Strontium Substituted Tricalcium Phosphate Bone Cement: Short and Long‐Term Time‐Resolved Studies and In Vitro Properties

Due to a significant influence of strontium (Sr) on bone regeneration, Sr substituted beta-tricalcium phosphate (Sr-TCP) cement is prepared and investigated by short- and long-term time-resolved techniques. For short-term investigations, energy-dispersive X-ray diffraction, infrared spectroscopy, and, for the first time, terahertz time-domain spectroscopy techniques are applied. For long-term time-resolved studies, angular dispersive X-ray diffraction, scanning electron microscopy, mechanical tests, and behavior in Ringer solution are carried out. After 45 min of the cement setting, the Sr-TCP phase is no longer detectable. During this time period, an appearance and constant increase of the final brushite phase are registered. The compressive strength of the Sr-TCP cement increases from 4.5 MPa after 2 h of setting and reaches maximum at 13.3 MPa after 21 d. After cement soaking for 21 d in Ringer solution, apatite final product, with an admixture of brushite and TCP phases is detected. The cytotoxicity aspects of the prepared cement are investigated using NCTC 3T3 fibroblast cell line, and the cytocompatibility-by human dental pulp mesenchymal stem cells. The obtained results allow to conclude that the developed Sr-TCP cement is promising for biomedical applications for bone tissue

Magnesium Filled Polylactic Acid (PLA) Material for Filament Based 3D Printing

The main objective of this research is to prove the viability of obtaining magnesium (Mg) filled polylactic acid (PLA) biocomposites as filament feedstock for material extrusion-based additive manufacturing (AM). These materials can be used for medical applications, thus benefiting of all the advantages offered by AM technology in terms of design freedom and product customization. Filaments were produced from two PLA + magnesium + vitamin E (α-tocopherol) compositions and then used for manufacturing test samples and ACL (anterior cruciate ligament) screws on a low-cost 3D printer. Filaments and implant screws were characterized using SEM (scanning electron microscopy), FTIR (fourier transform infrared spectrometry), and DSC (differential scanning calorimetry) analysis. Although the filament manufacturing process could not ensure a uniform distribution of Mg particles within the PLA matrix, a good integration was noticed, probably due to the use of vitamin E as a precursor. The results also show that the composite biomaterials can ensure and maintain implant screws structural integrity during the additive manufacturing process

In vitro characterization of novel nanostructured collagen-hydroxyapatite composite scaffolds doped with magnesium with improved biodegradation rate for hard tissue regeneration

New materials are required for bone healing in regenerative medicine able to temporarily substitute damaged bone and to be subsequently resorbed and replaced by endogenous tissues. Taking inspiration from basic composition of the mammalian bones, composed of collagen, apatite and a number of substitution ions, among them magnesium (Mg2+), in this work, novel composite scaffolds composed of collagen(10%)-hydroxyapatite (HAp)(90%) and collagen(10%)-HAp(80%)-Mg(10%) were developed. The lyophilization was used for composites preparation. An insight into the nanostructural nature of the developed scaffolds was performed by Scanning Electron Microscopy coupled with Energy Dispersive X-Ray and Transmission Electron Microscopy coupled with Energy Dispersive X-Ray. The HAp nanocrystallite clusters and Mg nanoparticles were homogeneously distributed within the scaffolds and adherent to the collagen fibrils. The samples were tested for degradation in Simulated Body Fluid (SBF) solution by soaking for up to 28 days. The release of Mg from collagen(10%)-HAp(80%)-Mg(10%) composite during the period of up to 21 days was attested, this composite being characterized by a decreased degradation rate with respect to the composite without Mg. The developed composite materials are promising for applications as bone substitute materials favouring bone healing and regeneration

Controlling the Degradation Rate of Biodegradable Mg–Zn-Mn Alloys for Orthopedic Applications by Electrophoretic Deposition of Hydroxyapatite Coating

Magnesium alloys as bioresorbable materials with good biocompatibility have raised a growing interest in the past years in temporary implant manufacturing, as they offer a steady resorption rate and optimal healing in the body. Magnesium exhibits tensile strength properties similar to those of natural bone, which determines its application in load-bearing mechanical medical devices. In this paper, we investigated the biodegradation rate of Mg-Zn-Mn biodegradable alloys (ZMX410 and ZM21) before and after coating them with hydroxyapatite (HAP) via the electrophoretic deposition method. The experimental samples were subjected to corrosion tests to observe the effect of HAP deposition on corrosion resistance and, implicitly, the rate of biodegradation of these in simulated environments. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) provided detailed information on the quality, structure, and morphology of the HAP coating. The obtained results demonstrate that coating of Mg-Zn-Mn alloys by HAP led to the improvement of corrosion resistance in simulated environments, and that the HAP coating could be used in order to control the biodegradation rate

