Evaluation of the in vitro biocompatibility of PMMA/high-load HA/carbon nanostructures bone cement formulations

Effect of surface modification of graphene oxide with a reactive silane coupling agent on the mechanical properties and biocompatibility of acrylic bone cements

Carbon allotrope materials (i.e. carbon nanotubes (CNTs), graphene, graphene oxide (GO)), have been used to reinforce acrylic bone cement. Nevertheless, the intrinsic incompatibility among the above materials produces a deficient interphase. Thus, in this work, the effect of the content of functionalized graphene oxide with a reactive silane on the mechanical properties and cell adhesion of acrylic bone cement was studied. GO was obtained by an oxidative process on natural graphite; subsequently, GO was functionalized with 3-methacryloxypropyltrimethoxysilane (MPS) to enhance the interphase between the graphenic material and acrylic polymeric matrix. Pristine GO and functionalized graphene oxide (GO-MPS) were characterized physicochemically (XPS, XRD, FTIR, and Raman) and morphologically (SEM and TEM). Silanized GO was added into the acrylic bone cement at different concentrations; the resulting materials were characterized mechanically, and their biocompatibility was also evaluated. The physicochemical characterization results showed that graphite was successfully oxidized, and the obtained GO was successfully functionalized with the silane coupling agent (MPS). SEM and TEM images showed that the GO is composed of few stacked layers. Compression testing results indicated a tendency of increasing stiffness and toughness of the acrylic bone cements at low concentration of functionalized GO. Additionally, the bending testing results showed a slightly increase in bone cement strain with the incorporation of GO-MPS. Finally, all samples exhibited cell viability higher than 70%, which means that materials are considered non-cytotoxic, according to the ISO 10993-5 standard.

Progress of research on graphene and its derivatives in bone and cartilage repair

In recent years, graphene and its derivatives have gained wide attention in the biomedical field due to their good physicochemical properties, biocompatibility, and bioactivity. Its good antibacterial, osteoinductive and drug-carrying properties make it a promising application in the field of orthopedic biomaterials. This paper introduces the research progress of graphene and its derivatives in bone tissue engineering and cartilage tissue engineering and presents an outlook on the future development of graphene-based materials in orthopedics.

Stretchable, conductive, breathable and moisture-sensitive e-skin based on CNTs/graphene/GelMA mat for wound monitoring

Deep skin wound needs a long wound healing process, in which external force on skin around wound can result in a sharp pain, wound re-damage and interstitial fluid flowing out, increasing the risk of deterioration and even amputation. While the conventional wound dressings cannot provide timely feedback of abnormal wound status and lose best time for wound treatment, real-time monitoring wound status is thus urgently needed for wound management. In this work, a breathable and stretchable electronic skin (i.e., e-skin) named CNTs/graphene/GelMA mat has been developed through electrospinning, ice-templating and in-situ loading method for evaluating wound status. The obtained porosity, swelling ratio and vapor transmission rate of the CNTs/graphene/GelMA mat are 55 %, 180 % and 3378.2 h^-1 day^-1, respectively. And owing to the good porous, nanofibrous architecture and excellent breathability of the mat, L929 cells grow and well spread on the CNTs/graphene/GelMA mat. In addition, the gauge factors of the prepared conductive CNTs/graphene/GelMA mat as a strain sensor are 15.4 and 72.9 in the strain ranges of 0-70 % and 70-85 %, respectively, matching the mechanical performance of human skin. The sensitivity coefficient of the mat for moisture sensing is 12.05, indicating its high efficiency for monitoring and warning interstitial fluid outflow from wound. Furthermore, the integration of CNTs/graphene/GelMA mat with a portable device is feasible to monitor strain and moisture on a rat model with abdominal wound. The healing process of the wounds treated with CNTs/graphene/GelMA mat is similar to that of GelMA mat, indicating that the dosage of CNTs and graphene in the CNTs/graphene/GelMA mat has negligible effect on the mat histocompatibility. The CNTs/graphene/GelMA mat demonstrates the application potential in wound management, home medical diagnosis and human-machine interactions.

