Preparation Techniques And Magnetic Properties Of CoNiWP Films By Electroless Deposition

Nitinol stents have been successfully applied in the treatment of stenosis. However, the restenosis due to the growth of tumor in lumen remains an unresolved problem, how to resolve the restenosis is a research focus. In this thesis, a new method to resolve the restenosis was designed, i.e. combining a magnetic stent with magnetic drug carriers treats stenosis and restenosis. For example, magnetic films are deposited on a nitinol stent so that it possesses proper magnetic properties. If implanted into a lumen, the magnetic stent not only can expand the patient's lumen as traditional stent does, but also can provide an internal magnetic field and adsorb the magnetic drug carriers, i.e. magnetically targeted therapy. One of the key materials to carry out the method—Magnetic stent has been investigated including the fabricating theory and technical parameters.CoNiWP magnetic films have been electrolessly deposited on nitinol. The microstructure and magnetic properties of CoNiWP films have been characterized by EDS, XRD, SEM, MFM, and VSM, and the influence of important technical parameters on the structure and magnetic properties of CoNiWP films have been investigated; the correlations between microstructure and magnetic properties of films have been studied, the preparing technique have been optimized; Animal modes bearing cholangiocarcinoma was built, and the magnetically targeted therapeutic efficacy of the resulting magnetic stent have been evaluated by animal experiments. The main results of this work are summarized as follows:Electroless depositing magnetic films on nitinol stent is an optimal method to fabricate magnetic stent. Adjusting the concentration of Co²⁺ and WO₄^2- in bath can effectively improve the magnetic properties of the CoNiWP films. When the concentration of CoSO₄ is 30g/L, the composition of the film is Co_52.1Ni_41.0W_0.7P_6.2, the magnetic properties of CoNiWP film reach optimal value.By adjusting the bath pH, the composition, grain size, microstructure and magnetic properties of CoNiWP films can be changed. The coercivity of CoNiWP film shows a maximum at pH 8.06, but the squareness is the lowest. The BH_max shows two peaks at pH 8.06 and 8.85 respectively, and exhibits a maximum (about 8.5kJ/m³) at pH 8.85.The coercivity of the films varies with bath pH values; the changing tendency is agreement with that of the grain size. Meanwhile, the coercivity is also influenced by the Co content and surface morphology. The exchange-coupling interaction is the key factor influencing the squareness of the CoNiWP films, at different bath pH the film can have different phase-separated structures and grain sizes, thus, the exchange-coupling interaction is affected, and finally the squareness of CoNiWP films is changed.Combining with the magnetic stents and magnetic 5-FU carriers, the 5-FU carriers are substantially localized around the tumor as a result of the internal magnetic field supplied by magnetic stent obtained above, and the growth of tumor are inhibited remarkably; compared with the blank group, the tumor volumes of experimental group decreased by 38.57% after 16 days. The experimental investigation confirms that to restenosis by magnetically targeted therapy using magnetic stent and magnetic drug carrier is superior, and the method of preparing magnetic stent by electroless deposition is feasible.