Carbon Nanotubes and Graphene as Nanoreinforcements in Metallic Biomaterials: a Review

Antibacterial conductive self-healing hydrogel wound dressing with dual dynamic bonds promotes infected wound healing

In clinical applications, there is a lack of wound dressings that combine efficient resistance to drug-resistant bacteria with good self-healing properties. In this study, a series of adhesive self-healing conductive antibacterial hydrogel dressings based on oxidized sodium alginate-grafted dopamine/carboxymethyl chitosan/Fe3+ (OSD/CMC/Fe hydrogel)/polydopamine-encapsulated poly(thiophene-3-acetic acid) (OSD/CMC/Fe/PA hydrogel) were prepared for the repair of infected wound. The Schiff base and Fe3+ coordination bonds of the hydrogel structure are dynamic bonds that can be repaired automatically after the hydrogel network is disrupted. Macroscopically, the hydrogel exhibits self-healing properties, allowing the hydrogel dressing to adapt to complex wound surfaces. The OSD/CMC/Fe/PA hydrogel showed good conductivity and photothermal antibacterial properties under near-infrared (NIR) light irradiation. In addition, the hydrogels exhibit tunable rheological properties, suitable mechanical properties, antioxidant properties, tissue adhesion properties and hemostatic properties. Furthermore, all hydrogel dressings improved wound healing in the infected full-thickness defect skin wound repair test in mice. The wound size repaired by OSD/CMC/Fe/PA3 hydrogel + NIR was much smaller (12%) than the control group treated with Tegaderm™ film after 14 days. In conclusion, the hydrogels have high antibacterial efficiency, suitable conductivity, great self-healing properties, good biocompatibility, hemostasis and antioxidant properties, making them promising candidates for wound healing dressings for the treatment of infected skin wounds.

Biomaterials as Implants in the Orthopedic Field for Regenerative Medicine: Metal versus Synthetic Polymers

Patients suffering bone fractures in different parts of the body require implants that will enable similar function to that of the natural bone that they are replacing. Joint diseases (rheumatoid arthritis and osteoarthritis) also require surgical intervention with implants such as hip and knee joint replacement. Biomaterial implants are utilized to fix fractures or replace parts of the body. For the majority of these implant cases, either metal or polymer biomaterials are chosen in order to have a similar functional capacity to the original bone material. The biomaterials that are employed most often for implants of bone fracture are metals such as stainless steel and titanium, and polymers such as polyethene and polyetheretherketone (PEEK). This review compared metallic and synthetic polymer implant biomaterials that can be employed to secure load-bearing bone fractures due to their ability to withstand the mechanical stresses and strains of the body, with a focus on their classification, properties, and application.

A Short Review on Nanostructured Carbon Containing Biopolymer Derived Composites for Tissue Engineering Applications

The development of new scaffolds and materials for tissue engineering is a wide and open realm of material science. Among solutions, the use of biopolymers represents a particularly interesting area of study due to their great chemical complexity that enables creation of specific molecular architectures. However, biopolymers do not exhibit the properties required for direct application in tissue repair-such as mechanical and electrical properties-but they do show very attractive chemical functionalities which are difficult to produce through in vitro synthesis. The combination of biopolymers with nanostructured carbon fillers could represent a robust solution to enhance composite properties, producing composites with new and unique features, particularly relating to electronic conduction. In this paper, we provide a review of the field of carbonaceous nanostructure-containing biopolymer composites, limiting our investigation to tissue-engineering applications, and providing a complete overview of the recent and most outstanding achievements.

MWCNTs-TiO2 Incorporated-Mg Composites to Improve the Mechanical, Corrosion and Biological Characteristics for Use in Biomedical Fields

