Materials for Orthopedic Bioimplants: Modulating Degradation and Surface Modification Using Integrated Nanomaterials

Effect of Gentamicin Sulfate and Polymeric Polyethylene Glycol Coating on the Degradation and Cytotoxicity of Iron-Based Biomaterials

The work is focused on the degradation, cytotoxicity, and antibacterial properties, of iron-based biomaterials with a bioactive coating layer. The foam and the compact iron samples were coated with a polyethylene glycol (PEG) polymer layer without and with gentamicin sulfate (PEG + Ge). The corrosion properties of coated and uncoated samples were studied using the degradation testing in Hanks' solution at 37 °C. The electrochemical and static immersion corrosion tests revealed that the PEG-coated samples corroded faster than samples with the bioactive PEG + Ge coating and uncoated samples. The foam samples corroded faster compared with the compact samples. To determine the cytotoxicity, cell viability was monitored in the presence of porous foam and compact iron samples. The antibacterial activity of the samples with PEG and PEG + Ge against Escherichia coli CCM 3954 and Staphylococcus aureus CCM 4223 strains was also tested. Tested PEG + Ge samples showed significant antibacterial activity against both bacterial strains. Therefore, the biodegradable iron-based materials with a bioactive coating could be a suitable successor to the metal materials studied thus far as well as the materials used in the field of medicine.

A new strategy to integrate silver nanowires with waterborne coating to improve their antimicrobial and antiviral properties

Purpose

This study aims to focus on the preparation and characterization of the silver nanowire (AgNWs), as well as their application as antimicrobial and antivirus activities either with incorporation on the waterborne coating formulation or on their own.

Design/methodology/approach

Prepared AgNWs are characterized by different analytical instruments, such as ultraviolet-visible spectroscope, scanning electron microscope and X-ray diffraction spectrometer. All the paint formulation's physical and mechanical qualities were tested using American Society for Testing and Materials, a worldwide standard test procedure. The biological activities of the prepared AgNWs and the waterborne coating based on AgNWs were investigated. And, their effects on pathogenic bacteria, antioxidants, antiviral activity and cytotoxicity were also investigated.

Findings

The obtained results of the physical and mechanical characteristics of the paint formulation demonstrated the formulations' greatest performance, as well as giving good scrub resistance and film durability. In the antimicrobial activity, the paint did not have any activity against bacterial pathogen, whereas the AgNWs and AgNWs with paint have similar activity against bacterial pathogen with inhibition zone range from 10 to 14 mm. The development of antioxidant and cytotoxicity activity of the paint incorporated with AgNWs were also observed. The cytopathic effects of herpes simplex virus type 1 (HSV-1) were reduced in all three investigated modes of action when compared to the positive control group (HSV-1-infected cells), suggesting that these compounds have promising antiviral activity against a wide range of viruses, including DNA and RNA viruses.

Originality/value

The new waterborne coating based on nanoparticles has the potential to be promising in the manufacturing and development of paints, allowing them to function to prevent the spread of microbial infection, which is exactly what the world requires at this time.

Improving the Surface Integrity of 316L Steel in the Context of Bioimplant Applications

Bioimplants should meet important surface integrity criteria, with the main goal of the manufacturing process to improve wear and corrosion resistance properties. This requires a special approach at the cutting stage. During this research, the impact of the cutting parameters on improving the surface integrity of AISI 316L steel was evaluated. In this context of bioimplant applications, the mean roughness Sa value was obtained in the range of 0.73-4.19 μm. On the basis of the results obtained, a significant effect was observed of both the cutting speed and the feed rate on changes in the microstructure of the near-surface layer. At a cutting speed of 150 m/min, the average grain size was approximately 31 μm. By increasing the cutting speed to 200 m/min, the average grain size increased to approximately 52 μm. The basic austenitic microstructure of AISI 316L steel with typical precipitation of carbides on the grain boundaries was refined at the near-surface layer after the machining process. Changing the cutting speed determined the hardness of the treated and near-surface layers. The maximum value of hardness is reached at a depth of 20 μm and decreases with the depth of measurement. It was also noted that at a depth of up to 240 μm, the maximum hardness of 270-305 HV1 was reached, hence the height of the machining impact zone can be determined, which is approximately 240 μm for almost all machining conditions.

Is nanomaterial- and vancomycin-loaded polymer coating effective at preventing methicillin-resistant Staphylococcus aureus growth on titanium disks? An in vitro study

PURPOSE

Periprosthetic joint infections induced by methicillin-resistant Staphylococcus aureus (MRSA) pose a major socioeconomic burden. Given the fact that MRSA carriers are at high risk for developing periprosthetic infections regardless of the administration of eradication treatment pre-operatively, the need for developing new prevention modalities is high.

