Electrochemical Strategies for Titanium Implant Polymeric Coatings: The Why and How

Fabrication of CO-releasing surface to enhance the blood compatibility and endothelialization of TiO2 nanotubes on titanium surface

Although the construction of nanotube arrays with the micro-nano structures on the titanium surfaces has demonstrated a great promise in the field of blood-contacting materials and devices, the limited surface hemocompatibility and delayed endothelial healing should be further improved. Carbon monoxide (CO) gas signaling molecule within the physiological concentrations has excellent anticoagulation and the ability to promote endothelial growth, exhibiting the great potential for the blood-contact biomaterials, especially the cardiovascular devices. In this study, the regular titanium dioxide nanotube arrays were firstly prepared in situ on the titanium surface by anodic oxidation, followed by the immobilization of the complex of sodium alginate/carboxymethyl chitosan (SA/CS) on the self-assembled modified nanotube surface, the CO-releasing molecule (CORM-401) was finally grafted onto the surface to create a CO-releasing bioactive surface to enhance the biocompatibility. The results of scanning electron microscopy (SEM), X-ray energy dispersion spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) revealed that the CO-releasing molecules were successfully immobilized on the surface. The modified nanotube arrays not only exhibited excellent hydrophilicity but also could slowly release CO gas molecules, and the amount of CO release increased when cysteine was added. Furthermore, the nanotube array can promote albumin adsorption while inhibit fibrinogen adsorption to some extent, demonstrating its selective albumin adsorption; although this effect was somewhat reduced by the introduction of CORM-401, it can be significantly enhanced by the catalytic release of CO. The results of hemocompatibility and endothelial cell growth behaviors showed that, as compared with the CORM-401 modified sample, although the SA/CS-modified sample had better biocompatibility, in the case of cysteine-catalyzed CO release, the released CO could not only reduce the platelet adhesion and activation as well as hemolysis rate, but also promote endothelial cell adhesion and proliferation as well as vascular endothelial growth factor (VEGF) and nitric oxide (NO) expression. As a result, the research of the present study demonstrated that the releasing CO from TiO₂ nanotubes can simultaneously enhance the surface hemocompatibility and endothelialization, which could open a new route to enhance the biocompatibility of the blood-contacting materials and devices, such as the artificial heart valve and cardiovascular stents.

Simultaneously Embedding Indomethacin and Electrodeposition of Polypyrrole on Various CoCr Alloys from Ionic Liquids

The aim of the present investigation is the electrochemical deposition of polypyrrole films from choline chloride-based ionic liquids at various potential, period times and simultaneously an indomethacin embedding and release. The electrodeposition films were performed on CoCr commercial type Wirobond C (WBC) and, Heraenium CE (Hera) using as electroprocedures for deposition cyclic voltammetry and chronoamperometry. The morphology of obtained films was investigated using scanning electron microscopy (SEM). An FT-IR investigation of CoCr alloys before and after electrodeposition was able to identify the presence of polymer and drug. The research included an evaluation of the hydrophilic character of all studied samples and their electrochemical characterization in Tanni Zuchi artificial saliva. In the electrochemical study, the following methods have been used: open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization. Indomethacin release from the polymeric film was determined using UV-VIS spectra. Based on Fick’s law of diffusion and indomethacin release profile, a kinetic law for release was established and discussed.

Innovative Coatings of Metallic Alloys Used as Bioactive Surfaces in Implantology: A Review

Metallic implants are widely used in the field of implantology, but there are still problems leading to implant failures due to weak osseointegration, low mechanical strength for the implant, inadequate antibacterial properties, and low patient satisfaction. Implant failure can be caused by bacterial infections and poor osteointegration. To improve the implant functionalization, many researchers focus on surface modifications to prepare the proper physical and chemical conditions able to increase biocompatibility and osteointegration between implant and bone. Improving the antibacterial performance is also a key factor to avoid the inflammation in the human body. This paper is a brief review for the types of coatings used to increase osseointegration and biocompatibility for the successful use of metal alloys in the field of implantology.