This study attempts to synthesize MgZn/TiO₂-MWCNTs composites with varying TiO₂-MWCNT concentrations using mechanical alloying and a semi-powder metallurgy process coupled with spark plasma sintering. It also aims to investigate the mechanical, corrosion, and antibacterial properties of these composites. When compared to the MgZn composite, the microhardness and compressive strength of the MgZn/TiO₂-MWCNTs composites were enhanced to 79 HV and 269 MPa, respectively. The results of cell culture and viability experiments revealed that incorporating TiO₂-MWCNTs increased osteoblast proliferation and attachment and enhanced the biocompatibility of the TiO₂-MWCNTs nanocomposite. It was observed that the corrosion resistance of the Mg-based composite was improved and the corrosion rate was reduced to about 2.1 mm/y with the addition of 10 wt% TiO₂-1 wt% MWCNTs. In vitro testing for up to 14 days revealed a reduced degradation rate following the incorporation of TiO₂-MWCNTs reinforcement into a MgZn matrix alloy. Antibacterial evaluations revealed that the composite had antibacterial activity, with an inhibition zone of 3.7 mm against Staphylococcus aureus. The MgZn/TiO₂-MWCNTs composite structure has great potential for use in orthopedic fracture fixation devices.

Microstructures, mechanical and corrosion properties of graphene nanoplatelet-reinforced zinc matrix composites for implant applications

Zinc (Zn)-based alloys and composites are gaining increasing interest as promising biodegradable implant materials due to their appropriate biodegradation rates and biological functionalities. However, the inadequate mechanical strength and ductility of pure Zn have restricted its application. In this study, Zn matrix composites (ZMCs) reinforced with 0.1-0.4 wt.% graphene nanoplatelets (GNP) fabricated via powder metallurgy were investigated as potential biodegradable implant materials. The microstructures, mechanical properties, and corrosion behaviors of the GNP-reinforced ZMCs were characterized using optical microscopy, scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, Raman spectroscopy, compression testing, and electrochemical and immersion testing in Hanks' balanced salt solution (HBSS). The microstructural study revealed that the GNP was uniformly dispersed in the ZMCs after ball milling and sintering at 420°C for 6 h. The microhardness, compressive yield strength, ultimate compressive strength, and compressive strain of the ZMC-0.2GNP were 69 HV, 123 MPa, 247 MPa, and 23 %, respectively, improvements of ∼ 18 %, 50%, ∼ 28%, and ∼ 15% compared to pure Zn. The corrosion rate of the ZMCs were lower than that of the pure Zn in HBSS, and the ZMC-0.2GNP composite exhibited the lowest corrosion rate of 0.09 mm/y as measured by electrochemical testing. Biocompatibility assessment indicated that the diluted extracts of pure Zn and GNP-reinforced ZMCs with concentrations of 12.5% and 6.25% exhibited no cytotoxicity after cell culturing for up to 5 days, and the diluted extracts of ZMC-0.2 GNP composite revealed more than 90% cell viability after cell culturing of 3 days, showing the satisfying cytocompatibility. STATEMENT OF SIGNIFICANCE: Biodegradable Zn is a promising candidate material for orthopedic implant applications. Nonetheless, the inadequate mechanical strength and ductility of pure Zn limited its clinical application. In this study, Zn matrix composites (ZMCs) reinforced with 0.1-0.4 wt.% graphene nanoplatelets (GNP) were developed via powder metallurgy, and the reinforcing efficacy of GNP on their mechanical properties was investigated. The addition of GNP significantly improved the compressive properties of ZMCs, with the Zn-0.2GNP composite exhibiting the best compressive properties, including 123 MPa compressive yield strength, 247 MPa ultimate compressive strength, and 22.9% compressive strain. Further, the 12.5% concentration extract of the ZMCs exhibited no cytotoxicity after cell culturing for 5 d toward SaOS2 cells.

PEEK for Oral Applications: Recent Advances in Mechanical and Adhesive Properties

Polyetheretherketone (PEEK) is a thermoplastic material widely used in engineering applications due to its good biomechanical properties and high temperature stability. Compared to traditional metal and ceramic dental materials, PEEK dental implants exhibit less stress shielding, thus better matching the mechanical properties of bone. As a promising medical material, PEEK can be used as implant abutments, removable and fixed prostheses, and maxillofacial prostheses. It can be blended with materials such as fibers and ceramics to improve its mechanical strength for better clinical dental applications. Compared to conventional pressed and CAD/CAM milling fabrication, 3D-printed PEEK exhibits excellent flexural and tensile strength and parameters such as printing temperature and speed can affect its mechanical properties. However, the bioinert nature of PEEK can make adhesive bonding difficult. The bond strength can be improved by roughening or introducing functional groups on the PEEK surface by sandblasting, acid etching, plasma treatment, laser treatment, and adhesive systems. This paper provides a comprehensive overview of the research progress on the mechanical properties of PEEK for dental applications in the context of specific applications, composites, and their preparation processes. In addition, the research on the adhesive properties of PEEK over the past few years is highlighted. Thus, this review aims to build a conceptual and practical toolkit for the study of the mechanical and adhesive properties of PEEK materials. More importantly, it provides a rationale and a general new basis for the application of PEEK in the dental field.

