Formation and in vitro mineralization of electrochemically deposited coatings prepared on micro-arc oxidized titanium alloy

Fighting Antibiotic-Resistant Bacterial Infections by Surface Biofunctionalization of 3D-Printed Porous Titanium Implants with Reduced Graphene Oxide and Silver Nanoparticles

Nanoparticles (NPs) have high multifunctional potential to simultaneously enhance implant osseointegration and prevent infections caused by antibiotic-resistant bacteria. Here, we present the first report on using plasma electrolytic oxidation (PEO) to incorporate different combinations of reduced graphene oxide (rGO) and silver (Ag) NPs on additively manufactured geometrically ordered volume-porous titanium implants. The rGO nanosheets were mainly embedded parallel with the PEO surfaces. However, the formation of ‘nano-knife’ structures (particles embedded perpendicularly to the implant surfaces) was also found around the pores of the PEO layers. Enhanced in vitro antibacterial activity against methicillin-resistant Staphylococcus aureus was observed for the rGO+Ag-containing surfaces compared to the PEO surfaces prepared only with AgNPs. This was caused by a significant improvement in the generation of reactive oxygen species, higher levels of Ag+ release, and the presence of rGO ‘nano-knife’ structures. In addition, the implants developed in this study stimulated the metabolic activity and osteogenic differentiation of MC3T3-E1 preosteoblast cells compared to the PEO surfaces without nanoparticles. Therefore, the PEO titanium surfaces incorporating controlled levels of rGO+Ag nanoparticles have high clinical potential as multifunctional surfaces for 3D-printed orthopaedic implants.

Electrochemical Deposition of Hydroxyapatite on Stainless Steel Coated with Tantalum/Tantalum Nitride Using Simulated Body Fluid as an Electrolytic Medium

In the present work the electrochemical deposition of hydroxyapatite using simulated body fluid (SBF) as an electrolytic medium was carried out on Ta and Ta/TaN coatings on BIOLINE stainless steel SS316LVM (SS). The electrochemical deposition performed on each substrate for 3000 and 6000 s, at different potentials were determined from cyclic voltammetry. The best conditions found were −1.4 V for bare SS and −1.7 V for Ta/TaN coating. The structural characterization was carried out by SEM, FTIR, XRD, and contact angle measurements. The electrochemical characterization was done by electrochemical impedance (EIS), which allowed us to know the capacitive and resistive character of the substrates. The substrate (Ta/TaN)/SS at −1.7 V 6000 s presented the largest formation of a nonstoichiometric hydroxyapatite with a uniform distribution on the substrate, implying that Ta–OH is formed on the tantalum metallic surface, due to formation of the passivation layer of tantalum oxide. These groups attract Ca2+ ions and PO43− ions absorbed on the surface will form the precursors of the apatite crystals that finally transform to hydroxyapatite. The electrodeposition of HAp the double layer Ta/TaN resulted in a more uniform and denser layer than SS alone.

Simultaneous Precipitation and Electrodeposition of Hydroxyapatite Coatings at Different Temperatures on Various Metal Substrates

The coating of orthopedic and dental implants with hydroxyapatite (HA) is recognized as a method to increase their integration ability. A new metal coating method, comprising simultaneous precipitation and electrodeposition, is presented. Two studies are described: the first is related to the influence of time/temperature increase on the morpho-structural characteristics of the deposited layer on the Ti substrate, while the second study presents the characteristics of the layers deposited on different metal substrates. For comparison, specimens were obtained using the classical electrochemical deposition under the same experimental conditions. The addition of Ca to the electrolyte creates more compact and more uniform coatings, while the addition of P creates more porous layers. Only a very small quantity of crystalline HA deposited on the C55, Cu, and Ni substrates when the classic electrodeposition method was employed, while using the new approach has clearly led to a larger crystalline HA amount electrodeposited on the same types of metals. With some exceptions, the advantages of using the new method are: better crystallinity, more uniform and continuous surface, higher roughness, and potentially higher anti-corrosion capabilities.

Construction of multi-layered Zn-modified TiO2 coating by ultrasound-auxiliary micro-arc oxidation: Microstructure and biological property

Surfaces with desirable cytocompatibility and bactericidal ability are favoured for orthopaedic implants to stimulate osteogenic activity and to prevent implant-associated infection. In this work, we creatively introduce ultrasonic vibration (UV) to micro-arc oxidation (MAO) process and explore its influence on the microstructure, corrosion property and biological responses of Zn-modified TiO₂ coating. With the introduction of UV, a uniform surface layer with homogeneously-distributed clusters could be produced as the outer layer, which possesses a fusion band with the underlying TiO₂. The microstructural modification associated with UV results in the enhanced corrosion resistance, increased adhesive strength and improved biological performances of the resultant coating relative to that with the absence of UV. Hence, the ultrasonic auxiliary micro-arc oxidation (UMAO) is regarded as a promising surface modification method to produce Ti-based orthopaedic implants of high quality.