Development of adhesion test for coated medical device

High biocompatibility is a basic requirement in medical technology. Polymer coatings can radically improve medical device biocompatibility, especially for surfaces like stainless steel. Adhesion is an important quality in a coating, and this was our rationale for developing a polymer adhesion testing protocol. We compared two biocompatible polymers, polyurethane (PUR) and poly-(DL-lactic-co-glycolic acid) (PDLG). Polymer layers were created on surface-treated stainless steel. The properties of different layers were compared. Adhesion of the coatings was characterised by concentration of coating solution, rate of the contacted surface and surface roughness of the carriers. PUR showed better adhesion under our test conditions.  DOI: 10.17489/biohun/2013/1/3

Investigation of metallic surface area of coronary stents

objectives: Endovascular stents, such as coronary stents, are widely used for the treatment of narrowed or blocked blood vessels caused by plaque formation in the arteries. The narrowing of expanded blood vessels (restenosis) is perhaps the major complication associated with endovascular stent implantation that is believed to be caused by insufficient metallic surface area (MSA) in some stent designs. Our aim was to compare three examination methods which were developed at our department, to measure stent surface areas.methods: The first method was manually performed using rotating equipment under a stereomicroscope. The second method, which has recently been developed, is an automated method using an integrated scanner and a rotating engine. Both methods aimed at converting the cylindrical stent into a flattened two-dimensional image in order to enable the measurement of stent surface area by imaging software. The third method is based on a calculation which uses various stent values such as diameter, length, and strut thickness. Each measurement process was tested on different types of stents.results: Our findings showed that the methods gave similar results. The largest differences between the methods were speed and accuracy.conclusions: The results lead us to propose favouring the automated rotation method.  DOI: 10.17489/biohun/2013/1/2

Microhardness testing of comparable bone substitutes

A periprotetikus csontpótló anyagokat gyakran teherviselő felületeken is alkalmazzuk például csípő vagy térdízület esetén ezért fontos szempont, hogy azok megfelelő mechanikai tulajdonságokkal rendelkezzenek. A biokompatibilis anyagok mechanikai vizsgálatában a Vickers-féle mikrokeménységmérés széleskörben elterjedt módszer, amely a csontpótló anyagok tanulmányozásában is hasznos eredményekkel szolgálhat. Kísérleteinkben három, klinikai alkalmazás tekintetében azonos indikációval rendelkező csontpótló anyag mikrokeménység vizsgálatát végeztük el. A liofilizált szivacsos humán csont allograft (allograft), liofilizált szivacsos szarvasmarha csontgraft (BioOss), valamint porózus szerkezetű béta-trikálcium-foszfát (β-TCP) mintákból arannyal bevont csiszolatokat készítettünk, majd és Buehler típusú berendezés segítségével megállapítottuk a mikrokeménységet. Annak ellenére, hogy a három minta közül szubjektíven a β-TCP volt a leginkább törékeny, a Vickers-féle mikrokeménység mérések szerint jelentősen keményebbnek bizonyult, mint a természetes eredetű csontpótlók. A liofilizált szarvasmarha és a liofilizált humán allograft hasonló keménységgel jellemezhető. Összefoglalva megállapíthatjuk, hogy a biológiai eredetű mineralizált csontgraftokhoz látszólag hasonló mesterséges β-TCP jelentősen keményebb, ridegebb szerkezetű, amely valószínűleg azt eredményezi, hogy élő szövetbe ültetve könnyebben törik. DOI: 10.17489/biohun/2013/2/02Bone-substitute materials are often employed in areas around load-bearing surfaces of implants, for example hip joints and ligaments around knees. It is important these materials have appropriate mechanical properties. Among mechanical tests, the Vickers microhardness measurement gives useful insights into bone-substitute materials. In these experiments microhardness was tanulmánytested for three bone-substitute materials used in similar clinical settings. Gold-coated samples of lyophilised trabecular human bone allograft, lyophilised trabecular bovine bone graft (BioOss), and porous-structured beta-tricalcium-phosphate (β-TCP) were measured for microhardness. Vickers-type microhardness measures ranked the β-TCP an order of magnitude harder than thenatural-source bone substitutes. The unusually high microhardness value of the β-TCP wasexplicable in terms of material-structure differences. The natural-origin bone substitutes are composite materials in which elastic protein fi lament cages hold inorganic calcium and magnesium during bone formation. In contrast, synthetic β-TCP is a single-phase dense material andlacks protein fi laments, explaining why its microhardness is an order of magnitude higher. To sum up, it was possible to establish that in comparison to mineralised, biological-origin bone grafts, artifi cial β-TCP was signifi cantly harder and brittler, probably meaning that when embeddedin living tissue it breaks more easily