The Fabrication Of Drug Release Barrier Layers Based On Free-Standing Polymer Nanofilms

With the development of nanotechnology, the free-standing polymer nanosheets have got more attention for their excellent advantages such as high flexibility, high transparency and huge aspect ratio values (up to106). Quite recently, the free-standing nanosheets with properties of biocompatibility and biodegradability start to be gradually used in biomedicine. The combination of drug controlled release coating and medical implanted devices can realize the drug’s directional release, but the coatings prepared by layer-by-layer technology often exist the serious fast release in the early stage and reduce the curative effect. The biodegradable polymer nanofilms with certain thickness fabricated through the free-standing film technology are used as barrier layers to adjust the drug release rate. So a new method which can improve even or avoid the early fast release will be developed, and it’s application prospect in biological materials, medical implant device, tissue engineering and the biomedical sciences will be broaden.Firstly, the poly-(lactic acid) nanoparticles (PLA NPs) which encapsulated pyrene as a model drug, were prepared by method of emulsion-solvent diffusion method, and PLA NPs morphology, diameter and surface potential were monitored by SEM and DLS. Secondly, PLA NPs and cation polyelectrolyte poly(ethyleneimine)(PEI) were chosen as primitives to build multilayer thin films. The results of UV-vis spectroscopy verified that the growth of multilayers is stable and homogeneous. Meanwhile, the morphology and roughness of the PLA NPs/PEI deposition films was characterized by SEM and AFM. The load of pyrene into the multilayer films was also verified by fluorescence spectroscopy. Furthermore, the free-standing PLA nanofilms were fabricated by a single step of spin-coating assisted deposition using Poly(vinyl alcohol)(PVA) as a a water-soluble sacrificial layer, and were used to envelop the surface of drug loading multilayer as barrier layer. Afterwards, the chemical composition, thickness, morphology and roughness of no-coating and coating barrier layer were characterized by XPS, SEM and AFM. Finally, the release profile of pyrene from the deposition films in PBS (pH=7.4) was further studied. The result indicated that PLA free-standing nanosheet as barrier layer can effectively control the fast release of pyrene. Release amount of pyrene in deposit films coated with double barrier layers is only about at15%in the early10hours and the release will stably keep more than15days.