Antimicrobial PMMA Bone Cement Containing Long Releasing Multi-Walled Carbon Nanotubes

Prosthetic joint infections (PJIs) ensued from total joint replacement (TJR) pose a severe threat to patients that involve poor health outcomes, severe pain, death (in severe cases), and negative influence patients' quality of life. Antibiotic-loaded bone cement (ALBC) is frequently used for the prevention and treatment of PJI. This work aims to study gentamicin release from carbon nanotubes (CNTs) incorporated in polymethyl methacrylate (PMMA) bone cement to prolong release over several weeks to provide prophylaxis from PJIs after surgery. Different CNT concentrations were tested with the presence of gentamicin as a powder or preloaded onto carboxyl functionalized CNTs. The different types of bone cement were tested for drug release, mechanical properties, water uptake, antimicrobial properties, and cytocompatibility with human osteoblast cells (MTT, LDH, alizarin red, and morphology). Results showed prolonged release of gentamicin from CNT-loaded bone cements over several weeks compared to gentamicin-containing bone cement. Additionally, the presence of CNT enhanced the percentage of gentamicin released without adversely affecting the nanocomposite mechanical and antimicrobial properties needed for performance. Cytotoxicity testing showed non-inferior performance of the CNT-containing bone cement to the equivalent powder containing cement. Therefore, the developed nanocomposites may serve as a novel PMMA bone cement to prevent PJIs.

Cytotoxicity and cell response of preosteoblast in calcium sulfate-augmented PMMA bone cement

Poly(methyl methacrylate) (PMMA) has been widely used in orthopedic applications, but bone ingrowth and toxic monomer release are drawback of this material. Particle reinforcement with osteoconductive substitute, such as calcium sulfate (CaSO₄), is one of the solutions used to modify PMMA bone cement. The current study investigated the mechanical, chemical and biological properties of CaSO₄-augmented bone cement. Mechanical strength was measured by a material testing machine. The concentration of methyl methacrylate (MMA) monomer from the various formulations of PMMA mixed with CaSO₄was measured by ultra-performance liquid chromatography (UPLC). CCK-8 assay and ALP assay were performed to evaluate cytotoxicity of released MMA monomer and cell differentiation. The attachment of cells to CaSO₄-augmented bone cement discs was observed by confocal and scanning electron microscopy, and surface topography was also evaluated by atomic force microscopy. The results revealed that increased CaSO₄weight ratios led to compromised mechanical strength and increased MMA monomer release. Cell density and cell differentiation on CaSO₄-augmented bone cement discs were decreased at CaSO₄weight ratios above 10%. In addition, the presence of micropores on the surface and surface roughness were both increased for PMMA composite discs containing higher levels of CaSO₄. These results demonstrated that fewer MC3T3-E1 cells on the surface of CaSO₄-PMMA composites was correlated to increased MMA monomer release, micropore number and surface roughness. In summary, the augmentation of a higher proportion of CaSO₄(>10 wt. %) to PMMA did not promote the biological properties of traditional PMMA bone cement.

Optimization of Mechanical and Setting Properties in Acrylic Bone Cements Added with Graphene Oxide

The extended use of acrylic bone cements (ABC) in orthopedics presents some disadvantages related to the generation of high temperatures during methyl methacrylate polymerization, thermal tissue necrosis, and low mechanical properties. Both weaknesses cause an increase in costs for the health system and a decrease in the patient’s quality of life due to the prosthesis’s loosening. Materials such as graphene oxide (GO) have a reinforcing effect on ABC’s mechanical and setting properties. This article shows for the first time the interactions present between the factors sonication time and GO percentage in the liquid phase, together with the percentage of benzoyl peroxide (BPO) in the solid phase, on the mechanical and setting properties established for cements in the ISO 5833-02 standard. Optimization of the factors using a completely randomized experimental design with a factorial structure resulted in selecting nine combinations that presented an increase in compression, flexion, and the setting time and decreased the maximum temperature reached during the polymerization. All of these characteristics are desirable for improving the clinical performance of cement. Those containing 0.3 wt.% of GO were highlighted from the selected formulations because all the possible combinations of the studied factors generate desirable properties for the ABC.