The improvement of periodontal tissue regeneration using a 3D-printed carbon nanotube/chitosan/sodium alginate composite scaffold

Periodontal disease is a common disease in the oral field, and many researchers are studying periodontal disease and try to find some biological scaffold materials to make periodontal tissue regenerative. In this study, we attempted to construct a carbon nanotube/chitosan/sodium alginate (CNT/CS/AL) ternary composite hydrogel and then prepare porous scaffold by 3D printing technology. Subsequently, characterizing the materials and testing the mechanical properties of the scaffold. Additionally, its effect on the proliferation of human periodontal ligament cells (hPDLCs) and its antibacterial effect on Porphyromonas gingivalis were detected. We found that CNT/CS/AL porous composite scaffolds with uniform pores could be successfully prepared. Moreover, with increasing CNT concentration, the degradation rate and the swelling degree of scaffold showed a downward trend. The compressive strength test indicated the elastic modulus of composite scaffolds ranged from 18 to 80 kPa, and 1% CNT/CS/AL group had the highest quantitative value. Subsequently, cell experiments showed that the CNT/CS/AL scaffold had good biocompatibility and could promote the proliferation of hPDLCs. Among 0.1%-1% CNT/CS/AL groups, the biocompatibility of 0.5% CNT/CS/AL scaffold performed best. Meanwhile, in vitro antibacterial experiments showed that the CNT/CS/AL scaffold had a certain bacteriostatic effect on P. gingivalis. When the concentration of CNT was more than 0.5%, the antimicrobial activity of composite scaffold was significantly promoted, and about 30% bacteria were inactivated. In conclusion, this 3D-printed CNT/CS/AL composite scaffold, with good material properties, biocompatibility and bacteriostatic activity, may be used for periodontal tissue regeneration, providing a new avenue for the treatment of periodontal disease.

Advances in Multifunctional Bioactive Coatings for Metallic Bone Implants

To fix the bone in orthopedics, it is almost always necessary to use implants. Metals provide the needed physical and mechanical properties for load-bearing applications. Although widely used as biomedical materials for the replacement of hard tissue, metallic implants still confront challenges, among which the foremost is their low biocompatibility. Some of them also suffer from excessive wear, low corrosion resistance, infections and shielding stress. To address these issues, various coatings have been applied to enhance their in vitro and in vivo performance. When merged with the beneficial properties of various bio-ceramic or polymer coatings remarkable bioactive, osteogenic, antibacterial, or biodegradable composite implants can be created. In this review, bioactive and high-performance coatings for metallic bone implants are systematically reviewed and their biocompatibility is discussed. Updates in coating materials and formulations for metallic implants, as well as their production routes, have been provided. The ways of improving the bioactive coating performance by incorporating bioactive moieties such as growth factors, osteogenic factors, immunomodulatory factors, antibiotics, or other drugs that are locally released in a controlled manner have also been addressed.

Preparation and Curing Mechanism of Modified Corn Straw by 3-Glycidyl Ether Oxypropyl Trimethoxysilane/Epoxy Resin Composites

