Tissue-engineered constructs

Desai TA. Micro- and nanoscale structures for tissue engineering constructs [J]. Med Eng Phys, 2000, 22, 595-606. 

Lyons, F. G., Al-Munajjed, A. A., Kieran, S. M., Toner, M. E., Murphy, . M., Duffy, G. P., and O Brien, F. J. (2010). The healing of bony defects by cell-free collagen-based scaffolds compared to stem cell-seeded tissue engineered constructs. Biomaterials 31, 9232-9245. 

Despite these failures, the need still exists for alternative liver therapies. Several new techniques including cell transplantation, tissue-engineered constructs, and extra- and paracorporeal devices seek to relieve some of the demands placed on a compromised liver. Liver assist devices allow the liver to regenerate its function by removing some of the demands. Bridge-to-transplant devices seek to maintain patients until suitable donors are available. Some therapies seek to remove toxins from the blood, and they have a place in the treatment scheme, but due to the complex and multifunctional nature of the organ, some type of cell-based therapy is considered a more complete solution. 

Implantable tissue-engineered constructs are derivatives of cell therapies. They have certain advantages over implanting cells in that the culturing process is more easily controlled and tested before risking implantation. The technique is highly experimental and not without problems. We cover this more completely in later sections. 

The proposed model consists of a biphasic mechanical description of the tissue engineered construct. The resulting fluid velocity and displacement fields are used for evaluating solute transport. Solute concentrations determine biosynthetic behavior. A finite deformation biphasic displacement-velocity-pressure (u-v-p) formulation is implemented [12, 7], Compared to the more standard u-p element the mixed treatment of the Darcy problem enables an increased accuracy for the fluid velocity field which is of primary interest here. The system to be solved increases however considerably and for multidimensional flow the use of either stabilized methods or Raviart-Thomas type elements is required [15, 10]. To model solute transport the input features of a standard convection-diffusion element for compressible flows are employed [20], For flexibility (non-linear) solute uptake is included using Strang operator splitting, decoupling the transport equations [9],... 

Fig. 1 Overview of the components utilized in tissue engineering constructs.

The multiscale system also appears to be capable of providing more enhanced biological functionality, particularly for vascularization, which is favored by the interaction of ECs with the nanofibrous network.s that allow suitable cell architecture and orientation for microtubule formation. Thus, the synergistic effect of micro- and nanoscales could successfully regenerate natural tissues in vivo in the near future. Future work should focus on optimizing this process to better recapitulate key features of the native ECM, including its mechanical and biochemical properties, which would enhance the functionality of these 3D multiscale scaffolds in order to fabricate functional tissue engineered constructs. 

These requirements can be satisfied through the use of a tissue-engineered construct that gradually replaces S5mthetic materials with natural tissue, assembling a new vessel native to the individual. " ... 

Prechtel, E., Yoimg, K., Goldman, S. et al.. Design, synthesis, and mechanical characterization of a resorbable composite small diameter vascular graft as a tissue engineered construct, Trans. Soc. Biomater., 28, 200, 2002. 

Rouwkema, J., de Boer, J., Van Blitterswijk, C.A. Endothehal cells assemble into a 3-dimensional prevascular network in a bone tissue engineering construct. Tissue Eng. 12, 2685-2693 (2006)... 

Referring to microbial cellulose applications, bacterial nanocellulose has proven to be a remarkably versatile biomaterial with use in paper products, electronics, acoustic membranes, reinforcement of composite materials, membrane filters, hydraulic fracturing fluids, edible food packaging films, and due to its unique nanostructure and properties, in numerous medical and tissue-engineered applications (tissue-engineered constructs, wound healing devices, etc). 

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