Current Knowledge on Biomaterials for Orthopedic Applications Modified to Reduce Bacterial Adhesive Ability

Abstract

A significant challenge in orthopedics is the design of biomaterial devices that are able to perform biological functions by substituting or repairing various tissues and controlling bone repair when required. This review presents an overview of the current state of our recent research into biomaterial modifications to reduce bacterial adhesive ability, compared with previous reviews and excellent research papers, but it is not intended to be exhaustive. In particular, we investigated biomaterials for replacement, such as metallic materials (titanium and titanium alloys) and polymers (ultra-high-molecular-weight polyethylene), and biomaterials for regeneration, such as poly(ε-caprolactone) and calcium phosphates as composites. Biomaterials have been designed, developed, and characterized to define surface/bulk features; they have also been subjected to bacterial adhesion assays to verify their potential capability to counteract infections. The addition of metal ions (e.g., silver), natural antimicrobial compounds (e.g., essential oils), or antioxidant agents (e.g., vitamin E) to different biomaterials conferred strong antibacterial properties and anti-adhesive features, improving their capability to counteract prosthetic joint infections and biofilm formation, which are important issues in orthopedic surgery. The complexity of biological materials is still far from being reached by materials science through the development of sophisticated biomaterials. However, close interdisciplinary work by materials scientists, engineers, microbiologists, chemists, physicists, and orthopedic surgeons is indeed necessary to modify the structures of biomaterials in order to achieve implant integration and tissue regeneration while avoiding microbial contamination.

Keywords: UHMWPE; antibacterial properties; essential oils; multifunctional biomaterials; oxidation; poly(ε-caprolactone); prosthetic joint infections; septic loosening; silver; titanium alloys; vitamin E.

Figure 1

Orthopedic prosthetic surgery for the functional restoration of bone and joints is achieved surgically in total joint arthroplasties by using permanently implanted biomaterials such as titanium and polyethylene. Additionally, numerous bone fractures and other musculoskeletal problems need to be addressed using biodegradable biomaterials, such as poly(ε-caprolactone). The presence of a foreign body is a triggering event for prosthetic joint infection because the implant surface attracts free-floating bacteria, and this bacterium–surface interaction becomes irreversible thanks to biofilm formation.

Figure 2

The development of biomaterials that incorporate antimicrobial agents—e.g., silver nitrate, peppermint essential oil, silver ions, and vitamin E—can reduce microbial adhesion (via contact-killing or release-killing modes, or both) on these surfaces, preventing implant-related infection.