NER: Magnetically Activated Nanoporous Structures for Biomedical Applications

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This proposal was received in response to the Nanoscale Science and Engineering Initiative, Program Solicitation NSF 01-157, in the NER category. The proposal focuses on innovative materials synthesis strategies to create both passive, and magnetically-driven mechanically active precision separation membranes. Of particular interest is the development and characterization of well-controlled, stable, and uniform nano-dimensional membranes capable of the separation of viruses and/or proteins during the blood fractionation processes and the blocking of antibodies and complement molecules from encapsulated xenogeneic cells. It is hypothesized that high surface area cylindrical capsules the walls of which are comprised of nanoporous membranes, created via a two-step process of electric-field driven anodization of aluminum or titanium, can be used for the absolute filtration or exclusion of biomolecules in the nanometer range. For a given capsule, a windowpane structure is used with anodized nanoporous windows, and un-anodized aluminum struts for structural support. The aluminum anodization process enables precise control of pore size, with a controllable pore diameter of approximately 10 nm to 100 nm depending upon anodizing voltage. Beyond making passive membranes, the investigators propose fabrication of cylindrical nanoporous biocapsules incorporating magnetoelastic elements. Incorporation of the magnetoelastic elements enable the biocapsule to be mechanically vibrated, remotely from a distance, by application of a time-varying magnetic field that should enable controlled transport through the membrane. A magnetoelastic thick film layer will be electroplated onto the aluminum structural supports of the capsule. Such capsules could possibly find application as in-vivo drug delivery devices, where needed medicine is delivered in precise amounts by external application of a magnetic field. As a further aspect of the proposed research, the investigators seek to build upon their expertise in fabrication of nanoporous alumina films of high uniformity to fabricate surface coatings comprised of perpendicularly oriented gold-coated magnetostrictive nanowire arrays. The utility of these arrays will be investigated for their utility in prevention of biofouling. It is hypothesized that the needle-like shape of the nanowire array elements, and the wave-like movement of the magnetostrictive nanowire array in response to a time-varying non-uniform magnetic field, will help prevent protein attachment to the surface, and could ultimately be used to move or transfer cells across the surface. The proposed research will determine optimal routes for fabrication of the nanoporous capsules with attention to membrane functionality as biological filters. The application of passive nanoporous biocapsules for cellular encapsulation and immunoisolation, and mechanically active biocapsules for controlled transport and delivery through the nanoporous membranes will be investigated. In addition, the use of magnetostrictive nanowire arrays will be investigated for their use in the prevention of biofouling. The proposed outcomes are: (1) Determining a path for in-situ or in-vivo controlled drug delivery by application of an external time varying magnetic field. (2) Determination of a surface that would prevent biofouling, facilitating the introduction of medical devices into the human body.