Bioactive, Ion-Releasing PMMA Bone Cement Filled with Functional Graphenic Materials

Graphene oxide and functionalized graphenic materials (FGMs) have promise as platforms for imparting programmable bioactivity to poly(methyl methacrylate) (PMMA)-based bone cement. To date, however, graphenic fillers have only been feasible in PMMA cements at extremely low loadings, limiting the bioactive effects. At higher loadings, graphenic fillers decrease cement strength by aggregating and interfering with curing process. Here, these challenges are addressed by combining bioactive FGM fillers with a custom cement formulation. These cements contain an order of magnitude more graphenic filler than previous reports. Even at 1 wt% FGM, these cements have compressive strengths of 78- 88 MPa, flexural strengths of 74-81 MPa, and flexural stiffnesses of 1.8-1.9 GPa, surpassing the ASTM requirements for bone cement and competing with traditional PMMA cement. Further, by utilizing designer FGMs with programmed bioactivity, these cements demonstrate controlled release of osteogenic calcium ions (releasing a total of 5 ± 2 µmol of Ca2+ per gram of cement over 28 d) and stimulate a 290% increase in expression of alkaline phosphatase in human mesenchymal stem cells in vitro. Also, design criteria are described to guide creation of future generations of bone cements that utilize FGMs as platforms to achieve dynamic biological activity.

The Role of Chitosan and Graphene Oxide in Bioactive and Antibacterial Properties of Acrylic Bone Cements

Acrylic bone cements (ABC) are widely used in orthopedics for joint fixation, antibiotic release, and bone defect filling, among others. However, most commercially available ABCs exhibit a lack of bioactivity and are susceptible to infection after implantation. These disadvantages generate long-term loosening of the prosthesis, high morbidity, and prolonged and expensive treatments. Due to the great importance of acrylic bone cements in orthopedics, the scientific community has advanced several efforts to develop bioactive ABCs with antibacterial activity through several strategies, including the use of biodegradable materials such as chitosan (CS) and nanostructures such as graphene oxide (GO), with promising results. This paper reviews several studies reporting advantages in bioactivity and antibacterial properties after incorporating CS and GO in bone cements. Detailed information on the possible mechanisms by which these fillers confer bioactive and antibacterial properties to cements, resulting in formulations with great potential for use in orthopedics, are also a focus in the manuscript. To the best of our knowledge, this is the first systematic review that presents the improvement in biological properties with CS and GO addition in cements that we believe will contribute to the biomedical field.

Acrylic Bone Cements Modified with Graphene Oxide: Mechanical, Physical, and Antibacterial Properties

Bacterial infections are a common complication after total joint replacements (TJRs), the treatment of which is usually based on the application of antibiotic-loaded cements; however, owing to the increase in antibiotic-resistant microorganisms, the possibility of studying new antibacterial agents in acrylic bone cements (ABCs) is open. In this study, the antibacterial effect of formulations of ABCs loaded with graphene oxide (GO) between 0 and 0.5 wt.% was evaluated against Gram-positive bacteria: Bacillus cereus and Staphylococcus aureus, and Gram-negative ones: Salmonella enterica and Escherichia coli. It was found that the effect of GO was dependent on the concentration and type of bacteria: GO loadings ≥0.2 wt.% presented total inhibition of Gram-negative bacteria, while GO loadings ≥0.3 wt.% was necessary to achieve the same effect with Gram-positives bacteria. Additionally, the evaluation of some physical and mechanical properties showed that the presence of GO in cement formulations increased wettability by 17%, reduced maximum temperature during polymerization by 19%, increased setting time by 40%, and increased compressive and flexural mechanical properties by up to 17%, all of which are desirable behaviors in ABCs. The formulation of ABC loading with 0.3 wt.% GO showed great potential for use as a bone cement with antibacterial properties.

