Fluoride Treatment and In Vitro Corrosion Behavior of Mg-Nd-Y-Zn-Zr Alloys Type

Fluoride conversion coatings on Mg present many advantages, among which one can find the reduction of the corrosion rate under “in vivo” or “in vitro” conditions and the promotion of the calcium phosphate deposition. Moreover, the fluoride ions released from MgF2 do not present cytotoxic effects and inhibit the biofilm formation, and thus these treated alloys are very suitable for cardiovascular stents and biodegradable orthopedic implants. In this paper, the biodegradation behavior of four new magnesium biodegradable alloys that have been developed in the laboratory conditions, before and after surface modifications by fluoride conversion (and sandblasting) coatings, are analyzed. We performed structural and surface analysis (XRD, SEM, contact angle) before and after applying different surface treatments. Furthermore, we studied the electrochemical behavior and biodegradation of all experimental samples after immersion test performed in NaCl solution. For a better evaluation, we also used LM and SEM for evaluation of the corroded samples after immersion test. The results showed an improved corrosion resistance for HF treated alloy in the NaCl solution. The chemical composition, uniformity, thickness and stability of the layers generated on the surface of the alloys significantly influence their corrosion behavior. Our study reveals that HF treatment is a beneficial way to improve the biofunctional properties required for the studied magnesium alloys to be used as biomaterials for manufacturing the orthopedic implants.

Mechanical Analysis and Corrosion Analysis of Zinc Alloys for Bioabsorbable Implants for Osteosynthesis

Zinc alloys have recently been researched intensely for their great properties as bioabsorbable implants for osteosynthesis. Pure zinc (Zn) itself has relatively poor strength, which makes it insufficient for most clinical use. Research has already proven that the mechanical strength of zinc can be enhanced significantly by alloying it with silver. This study evaluated zinc silver alloys (ZnAg) as well as novel zinc silver titanium alloys (ZnAgTi) regarding their mechanical properties for the use as bioabsorbable implants. Compared to pure zinc the mechanical strength was enhanced significantly for all tested zinc alloys. The elastic properties were only enhanced significantly for the zinc silver alloys ZnAg6 and ZnAg9. Regarding target values for orthopedic implants proposed in literature, the best mechanical properties were measured for the ZnAg3Ti1 alloy with an ultimate tensile strength of 262 MPa and an elongation at fracture of 16%. Besides the mechanical properties, the corrosion rates are important for bioabsorbable implants. This study tested the corrosion rates of zinc alloys in PBS solution (phosphate buffered solution) with electrochemical corrosion measurement. Zinc and its alloys showed favorable corrosion rates, especially in comparison to magnesium, which has a much lower degradation rate and no buildup of hydrogen gas pockets during the process. Altogether, this makes zinc alloys highly favorable for use as material for bioabsorbable implants for osteosynthesis.

Effect of Heat Treatment on the Mechanical and Corrosion Properties of Mg–Zn–Ga Biodegradable Mg Alloys

Mg alloys have mechanical properties similar to those of human bones, and have been studied extensively because of their potential use in biodegradable medical implants. In this study, the influence of different heat treatment regimens on the microstructure and mechanical and corrosion properties of biodegradable Mg–Zn–Ga alloys was investigated, because Ga is effective in the treatment of disorders associated with accelerated bone loss. Solid–solution heat treatment (SSHT) enhanced the mechanical properties of these alloys, and a low corrosion rate in Hanks’ solution was achieved because of the decrease in the cathodic-phase content after SSHT. Thus, the Mg–4 wt.% Zn–4 wt.% Ga–0.5 wt.% Y alloy after 18 h of SSHT at 350 °C (ultimate tensile strength: 207 MPa; yield strength: 97 MPa; elongation at fracture: 7.5%; corrosion rate: 0.27 mm/year) was recommended for low-loaded orthopedic implants.

