Bioactive coatings

Abstract

From traditional approaches of employing bulk materials to the new generation of bioactive coated implants, the design of such medical tools is being directed towards the implementation bioactive compounds to allow the direct bonding of living tissues and osteoconduction. However, the development of an optimal bioactive implant for tissue regeneration has not been achieved. The research for novel materials is hindered by the biocompatibility and bioactivity of the compound as well as their mechanical properties. To improve the bioactivity of the implants, the increase of surface area of the implant as well as the use of resorbable compounds is being studied with promising results. Among all different materials and composite employed, the common materials include calcium phosphates and resorbable bioglasses inspired in natural scaffold composition of bones and teeth. In some cases, this material is being used as a coating and combined with further treatments and functional coatings which may reinforce its bioresponsive properties, and in some cases, it can provide additional properties such as antimicrobial activity. In addition, a specific class of bioactive coatings based on biodegradable polymers has also been developed. These coatings temporally aim at accelerating wound healing and forming new tissue at the material-tissue interface around implanted devices or protecting those implants against biomaterial-associated infections. Bioactive, degradable coatings can be generated both from natural and synthetic polymers. Common strategies, reviewed here, are based on natural polymers like proteins, polysaccharides, or glycosaminoglycanes to improve their bioactivity either by chemical functionalization of the biopolymer itself (e.g. introduction of bioactive groups) or by immobilization of bioactive components (e.g. cell adhesion peptides). Degradable or at least water-soluble synthetic polymers as polylactones or polyethylene glycols have been used for long time to create carrier materials for bioactive agents. As exemplary illustrated, those polymers are also used creating either substrate-adhering nanofilms or hydrogel-based thick coatings with high bioactivity to stimulate cell adhesion or avoid microbial adhesion. This chapter aims to summarize all recent approaches in the development of various bioactive coating materials, as well as the coating techniques and further treatment, functionalization and surface modification.