Trabecular Titanium for Orthopedic Applications: Balancing Antimicrobial with Osteoconductive Properties by Varying Silver Contents

Abstract

Periprosthetic joint infection (PJI) and implant loosening are the most common complications after joint replacement surgery. Due to their increased surface area, additively manufactured porous metallic implants provide optimal osseointegration but they are also highly susceptible to bacterial colonization. Antibacterial surface coatings of porous metals that do not inhibit osseointegration are therefore highly desirable. The potential of silver coatings on arthroplasty implants to inhibit PJI has been demonstrated, but the optimal silver content and release kinetics have not yet been defined. A tight control over the silver deposition coatings can help overcome bacterial infections while reducing cytotoxicity to human cells. In this regard, porous titanium sputtered with silver and titanium nitride with increasing silver contents enabled controlling the antibacterial effect against common PJI pathogens while maintaining the metabolic activity of human primary cells. Electron beam melting additively manufactured titanium alloys, coated with increasing silver contents, were physico-chemically characterized and investigated for effects against common PJI pathogens. Silver contents from 7 at % to 18 at % of silver were effective in reducing bacterial growth and biofilm formation. Staphylococcus epidermidis was more susceptible to silver ions than Staphylococcus aureus. Importantly, all silver-coated titanium scaffolds supported primary human osteoblasts proliferation, differentiation, and mineralization up to 28 days. A slight reduction of cell metabolic activity was observed at earlier time points, but no detrimental effects were found at the end of the culture period. Silver release from the silver-coated scaffolds also had no measurable effects on primary osteoblast gene expression since similar expression of genes related to osteogenesis was observed regardless the presence of silver. The investigated silver-coated porous titanium scaffolds may thus enhance osseointegration while reducing the risk of biofilm formation by the most common clinically encountered pathogens.

Trabecular titanium cups in hip revision surgery: a systematic review of the literature

“…The Delta TT revision system, introduced into clinical practice in 2008, consists of two revision cups, the Delta One TT and the Delta Revision TT. Delta One TT is a hemispherical multi-hole acetabular shell made of 3D-printed titanium alloy ( 17 , 18 ) ( Figure 1 ). Delta TT Revision is a cup-cage with a caudal hook and three cranial wings to achieve primary cup stability in severe defects.…”

“…The Delta Trabecular Titanium (TT) revision system (Lima Corporate, Udine, Italy) outer surface is characterized by a highly porous area similar to the cancellous bone. The diameter porosity should stimulate implant osteoblast adhesion, promoting cup osteointegration with natural bone and early and strong bone growth ( 17 , 18 ). This study reviewed the current literature on using Delta TT revision cups.…”

Ion incorporation into bone grafting materials

“…[60][61][62] Research has strived to pinpoint the ideal silver content and release kinetics that maximize antimicrobial action while minimizing host toxicity. [63][64][65] However, in vitro tests have shown their constraints: they do not fully capture the complexities of in vivo environments, and different cells vary in their tolerance to silver ions. For instance, while osteoblast proliferation and mesenchymal stem cell differentiation remain largely unaffected at antimicrobial silver concentrations, 60,[66][67][68] low silver levels can hinder macrophage metabolic activity and induce neutrophil apoptosis.…”

“…It is crucial to strike a balance between antimicrobial efficacy and biocompatibility 60–62 . Research has strived to pinpoint the ideal silver content and release kinetics that maximize antimicrobial action while minimizing host toxicity 63–65 . However, in vitro tests have shown their constraints: they do not fully capture the complexities of in vivo environments, and different cells vary in their tolerance to silver ions.…”

Deposition of Antioxidant and Cytocompatible Caffeic Acid-Based Thin Films onto Ti6Al4V Alloys through Hexamethylenediamine-Mediated Crosslinking

“…The ordinary need for novel implants for bone and joint replacement or to support damaged bones has recently motivated research on the optimization of the surface properties of Ti6Al4V in order to promote tissue healing even in adverse conditions such as inflammation or infection . Improvement of osteointegration and antibacterial or anti-microfouling bioactivity of the materials has recently been gained, for example, by bioactive coatings, − chemical/electrochemical treatments to get bioactive oxide layers, , and modification of surface topography to get porous structures favoring the proliferation of human bone marrow stromal cells as well as the in-growth of the mature osteoblasts and the colonization of the implant by the progenitor cells migrating from the surrounding healthy tissue. − Moreover, the ability of the implantable materials to prevent bacterial colonization and biofilm formation is of crucial importance since infections still represent a major issue in orthopedics; for example, in their clinical revisions, Hardes et al and Wafa et al . reported an infection incidence of 17.6 and 22.4%, respectively, for patients carrying Ti implants devoid of antibacterial agents.…”