Electrodeposited Biocoatings, Their Properties and Fabrication Technologies: A Review

Coatings deposited under an electric field are applied for the surface modification of biomaterials. This review is aimed to characterize the state-of-art in this area with an emphasis on the advantages and disadvantages of used methods, process determinants, and properties of coatings. Over 170 articles, published mainly during the last ten years, were chosen, and reviewed as the most representative. The most recent developments of metallic, ceramic, polymer, and composite electrodeposited coatings are described focusing on their microstructure and properties. The direct cathodic electrodeposition, pulse cathodic deposition, electrophoretic deposition, plasma electrochemical oxidation in electrolytes rich in phosphates and calcium ions, electro-spark, and electro-discharge methods are characterized. The effects of electrolyte composition, potential and current, pH, and temperature are discussed. The review demonstrates that the most popular are direct and pulse cathodic electrodeposition and electrophoretic deposition. The research is mainly aimed to introduce new coatings rather than to investigate the effects of process parameters on the properties of deposits. So far tests aim to enhance bioactivity, mechanical strength and adhesion, antibacterial efficiency, and to a lesser extent the corrosion resistance.

Electrophoretic Deposition and Characterization of Chitosan/Eudragit E 100 Coatings on Titanium Substrate

Currently, a significant problem is the production of coatings for titanium implants, which will be characterized by mechanical properties comparable to those of a human bone, high corrosion resistance, and low degradation rate in the body fluids. This paper aims to describe the properties of novel chitosan/Eudragit E 100 (chit/EE100) coatings deposited on titanium grade 2 substrate by the electrophoretic technique (EPD). The deposition was carried out for different parameters like the content of EE100, time of deposition, and applied voltage. The microstructure, surface roughness, chemical and phase composition, wettability, mechanical and electrochemical properties, and degradation rate at different pH were examined in comparison to chitosan coating without the addition of Eudragit E 100. The applied deposition parameters significantly influenced the morphology of the coatings. The chit/EE100 coating with the highest homogeneity was obtained for Eudragit content of 0.25 g, at 10 V, and for 1 min. Young’s modulus of this sample (24.77 ± 5.50 GPa) was most comparable to that of human cortical bone. The introduction of Eudragit E 100 into chitosan coatings significantly reduced their degradation rate in artificial saliva at neutral pH while maintaining high sensitivity to pH changes. The chit/EE100 coatings showed a slightly lower corrosion resistance compared to the chitosan coating, however, significantly exceeding the substrate corrosion resistance. All prepared coatings were characterized by hydrophilicity.

Polyethylene Glycol Pulsed Electrodeposition for the Development of Antifouling Coatings on Titanium

Titanium dental implants are widely used for the replacement of damaged teeth. However, bacterial infections at the interface between soft tissues and the implant can impair the functionality of the device and lead to failure. In this work, the preparation of an antifouling coating of polyethylene glycol (PEG) on titanium by pulsed electrodeposition was investigated in order to reduce Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) adhesion while maintaining human fibroblast adhesion. Different pulsed conditions were prepared and characterized by contact angle, Focused Ion Beam (FIB), Fourier Transformed Infrared Spectroscopy in the Attenuated Total Reflectance mode (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). XPS tested fibronectin adsorption. S. aureus, E. coli and human fibroblast adhesion was tested in vitro in both mono and co-culture settings. Physicochemical characterization proved useful for confirming the presence of PEG and evaluating the efficiency of the coating methods. Fibronectin adsorption decreased for all of the conditions, but an adsorption of 20% when compared to titanium was maintained, which supported fibroblast adhesion on the surfaces. In contrast, S. aureus and E. coli attachment on coated surfaces decreased up to 90% vs. control titanium. Co-culture studies with the two bacterial strains and human fibroblasts showed the efficacy of the coatings to allow for eukaryotic cell adhesion, even in the presence of pre-adhered bacteria.

Surface Characterization of Electro-Assisted Titanium Implants: A Multi-Technique Approach

The understanding of chemical-physical, morphological, and mechanical properties of polymer coatings is a crucial preliminary step for further biological evaluation of the processes occurring on the coatings' surface. Several studies have demonstrated how surface properties play a key role in the interactions between biomolecules (e.g., proteins, cells, extracellular matrix, and biological fluids) and titanium, such as chemical composition (investigated by means of XPS, TOF-SIMS, and ATR-FTIR), morphology (SEM-EDX), roughness (AFM), thickness (Ellipsometry), wettability (CA), solution-surface interactions (QCM-D), and mechanical features (hardness, elastic modulus, adhesion, and fatigue strength). In this review, we report an overview of the main analytical and mechanical methods commonly used to characterize polymer-based coatings deposited on titanium implants by electro-assisted techniques. A description of the relevance and shortcomings of each technique is described, in order to provide suitable information for the design and characterization of advanced coatings or for the optimization of the existing ones.