TEPHA LIBRARY : ARTICLES & PAPERS Welcome to Tepha's online collection of abstracts and full texts related to our technology and our business. Please feel free to browse our library.   Medical Applications of Poly-4-Hydroxybutyrate: a strong flexible absorbable biomaterial. David P. Martin and Simon F. Williams. Poly-4-hydroxybutyrate (P4HB) is being developed as a new absorbable material for implantable medical applications. P4HB promises to open up new opportunities for the development of medical applications by offering a new set of properties that are not currently available. The absorbable biomaterial is strong yet flexible, and degrades in vivo at least in part by a surface erosion process. While the chemical structure of P4HB is similar to that of current absorbable polyesters used in implantable medical products, P4HB is produced by a fermentation process rather than through a chemical synthesis. P4HB is a thermoplastic material that can be processed using standard plastics processing techniques, such as solution casting or melt extrusion. The strength of P4HB fibers prepared by melt extrusion compare well with that of traditional suturing materials, however, P4HB is typically more flexible. P4HB should find use in a wide variety of medical fields such as cardiovascular, wound healing, orthopedic, drug delivery, and tissue engineering applications. This paper describes some of the basic properties of P4HB and several of its potential applications in medicine.   ...more     The Design of Scaffolds for Use in Tissue Engineering. Part I. Traditional Factors. Shoufeng Yang, Ph.D., Kah-Fai Leong, M.S.E., M.S.M.E., Zhaohui Du, Ph.D.,and Chee-Kai Chua, Ph.D. In tissue engineering, a highly porous artificial extracellular matrix or scaffold is required to accommodate mammalian cells and guide their growth and tissue regeneration in three dimensions. However, existing three-dimensional scaffolds for tissue engineering proved less than ideal for actual applications, not only because they lack mechanical strength, but they also do not guarantee interconnected channels. In this paper, the authors analyze the fac-tors necessary to enhance the design and manufacture of scaffolds for use in tissue engi-neering in terms of materials, structure, and mechanical properties and review the tradi-tional scaffold fabrication methods. Advantages and limitations of these traditional methods are also discussed.  ...more     Rationalizing the design of polymeric biomaterials. Nela Angelova and David Hunkeler Polymers are a promising class of biomaterials that can be engineered to meet specific end-use requirements. They can be selected according to key ‘device’ characteristics such as mechanical resistance, degradability, permeability, solubility and transparency, but the currently available polymers need to be improved by altering their surface and bulk properties. The design of macromolecules must therefore be carefully tailored in order to provide the combination of chemical, interfacial, mechanical and biological functions necessary for the manufacture of new and improved biomaterials.  ...more     Novel peptide-based biomaterial scaffolds for tissue engineering. Todd C. Holmes Biomaterial scaffolds are components of cell-laden artificial tissues and transplantable biosensors. Some of the most promising new synthetic biomaterial scaffolds are composed of self-assembling peptides that can be modified to contain biologically active motifs. Peptide-based biomaterials can be fabricated to form two- and three-dimensional structures. Recent studies show that biomaterial promotion of multi-dimensional cell–cell interactions and cell density are crucial for proper cellular differentiation and for subsequent tissue formation. Other refinements in tissue engineering include the use of stem cells, cell pre-selection and growth factor pre-treatment of cells that are used for seeding scaffolds. These cell-culture technologies, combined with improved processes for defining the dimensions of peptide-based scaffolds, might lead to further improvements in tissue engineering. Novel peptide-based biomaterial scaffolds seeded with cells show promise for tissue repair and for other medical applications.  ...more     Metabolic Engineering of Poly(3-Hydroxyalkanoates): From DNA to Plastic. Lara L. Madison and Gjalt W. Huisman Poly(3-hydroxyalkanoates) (PHAs) are a class of microbially produced polyesters that have potential applications as conventional plastics, specifically thermoplastic elastomers. A wealth of biological diversity in PHA formation exists, with at least 100 different PHA constituents and at least five different dedicated PHA biosynthetic pathways. This diversity, in combination with classical microbial physiology and modern molecular biology, has now opened up this area for genetic and metabolic engineering to develop optimal PHA-producing organisms.  ...more     Development of biocompatible synthetic extracellular matrices for tissue engineering. Byung-Soo Kim and David J. Mooney Tissue engineering may provide an alternative to organ and tissue transplantation, both of which suffer from a limitation of supply. Cell transplantation using biodegradable synthetic extracellular matrices offers the possibility of creating completely natural new tissues and so replacing lost or malfunctioning organs or tissues. Synthetic extracellular matrices fabricated from biocompatible, biodegradable polymers play an important role in the formation of functional new tissue from transplanted cells. They provide a temporary scaffolding to guide new tissue growth and organization, and may provide specific signals intended to retain tissue-specific gene expression.  ...more     PHA applications: addressing the price performance issue. Williams, S.F. et al., Int. J. Biol. Macromol. This paper describes the development of medical applications for polyhydroxyalkanoates (PHAs), a class of natural polymers with a wide range of thermoplastic properties. Methods are described for preparing PHAs with high purity, modifying these materials to change their surface and degradation properties, and methods for fabricating them into different forms, including tissue engineering scaffolds. Preliminary reports characterizing their in vivo behavior are given, as well as methods for using the natural polymers in tissue engineering applications.  ...more     Applications of PHAs in Medicine and Pharmacy. Dr. Simon F. Williams, Dr.David P. Martin. Polyhydroxyalkanoates (PHAs)are a class of naturally occurring polyesters that are pro- duced by a wide variety of different micro- organisms (Steinb ¸chel,1991).Although they are derived biologically,the structures of these polymers bear a fairly close resem- blance to some of the synthetic absorbable polymers currently used in medical applica- tions.Owing to their limited availability,the PHAs have remained largely unexplored,yet these polymers offer an extensive range of properties that extend far beyond those currently offered by their synthetic counter- parts.  ...more