Analytical Techniques for the Characterization of Bioactive Coatings for Orthopaedic Implants

The development of bioactive coatings for orthopedic implants has been of great interest in recent years in order to achieve both early- and long-term osseointegration. Numerous bioactive materials have been investigated for this purpose, along with loading coatings with therapeutic agents (active compounds) that are released into the surrounding media in a controlled manner after surgery. This review initially focuses on the importance and usefulness of characterization techniques for bioactive coatings, allowing the detailed evaluation of coating properties and further improvements. Various advanced analytical techniques that have been used to characterize the structure, interactions, and morphology of the designed bioactive coatings are comprehensively described by means of time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), 3D tomography, quartz crystal microbalance (QCM), coating adhesion, and contact angle (CA) measurements. Secondly, the design of controlled-release systems, the determination of drug release kinetics, and recent advances in drug release from bioactive coatings are addressed as the evaluation thereof is crucial for improving the synthesis parameters in designing optimal bioactive coatings.

The Effect of Neutrophil-Derived Products on the Function of Leukocytes Obtained after Titanium Implantation in the Ovine Model

Titanium (Ti) is currently the most common biomaterial used for orthopedic implants; however, these implants may cause deleterious immune response. To investigate the possible mechanisms involved in excessive inflammation, we assessed the activity of neutrophils and monocyte-derived macrophages (MDMs) during the insertion of the Ti implant in a sheep model. The study was conducted on 12 sheep, 4 of which were control animals and 8 were in the experimental group with inserted Ti implant. Neutrophil secretory response was estimated at two time points T0 before surgery and T1 1 h after implantation and was based on the release of enzymes from neutrophil granules and reactive oxygen and nitrogen species (RONS) generation. MDM function was evaluated 5 months after implantation, on the basis of RONS generation arginase activity and morphological changes. Moreover, the influence of some autologous neutrophil derived products, namely, antimicrobial neutrophil extract (ANE) and neutrophil degranulation products (DGP) on leukocytes was estimated. Our study revealed that Ti implant insertion did not cause any adverse effects up to 5 months after surgical procedure. Stimulation of neutrophil cultures with ANE decreased the enzyme release as well as superoxide generation. Treatment of MDM with ANE diminished superoxide and NO generation and increased arginase activity. On the other hand, MDM stimulated with DGP showed elevated superoxide and NO generation as well as decreased arginase activity. To summarize, ANE exerted an anti-inflammatory and pro-resolving effect on studied leukocytes, whereas DGP acted as pro-inflammatory.

Thin TiO2 Nanocoating of Porous Titanium through Radio Frequency Magnetron Sputtering to Improve the Biological Response of Orthopedic Implants

: The present study applied a TiO2 nanocoating on a titanium foam substrate produced by powder metallurgy through magnetron sputtering. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were employed to investigate the surface morphologies of the porous specimens and pre- and post-coating phases, respectively. Also, the growth and proliferation of MG-63 cells (osteoblasts) and their attachment and proliferation on the coated porous titanium specimen (relative to the uncoated specimens) were studied using in vitro and methyl thiazol tetrazolium (MTT) cytotoxicity tests. Considering the porous macrostructure of the coated titanium specimen and the nanostructure of the TiO2 coating on the porous surface and macro-pore walls, the coated specimen was found to be effective in the biocompatibility improvement of dental and orthopedic implants.

Review of Nanofluids and Their Biomedical Applications

Numerous researchers have reported significant improvements in nanofluid (NF) heat transfer (HT), suspension stability, thermal conductivity (TC), and rheological and mass transfer properties. As a result, nanofluids (NFs) play an important role in a variety of applications, including the health and biomedical engineering industries. The majority of the nanofluids (NFs) literature focuses on analyzing and comprehending the behavior of nanofluid models as heating or cooling mechanisms in various fields. This article represents a comprehensive study on nanofluids (NFs). It involves commonly used nanoparticles (NPs), magnetic nanofluids (MNFs), thermal conductivity (TC) enhancement, heat transfer (HT) enhancement, nanofluids (NFs) synthesis methods, stability evaluation methods, stability enhancement, nanofluids (NFs) applications in the biomedical field, and their impact on health and the environment. Nanofluids (NFs) play vital role in biomedical applications. It can be implemented in drug delivery systems, hyperthermia, sterilization processes, bioimaging, lubrication of orthopedic implants, and micro-pumping systems for drugs and hormones.