Polymethyl Methacrylate-Based Bone Cements Containing Carbon Nanotubes and Graphene Oxide: An Overview of Physical, Mechanical, and Biological Properties

Every year, millions of people in the world get bone diseases and need orthopedic surgery as one of the most important treatments. Owing to their superior properties, such as acceptable biocompatibility and providing great primary bone fixation with the implant, polymethyl methacrylate (PMMA)-based bone cements (BCs) are among the essential materials as fixation implants in different orthopedic and trauma surgeries. On the other hand, these BCs have some disadvantages, including Lack of bone formation and bioactivity, and low mechanical properties, which can lead to bone cement (BC) failure. Hence, plenty of studies have been concentrating on eliminating BC failures by using different kinds of ceramics and polymers for reinforcement and also by producing composite materials. This review article aims to evaluate mechanical properties, self-setting characteristics, biocompatibility, and bioactivity of the PMMA-based BCs composites containing carbon nanotubes (CNTs), graphene oxide (GO), and carbon-based compounds. In the present study, we compared the effects of CNTs and GO as reinforcement agents in the PMMA-based BCs. Upcoming study on the PMMA-based BCs should concentrate on trialing combinations of these carbon-based reinforcing agents as this might improve beneficial characteristics.

Incorporation of chitosan/graphene oxide nanocomposite in to the PMMA bone cement: Physical, mechanical and biological evaluation

One of the most popular types of bone cements is polymethylmethacrylate (PMMA). The properties of this bone cement have attracted many researchers effort to modify its properties. In this study, after preparation of chitosan (Cs) powder and Cs/graphene oxide (GO) nanocomposite powder, they were added homogeneously to the PMMA bone cement with different percentages. The results showed that the addition of 25 wt% of Cs/GO nanocomposite powder to the PMMA bone cement cause to increase the compressive strength by 16.2%, the compressive modulus by 69.1% and the bending strength by 24.0%. The obtained results showed that by adding Cs/GO nanocomposite powder to the PMMA bone cement, setting time and injectability were increased, maximum temperature was decreased and apatite-like deposition was increased after 4 weeks of incubation in SBF solution. The results of MG-63 cell culture confirmed the improvement of cell viability, growth and cell adhesion for 25 wt% PMMA-Cs/GO composite bone cement. Therefore, it can be concluded that 25 wt% PMMA-Cs/GO composite bone cement with improved mechanical, physical and biological properties can be a good replacement for common commercial bone cements in orthopedic applications.

Graphene Oxide and Graphene Reinforced PMMA Bone Cements: Evaluation of Thermal Properties and Biocompatibility

The incorporation of well-dispersed graphene oxide (GO) and graphene (G) has been demonstrated as a promising solution to improve the mechanical performance of polymethyl methacrylate (PMMA) bone cements in an attempt to enhance the long-term survival of the cemented orthopaedic implants. However, to move forward with the clinical application of graphene-based PMMA bone cements, it is necessary to ensure the incorporation of graphene-based powders do not negatively affect other fundamental properties (e.g., thermal properties and biocompatibility), which may compromise the clinical success of the implant. In this study, the effect of incorporating GO and G on thermal properties, biocompatibility, and antimicrobial activity of PMMA bone cement was investigated. Differential scanning calorimetry studies demonstrated that the extent of the polymerisation reaction, heat generation, thermal conductivity, or glass transition temperature were not significantly (p > 0.05) affected by the addition of the GO or G powders. The cell viability showed no significant difference (p > 0.05) in viability when MC3-T3 cells were exposed to the surface of G- or GO-PMMA bone cements in comparison to the control. In conclusion, this study demonstrated the incorporation of GO or G powder did not significantly influence the thermal properties or biocompatibility of PMMA bone cements, potentially allowing its clinical progression.

