Browsing by Subject "valoaktiivisuus"

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  • Kraft, Hanna (2018)
    Liposomes are nanosized drug delivery vesicles composed of phospholipid membranes. They present an attractive drug delivery system due to their bioavailability and flexibility. Liposomes can be prepared by different techniques. They can carry both hydrophobic and hydrophilic molecules and their surface can be modified with targeting molecules. Coating the liposome surface with the PEG derivative makes their pharmacokinetics easier to predict. There are several liposome-based medicinal products already on the market. Triggering of drug delivery systems by different external or internal stimuli allows precise control of drug release. Light-triggered drug release is an attractive alternative due to the easy control and regulation of the stimulus. The problem with light-triggered therapy has previously been the need to use high-energy ultraviolet light that penetrates badly to the tissues and is not safe. In TTA-UC process the low-energy red or green light is converted to high-energy blue light. In this process photosensitive molecules are excited by visible light and after that the energy is transferred from sensitizer to annihilator molecules. Collision of two annihilators leads to the excitation of the other molecule while the other returns back to its general energy state. The excitation breaks up with fluorescence. In this process the highly permeable and safe red light is converted to blue light which has enough energy to induce drug release. The aim of this work was to optimize liposomal preparation method and prepare a pegylated and stabile liposome formulation for TTA-UC process. Hydrophobic light sensitive molecules were loaded into the phospholipid membrane as much as possible. One of the problems in this work was to find proper methods to measure the concentrations of these molecules. The lipid composition for formulation was chosen after thermostability studies. As a quality control, the size, capability to load calcein and phase transition temperature of liposomes were measured. The quality control of light sensitive molecules was operated too. In this work, the formulation for TTA-UC was prepared. In further studies TTA-UC process happened with sufficient efficacy. The formulation was pegylated and stable in physiological conditions and the concentrations of the molecules were high enough. This was the very first time to get TTA-UC to happen in this kind of liposome formulation that may be useful as a drug carrier. Long-term stability studies and further optimization of TTA-UC method are needed in the future. Some drug release studies are important to arrange in the future, too.