Thin coatings of biomaterials for hard tissue applications

Abstract

The goal of the present study is the production of new-generation coatings suitable for hard tissue implants, intended to decrease the healing time, limit infections and rejections and improve patients' life quality. Materials designed for implant coatings are mainly bioactive ceramics. Belonging to this class of biomaterials, hydroxyapatite (HAp), bioglass (BG) and glass-ceramic (BGC) are indicated for application in hard tissue replacement and regeneration. However the use of each one has strengths and weaknesses; therefore the attention has been focused on their peculiarity in the coating of metallic materials, suitable for hard tissue replacement. In particular, in order to overcome their drawback and enhance their strengths, possible solutions, like the adding of helpful component in the basic material or the choice of composites, have been investigated. The main technique used for the coatings production has been the Pulsed Laser Deposition (PLD). Furthermore the Electrophoretic Deposition (EPD) has been performed to produce composite biopolymer/bioceramic coatings, which cannot be accomplished by the conventional PLD. Hydroxyapatite has been deposited with IONPs (iron oxide nanoparticles). The IONPs have been previously obtained by the means of a really "green" technique, the PLAL (pulsed laser ablation in liquid). The obtaining of HAp/IONPs films has demonstrated how PLD is a successful deposition technique for the production of magnetic composite coatings. BG_Cu films have been also successfully deposited trough PLD and their bioactivity has been demonstrated by the hydroxyapatite growth on their surface during the soaking in simulated body fluid (SBF). The use of electrophoretic deposition (EPD) has allowed the coating of SS substrate with polymer/bioglass composite films. Also in this case a Cu-doped bioaglass has been used together with a protein-based polymer, zein, and the films bioactivity has been proved. RKKP (glass-ceramic) pulsed laser deposited has been proved functional coatings for celldelivery implantation and for the reduction of the corrosion of biodegradable implant. Although glass-ceramics show superior mechanical properties than bioglasses, they are still not enough for load-bearing application. Therefore, RKKP&C60 has been used as target for the deposition of composite films with improved hardness. Finally, RKKP has been modified by the adding of another component, manganese, useful for the bone regeneration, and its biocompatibility has been proved. [edited by author]