Poly (Methyl Methacrylate)/Biphasic Calcium Phosphate/Nano Graphene Bone Cement for Orthopedic Application

Background:

The aim of this study was to make a bioactive bone cement based on poly (methyl methacrylate) (PMMA) with suitable mechanical properties.

Methods:

PMMA has been modified by fabricating a composite consisting of biphasic calcium phosphate (BCP) 68 wt%, PMMA 31 wt% and graphene (Gr) 1 wt% (PMMA/BCP/Gr), 32 wt% of PMMA, and 68 wt% of BCP (PMMA/BCP) and pure PMMA by milling, mixing with monomer liquid, and casting. The modified cements were evaluated regarding mechanical properties, bioactivity, degradation rate, and biocompatibility.

Results:

The scanning electron microscopy (SEM) images of hydroxyapatite (HA) formed on samples surface after 28 days of immersion in simulated body fluid (SBF) demonstrated that bioactivity was obtained due to the addition of BCP, and the degradation rate of the cement was enhanced as well. Investigations of mechanical properties revealed that BCP increased the elastic modulus of PMMA more than 1.5 times, but predictably decreased elongation. The addition of 1 wt% Gr increased elongation and yield strength from 16.39% ± 1.02% and 61.67 ± 1.52 Mpa for PMMA/BCP to 35.18% ± 2.42% and 78.40 ± 2.06 Mpa for PMMA/BCP/Gr, respectively. MG63 cells survival and proliferation improved from 127.55% ± 7.03% for PMMA to 201.41% ± 10.7% for PMMA/BCP/Gr on Day 4 of culture.

Conclusion:

According to the obtained results of mechanical and biological tests, it seems that new PMMA/BCP/Gr bone cement has a potentiality for usage in orthopedic applications.

Calcium sulfate bone cements with nanoscaled silk fibroin as inducer

Both nanostructures and conformations of different protein/polysaccharide additives have critical influence on the performance of calcium sulfate (CS) bone cements. Silk fibroin (SF) as matrix and additives has been introduced to develop bone scaffolds and cements. Here, β-sheet-rich SF nanofibers (SFF) was used to tune the solidification of CS, achieving better mechanical and biological properties. The ratio of SFF was adjusted to further optimize CS functions. Compared to that regulated with natural silk fibers (NSF) and SF solutions (SFS), the SFF-induced CS showed smaller size and more filament structures. Better mechanical properties were achieved, suggesting the superiority of the SFF as the solidifying solution to combine with α-calcium sulfate hemihydrate (α-CSH) at the same liquid/solid (L/S) ratio. Scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, setting time, porosity, mechanical performance test, degradation performance test, and water resistance test were used to demonstrate the properties of this bone repair cement. Cell culture experiments in vitro was used to evaluate the biocompatibility of this composited material. In conclusion, the results demonstrated that nanofibers was a better form of SF in the modification of CSH cement. And the research conducted in this article on improving the mechanical and biological properties of CSH would supported the reference for later clinical experiments. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2611-2619, 2019.

