Chemical modification of titanium surfaces for covalent attachment of biological molecules

Abstract

Abstract:The surface of implantable biomaterials is in direct contact with the host tissue and plays a critical role in determining biocompatibility. In order to improve the integration of implants, it is desirable to control interfacial reactions such that nonspecific adsorption of proteins is minimized and tissue-healing phenomena can be controlled. In this regard, our goal has been do develop a method to functionalize oxidized titanium surfaces by the covalent immobilization of bioactive organic molecules. Titanium first was chemically treated with a mixture of sulfuric acid and hydrogen peroxide to eliminate surface contaminants and to produce a consistent and reproducible titanium oxide surface layer. An intermediary aminoalkylsilane spacer molecule was then covalently linked to the oxide layer, followed by the covalent binding of either alkaline phosphatase or albumin to the free terminal NH 2 groups using glutaraldehyde as a coupling agent. Surface analyses following coating procedures consisted of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Enzymatic activity of coupled alkaline phosphatase was assayed colorimetrically, and surface coverage by bound albumin was evaluated by SEM visualization of colloidal gold immunolabeling. Our results indicate that the linkage of the aminoalkylsilane to the oxidized surface is stable and that bound proteins such alkaline phosphatase and albumin retain their enzymatic activity and antigenicity, respectively. The density of immunolabeling for albumin suggests that the binding and surface coverage obtained is in excess of what would be expected for inducing biological activity. In conclusion, this method offers the possibility of covalently linking selected molecules with known biological activity to oxidized titanium surfaces in order to guide and promote the tissue healing that occurs during implant integration in bone and soft tissues.

Attachment of hyaluronan to metallic surfaces

“…The most common ones use silane coupling agents that react with the oxide layer formed on metal surfaces. [21][22][23][24][25][26][27] In most cases, the silane coupling agent consists of a trimethoxy or triethoxy silane where the fourth bond of the silane molecule is an organo-functional group that can be further reacted to attach a variety of organic compounds or polymers. The methoxy or ethoxy groups hydrolyze, leaving the silanol to react with the metal oxides.…”

“…These metal-O-Si bonds in and of themselves are not strong and may hydrolyze in water; however, the use of trimethoxy or triethoxy functional groups leads to a polymer network with multiple attachment points to the metal, thus securing the attached silane layer. 21,28 Nanci et al 23 did studies on the aqueous stability of silanized Ti and showed that, after a small initial decrease, the elemental concentrations of the various components of the amino silane remained constant up to 168 h. Puleo has shown that trypsin retained its enzymatic activity when immobilized on Ti and Co alloys via a ␥-aminopropyltriethoxy silane. 24,29 Further studies revealed that this enzymatic activity was retained for up to 96 h in standard cell culture.…”

Effect of different Ti–6Al–4V surface treatments on osteoblasts behaviour

“…The surface of material can change with time, and is often distinctly different from the bulk properties, because of oxidation and contamination. Although the surface clearly plays an important role in implant/cell interactions, the relationships between surfaces of the implant, its reactivity with tissue constituents, and long-term integrity and clinical efficacy are still poorly understood [1,2].…”

Nanoscale Oxidative Patterning of Metallic Surfaces to Modulate Cell Activity and Fate

“…[24][25][26] The rationale for using H 2 SO 4 /H 2 O 2 to nanotexture metals was to permit simultaneous etching and oxidation of the surface in a controlled manner. 29 This method is effective, but the range of nanoporosity achieved so far is narrow. In this paper, we introduce five new bicomponent reagents for nanotexturing, which extend the range of surface modifications that can be achieved by simple chemical oxidative etching.…”