Osseointegration of Ti-6Al-4V alloy implants with a titanium nitride coating produced by a PIRAC nitriding technique: a long-term time course study in the rat

Molecular mechanisms of poor osseointegration in irradiated bone: In vivo study in a rat tibia model

AIM

Radiotherapy is associated with cell depletion and loss of blood supply, which are linked to compromised bone healing. However, the molecular events underlying these effects at the tissue-implant interface have not been fully elucidated. This study aimed to determine the major molecular mediators associated with compromised osseointegration due to previous exposure to radiation.

MATERIALS AND METHODS

Titanium implants were placed in rat tibiae with or without pre-exposure to 20 Gy irradiation. Histomorphometric, biomechanical, quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay analyses were performed at 1 and 4 weeks after implantation.

RESULTS

The detrimental effects of irradiation were characterized by reduced bone-implant contact and removal torque. Furthermore, pre-exposure to radiation induced different molecular dysfunctions such as (i) increased expression of pro-inflammatory (Tnf) and osteoclastic (Ctsk) genes and decreased expression of the bone formation (Alpl) gene in implant-adherent cells; (ii) increased expression of bone formation (Alpl and Bglap) genes in peri-implant bone; and (iii) increased expression of pro-inflammatory (Tnf) and pro-fibrotic (Tgfb1) genes in peri-implant soft tissue. The serum levels of pro-inflammatory, bone formation and bone resorption proteins were greater in the irradiated rats.

CONCLUSIONS

Irradiation causes the dysregulation of multiple biological activities, among which perturbed inflammation seems to play a common role in hindering osseointegration.

Comparison of the Physicochemical Properties of Carboxylic and Phosphonic Acid Self-Assembled Monolayers Created on a Ti-6Al-4V Substrate

This study compared the tribological properties in nano- and millinewton load ranges of Ti‑6Al-4V surfaces that were modified using self-assembled monolayers (SAMs) of carboxylic and phosphonic acids. The effectiveness of the creation of SAMs with the use of the liquid phase deposition (LPD) technique was monitored by the contact angle measurement, the surface free energy (SFE) calculation, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR) measurements. The obtained results indicated that more stable and well-ordered layers, which were characterized by the lowest values of the coefficient of friction, adhesion, and wear rate, were obtained using phosphonic acid as a surface modifier. Based on the obtained results, it was found that the Ti-6Al-4V alloy modified by phosphonic acid would be the most advantageous for practical applications, especially in micro- and nanoelectromechanical systems (MEMS/NEMS).

SiCxNyOz Coatings Enhance Endothelialization and Bactericidal activity and Reduce Blood Cell Activation

For biomedical applications, a number of ceramic coatings have been investigated, but the interactions with the components of living system remain unexplored for oxycarbonitride coatings. While addressing this aspect, the present study aims to provide an understanding of the biocompatibility of novel SiC_xN_yO_z coatings that could validate the hypothesis that such coatings may not only enhance the cell-material interaction by re-endothelialization but also can help to reduce bacterial adhesion and activation of blood cells. This work reports the physicochemical properties, hemocompatibility, endothelialization, and antibacterial properties of novel amorphous SiC_xN_yO_z coatings deposited on commercial pure titanium (Ti) by radiofrequency (RF) magnetron sputtering at varied nitrogen (N₂) flow rates. A comparison is made with diamond-like carbon (DLC) coatings, which are clinically used. The surface roughness, surface wettability, nanoscale hardness, and surface energy of SiC_xN_yO_z coatings were found to be dependent on the nitrogen (N₂) flow rate. Importantly, the as-deposited SiC_xN_yO_z coatings exhibited much better nanoscale hardness and scratch resistance than DLC coatings. Furthermore, Raman spectroscopy analysis of the SiC_xN_yO_z coating deposited on Ti showed a change in the graphitic/disordered carbon content. Cytocompatibility and hemocompatibility properties of the as-deposited SiC_xN_yO_z coating were evaluated using the Mus musculus lymphoid endothelial cell line (SVEC4-10) and rabbit blood in vitro. WST-1 assay analysis showed that these coatings, when compared to DLC, exhibited a better proliferation of endothelial cells, which can potentially result in improved surface endothelialization. Furthermore, qualitative and quantitative analyses of immunofluorescence images revealed a dense cellular layer of SVEC4-10 on SiC_xN_yO_z coatings, deposited at 15 and 30 sccm nitrogen flow rates. As far as compatibility with rabbit blood is concerned, the hemolysis of the SiC_xN_yO_z coatings was less than 4%, with slightly lower values for coatings deposited without N₂ flow. The SiC_xN_yO_z coatings support less platelet adhesion and aggregation, with no signature of morphological deformation, as compared to the uncoated titanium substrate or DLC coatings. Furthermore, SiC_xN_yO_z coatings were also found to be effectively extending the blood coagulation time for a period of 60 min. The antimicrobial study of as-deposited SiC_xN_yO_z coatings on E. coli and S. aureus bacteria revealed the effective inhibition of bacterial proliferation after 24 h of culture. An attempt has been made to explain the cyto- and hemocompatibility properties with antimicrobial efficacy of coatings in terms of the variation in the coating composition and surface energy. Taken together, we conclude that SiC_1.3N_0.76O_0.87 coating having a roughness of 17 nm and a surface free energy of 54.0 ± 0.7 mN/m can exhibit the best combination of hardness, elastic modulus, scratch resistance, cytocompatibility, hemocompatibility, and bactericidal properties.

