Tissues, substitute

Liu Y, Gan L, Carlsson DJ, Fagerholm P, Lagali N, Watsky MA, Munger R, Hodge WG, Priest D, Griffith M. A simple, cross-linked collagen tissue substitute for corneal implantation. Invest Ophthalmol Vis Sci 47 1869-1875 (2006). 

In the biomedical area, SPHs and SPH composites can be used to make various biomedical devices, such as artificial pancreas, artificial cornea, and artihcial skin, articular cartilage, soft tissue substitutes, cell growth substrates in tissue engineering, burn dressings, surgical augmentation of the female breast, or hemoperfusion in blood detoxification and in the treatment of uremia. 

Polyelectrolytes have been widely investigated as components of biocompatible materials. Biomaterials come into contact with blood when used as components in invasive instruments, implant devices, extracorporeal devices in contact with blood flow, implanted parts of hard structural elements, implanted parts of organs, implanted soft tissue substitutes and drug delivery devices. Approaches to the development of blood compatible materials include surface modification to give blood compatibility, polyelectrolyte-based systems which adsorb and/or release heparin as well as polyelectrolytes which mimic the biological activity of heparin. 

The development of biomechanical models derived from continuum formulations for transport of water and charged species in porous media has been carried out for various soft tissues [1-3] and implemented using finite element models (FEMs) [4-8], Such models provide quantitative views of the response of these complex structures that is especially useful in the study of orthopedic, vascular, ocular, and soft tissue substitutes developed by tissue engineering. In this paper a formulation and FEM are described that incorporate and extend these works in a very general model that identifies physical material properties and allows transient analyses of both natural and artificial soft tissue structures. 

Besides the promising use of BASYC in experimental vascular surgery we see the possibility for the application of BC as a soft-tissue substitution material in various medical fields because of its extraordinary properties. 

It is anticipated that in the coming years, a number of HA-derivatives will appear for clinical application in Dermatology that contain cross-linked HA polymers as well as HA-ester derivatives obtained by the conjugation of the carboxylic acid of HA with various drugs in their alcohol forms. The HA polymer, because of its intrinsic biocompatibility, reactivity, and degradability, will have many uses in the rapidly expanding field of tissue engineering and in the tissue substitutes of the future. 

Included in this entry is a review of the development of tissue engineering, from theorized concepts and early experiments through advancements made in developing tissue substitutes in the recent past. A review of biological systems and components precedes... 

For a tissue substitute to function properly, many biological aspects of the tissue and component cells must be understood. Some aspects include the extracellular matrix, cell-specific gene expression and surface markers, cell growth parameters, population arrangement and behavior, and the immune system. 

Since the 1950s, polyethylene (PE) has been applied in surgery. At that time after PE implantation, only formation of so-called granulated tissue around a polymer was found, that is a weak response of the body to the implant. PE is not widely used for the substitution of soft tissues, but it is an important substitute for bone tissues, i.e. the head of the hip bone and other elements of the pelvis bones. The wear resistance property of low pressure PE makes its application in bone tissue substitution. HOPE can be widely used in pelvic prostheses [54]. 

Photopolymerizable systems have received a lot of recent attention in biomaterial applications due to the ability to rapidly form a solid polymer (gel) from a liquid precursor solution (monomer or macromer) with spatial and temporal control under physiological conditions. The development of cytocompatible systems has provided the ability to form materials in the presence of proteins, cells, and tissues to allow for minimally invasive biomaterial-based therapies. In particular, photopolymerizable systems have been used extensively as dental restoratives, controlled microenvironments to study cellular behavior and develop tissue substitutes, and to encapsulate growth fartors and cytokines in a polymer matrix for controlled release applications. 

Besides temporary wound-dressing devices, BNC has been reported to have potential application as a human tissue substitute for use, for example, in cases where extensive loss of both the dermal and epidermal layers has taken place [51]. Despite the fact that microbial cellulose is not a biodegradable material in the short term, it could stay in the body forever without causing any toxic or inflammatory reactions [46]. 

De Peppo, G.M., Marcos-Campos, L, Kahler, D.J., Alsahnan, D., Shang, L., Vunjak-Novakovic, G., Marolt, D., 2013. Engineering bone tissue substitutes from human induced pluripotent stem cells. Proc. Natl. Acad. Sci. USA 110, 8680-8685. 

ICRU (1989a) Stopping powers for electrons and positrons, report 37. International Commission on Radiation Units and Measurements, Bethesda ICRU (1989b) Tissue substitutes in radiation dosimetry and measurement, report 44. International Commission on Radiation Units and Measurements, Bethesda... 

Wan ACA, Khor E, Hastings GW (1997) Hydroxyapatite modified chitin as potential hard tissue substitute material. J Biomed Mater Res 38 235-241... 

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