Electrochemical and In Vitro Biological Evaluation of Bio-Active Coatings Deposited by Magnetron Sputtering onto Biocompatible Mg-0.8Ca Alloy

The use of resorbable magnesium alloys in the design of implants represents a new direction in the healthcare domain. Two main research avenues are currently explored for developing or improving metallic biomaterials: (i) increase of their corrosion resistance by designed compositional and structural modifications, and (ii) functionalization of their surfaces by coating with ceramic or polymeric layers. The main objective of this work was to comparatively assess bio-functional coatings (i.e., highly-crystallized hydroxyapatite and silica-rich glass) deposited by radio-frequency magnetron sputtering (RF-MS) on a biodegradable Mg-0.8Ca alloy (0.8 wt.% of Ca). After probing their morphology (by scanning electron microscopy) and structure (by Fourier transform infrared spectroscopy and grazing incidence X-ray diffraction), the corrosion resistance of the RF-MS coated Mg-0.8Ca substrates was electrochemically tested (in synthetic biological media with different degrees of biomimicry), and their cytocompatibility was assessed in osteoblast and fibroblast cell cultures. By collective assessment, the most promising performances, in terms of mass loss (~7% after 12 days), hydrogen release rate (~6 mL/cm2 after 12 days), electrochemical corrosion parameters and cytocompatibility, were obtained for the crystalline HA coating

Additive Manufactured Magnesium-Based Scaffolds for Tissue Engineering

Additive manufacturing (AM) is an important technology that led to a high evolution in the manufacture of personalized implants adapted to the anatomical requirements of patients. Due to a worldwide graft shortage, synthetic scaffolds must be developed. Regarding this aspect, biodegradable materials such as magnesium and its alloys are a possible solution because the second surgery for implant removal is eliminated. Magnesium (Mg) exhibits mechanical properties, which are similar to human bone, biodegradability in human fluids, high biocompatibility, and increased ability to stimulate new bone formation. A current research trend consists of Mg-based scaffold design and manufacture using AM technologies. This review presents the importance of biodegradable implants in treating bone defects, the most used AM methods to produce Mg scaffolds based on powder metallurgy, AM-manufactured implants properties, and in vitro and in vivo analysis. Scaffold properties such as biodegradation, densification, mechanical properties, microstructure, and biocompatibility are presented with examples extracted from the recent literature. The challenges for AM-produced Mg implants by taking into account the available literature are also discussed

In Vitro Antibacterial Activity of Some Plant Essential Oils against Four Different Microbial Strains

This study evaluates the antimicrobial and antioxidant activities of five essential oils (EO): pine oil, thyme oil, sage oil, fennel oil, and eucalyptus essential oils. To identify the chemical composition of the essential oils, we used gas chromatography coupled to a mass spectrometer (GC-MS). EO are predominantly characterized by the presence of monoterpene hydrocarbons and oxygenated monoterpenes, except in the case of fennel essential oil which contains phenylpropanoids as its main components. The antimicrobial activity of the EO was highlighted on four standard microbial strains (two Gram-negative strains-Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853; one Gram-positive strain Staphylococcus aureus ATCC 25923, and one yeast strain-Candida albicans ATCC 10231). Antimicrobial activity was assessed by measuring the diameter of the inhibition zone, and by determining the values of the minimum inhibitory concentration (MIC) and minimum concentration of biofilm eradication (MCBE). Analyzing the diameter values of the inhibition zones we observed increased efficiency of thyme essential oil, which showed the highest values for all tested microbial species. The results of tests performed in a liquid confirm the high sensitivity of the standard strain Escherichia coli ATCC 25922 to the action of all essential oils, the lowest values of MIC being recorded for sage and thyme essential oils. For the most essential oils tested in this study, the MCBE values are close to the MIC values, except for the pine EO which seems to have stimulated the adhesion of the yeast strain at concentrations lower than 5%. The study highlights the antimicrobial activity of the tested essential oils on Gram-positive and Gram-negative strains

