Hyaluronic Acid as a Matrix for Increased Functionality of Biomedical Alloys

Despite extensive knowledge on the various methods for surface modification and interface formation, many questions still remain unresolved, especially regarding the relationships between composition of the bio-environment and biomechanical, structural and chemical properties of metal surface. In vitro corrosion studies were mostly carried out is simple solutions of inorganic salts, which can be regarded only as first tests of in vivo behavior of a metal, but not sufficient for deeper understanding of in vivo behavior (1-3). Some studies were performed in biologically more relevant media like MEM and serum; some investigated the effect of addition of protein or amino acids to solution of inorganic salts (2). Hyaluronic acid (HA) is a component of synovial joint fluid that regulates many important physiological and pathophysiological reactions. It is a glycosaminoglycan (GAG) or mucopolysaccharide, a long, unbranched polysaccharide composed of repeating units of disaccharide N-acetyl-D-glucosamine and D-glucuronic acid ‒ the only non-sulfated GAG and a high molecular mass polymer in excess of 10⁶Da. It affects cell proliferation and migration and is responsible for the viscosity and resistance to compressive stress of synovial fluid. The behaviour of orthopaedic alloys in its presence is scarcely known and needs to be assessed.

It was recently reported (4) that the addition of HA significantly affect the behavior of CoCrMo alloy, especially in simulated Hanks’ physiological solution containing inorganic salts. It results in the formation of a thick layer of calcium phosphate, which is approximately ten times thicker than that in the absence of hyaluronic acid. This layer is homogeneous at the nano-level. Due to its formation, the underlying layer of chromium oxide cannot be detected. The presence of Ca²⁺ and PO₄^3-ions is essential for the interaction between the chromium oxide surface and the hyaluronic chain. Under the experimental conditions used the addition of hyaluronic acid does not statistically significantly affect the viability of osteoblast-like cells but does increase the activity of alkaline phosphatase, indicating its beneficial effect on osteogenic activity.

In addition to osseointegration ability, another important functional property of biomedical, especially orthopaedic alloy, is its ability to resist infection. The antimicrobial effect of silver salts has been well known; recently the use of silver nanoparticles as effective microbial growth inhibitor has been reported and recognized for possible applications for diverse medical devices (5). The combination of HA and silver nanoparticles will be presented as a way of increasing functional performance of orthopaedic alloy. Method of preparation includes green synthesis of silver nanoparticles where HA plays a role of reducing and stabilizing agent (6). Synthesized complex was characterized using several experimental methods (UV/Vis, FTIR, XPS, SEM, TEM). When deposited onto metal plates, its antimicrobial activity was assessed for resistance to attachment of common bacterial strains.   

References:

1. S. Virtanen, I. Milošev, et al., Acta Biomaterialia, 4 (2008) 468-476.

2. I. Milošev, In: Surface Treatments for Biomedical Applications”, ed. S. Djokic, Modern Aspects of Electrochemistry series, Springer, vol. 55, 2012, p. 1-72.

3. I. Milošev, Electrochim. Acta, 78 (2012) 259-273.

4. I. Milošev, J. Hmeljak, A, Cör, J. Mater . Sci. Mater . Med., 24 (2013) 555-571.

5. J.S. Kim et al., Nanomedicine: Nanotechnology, Biology and Medicine, 3 (2007) 95-101.

6. A.M. Abdel-Mohsen et al., Carbohyd. Polym. 89 (2012) 411-422.