Adhesion, biological corrosion resistance and biotribological properties of carbon films deposited on MAO coated Ti substrates

Analysis of the CPZ/Wnt4 osteogenic pathway for high-bonding-strength composite-coated magnesium scaffolds through transcriptomics

Magnesium (Mg)-based scaffolds are garnering increasing attention as bone repair materials owing to their biodegradability and mechanical resemblance to natural bone. Their effectiveness can be augmented by incorporating surface coatings to meet clinical needs. However, the limited bonding strength and unclear mechanisms of these coatings have impeded the clinical utility of scaffolds. To address these issues, this study introduces a composite coating of high-bonding-strength polydopamine-microarc oxidation (PDA-MHA) on Mg-based scaffolds. The results showed that the PDA-MHA coating achieved a bonding strength of 40.56 ± 1.426 MPa with the Mg scaffold surface, effectively enhancing hydrophilicity and controlling degradation rates. Furthermore, the scaffold facilitated bone regeneration by influencing osteogenic markers such as RUNX-2, OPN, OCN, and VEGF. Transcriptomic analyses further demonstrated that the PDA-MHA/Mg scaffold upregulated carboxypeptidase Z expression and activated the Wnt-4/β-catenin signaling pathway, thereby promoting bone regeneration. Overall, this study demonstrated that PDA can synergistically enhance bone repair with Mg scaffold, broadening the application scenarios of Mg and PDA in the field of biomaterials. Moreover, this study provides a theoretical underpinning for the application and clinical translation of Mg-based scaffolds in bone tissue engineering endeavors.

Improved Corrosion Resistance and Cytotoxicity of Nickel-based alloy using Novel Plasma processing technique.. [DOI: 10.21203/rs.3.rs-3200844/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Nickel-based (NiCr) alloys are mostly utilized in the dental industry because of their good corrosion resistance, ease of casting, and adequate thermal coefficient of friction with ceramic porcelain. However, leakage of toxic metal ions (Ni and Cr) due to breakage or damage of protective metal oxide layers in aggressive body fluids affects corrosion resistance, tribological properties, and cytotoxicity. These drawbacks ultimately affect the biocompatibility of NiCr alloys for medical applications. This study employs magnetron sputtering in conjunction with cathodic cage plasma nitriding (CCPN) to perform a novel duplex plasma treatment on Ni-Cr alloy. Moreover, the cathodic cage plasma-treated TiN (CCPN-TiN) samples showed further enhanced corrosion resistance and low metal ion leakage. These findings made duplex plasma treatment an efficient method for the surface modification of metallic alloys against the leaching of toxic ions in chloride-aggressive electrolytes, thus proving an excellent strategy for various biomedical applications.

Probing Friction Properties of Hydrogen-Free DLC Films in a Nitrogen Environment Based on ReaxFF Molecular Dynamics

In this paper, ReaxFF molecular dynamics simulations were used to look at how load and the number of nitrogen molecules affect how friction behavior in hydrogen-free diamond-like carbon (DLC). The presence of nitrogen molecules will inhibit the formation of C-C covalent bonds between the contact surfaces of the upper and lower DLC, thereby effectively suppressing the increase in friction during the initial friction phase. After the initial friction stage, the mechanical mixing of the contact surfaces brought on by the diffusion of nitrogen molecules results in considerable shear stress, which has significant impacts on the friction force. In addition, due to the existence of nitrogen molecules, the effect of graphitization of hydrogen-free DLC on friction is almost negligible.

Mechanical properties, corrosion resistance, and anti-adherence characterization of pure titanium fabricated by casting, milling, and selective laser melting

Milling and selective laser melting (SLM) technology have become new options for removable partial denture (RPD) processing. However, whether milling and SLM technology has an impact on the properties of RPD remains unclear, which is also the aim of our study. To investigate the effects of milling and SLM technology on pure titanium, mechanical property, corrosion resistance, and anti-adherence of specimens were evaluated, and specimens processed by lost-wax casting were used as control. Compared with casting and milling groups, the SLM group showed enhanced Vickers hardness (402.1 ± 13.0 HV), tensile stress (694.4 ± 4.5 MPa), and larger electrochemical capacitance arc radius compared with casting and milling groups. A series of adhesion-related genes (Als1, Als3, and HWP1) of Candida albicans cultured on SLM specimens were upregulated for more than two times that of casting and milling groups. However, images from scanning electron microscopy and confocal laser scanning microscopy exhibited similar biofilm morphology and biomass of C. albicans on a titanium disk processed by casting, milling, and SLM. Dwindled water contact angle (64.7 ± 0.6°) and higher TiO₂ constituents (40.82%) in the SLM group might lead to the incompatibility of genetic expression and biofilm generation. Our findings indicated that SLM is an ideal process to produce titanium dentures, providing a reference on the selection of processing technology for dentists.

Enhanced Properties of Micro Arc Oxidation Coating with Cu Addition on TC4 Alloy in Marine Environment

By contrast with the traditional method of adding hard particles into micro arc oxidation (MAO) coating to improve its wear performance, this study introduced copper into the MAO coating on TC4 alloy by adding copper pyrophosphate to enhance the wear property in a marine environment and the antibacterial property. The results demonstrated that the MAO coating with copper pyrophosphate addition showed a porous structure, and Cu was mainly concentrated around micropores. CuO and Cu2O were formed in this MAO coating. This MAO coating with Cu had a high bonding strength to the substrate. Although the hardness of the coating with Cu had been reduced, it could reduce the friction coefficient and enhance the wear property in simulated seawater due to the lubrication of Cu. Furthermore, this MAO coating with Cu addition had obvious antibacterial and bactericidal effects due to the antibacterial effect of Cu.

Preparation and Corrosion Behavior in Marine Environment of MAO Coatings on Magnesium Alloy

To improve the corrosion performance of magnesium alloys in the marine environment, the MAO, MAO-Cu₂CO₃(OH)₂·H₂O and MAO-Cu₂P₂O₇ ceramic coatings were deposited on AZ91D magnesium alloys in basic electrolyte and the discoloration mechanism of the Cu-doped MAO coatings and the corrosion behavior of the three MAO coatings in the artificial seawater solution were investigated by SEM, EDS and XPS. The results indicated that the formation and discoloration mechanism of the brown MAO ceramic coatings were attributable to the formation of Cu₂O in the coatings. Though the three MAO coatings had a certain protective effect against the corrosion of AZ91D substrate in the artificial seawater, the distinctive stratification phenomenon was found on the MAO-Cu₂P₂O₇ coated sample and the corrosion model of the MAO-Cu₂P₂O₇ coatings in the immersion experiment was established. Therefore, the brown Cu-doped MAO coatings were speculated to significantly reduce the risk of the magnesium parts in marine environments.