Engineered growth

To overcome these limitations, we have developed culture substrates that enable the highly efficient expansion of specific cells in adherent cultures [37, 85-88]. An important characteristic of these substrates is that specifically engineered growth factors are immobilized on the surface. Extensive protein engineering techniques were used to optimize the presentation of growth factors to cells. 

Unger, R.E., Peters, K., Wolf, M., Motta, A., Migliaresi, C., and Kirkpatrick, C.J. "Endothelializa-tion of a non-woven silk fibroin net for use in tissue engineering Growth and gene regulation of hunian endothelial cells". Biomaterials 25(21), 5137-5146 (2004). 

Vacant , C. A. et al.. Tissue-engineered growth of bone and cartilage. Transplant. Proc., 25, 1019, 1993. 

Vacanti CA, Kim WS, Upton J, Vacanti MP, Mooney D, Schloo B, Vacanti JP. Tissue Engineered Growth of Bone and Cartilage. Transplantation Proceedings, 1993 (In Press). 

Puelacher,W.C.,Wisser,J.,Vacanti,C. A., Ferraro,N.E,JaramiUo,D., Vacant , J.P.1994.Temporomandibular joint disc replacement made by tissue-engineered growth of cartilage. / Oral Maxillofac Surg 52(ll) 1172-7. 

In the Languimir-Blodgett assemblies described by Shimomura (this volume, Chapter 11) the recognition between the substrate and the first layer, and between subsequently transferred layers, represents the supramolecular component. A chemical reaction can in some cases occur between the monolayer and the substrate. In other cases a phase change from a two-dimensional liquid crystalline phase on the water surface to a crystalline phase over the substrate may occur [160,161]. The engineered growth is instead controlled by the applied deposition pressure, the type of deposition (Y-, Z-, and X-type), and by the number of transferred layers [160]. Variations in the orientation of consecutive layers may also be obtained [162]. 

Mitchell, A.C., Briquez, P.S., Hubbell, J.A., Cochran, J.R., 2016. Engineering growth factors for regenerative medicine applications. Acta Biomater. 30, 1-12. 

Growth reactions at surfaces will certainly continue to be tlie focus of much research. In particular, the synthesis of novel materials is an exciting field that holds much promise for the nanoscale engineering of materials. Undoubtedly, the advent of STM as a means of investigating growth reactions on the atomic scale will influence the llitiire of nanoscale teclmology. 

We noted above that the presence of monomer with a functionality greater than 2 results in branched polymer chains. This in turn produces a three-dimensional network of polymer under certain circumstances. The solubility and mechanical behavior of such materials depend critically on whether the extent of polymerization is above or below the threshold for the formation of this network. The threshold is described as the gel point, since the reaction mixture sets up or gels at this point. We have previously introduced the term thermosetting to describe these cross-linked polymeric materials. Because their mechanical properties are largely unaffected by temperature variations-in contrast to thermoplastic materials which become more fluid on heating-step-growth polymers that exceed the gel point are widely used as engineering materials. 

I ovolac Synthesis and Properties. Novolac resins used in DNQ-based photoresists are the most complex, the best-studied, the most highly engineered, and the most widely used polymers in microlithography. Novolacs are condensation products of phenoHc monomers (typically cresols or other alkylated phenols) and formaldehyde, formed under acid catalysis. Figure 13 shows the polymerization chemistry and polymer stmcture formed in the step growth polymerization (31) of novolac resins. 

Butanediol. 1,4-Butanediol [110-63-4] made from formaldehyde and acetylene, is a significant market for formaldehyde representing 11% of its demand (115). It is used to produce tetrahydrofuran (THF), which is used for polyurethane elastomers y-butyrolactone, which is used to make various pyrroHdinone derivatives poly(butylene terephthalate) (PBT), which is an engineering plastic and polyurethanes. Formaldehyde growth in the acetylenic chemicals market is threatened by alternative processes to produce 1,4-butanediol not requiring formaldehyde as a raw material (140) (see Acetylene-derived chemicals). 

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