Luminescence of Eu3+ ions in hybrid polymer-inorganic composites based on poly(methyl methacrylate) and zirconia nanoparticles

Spherical nanoparticles of ZrO₂ with 2 and 10 mol% EuO_1.5 up to 20 nm size were prepared by the method of hydrothermal synthesis for luminescent functionalization of the polymer-inorganic nanocomposites based on poly(methyl methacrylate). Surface modification of oxide nanoparticles was carried out by 3-(trimethoxysilyl)propyl methacrylate, dimethoxymethylvinyl silane and 2-hydroxyethyl methacrylate to provide uniform distribution and to prevent agglomeration of nanosized filler in the polymer matrix. Polymer-inorganic composites were synthesized by in situ free radical polymerization in bulk. Structuring of ZrO₂ -EuO_1.5 nanoparticles in the poly(methyl methacrylate) was studied by very-small-angle neutron scattering. According to the results, the dependence of photoluminescent properties of ZrO₂ -EuO_1.5 nanoparticles on the content of lanthanide, the symmetry of the crystal field, surface treatment and the polymer matrix were established. A correlation was shown between Stark splitting in luminescence spectra of ZrO₂ -EuO_1.5 nanoparticles and their phase composition. Using MMT-assay it was shown that composites based on poly(methyl methacrylate) and ZrO₂ -EuO_1.5 nanoparticles do not have cytotoxic properties, which makes it possible to use them as prosthesis materials with contrasted and luminescent imaging properties.

Safety, osseointegration, and bone ingrowth analysis of PMMA-based porous cement on animal metaphyseal bone defect model

Bone defects created after curettage of benign bone tumors are customarily filled with solid poly(methyl methacrylate) (PMMA) or other bone substitutes. In this study, we depicted a porous PMMA-based cement (produced by mixing sodium bicarbonate and citric acid) and evaluated the prospect of its clinic application. Cement samples were characterized by high-performance liquid chromatography (HPLC) coupled to mass spectrometry and its cytotoxicity evaluated in fibroblast cultures. Implantation in rabbits allowed the histologic analysis of bone, kidneys, and liver for toxicity and coagulation tests, and MRI images for hemostasis evaluation. Osseointegration was analyzed through radiography, microtomography (micro-CT), SEM, and histology of sheep specimens. Rabbit specimens were analyzed 1, 4, and 7 days after implantation of porous or solid bone cement in 6.0 mm femoral defects. Sheep specimens were analyzed 3 and 6 months after implantation or not of porous or solid cement in 15.0 mm subchondral tibial defects. The production process did not release any detectable toxic substance but slightly reduced fibroblast proliferation in vitro. Until 7 days after surgery, no local or systemic alterations could be detected in histology, or hematoma formation in histology or MRI. Sheep implants showed 6 mm linear ingrowth from the bone-cement interface and 20% bone ingrowth considering the whole defect area. Radiography, micro-CT, SEM, and histology confirmed these findings. We conclude that our porous PMMA-based cement is an attractive alternative treatment for bone defect filling that combines osseointegration and early weight bearing. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 649-658, 2018.

Polymeric Biomaterials for Medical Implants and Devices

In this review article, we focus on the various types of materials used in biomedical implantable devices, including the polymeric materials used as substrates and for the packaging of such devices. Polymeric materials are used because of the ease of fabrication, flexibility, and their biocompatible nature as well as their wide range of mechanical, electrical, chemical, and thermal behaviors when combined with different materials as composites. Biocompatible and biostable polymers are extensively used to package implanted devices, with the main criteria that include gas permeability and water permeability of the packaging polymer to protect the electronic circuit of the device from moisture and ions inside the human body. Polymeric materials must also have considerable tensile strength and should be able to contain the device over the envisioned lifetime of the implant. For substrates, structural properties and, at times, electrical properties would be of greater concern. Section 1 gives an introduction of some medical devices and implants along with the material requirements and properties needed. Different synthetic polymeric materials such as polyvinylidene fluoride, polyethylene, polypropylene, polydimethylsiloxane, parylene, polyamide, polytetrafluoroethylene, poly(methyl methacrylate), polyimide, and polyurethane have been examined, and liquid crystalline polymers and nanocomposites have been evaluated as biomaterials that are suitable for biomedical packaging (section 2). A summary and glimpse of the future trend in this area has also been given (section 3). Materials and information used in this manuscript are adapted from papers published between 2010 and 2015 representing the most updated information available on each material.