METHODS

The antibacterial and antibiofilm properties of vancomycin, Al₂O₃ nanowires, and TiO₂ nanoparticles were evaluated in vitro using MIC and MBIC assays. MRSA biofilms were grown on titanium disks simulating orthopedic implants, and the infection prevention potential of vancomycin-, Al₂O₃ nanowire-, and TiO₂ nanoparticle-supplemented Resomer® coating was evaluated against biofilm controls using the XTT reduction proliferation assay.

RESULTS

Among the tested modalities, high- and low-dose vancomycin-loaded Resomer® coating yielded the most satisfactory metalwork protection against MRSA (median absorbance was 0.1705; [IQR = 0.1745] vs control absorbance 0.42 [IQR = 0.07]; p = 0.016; biofilm reduction was 100%; and 0.209 [IQR = 0.1295] vs control 0.42 [IQR = 0.07]; p < 0.001; biofilm reduction was 84%, respectively). On the other hand, polymer coating alone did not provide clinically meaningful biofilm growth prevention (median absorbance was 0.2585 [IQR = 0.1235] vs control 0.395 [IQR = 0.218]; p < 0.001; biofilm reduction was 62%).

CONCLUSIONS

We advocate that apart from the well-established preventative measures for MRSA carriers, loading implants with bioresorbable Resomer® vancomycin-supplemented coating may decrease the incidence of early post-op surgical site infections with titanium implants. Of note, the payoff between localized toxicity and antibiofilm efficacy should be considered when loading polymers with highly concentrated antimicrobial agents.

Nanomaterial reinforced composite for biomedical implants applications: a mini-review

There is heavy demand for suitable implant materials with improved mechanical and biological properties. Classically, the demand was catered by conventional materials like metals, alloys, and polymer-based materials. Recently, nanomaterial reinforced composites have played a significant role in replacing conventional materials due to their excellent properties such as biocompatibility, bioactivity, high strength to weight ratio, long life, corrosion & wear resistance, and tailor-ability. Herein, we composed a systematic focus review on the role of nanoparticles in the form of composite materials for the advancements in orthopedic implants. Several nano materials-based reinforcements have been reviewed with various matrix materials, including metals, alloys, ceramics, composites, and polymers for biomedical implant applications. Moreover, the improved biological properties, mechanical properties, and other functionalities like infection resistance, drug delivery at the target, sensing, and detection of bone diseases, and corrosion & wear resistance are elaborated. At last, a particular focus has been given to the un-resolved challenges in orthopedic implant development.

Engineering biomaterials to 3D-print scaffolds for bone regeneration: practical and theoretical consideration

There are more than 2 million bone grafting procedures performed annually in the US alone. Despite significant efforts, the repair of large segmental bone defects is a substantial clinical challenge which requires bone substitute materials or a bone graft. The available biomaterials lack the adequate mechanical strength to withstand the static and dynamic loads while maintaining sufficient porosity to facilitate cell in-growth and vascularization during bone tissue regeneration. A wide range of advanced biomaterials are being currently designed to mimic the physical as well as the chemical composition of a bone by forming polymer blends, polymer-ceramic and polymer-degradable metal composites. Transforming these novel biomaterials into porous and load-bearing structures via three-dimensional printing (3DP) has emerged as a popular manufacturing technique to develop engineered bone grafts. 3DP has been adopted as a versatile tool to design and develop bone grafts that satisfy porosity and mechanical requirements while having the ability to form grafts of varied shapes and sizes to meet the physiological requirements. In addition to providing surfaces for cell attachment and eventual bone formation, these bone grafts also have to provide physical support during the repair process. Hence, the mechanical competence of the 3D-printed scaffold plays a key role in the success of the implant. In this review, we present various recent strategies that have been utilized to design and develop robust biomaterials that can be deployed for 3D-printing bone substitutes. The article also reviews some of the practical, theoretical and biological considerations adopted in the 3D-structure design and development for bone tissue engineering.

Recent Advancements in Materials and Coatings for Biomedical Implants

Metallic materials such as stainless steel (SS), titanium (Ti), magnesium (Mg) alloys, and cobalt-chromium (Co-Cr) alloys are widely used as biomaterials for implant applications. Metallic implants sometimes fail in surgeries due to inadequate biocompatibility, faster degradation rate (Mg-based alloys), inflammatory response, infections, inertness (SS, Ti, and Co-Cr alloys), lower corrosion resistance, elastic modulus mismatch, excessive wear, and shielding stress. Therefore, to address this problem, it is necessary to develop a method to improve the biofunctionalization of metallic implant surfaces by changing the materials' surface and morphology without altering the mechanical properties of metallic implants. Among various methods, surface modification on metallic surfaces by applying coatings is an effective way to improve implant material performance. In this review, we discuss the recent developments in ceramics, polymers, and metallic materials used for implant applications. Their biocompatibility is also discussed. The recent trends in coatings for biomedical implants, applications, and their future directions were also discussed in detail.