A modified corn straw (CS)/epoxy resin (EP) composite was prepared using bisphenol A EP (i.e., E-51) as matrix, 2-methylimidazole as curing agent, and CS modified by 3-glycidyl ether oxypropyl trimethoxysilane (KHCS) as filler. Its chemical structure was characterized by Fourier transform infrared spectroscopy (FTIR). The dynamic thermodynamic properties, mechanical properties, flame retardant property, and fracture morphology were studied using dynamic mechanical analysis (DMA), a universal testing machine, a micro combustion calorimeter, and a scanning electron microscope (SEM), respectively. The effects of different contents of KHCS on various properties were discussed. The experimental result showed that the CS was bonded toKH560 by a covalent bond. The impact strength, tensile strength, and flexural strength of the composites were all improved compared with those of pure EP. When the content of KHCS was 15 wt%, the maximum impact strength of the composites was 3.31 kJ/m², which was 1.43 times that of the pure EP. The p HRR and THR of MCSEC-20 were 512.44 W/g and 25.03 kJ/g, respectively, which were 40.71% and 27.76% lower than those of pure EP, when the content of KHCS was 20 wt%. Moreover, the mechanism of the curing composites was investigated.

Conductive Hydrogel Conduits with Growth Factor Gradients for Peripheral Nerve Repair in Diabetics with Non-Suture Tape

Diabetic patients suffer from peripheral nerve injury with slow and incomplete regeneration owing to hyperglycemia and microvascular complications. This study develops a graphene-based nerve guidance conduit by incorporating natural double network hydrogel and a neurotrophic concentration gradient with non-invasive treatment for diabetics. GelMA/silk fibroin double network hydrogel plays quadruple roles for rapid setting/curing, suitable mechanical supporting, good biocompatibility, and sustainable growth factor delivery. Meanwhile, graphene mesh can improve the toughness of conduit and enhance conductivity of conduit for regeneration. Here, novel silk tapes show quick and tough adhesion of wet tissue by dual mechanism to replace suture step. The in vivo results demonstrate that gradient concentration of netrin-1 in conduit have better performance than uniform concentration caused by chemotaxis phenomenon for axon extension, remyelination, and angiogenesis. Altogether, GelMA/silk graphene conduit with gradient netrin-1 and dry double-sided adhesive tape can significantly promote repairing of peripheral nerve injury and inhibit the atrophy of muscles for diabetics.

Future Prospects for Clinical Applications of Nanocarbons Focusing on Carbon Nanotubes

Over the past 15 years, numerous studies have been conducted on the use of nanocarbons as biomaterials towards such applications as drug delivery systems, cancer therapy, and regenerative medicine. However, the clinical use of nanocarbons remains elusive, primarily due to short- and long-term safety concerns. It is essential that the biosafety of each therapeutic modality be demonstrated in logical and well-conducted experiments. Accordingly, the fundamental techniques for assessing nanocarbon biomaterial safety have become more advanced. Optimal controls are being established, nanocarbon dispersal techniques are being refined, the array of biokinetic evaluation methods has increased, and carcinogenicity examinations under strict conditions have been developed. The medical implementation of nanocarbons as a biomaterial is in sight. With a particular focus on carbon nanotubes, these perspectives aim to summarize the contributions to date on nanocarbon applications and biosafety, introduce the recent achievements in evaluation techniques, and clarify the future prospects and systematic introduction of carbon nanomaterials for clinical use through practical yet sophisticated assessment methods.

Graphene oxide encapsulated forsterite scaffolds to improve mechanical properties and antibacterial behavior

It is very desirable to have good antibacterial properties and mechanical properties at the same time for bone scaffolds. Graphene oxide (GO) can increase the mechanical properties and antibacterial performance, while forsterite (Mg2SiO4) as the matrix can increase forsterite/GO scaffolds' biological activity for bone tissue engineering. Interconnected porous forsterite scaffolds were developed by space holder processes for bone tissue engineering in this research. The forsterite/GO scaffolds had a porosity of 76-78% with pore size of 300-450 μm. The mechanism of the mechanical strengthening, antibacterial activity, and cellular function of the forsterite/GO scaffold was evaluated. The findings show that the compressive strength of forsterite/1wt.% GO scaffold (2.4±0.1 MPa) was significantly increased, in comparison to forsterite scaffolds without GO (1.4±0.1 MPa). Validation of the samples' bioactivity was attained by forming a hydroxyapatite (HAp) layer on the forsterite/GO surface within in vitro immersion test. The results of cell viability demonstrated that synthesized forsterite scaffolds with low GO did not show cytotoxicity and enhanced cell proliferation. Antibacterial tests showed that the antibacterial influence of forsterite/GO scaffold was strongly correlated with GO concentration from 0.5 to 2 wt.%. The scaffold encapsulated with 2wt.% GO had the great antibacterial performance with bacterial inhibition rate around 90%. As results show, the produced forsterite/1wt.% GO can be an attractive option for bone tissue engineering.

