Ana Todorović, et al., Biocompatibility evaluation of Cu-Al-Ni shape memory alloys Contemporary Materials, V−2 (2014) Page 228 of 238 Original scientific papers UDK 615.46:616.314 doi: 10.7251/COMEN1402228T BIOCOMPATIBILITY EVALUATION OF Cu-Al-Ni SHAPE MEMORY ALLOYS Ana Todorović 1,* , Rebeka Rudolf 2 , Nebojša Romčević 3 , Igor Đorđević 1 , Nataša Milošević 1 , Branka Trifković 1 , Valentina Veselinović 4 , Miodrag Čolić 5 1 University of Belgrade, Faculty of Dental Medicine, Rankeova 4, 11000 Belgrade 2 University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor 3 University of Belgrade, Institute for Physics, Pregrevica 118, 11080 Belgrade 4 University of Banja Luka, Faculty of Medicine, Save Mrkalja 14, 78000 Banja Luka 5 Military Medicine Academy, Institute of Medical Research, Crnotravska 17, 11002 Belgrade Abstract: Shape memory alloys belong to a group of smart, functional materials with a unique ability to "remember" the shape that they had before the pseudo-elastic deformation. Cu-Al-Ni shape memory alloys are today the only available high-temperature SMA, showing good resistance to functional load, however their biomedical application is still limited. Using melt spinning technique, thin Cu-Al-Ni ribbons can be produced directly from the melt. The aim of our study was to evaluate the biocompatibility of Cu-Al-Ni alloys in vitro. Thin Cu-Al-Ni ribbons were produced by the technique of melt spinning and used for the tests. The base alloy for casting of the same composition, but without shape memory effect, was used as control. The results of MTT test showed that Cu-Al-Ni base alloys (alloys control) almost completely reduced metabolic activity of peripheral blood mononuclear cells (PBC), while none of Cu-Al-Ni ribbons types showed a statistically significant effect on the metabolic activity of cells compared with control (cells cultivated only in the medium). Rapid solidi- fied ribbons with memory effect stimulate the production of proinflammatory cytokines, but not Th1 and Th2 cytokines by activated PBC. However, in addition to IL-1β, their stimulatory potential is significantly lower compared to the control Cu-Al-Ni alloy. Keywords: alloys, shape memory effect, biocompatibility. 1. INTRODUCTION Cu-Al-Ni alloys with the shape memory effect (SMAs) are now the only available high-temperature SMA, which show good resistance to functional load. In polycrystalline state they are very brittle and in general show only a small reversible deformation. By using the melt spinning technique, thin Cu-Al-Ni strips can be produced directly from the melt. The corresponding parameters of the casting can provide single-layer columnar structure with a fibrous texture, which significantly increases the maximum reversible voltage in longitudinal direction. Technical significance of most engineering materials is based on their mechanical, electrical or magnetic properties that would normally supposed to be independent from environmental influences. Apart from these conventional materials, there is another group called functional materials. These materials are not as interesting due to their properti- es under certain conditions, but much more how to react to changes in the conditions. Among others, the shape memory alloys belong to this group [1−4]. 1.1 Cu-Al-Ni shape memory alloys The most commonly used SMAs based on Cu are Cu-Zn-Al and Cu-Al-Ni alloys. The last have higher cost than the first, but the SMA alloys based on Cu are the most resistant to reduction of functio- nal characteristics due to the undesirable effects of aging. Many characteristics of Cu-Al-Ni are inferior to Ni-Ti SMA and alloys based on Fe. The biggest disadvantage of polycrystalline Cu-Al-Ni alloys is in * Corresponding author: anatod2004@yahoo.com