Design and finite element analysis of femoral stem prosthesis using functional graded materials

Conventionally biometals were used for design and development of bioimplants. However, the Young's Modulus (YM) of these bioimplants is higher than that of a natural bone. Asymmetric load transfer from a bone to the bioimplant results in aseptic loosening and stress shielding. Here-in, the use of functionally graded materials (FGM) has been introduced to design the femoral stem prosthesis as a model bioimplant using computational biomechanics. The material properties variations in these FGMs in longitudinal and radial directions are explored to minimize the aseptic loosening and stress-shielding that plays a vital role in defining the performance and longevity of the prosthesis. Three groups of FGM (Ti-HA, SS316L-HA and CoCr alloy-HA) have been explored to design the stem prosthesis and the finite element analysis (FEA) was carried out using computational biomechanics. The stress distribution profile in the designed stem prosthesis demonstrated an increase in the stress values with an increase in the volume fraction exponent. The results corroborated with the stress distribution obtained from the simulation results of a cortico-cancellous bone. The stress distribution in the Ti-HA prosthesis is observed to be more uniform than CoCr-HA and SS316L-HA prosthesis. In addition, the reduced number of stress shielding points were observed for the Ti-HA prosthesis when compared with the CoCr-HA and SS 316 L-HA stem prostheses. Hence, the results suggested that the Ti-HA prosthesis could be considered as a mechanically stable prosthesis and the same could offer safe design for further development of a femoral bioimplant.

The Research of Toxicity and Sensitization Potential of PEGylated Silver and Gold Nanomaterials

Polyethylene glycol (PEG) is a polymer used for surface modification of important substances in the modern pharmaceutical industry and biopharmaceutical fields. Despite the many benefits of PEGylation, there is also the possibility that the application and exposure of the substance may cause adverse effects in the body, such as an immune response. Therefore, we aimed to evaluate the sensitization responses that could be induced through the intercomparison of nanomaterials of the PEG-coated group with the original group. We selected gold/silver nanomaterials (NMs) for original group and PEGylated silver/gold NMs in this study. First, we measured the physicochemical properties of the four NMs, such as size and zeta potential under various conditions. Additionally, we performed the test of the NM's sensitization potential using the KeratinoSens™ assay for in vitro test method and the LLNA: 5-bromo-2-deoxyuridine (BrdU)-FCM for in vivo test method. The results showed that PEGylated-NMs did not lead to skin sensitization according to OECD TG 442 (alternative test for skin sensitization). In addition, gold nanomaterial showed that cytotoxicity of PEGylated-AuNMs was lower than AuNMs. These results suggest the possibility that PEG coating does not induce an immune response in the skin tissue and can lower the cytotoxicity of nanomaterials.

A Combined Strategy to Improve the Performance of Dental Alloys Using a New CoCrNbMoZr Alloy with Mn and Si Coated via an Anodic Oxidation Procedure

The aim of the paper is based on a combined approach to improve dental alloy performance using a new Ni-free Co–Cr composition with Mo, Nb and Zr and coated with an anodic oxidation film. The coated and uncoated samples were surface characterized by performing SEM (scanning electronic microscopy), XRD (X-rays diffraction) contact angle measurements and corrosion studies with open circuit potential, potentiodynamic polarization and EIS (impedance electrochemical spectroscopy) procedures. The SEM equipment with an EDX (Energy-dispersive X-ray spectroscopy) module indicated the sample morphology and the XRD investigations established the formation of the oxides. The electrochemical procedures were performed in Ericsson artificial saliva for coated samples in various conditions. Based on all the experiments, including the decrease in the hydrophobic character of the uncoated samples and the decrease in the hydrophilic values of the anodized alloys, the improved performance of the coated samples was established as a conclusion.