Latest Trends in Surface Modification for Dental Implantology: Innovative Developments and Analytical Applications

An increase in the world population and its life expectancy, as well as the ongoing concern about our physical appearance, have elevated the relevance of dental implantology in recent decades. Engineering strategies to improve the survival rate of dental implants have been widely investigated, focusing on implant material composition, geometry (usually guided to reduce stiffness), and interface surrounding tissues. Although efforts to develop different implant surface modifications are being applied in commercial dental prostheses today, the inclusion of surface coatings has gained special interest, as they can be tailored to efficiently enhance osseointegration, as well as to reduce bacterial-related infection, minimizing peri-implantitis appearance and its associated risks. The use of biomaterials to replace teeth has highlighted the need for the development of reliable analytical methods to assess the therapeutic benefits of implants. This literature review considers the state-of-the-art strategies for surface modification or coating and analytical methodologies for increasing the survival rate for teeth restoration.

The Effect of Co-Encapsulated GO-Cu Nanofillers on Mechanical Properties, Cell Response, and Antibacterial Activities of Mg-Zn Composite

Magnesium-based composites have recently been studied as biodegradable materials for preparing orthopedic implants. In this article, the graphene oxide (GO) and GO-Cu nanosystem has been homogenously dispersed as a reinforcement in the matrix of Mg-Zn (MZ) alloy using the semi powder metallurgy (SPM) method, and subsequently, the composite has been successfully manufactured using the spark plasma sintering (SPS) process. GO and GO-Cu reinforced composite displayed a higher compressive strength (~55%) than the unreinforced Mg-Zn sample. GO and GO-Cu dual nanofillers presented a synergistic effect on enhancing the effectiveness of load transfer and crack deflection in the Mg-based matrix. Besides, the GO-Cu dual nanofillers displayed a synergistic influence on antibacterial activity through combining the capturing influences of GO nanosheets with the killing influences of Cu. However, electrochemical and in-vitro immersion evaluation showed that Cu-GO reinforcement had a slightly negative effect on the corrosion behavior of the Mg-Zn sample, but the incorporation of GO enhanced corrosion resistance of the composite. Moreover, MZ/GO and MZ/GO-Cu nanocomposites showed acceptable cytotoxicity to MG-63 cells and revealed a high potential for use as an orthopedic implant material. Based on the research results, MZ/GO-Cu nanocomposite could be used in bone tissue engineering applications.

Dual Synergistic Effects of MgO-GO Fillers on Degradation Behavior, Biocompatibility and Antibacterial Activities of Chitosan Coated Mg Alloy

The aim of this work was to establish and characterize chitosan/graphene oxide- magnesium oxide (CS/GO-MgO) nanocomposite coatings on biodegradable magnesium-zinc-cerium (Mg-Zn-Ce) alloy. In comparison to that of pure CS coatings, all composite coatings encapsulating GO-MgO had better adhesion strength to the Mg-Zn-Ce alloy substrate. The result depicted that the co-encapsulation of GO-MgO into the CS layer leads to diminish of contact angle value and hence escalates the hydrophilic characteristic of coated Mg alloy. The electrochemical test demonstrated that the CS/GO-MgO coatings significantly increased the corrosion resistance because of the synergistic effect of the GO and MgO inside the CS coating. The composite coating escalated cell viability and cell differentiation, according to cytocompatibility tests due to the presence of GO and MgO within the CS. The inclusion of GO-MgO in CS film, on the other hand, accelerates the formation of hydroxyapatite (HA) during 14 days immersion in SBF. Immersion results, including weight loss and hydrogen evolution tests, presented that CS/GO-MgO coating enables a considerably reduced degradation rate of Mg-Zn-Ce alloy when compared to the bare alloy. In terms of antibacterial-inhibition properties, the GO-MgO/CS coatings on Mg substrates showed antibacterial activity against Escherichia coli (E. coli), with a large inhibition area around the specimens, particularly for the coating containing a higher concentration of GO-MgO. Bacterial growth was not inhibited by the bare Mg alloy samples. The CS/GO-MgO composite coating is regarded as a great film to enhance the corrosion resistance, bioactivity, and antibacterial performance of Mg alloy implants.

