engineering-platform-experimental-protocol-for-design-evaluation

Engineering Platform and Experimental Protocol for Design and Evaluation of a Neurally-controlled Powered Transfemoral Prosthesis

To enable intuitive operation of powered artificial legs, an interface between user and prosthesis that can recognize the user's movement intent is ...

Current mechanical testing methods used to determine the biaxial properties of planar connective tissues may lead to artifactual observations of material behavior. The method of sample gripping affects the constraint on the extracellular fibers at the bounds of the sample. This applied constraint not only affects how the load is transferred to the sample, but also how the load is transmitted throughout the rest of the material - thereby influencing the resulting mechanical behavior of the tissue. In this study, we compared the dynamic biaxial mechanical response of pericardial tissue samples under two different gripping methods: (i) the common method of suturing sample edges and (ii) a new biaxial clamping method. Tissue samples were repeatedly testing using both gripping methods under the same conditions. The tissue samples appeared to be stiffer and less extensible when mechanically tested with clamped sample edges, as opposed to when tested with sutured sample edges. Thus, the influence of the sample boundaries affected the response of the material - precisely the situation to be avoided for reliable material testing. This casts doubt on whether any in vitro mechanical testing method can used to determine the "real" properties of the tissue since the boundary conditions of the tissue in situ are presently unknown.

Boundary conditions during biaxial testing of planar connective tissues. Part 1: dynamic behavior.

Aktuelle Mechanische Pr&uuml;fverfahren zur Bestimmung die biaxialen Eigenschaften der planaren Bindegewebe f&uuml;hren zu artifactual Beobachtungen des Materialverhaltens. Die Methode Griff zu Beispiel betrifft die Einschr&auml;nkung auf die extrazellul&auml;ren Fasern an die Grenzen der Probe. Diese angewandte Einschr&auml;nkung betrifft nicht nur wie die Belastung der Probe &uuml;bertragen wird, sondern auch, wie die Last im Rest des Materials - dadurch beeinflussen das resultierende mechanische Verhalten des Gewebes &uuml;bertragen wird. In dieser Studie verglichen wir die dynamische biaxiale mechanische Reaktion der Perikardh&ouml;hle Gewebeproben unter zwei verschiedenen Methoden packende: (i) die &uuml;bliche Methode der Wundverschlu&szlig; Beispiel Kanten und (Ii) eine neue biaxial-Spannvorrichtung-Methode. Gewebeproben wurden immer wieder Tests mit beiden packenden Verfahren unter den gleichen Bedingungen. Die Gewebeproben schien steifer und weniger erweiterbar wird mechanisch mit eingespannten Probe Kanten, im Gegensatz zu gepr&uuml;ft, wenn mit gen&auml;hter Beispiel Kanten getestet. So beeinflusst der Einfluss der Probe Grenzen die Antwort des Materials - genau die Situation f&uuml;r zuverl&auml;ssige Materialpr&uuml;fung vermieden werden. Dies wirft Zweifel auf, ob alle mechanischen in-vitro-Testverfahren verwendet werden kann, um die &quot;echten&quot; Eigenschaften des Gewebes zu bestimmen, da die Randbedingungen des Gewebes in-situ derzeit unbekannt sind.

Randbedingungen w&auml;hrend der biaxialen Tests der planaren Bindegewebe. Teil 1: dynamisches Verhalten.

We performed a genome-wide linkage analysis to identify susceptibility loci in a large six-generation extended family previously reported with early-onset osteoarthritis (OA) DNA sequencing was performed to investigate involvement of the COMP (Cartilage oligomeric matrix protein) gene in this family. The region covering D19S884, D19S226, and D19S414 on chromosome 19p following genome-wide scan from 70 individuals of this kindred showed significant linkage, with a maximum point LOD (logarithm of the odds ratio) score of 2.51 at D19S226. Direct sequencing of the COMP gene, the most plausible candidate gene in the region, identified a c.2152C>T substitution in exon 18 which resulted in a substitution of tryptophan for arginine at position 718 located in the C terminal globular domain of the gene product. A total of 26 individuals were identified with this mutation of which 21 affected individuals had the mutation, and the other five younger individuals (18.6 ± 11.3 years of age) carried the mutation without symptoms. The results indicate that COMP is the disease susceptibility gene and the c.2152C>T mutation in exon 18 could cause early-onset OA phenotypes in this kindred, which is compatible with a previous report that this mutation also causes a mild form of multiple epiphyseal dysplasia (MED).

A mutation in cartilage oligomeric matrix protein (COMP) causes early-onset osteoarthritis in a large kindred study.

While macrophages have been implicated in the failure of bioprosthetic heart valves, the macrophage response to crosslinked native pericardial collagen has not been previously investigated. Using decellularized bovine pericardium (DBP) as a model for native collagen, this study investigated the response of macrophage-like cells (U937s) to DBP, either: (i) untreated, or (ii) exogenously crosslinked with glutaraldehyde or 1-ethyl-3-(3-dimethyl-aminopropyl)-carbodiimide (EDC). We have previously validated the use of U937 cells as models for the response of human monocyte-derived macrophages to decellularized pericardial materials and, per our previous work, differentiated the U937 cells directly on the three material surfaces. After 72h in culture, the cells and medium were analyzed for DNA content, acid phosphatase activity, and cytokine and matrix metalloproteinase release. As well, cell/substrate samples were fixed for SEM. Fewer cells attached to or survived on the glutaraldehyde-treated substrate, and some showed an abnormal morphology compared to cells cultured on the other surfaces. Further, cells on glutaraldehyde-treated surfaces released more pro-inflammatory cytokines, more MMP-1 and less MMP-2 and MMP-9. The poor performance of the U937 macrophage-like cells on the glutaraldehyde-treated surfaces appears to be due to surface characteristics rather than to soluble aldehyde or other components leaching from the crosslinked material. These results provide evidence that crosslinking with glutaraldehyde is cytotoxic to macrophage-like cells, and that crosslinking with a zero-length crosslinker like EDC can be an acceptable alternative crosslinking treatment for biomaterials.

Article	Year
Boundary conditions during biaxial testing of planar connective tissues. Part 1: dynamic behavior. Journal of materials science. Materials in medicine\| PubMed ID: 15348186	2002
A mutation in cartilage oligomeric matrix protein (COMP) causes early-onset osteoarthritis in a large kindred study. Annals of human genetics\| PubMed ID: 21834907	2011
Interactions of U937 macrophage-like cells with decellularized pericardial matrix materials: influence of crosslinking treatment. Acta biomaterialia\| PubMed ID: 23454057	2013

Michael Lee

Biography

JoVE Journal Publications

Other Publications