Nanoscale surface modifications of medically relevant metals: state-of-the art and perspectives

Abstract

Evidence that nanoscale surface properties stimulate and guide various molecular and biological processes at the implant/tissue interface is fostering a new trend in designing implantable metals. Cutting-edge expertise and techniques drawn from widely separated fields, such as nanotechnology, materials engineering and biology, have been advantageously exploited to nanoengineer surfaces in ways that control and direct these processes in predictable manners. In this review, we present and discuss the state-of-the-art of nanotechnology-based approaches currently used to modify the surface of metals used for orthopedic and dental applications, and also briefly consider their use in the cardiovascular field. The effects of nanoengineered surfaces on various in vitro molecular and cellular events are firstly discussed. Importantly, this review also provides an overview of in vivo and clinical studies with nanostructured metallic implants, and addresses the potential influence of nanotopography on biomechanical events at interfaces. Ultimately the objective of this work is to give the readership a comprehensive picture of the current advances, future developments and challenges in the application of the infinitesimally small to biomedical surface science. We believe that an integrated understanding of the in vitro and particularly of the in vivo behavior is mandatory for the proper exploitation of nanostructured implantable metals and, as a matter of fact, all biomaterials.

Titanium Oxide Antibacterial Surfaces in Biomedical Devices

“…This nanometric layer preserves the properties of the bulk material and interacts with biological fluids, resulting in a modulation of specific responses with the contact biological tissues (48). The comprehension of the role of TiO 2 film on biomedical Ti alloys paved the way to intense research activity focused on technologies for modifying and structuring the natural oxide layer in order to increase its resistance and give rise to novel properties (see, for instance, the results obtained in increasing the corrosion resistance of Ti alloys by increasing the oxide layer thickness in (49)) (48,(50)(51)(52). Industrial applications of photoactive materials, such as antifogging and self-cleaning surfaces, became popular in the last decade: however, their medical applications are still limited and seem to be still under development (4).…”

Large-scale functionalization of biomedical porous titanium scaffolds surface with TiO2 nanostructures

“…The magnified SEM images (Fig. 7a1-d1) show that the BMSCs attach to the scaffold surface via filopodia, and the bonding between the filopodia and the nanostructures would guide cells to perceive and respond to the nanotopographical cues [29,30].…”

Ultrasound-driven titanium modification with formation of titania based nanofoam surfaces

“…femoral stems, dental screws and cardiovascular stents); 2) possibility to modify at the nanoscale commercially available biocompatible metals and implants; 3) simple integration into industrial process lines [4]. According to the above mentioned features, chemical treatments seem to be attractive for large-scale manufacturing, because they provide uniform access of the reactive substance to all surfaces, but this leaves often unwanted residuals.…”

“…Straight-forward known surface treatments of Ti and its alloys (Ti6Al4V)can be divided into three main groups: mechanical, chemical and physical methods [4]. Polishing, machining, blasting belong to the mechanical methods.…”

“…Artificial heart valves and joint components, dental implants, orthopedic screws, pacemaker cases, vascular stents are commonly used biomedical applications of titaniumbased implants [1]. Titanium is a bioinert metal, it induces a tolerable reaction in the host tissue, shows an adequate resistance to the corrosive in-vivo environment, and has the necessary strength, ductility and endurance limit to withstand loading experienced in everyday life [2].…”