Conductive Scaffolds for Bone Tissue Engineering: Current State and Future Outlook

Bone tissue engineering strategies attempt to regenerate bone tissue lost due to injury or disease. Three-dimensional (3D) scaffolds maintain structural integrity and provide support, while improving tissue regeneration through amplified cellular responses between implanted materials and native tissues. Through this, scaffolds that show great osteoinductive abilities as well as desirable mechanical properties have been studied. Recently, scaffolding for engineered bone-like tissues have evolved with the use of conductive materials for increased scaffold bioactivity. These materials make use of several characteristics that have been shown to be useful in tissue engineering applications and combine them in the hope of improved cellular responses through stimulation (i.e., mechanical or electrical). With the addition of conductive materials, these bioactive synthetic bone substitutes could result in improved regeneration outcomes by reducing current factors limiting the effectiveness of existing scaffolding materials. This review seeks to overview the challenges associated with the current state of bone tissue engineering, the need to produce new grafting substitutes, and the promising future that conductive materials present towards alleviating the issues associated with bone repair and regeneration.

Rivet-Inspired Modification of Carbon Nanotubes by In Situ-Reduced Ag Nanoparticles To Enhance the Strength and Ductility of Zn Implants

Zinc shows promise for bone repair applications, while its strength and ductility require to be improved. Carbon nanotubes (CNTs) are exceptional reinforcements due to their superior strength, ultrahigh Young's modulus, and large aspect ratio. However, their strong agglomeration and weak interfacial bonding with the matrix are key bottleneck problems restricting the reinforcing effect. In this study, Ag nanoparticles were in situ reduced on CNTs and then the CNT@Ag powders were used to prepare Zn-CNT@Ag implants by laser powder bed fusion. Results showed that Ag reacted with Zn to form a "knot"-like AgZn₃ phase. It had the same lattice structure (HCP) with Zn, which indicated a good lattice matching with the matrix, thus improving the dispersion of CNTs. More significantly, the knot played a "rivet" role and enhanced the load transfer capacity, which advantaged the CNT strengthening effects by assisting in transferring the load. Moreover, it enhanced the heterogeneous nucleation effects during solidification, which weakened the texture strength of the matrix and thus increased the ductility by improving the sliding capacity. The compressive yield strength, ultimate tensile strength, and elongation of the Zn-CNT@Ag implant were increased by 22, 26, and 17% in comparison to Zn-CNTs. Moreover, the Zn-CNT@Ag implant exhibited favorable antibacterial activity with a bacterial inhibition rate of 87.79%. Additionally, it also exhibited a suitable degradation rate and acceptable biocompatibility.

Advances in Use of Nanomaterials for Musculoskeletal Regeneration

Since the worldwide incidence of bone disorders and cartilage damage has been increasing and traditional therapy has reached its limits, nanomaterials can provide a new strategy in the regeneration of bones and cartilage. The nanoscale modifies the properties of materials, and many of the recently prepared nanocomposites can be used in tissue engineering as scaffolds for the development of biomimetic materials involved in the repair and healing of damaged tissues and organs. In addition, some nanomaterials represent a noteworthy alternative for treatment and alleviating inflammation or infections caused by microbial pathogens. On the other hand, some nanomaterials induce inflammation processes, especially by the generation of reactive oxygen species. Therefore, it is necessary to know and understand their effects in living systems and use surface modifications to prevent these negative effects. This contribution is focused on nanostructured scaffolds, providing a closer structural support approximation to native tissue architecture for cells and regulating cell proliferation, differentiation, and migration, which results in cartilage and bone healing and regeneration.

