In vitro engineering

Cellular scaffolds represent a middle ground between in vivo and in vitro engineering. Engineers can create a scaffold in a laboratory environment and... 

Salerno et al. cocultured human hepatocytes with human umbilical vein ECs (HUVECs) on a polyetheretherketone PU membrane to promote vascularization of an in vitro engineered liver tissue [102]. There was improved hepatocyte function and the formation of luminal structures occurred within 3 days of coculture on the PU versus hepatocyte-only samples [102]. Another study demonstrated that coculturing bone marrow-derived mesenchymal stromal cells with hepatocytes greatly reduced the secretion of stress enzymes by the hepatocytes and that the cells attached better to nanoflber PU versus unstructured PU [103]. 

Zacchi V, Soranzo C, Cotivo R, Radice M, Brun P, Abatangelo G. In vitro engineering of human skin-like tissue. J Biomed Mater Res 1998 40(2) 187-94. 

Kramer, G., Kudbcki, W., and Hardesty, B., In vitro engineering using synthetic tRNAs with altered anticodons including four-nucleotide anticodons. Methods Mol. Biol., 77,105,1998. 

The stage was set for the fifth period of the industry by genetic engineering (qv) discoveries (5—7), ie, the in vitro manipulation of microorganisms. 

Stability and Purification of the Recombinant Protein. There are no hard and fast rules specifying, eg, whether a recombinant protein is available in a soluble state in the cell. In some cases, the expression system must be engineered by in vitro mutagenesis to optimize overall yield of the protein. 

Protein engineering is now routinely used to modify protein molecules either via site-directed mutagenesis or by combinatorial methods. Factors that are Important for the stability of proteins have been studied, such as stabilization of a helices and reducing the number of conformations in the unfolded state. Combinatorial methods produce a large number of random mutants from which those with the desired properties are selected in vitro using phage display. Specific enzyme inhibitors, increased enzymatic activity and agonists of receptor molecules are examples of successful use of this method. 

Oligonucleic acid or peptide molecules that bind a specific target molecule. Nucleic acid aptamer species can be engineered through treated rounds of in vitro selection to bind to various molecular targets such as... 

While the mechanical performance of artificial materials in the human body can be predicted with some rehabihty, forecasting their biological performance is difficnlt. The problem of interactions at surfaces has already been mentioned. Research frontiers also include developing ways to simulate in vivo processes in vitro and extending the power and apphcability of such simulations to allow for better prediction of the performance of biomedical materials and devices in the patient. Fundamental information on the correlation between the in vivo and in vitro responses is limited. Chemical engineers might also make contribntions to the problem of noninvasive monitoring of implanted materials. 

Hoerstrup SP, Sodian R, Sperling JS, Vacanti JP, and Mayer JE Jr. New pulsatile bioreactor for in vitro formation of tissue engineered heart valves[J]. Tissue Eng, 2000, 6(1), 75-79. 

Andersen ME, Krishman K. 1994. Relating in vitro to in vivo exposures with physiologically-based tissue dosimetry and tissue response models. In H. Salem, ed. Current concepts and approaches on animal test alternatives. U.S. Army Chemical Research Development and Engineering Center, Aberdeen Proving Ground, Maryland. 

The ability of these peptidomimetic collagen-structures to adopt triple helices portends the development of highly stable biocompatible materials with collagenlike properties. For instance, it has been found that surface-immobilized (Gly-Pro-Meu)io-Gly-Pro-NH2 in its triple-helix conformation stimulated attachment and growth of epithelial cells and fibroblasts in vitro [77]. As a result, one can easily foresee future implementations of biostable collagen mimics such as these, in tissue engineering and for the fabrication of biomedical devices. 

NMOR is a potent hepatocarcinogen in the rat and induces tracheal and nasal cavity tumors in the Syrian golden hamster (43, 44, 45). It is formed readily from nitrite and morpholine in vitro and administration of these precursors to rodents causes tumors indicative of NMOR formation in vivo (44, 55, 56), NMOR has been detected in crankcase emissions of diesel engines and in factories engaged in rubber and tire manufacturing (57, 58). 

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