Klod Kokini

Bio: Klod Kokini is an academic researcher from Purdue University. The author has contributed to research in topics: Thermal barrier coating & Ceramic. The author has an hindex of 26, co-authored 77 publications receiving 3546 citations. Previous affiliations of Klod Kokini include University of Pittsburgh.

Tensile mechanical properties of three-dimensional type I collagen extracellular matrices with varied microstructure.

Abstract: The importance and priority of specific micro-structural and mechanical design parameters must be established to effectively engineer scaffolds (biomaterials) that mimic the extracellular matrix (ECM) environment of cells and have clinical applications as tissue substitutes. In this study, three-dimensional (3-D) matrices were prepared from type I collagen, the predominant compositional and structural component of connective tissue ECMs, and structural-mechanical relationships were studied. Polymerization conditions, including collagen concentration (0.3-3 mg/mL) and pH (6-9), were varied to obtain matrices of collagen fibrils with different microstructures. Confocal reflection microscopy was used to assess specific micro-structural features (e.g., diameter and length) and organization of component fibrils in 3-D. Microstructural analyses revealed that changes in collagen concentration affected fibril density while maintaining a relatively constant fibril diameter. On the other hand, both fibril length and diameter were affected by the pH of the polymerization reaction. Mechanically, all matrices exhibited a similar stress-strain curve with identifiable "toe," "linear," and "failure" regions. However the linear modulus and failure stress increased with collagen concentration and were correlated with an increase in fibril density. Additionally, both the linear modulus and failure stress showed an increase with pH, which was related to an increasedfibril length and a decreasedfibril diameter. The tensile mechanical properties of the collagen matrices also showed strain rate dependence. Such fundamental information regarding the 3-D microstructural-mechanical properties of the ECM and its component molecules are important to our overall understanding of cell-ECM interactions (e.g., mechanotransduction) and the development of novel strategies for tissue repair and replacement.

The use of xenogeneic small intestinal submucosa as a biomaterial for Achille's tendon repair in a dog model

Abstract: A study was conducted to evaluate the tissue response to a xenogeneic biomaterial when this material was used to repair an experimentally induced Achilles tendon defect in the dog. Twenty dogs had a 1.5 cm segmental defect of the Achilles tendon created surgically which was then repaired with acellular connective tissue derived from porcine small intestinal submucosa (SIS). The animals were sacrificed at 1, 2, 4, 8, 12, 16, 24, and 48 weeks and the neotendons examined for uniaxial longitudinal tensile strength, morphologic appearance, hydroxyproline (collagen) content, and disappearance of the originally implanted SIS material over time. The contralateral normal Achilles tendons served as controls as did four additional dogs that had a 1.5 cm segmental Achilles tendon defect created surgically without subsequent surgical repair with SIS. Results showed the SIS remodeled neotendons to be stronger than the musculotendinous origin or the boney insertion (> 1000 N) by 12 weeks after surgery and to consist of organized collagen-rich connective tissue similar to the contralateral normal tendons. The four dogs in which no SIS was implanted showed inferior strength at the comparable time points of 4, 8, 12, and 16 weeks. Immunohistochemical studies suggest that the SIS biomaterial becomes degraded within the first eight weeks and serves as a temporary scaffold around which the body deposits appropriate and organized connective tissue. SIS is a promising biomaterial worthy of further investigation for orthopedic soft tissue applications.

Small Intestinal Submucosa as a Vascular Graft: A Review

Abstract: Continuing investigations of vascular graft materials suggest that unacceptable graft complications continue and that the ideal graft material has not yet been found. We have developed and tested a biologic vascular graft material, small intestine submucosa (SIS), in normal dogs. This material, when used as an autograft, allograft, or xenograft has demonstrated biocompatibility and high patency rates in aorta, carotid and femoral arteries, and superior vena cava locations. The grafts are completely endothelialized at 28 days post-implantation. At 90 days, the grafts are histologically similar to normal arteries and veins and contain a smooth muscle media and a dense fibrous connective tissue adventitia. Follow-up periods of up to 5 years found no evidence of infection, intimal hyperplasia, or aneurysmal dilation. One infection-challenge study suggested that SIS may be infection resistant, possibly because of early capillary penetration of the SIS (2 to 4 days after implantation) and delivery of body defenses to the local site. We conclude that SIS is a suitable blood interface material and is worthy of continued investigation. It may serve as a structural framework for the application of tissue engineering technologies in the development of the elusive ideal vascular graft material.

Production of a tissue-like structure by contraction of collagen lattices by human fibroblasts of different proliferative

Abstract: Fibroblasts can condense a hydrated collagen lattice to a tissue-like structure 1/28th the area of the starting gel in 24 hr. The rate of the process can be regulated by varying the protein content of the lattice, the cell number, or the con- centration of an inhibitor such as Colcemid. Fibroblasts of high population doubling level propagated in vitro, which have left the cell cycle, can carry out the contraction at least as efficiently as cycling cells. The potential uses of the system as an immu- nologically tolerated "tissue" for wound hea ing and as a model for studying fibroblast function are discussed.

Ceramic materials for thermal barrier coatings

Abstract: This paper summarizes the basic properties of ceramic materials for thermal barrier coatings. Ceramics, in contrast to metals, are often more resistant to oxidation, corrosion and wear, as well as being better thermal insulators. Except yttria stabilized zirconia, other materials such as lanthanum zirconate and rare earth oxides are also promising materials for thermal barrier coatings.