Nanocapsules via Layer-by-Layer self-assembly technique

Since the drug molecules inside human body (in the blood vessel) are recognised as being alien, and quickly eliminated or degraded, it is necessary to find a way to protect and direct these effective components to the target zone. Therefore, the design and preparation of the therapeutic delivery systems in vivo has attracted considerable attention in recent decades. Nanocapsules, as a relatively new delivery approach, have many advantages. Compared with micron or larger delivery systems, nanocapsules are smaller and hence can migrate to diseased organs without blocking the bloody vessels. Also unlike nanospheres, nanocapsules could provide more capacity space for the therapeutics loading. Therefore, in this thesis the design and preparation of nanocapsules for the drug delivery system is discussed. A Layer-by-Layer self-assembly method onto nanospheres as a template has been developed. This method allows easy control of the size of the capsules and the thickness of the capsule walls; moreover, its flexibility has enabled various types of materials to be used to form the walls of the capsules, such as polyelectrolytes, proteins and various inorganic particles. In this project, two different core templates (silica and polystyrene nanoparticles) were prepared. Hollow capsules based on silica nanoparticles (95 nm and 114 nm) were obtained from the deposition of 9 layers of Chitosan (CHI) and Dextran sulphate sodium salt (DS), subsequently the silica cores were removed by dissolving in an HF/NH4F buffer solution. For the nanocapsules based on polystyrene particles (130 nm and 480 nm), a layer of the synthetic inorganic clay, Laponite, was introduced to improve the strength of the nanocapsules. After the core-removal process (by dissolving in tetrahydrofuran THF), a high productivity of hollow nanocapsules was observed for both particle sizes. Gold (4-10 nm) and magnetite (10 nm) nanoparticles were also incorporated into the capsule walls to modify the properties of nanocapsules obtained from the polystyrene nanoparticles of 130 nm; these materials make the particles sensitive to near infer red light and a magnetic field respectively. Furthermore, nanocapsules consisting of proteins (lysozyme and bovine serum albumin BSA) and polyelectrolytes (Poly(diallydimethylammonium chloride) PDADMAC and DS) were also fabricated. In the final part of the thesis, loading materials into the nanocapsules were tried. Instead of directly loading into the nanocapsules, the insulin was first prepared as insulin nanoparticles and these nanoparticles were then coated with the polyelectrolyte/protein layers to form the nanocapsules loaded with drug molecules. This project has extended the size range of nanocapsules that can be synthesized, and also the range of materials, and hence the properties, that can be included in the walls of the nanocapsules