The Galvanic Effect of Titanium and Amalgam in the Oral Environment

The effects of the presence of amalgam on titanium (Ti) dissolution in the oral environment under acidic, neutral, and basic conditions was studied. The presence of amalgam was found to suppress Ti release under acidic conditions due to the redeposition of TiO_x/SnO_x on the surface of the Ti. The redeposition of SnO_x was due to the amalgam releasing its components (Hg, Cu, Sn, Ag) and the thermodynamic preference of Sn to oxidize, which was confirmed using mass measurements, ICP-MS analyses, and X-ray Photoelectron Spectroscopy (XPS). XPS depth profiling was performed to characterize the composition and oxidation states of the redeposited SnO_x/TiO_x film. Under basic conditions, the amalgam hindered Ti dissolution, but no redeposition of amalgam components was observed for the Ti.

Hollow cathode plasma nitriding of medical grade Ti6Al4V: A comprehensive study

Ti6Al4V used in biomedical applications still has several surface-related problems, such as poor bone compatibility and low wear resistance. In this work, the formation of a protective layer of titanium nitride obtained by plasma treatment in hollow cathode was studied, and the best experimental conditions were verified by a statistical factorial design of experiments. The samples were characterized in terms of their physical and chemical properties, correlating the effects of time (min) and temperature (°C). An achieved ideal condition was further analysed in terms of in vitro cytotoxicity, micro-abrasion, and electrochemical properties. The carried-out assessment has shown that nitrided condition has an improvement in wettability, microhardness, along with TixNy formation and roughness increment, when compared to pristine condition.

Short-term exposure to titanium, aluminum and niobium (Ti-6Al-4Nb) alloy powder can disturb the serum low-density lipoprotein concentrations and antioxidant profile in vital organs but not the behavior of male albino mice

A group of seven-week-old albino mice of both genders were orally administered with a suspension of 25 mg Ti-6Al-4Nb/ml of saline/kg body weight and evaluated in comparison with a control group of animals treated with saline. Evaluation of both the groups was conducted through behavioral tests (Rota rod, open field, novel object and light dark box test), blood biochemical tests [complete blood count and selected serum parameters ([cholesterol, high-density lipoproteins, low-density lipoproteins, creatinine and triglycerides)] and on the basis of measured concentration of antioxidant metabolites (superoxide dismutase, catalase and lipid peroxidation) in vital organs (brain, heart, liver, kidney and lungs). Based upon the results of these tests, it has been found that the applied dose of Ti-6Al-4Nb alloy powder has not effect on physical and neurological outcome of these animals. However, it can increase low-density lipoprotein concentrations as well as disturb the H₂O₂ and lipid peroxidation associated metabolic pathways, especially in male albino mice. Whereas all other hematological indices and antioxidative stress parameters were unaffected.