Fabrication of bioactive osteogenic controlled-release systems, cellular platforms, and cellular capsules using layer -by -layer nanoassembly

There is an ever-increasing awareness that the field of tissue engineering offers many potential solutions to clinical problems. While advances along these lines have been made, the design and implementation of an "off the shelf" tissue is yet to be realized. Thus, the objectives of this work were largely aimed at the design and fabrication of biocompatible, bioactive structures which could be integrated into existing biomaterial products. The electrostatic layer-by-layer (LbL) self-assembly technique was used to incorporate biologically relevant molecules within controlled release systems, cell culture platforms, and 3-D cellular capsules. Two delivery systems were investigated to determine the release of a model drug, dexamethasone (DEX). In the first system, nanothin polyelectrolyte (PE) layers were applied to the micronized drug crystals as a diffusion barrier. In the second system, DEX was physically entrapped within calcium alginate microspheres which were further modified with PE layers. The fabrication of cell culture platforms functionalized with nanothin layers of PEs, TiO2 nanoparticles, and the growth factor TGFβ1 was achieved through ultrasonic nebulization. Finally, individual cellular capsules were fabricated by elaborating the LbL process on mesenchymal stem cell and human dermal fibroblast templates. Materials characterization and cell culture testing were performed as preliminary indicators of potential cytotoxicity. Release of the drug DEX was enhanced when directly templated with polyelectrolyte layers while DEX entrapment within polyelectrolyte-modified alginate microspheres reduced drug release by a factor of three. An encouraging result of in vitro cell culture assessment was the distinct change in fibrochondrocyte morphology when compared with positive and negative controls. An ultrasonic nebulizer produced 14-layered cell culture substrates containing DEX, TiO2 nanoparticles, and the growth factor TGFβ1. In comparison with traditionally dipped substrates, layer fabrication was expedited ...