[Advantages and challenges of carbon nanotubes as bone repair materials]

With the in-depth research on bone repair process, and the progress in bone repair materials preparation and characterization, a variety of artificial bone substitutes have been fully developed in the treatment of bone related diseases such as bone defects. However, the current various natural or synthetic biomaterials are still unable to achieve the structure and properties of natural bone. Carbon nanotubes (CNTs) have provided a new direction for the development of new materials in the field of bone repair due to their excellent structural stability, mechanical properties, and functional group modifiability. Moreover, CNTs and their composites have broad prospects in the design of bone repair materials and as drug delivery carriers. This paper describes the advantages of CNTs related to bone tissue regeneration from the aspects of morphology, chemistry, mechanics, electromagnetism, and biosafety, as well as the application of CNTs in drug delivery carriers and reinforcement components of scaffold materials. In addition, the potential problems and prospects of CNTs in bone regenerative medicine are discussed.

Recent research and progress of biodegradable zinc alloys and composites for biomedical applications: Biomechanical and biocorrosion perspectives

Biodegradable metals (BMs) gradually degrade in vivo by releasing corrosion products once exposed to the physiological environment in the body. Complete dissolution of biodegradable implants assists tissue healing, with no implant residues in the surrounding tissues. In recent years, three classes of BMs have been extensively investigated, including magnesium (Mg)-based, iron (Fe)-based, and zinc (Zn)-based BMs. Among these three BMs, Mg-based materials have undergone the most clinical trials. However, Mg-based BMs generally exhibit faster degradation rates, which may not match the healing periods for bone tissue, whereas Fe-based BMs exhibit slower and less complete in vivo degradation. Zn-based BMs are now considered a new class of BMs due to their intermediate degradation rates, which fall between those of Mg-based BMs and Fe-based BMs, thus requiring extensive research to validate their suitability for biomedical applications. In the present study, recent research and development on Zn-based BMs are reviewed in conjunction with discussion of their advantages and limitations in relation to existing BMs. The underlying roles of alloy composition, microstructure, and processing technique on the mechanical and corrosion properties of Zn-based BMs are also discussed.

Plastics in Total Knee Replacement: Processing to Performance

Polyethylene (PE) is the key component of total knee replacement (TKR). The wear of polyethylene, a common cause of revision surgeries, depends on multiple factors. The mechanical properties, wear characteristics, and oxidative resistance of PE can be manipulated by the techniques of processing, sterilization, and packaging methods. This article describes the making of conventional and cross-linked poly, packaging, sterilization, processing techniques, and a summary of commercially available plastics and their rationale in TKR including the latest advances.

CNT and rGO reinforced PMMA based bone cement for fixation of load bearing implants: Mechanical property and biological response

Polymethyl methacrylate (PMMA) bone cements (BCs) have some drawbacks, including limited bioactivity and bone formation, as well as inferior mechanical properties, which may result in failure of the BC. To deal with the mentioned issues, novel bioactive polymethyl methacrylate-hardystonite (PMMA-HT) bone cement (BC) reinforced with 0.25 and 0.5 wt% of carbon nanotube (CNT) and reduced graphene oxide (rGO) was synthesized. In this context, the obtained bone cements were evaluated in terms of their mechanical and biological characteristics. The rGO reinforced bone cement exhibited better mechanical properties to the extent that the addition of 0.5 wt% of rGO where its compressive and tensile strength of bioactive PMMA-HT/rGO cement escalated from 92.07 ± 0.72 MPa, and 40.02 ± 0.71 MPa to 187.48 ± 5.79 MPa and 64.92 ± 0.75 MPa, respectively. Besides, the mechanisms of toughening, apatite formation, and cell interaction in CNT and rGO encapsulated PMMA have been studied. Results showed that the existence of CNT and rGO in BCs led to increase of MG63 osteoblast viability, and proliferation. However, rGO reinforced bone cement was more successful in supporting MG63 cell attachment compared to the CNT counterpart due to its wrinkled surface, which made a suitable substrate for cell adhesion. Based on the results, PMMA-HT/rGO can be a proper bone cement for the fixation of load-bearing implants.

A Review on Recent Advancements of Graphene and Graphene-Related Materials in Biological Applications

Graphene is the most outstanding material among the new nanostructured carbonaceous species discovered and produced. Graphene’s astonishing properties (i.e., electronic conductivity, mechanical robustness, large surface area) have led to a deep change in the material science field. In this review, after a brief overview of the main characteristics of graphene and related materials, we present an extensive overview of the most recent achievements in biological uses of graphene and related materials.