Mechanical and Magnetic Properties Variation in Non-Oriented Electrical Steels with Different Cutting Technology: A Review

The problem of energy consumption reduction establishes important challenges for electric motor producers in the framework of new international regulations regarding the conditions that must be accomplished by motors in the near future. One of the most important topics is related to the core loss decrease directly linked to the effect of electrical steel degradation induced by the cutting technology. Understanding exactly how this phenomenon occurs by analyzing the chemical, mechanical, crystallographic, magnetic domain, and magnetic properties is of utmost importance when manufacturing processes must be changed and adapted to a new market characterized by high-efficiency motors. Today, mechanical and laser cutting technologies are the most used because of their reduced price and high-speed process. Still, unfortunately, these methods are not the best due to the fact that they lead, in most cases, to a high value of magnetic core losses, low electromagnetic torque, and hence reduced efficiency. This review paper shows that non-conventional technologies such as water jetting and electroerosion could be applied if proper modifications are added. This paper’s main idea is to present a comprehensive study regarding the impact of cutting technologies on microhardness and residual stresses, crystallographic texture, magnetic domain structure, and magnetic properties of some non-oriented electrical steels used in motor production. It provides a detailed analysis of the abovementioned aspects by including the authors’ research and findings in the wider context of other research group contributions. It also offers a general idea of the mechanisms present at the macro- and microscopic levels. The readers can find some of the most used analytical models, including the cutting process’s damaged effect on the magnetic properties’ variation based on a simple mathematical approach and examples of finite element modeling performed on real motor designs implemented in various programs. Last but not least, some practical implementations of the cutting procedure’s influence on motor working conditions are presented in the last section of the paper. It provides an up-to-date analysis regarding how the cutting method should be included in high-efficiency motor production by emphasizing the importance of the topic and identifying where supplementary research must be undertaken. From the investigated literature, by analyzing specific sample geometries associated with different characterization methods, it can be concluded that all the cutting technologies have an important contribution to the mechanical and magnetic quantities. When the magnetic core of an electric motor is produced through non-conventional methods, the overall influence of the cutting procedure has a low percentage in the motor efficiency, as presented in this paper

Microstructure and Corrosion Behaviour of Mg-Ca and Mg-Zn-Ag Alloys for Biodegradable Hard Tissue Implants

Trauma orthopaedic surgery was the first domain to use degradable metallic implants made of magnesium alloys since the early 20th century. Unfortunately, the major limitation that consists of rapid degradation and subsequent implant failure, which occur in physiological environments with a pH between 7.4 and 7.6, prevents its widespread application. The biggest challenge in corrosion assay is the choice of the testing medium in order to reproduce more closely in vivo conditions. The current study was focused on two Mg-Zn-Ag alloys (Mg7Zn1Ag and Mg6Zn3Ag) and the Mg1Ca alloy. Dulbecco’s Modified Eagle Medium (DMEM) and Kokubo’s simulated body fluid solution (SBF) were selected as testing mediums and we follow the corrosion evaluation by the corrosion rate and mass loss. Also, the corrosion behaviour was interpreted in correlation with the microstructural features and alloying elements of the experimental magnesium-based alloys revealed by optical microscopy (OM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDX). The experimental results highlight the more corrosive nature of the SBF environment and that a higher percentage of silver (2.5 wt.%) exhibited a better corrosion resistance. We consider that the magnesium alloy Mg6Zn3Ag showed valuable biodegradation characteristics to be considered as raw materials for manufacturing small trauma implants

Bone Cements Used for Hip Prosthesis Fixation: The Influence of the Handling Procedures on Functional Properties Observed during In Vitro Study

The failure of hip prostheses is a problem that requires further investigation and analysis. Although total hip replacement is an extremely successful operation, the number of revision surgeries needed after this procedure is expected to continue to increase due to issues with both bone cement types and cementation techniques (depending on the producer). To conduct a comparative analysis, as a surgeon prepared the bone cement and introduced it in the body, this study’s team of researchers prepared three types of commercial bone cements with the samples mixed and placed them in specimens, following the timeline of the surgery. In order to evaluate the factors that influenced the chemical composition and structure of each bone cement sample under specific intraoperative conditions, analyses of the handling properties, mechanical properties, structure, and composition were carried out. The results show that poor handling can impede prosthesis–cement interface efficacy over time. Therefore, it is recommended that manual mixing be avoided as much as possible, as the manual preparation of the cement can sometimes lead to structural unevenness