Nano‐porous Alumina Coatings for Improved Bone Implant Interfaces

Abstract

A new method is proposed for coating implants that produces a metal implant covered in a layer of nano-porous alumina ceramic. These layers are produced by first depositing a layer of aluminium on the implant surface and then anodising it in phosphoric acid to produce the nano-porous structure. This process results in the conversion of the aluminium to alumina containing 6-8wt% phosphate ions. The surface alumina layer is bonded to the substrate via an interfacial layer of fully dense anodised titanium oxide. Mechanical measurements have shown that the shear and tensile strength of this coating are in excess of 20MPa and 10MPa, respectively.The biological performance of nano-porous alumina material has been assessed and shown to be highly favourable, supporting normal osteoblastic activity and maintaining the osteoblastic phenotype. The filling of the nano-porous coating with bioactive material to achieve enhanced biological performance has been investigated using colloidal silica as an analogue for a Bioglass sol. The coating has been loaded with silica by dipping in colloidal silica with a pH of 5.6. Pore filling equivalent to 1.3 wt% SiO 2 in the coating as a whole has been achieved in this way.

Selective etching of injection molded zirconia-toughened alumina: Towards osseointegrated and antibacterial ceramic implants

“…The main benefit of selective etching when compared to other existing processes to produce nanoporous alumina on implants, such as for instance anodization [28,72], is that the layer obtained is not a coating. There is no interface with the bulk, which is highly beneficial in terms of reliability since it avoids any problem related to lack of adhesion or delamination.…”

Highly Ordered Anodic Porous Alumina Formation by Self‐Organized Anodizing

“…An electrochemical biosensor for the determination of blood glucose was constructed by the condensation polymerization of dimethyldichlorosilane at the surface of a porous alumina membrane [658]. Anodic porous alumina films can also be used as implants with enhanced bonebonding performance, by filling the nanopores with a bioactive material that supports normal osteoblastic activity [659]. …”

Neuronal cell biocompatibility and adhesion to modified CMOS electrodes

“…evaluation of the intrinsic nature of an uncoated porous alumina surface and with substrates configured in a manner that is conducive to subsequently forming an electrode such as closed conductive substrate rather than membrane (Prasad and Quijano 2006;Wolfrum et al 2006). Others have evaluated nonneuronal cell types on porous alumina, in particular osteoblasts, and shown good biocompatibility (Walpole et al 2003;Leary Swan et al 2005;Hoess et al 2007;Karlsson et al 2004). The objectives of our experiments were therefore to, firstly, evaluate the biocompatibility with neuronal cells of porous alumina configured in a manner compatible with CMOS processing and, secondly, to characterise adhesion versus alumina pore pitch.…”

“…Aluminium has also been associated with the pathogeny of Alzheimer's Disease, but a causal relationship has not been demonstrated (Perl and Moalem 2006). However, due to these concerns, Walpole et al (2003) and tested nano-porous alumina substrates for aluminium ion leakage and they concluded that the dissolution of ions into the culture was not toxic.…”