Graphene Family Nanomaterial Reinforced Magnesium-Based Matrix Composites for Biomedical Application: A Comprehensive Review

Together with the enhancement of the load-bearing implant process for bone substitution and reproduction, an increasing requirement was observed concerning biodegradable magnesium and its alloys with lighter density and outstanding characteristics. Regardless of the current great potential of Mg utilization currently, the broader use of Mg alloys continues to be constrained by several natural causes, such as low resistance of corrosion, inadequate mechanical integrity during the healing process, and poor antibacterial performance. In this perspective, Mg-based composite encapsulated within graphene family nanomaterials (GFNs) such as graphene (Gr), graphene oxide (GO), graphene nanoplatelets (GNPs), and reduced graphene oxide (rGO) as reinforcement agents present great antibacterial activity, as well as cellular response and depicted numerous benefits for biomedical use. Magnesium matrix nanocomposites reinforced with GFNs possess enhanced mechanical properties and high corrosion resistance (low concentration graphene). It is worth noting that numerous elements including the production technique of the Mg-based composite containing GFNs and the size, distribution, and amounts of GFNs in the Mg-based matrix have a crucial role in their properties and applications. Then, the antibacterial mechanisms of GFN-based composite are briefly described. Subsequently, the antibacterial and strengthening mechanisms of GFN-embedded Mg-based composites are briefly described. This review article is designed to wrap up and explore the most pertinent research performed in the direction of Mg-based composites encapsulated within GFNs. Feasible upcoming investigation directions in the field of GFN-embedded Mg-based composites are discussed in detail.

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.

Applications of Carbon Nanotubes in Bone Tissue Regeneration and Engineering: Superiority, Concerns, Current Advancements, and Prospects

With advances in bone tissue regeneration and engineering technology, various biomaterials as artificial bone substitutes have been widely developed and innovated for the treatment of bone defects or diseases. However, there are no available natural and synthetic biomaterials replicating the natural bone structure and properties under physiological conditions. The characteristic properties of carbon nanotubes (CNTs) make them an ideal candidate for developing innovative biomimetic materials in the bone biomedical field. Indeed, CNT-based materials and their composites possess the promising potential to revolutionize the design and integration of bone scaffolds or implants, as well as drug therapeutic systems. This review summarizes the unique physicochemical and biomedical properties of CNTs as structural biomaterials and reinforcing agents for bone repair as well as provides coverage of recent concerns and advancements in CNT-based materials and composites for bone tissue regeneration and engineering. Moreover, this review discusses the research progress in the design and development of novel CNT-based delivery systems in the field of bone tissue engineering.

Magnesium matrix nanocomposites for orthopedic applications: A review from mechanical, corrosion, and biological perspectives

Magnesium (Mg) and some of its alloys have attracted extensive interests for biomedical applications as they exhibit biodegradability and low elastic modulus that is closer to natural bones than the currently used metallic implant materials such as titanium (Ti) and its alloys, stainless steels, and cobalt-chromium (Co-Cr) alloys. However, the rapid degradation of Mg alloys and loss of their mechanical integrity before sufficient bone healing impede their clinical application. Our literature review shows that magnesium matrix nanocomposites (MMNCs) reinforced with nanoparticles possess enhanced strength, high corrosion resistance, and good biocompatibility. This article provides a detailed analysis of the effects of nanoparticle reinforcements on the mechanical properties, corrosion behavior, and biocompatibility of MMNCs as promising biodegradable implant materials. The governing equations to quantitatively predict the mechanical properties and underlying synergistic strengthening mechanisms in MMNCs are elucidated. The potential, recent advances, challenges and future research directions in relation to nanoparticles reinforced MMNCs are highlighted. STATEMENT OF SIGNIFICANCE: Critically reviewing magnesium metal matrix nanocomposites (MMNCs) for the biomedical application. Clear definitions of strengthening mechanisms using reinforcement particle in the magnesium matrix, as there were controversial in governing equations of strengthening parameters. Providing better understanding of the effect of particle size, volume fraction, interfacial bonding, and uniform dispersion of reinforcement particles on MMNCs.