Nanotechnology-Based Antimicrobial and Antiviral Surface Coating Strategies

Biocontamination of medical devices and implants is a growing issue that causes medical complications and increased expenses. In the fight against biocontamination, developing synthetic surfaces, which reduce the adhesion of microbes and provide biocidal activity or combinatory effects, has emerged as a major global strategy. Advances in nanotechnology and biological sciences have made it possible to design smart surfaces for decreasing infections. Nevertheless, the clinical performance of these surfaces is highly depending on the choice of material. This review focuses on the antimicrobial surfaces with functional material coatings, such as cationic polymers, metal coatings and antifouling micro-/nanostructures. One of the highlights of the review is providing insights into the virus-inactivating surface development, which might particularly be useful for controlling the currently confronted pandemic coronavirus disease 2019 (COVID-19). The nanotechnology-based strategies presented here might be beneficial to produce materials that reduce or prevent the transmission of airborne viral droplets, once applied to biomedical devices and protective equipment of medical workers. Overall, this review compiles existing studies in this broad field by focusing on the recent related developments, draws attention to the possible activity mechanisms, discusses the key challenges and provides future recommendations for developing new, efficient antimicrobial and antiviral surface coatings.

Environmental Impact of Nanoparticles' Application as an Emerging Technology: A Review

The unique properties that nanoparticles exhibit, due to their small size, are the principal reason for their numerous applications, but at the same time, this might be a massive menace to the environment. The number of studies that assess the possible ecotoxicity of nanomaterials has been increasing over the last decade to determine if, despite the positive aspects, they should be considered a potential health risk. To evaluate their potential toxicity, models are used in all types of organisms, from unicellular bacteria to complex animal species. In order to better understand the environmental consequences of nanotechnology, this literature review aims to describe and classify nanoparticles, evaluating their life cycle, their environmental releasing capacity and the type of impact, particularly on living beings, highlighting the need to develop more severe and detailed legislation. Due to their diversity, nanoparticles will be discussed in generic terms focusing on the impact of a great variety of them, highlighting the most interesting ones for the industry.

Science-Based Strategies of Antiviral Coatings with Viricidal Properties for the COVID-19 Like Pandemics

The worldwide, extraordinary outbreak of coronavirus pandemic (i.e., COVID-19) and other emerging viral expansions have drawn particular interest to the design and development of novel antiviral, and viricidal, agents, with a broad-spectrum of antiviral activity. The current indispensable challenge lies in the development of universal virus repudiation systems that are reusable, and capable of inactivating pathogens, thus reducing risk of infection and transmission. In this review, science-based methods, mechanisms, and procedures, which are implemented in obtaining resultant antiviral coated substrates, used in the destruction of the strains of the different viruses, are reviewed. The constituent antiviral members are classified into a few broad groups, such as polymeric materials, metal ions/metal oxides, and functional nanomaterials, based on the type of materials used at the virus contamination sites. The action mode against enveloped viruses was depicted to vindicate the antiviral mechanism. We also disclose hypothesized strategies for development of a universal and reusable virus deactivation system against the emerging COVID-19. In the surge of the current, alarming scenario of SARS-CoV-2 infections, there is a great necessity for developing highly-innovative antiviral agents to work against the viruses. We hypothesize that some of the antiviral coatings discussed here could exert an inhibitive effect on COVID-19, indicated by the results that the coatings succeeded in obtaining against other enveloped viruses. Consequently, the coatings need to be tested and authenticated, to fabricate a wide range of coated antiviral products such as masks, gowns, surgical drapes, textiles, high-touch surfaces, and other personal protective equipment, aimed at extrication from the COVID-19 pandemic.

Hydroxyapatite as a biomaterial - a gift that keeps on giving

The synthetic analogue to biogenic apatite, hydroxyapatite (HA) has a number of physicochemical properties that make it an attractive candidate for diagnosis, treatment of disease and augmentation of biological tissues. Here we describe some of the recent studies on HA, which may provide bases for a number of new medical applications. The content of this review is divided to different medical application modes utilizing HA, including tissue engineering, medical implants, controlled drug delivery, gene therapies, cancer therapies and bioimaging. A number of advantages of HA over other biomaterials emerge from this discourse, including (i) biocompatibility, (ii) bioactivity, (iii) relatively simple synthesis protocols for the fabrication of nanoparticles with specific sizes and shapes, (iv) smart response to environmental stimuli, (v) facile functionalization and surface modification through noncovalent interactions, and (vi) the capacity for being simultaneously loaded with a wide range of therapeutic agents and switched to bioimaging modalities for uses in theranostics. A special section is dedicated to analysis of the safety of particulate HA as a component of parenterally administrable medications. It is concluded that despite the fact that many benefits come with the usage of HA, its deficiencies and potential side effects must be addressed before the translation to the clinical domain is pursued. Although HA has been known in the biomaterials world as the exemplar of safety, this safety proves to be the function of size, morphology, surface ligands and other structural and compositional parameters defining the particles. For this reason, each HA, especially when it comes in a novel structural form, must be treated anew from the safety research angle before being allowed to enter the clinical stage.