Hydrophobicity of graphene as a driving force for inhibiting biofilm formation of pathogenic bacteria and fungi

Potential of Graphene-Functionalized Polymer Surfaces for Dental Applications: A Systematic review

Graphene, a two-dimensional carbon nanomaterial, has garnered widespread attention across various fields due to its outstanding properties. In dental implantology, researchers are exploring the use of graphene-functionalized polymer surfaces to enhance both the osseointegration process and the long-term success of dental implants. This review consolidates evidence from in-vivo and in-vitro studies, highlighting graphene's capacity to improve bone-to-implant contact, exhibit antibacterial properties, and enhance mechanical strength. This research investigates the effects of incorporating graphene derivatives into polymer materials on tissue response and compatibility. Among 123 search results, 14 articles meeting the predefined criteria were analyzed. The study primarily focuses on assessing the impact of GO and rGO on cellular function and stability in implants. Results indicate promising improvements in cellular function and stability with the use of GO-coated or composited implants. However, it is noted that interactions between Graphene derivatives and polymers may alter the inherent properties of the materials. Therefore, further rigorous research is deemed imperative to fully elucidate their potential in human applications. Such comprehensive understanding is essential for unlocking the extensive benefits associated with the utilization of Graphene derivatives in biomedical contexts.

Graphene nanocoating on titanium maintains structural and antibiofilm properties post-sterilization

OBJECTIVE

To evaluate the impact of sterilization methods on the structural integrity and antimicrobial properties of graphene nanocoating on titanium (GN).

METHODS

GN was transferred to titanium using wet (WT) or dry transfer (DT) techniques and sterilized using an autoclave (AC), glutaraldehyde (GA), or ethylene oxide (EtO). The GN structure was characterized using Raman spectroscopy before and after sterilization. Additional specimens were characterized by Raman after AC and water jetting. Biofilm formation was assessed before and after AC using colony-forming units (CFU), biofilm biomass, and SEM (uncoated titanium was the control). Three independent samples were used for structural characterization and biofilm quantification. Statistical analyses were conducted using one-way analysis of variance (ANOVA) and Tukey's test (α = 0.05).

RESULTS

WT and DT demonstrated high structural stability after sterilization and water jetting, with negligible coating quality or coverage loss. GN exhibited lower biofilm formation even after AC sterilization, as shown by the reduction in CFU counts, biofilm biomass, and SEM images compared to the control.

SIGNIFICANCE

GN demonstrated high resistance to the stresses imposed by all sterilization methods tested, maintaining its structural integrity, resistance to water-jet cleaning, and antibiofilm potential. The findings suggest that standard industrial practices can effectively sterilize highly resilient GN on titanium implants and possibly other biomaterials.

Microbial corrosion of metallic biomaterials in the oral environment

A wide variety of microorganisms have been closely linked to metal corrosion in the form of adherent surface biofilms. Biofilms allow the development and maintenance of locally corrosive environments and/or permit direct corrosion including pitting corrosion. The presence of numerous genetically distinct microorganisms in the oral environment poses a threat to the integrity and durability of the surface of metallic prostheses and implants used in routine dentistry. However, the association between oral microorganisms and specific corrosion mechanisms is not clear. It is of practical importance to understand how microbial corrosion occurs and the associated risks to metallic materials in the oral environment. This knowledge is also important for researchers and clinicians who are increasingly concerned about the biological activity of the released corrosion products. Accordingly, the main goal was to comprehensively review the current literature regarding oral microbiologically influenced corrosion (MIC) including characteristics of biofilms and of the oral environment, MIC mechanisms, corrosion behavior in the presence of oral microorganisms and potentially mitigating technologies. Findings included that oral MIC has been ascribed mostly to aggressive metabolites secreted during microbial metabolism (metabolite-mediated MIC). However, from a thermodynamic point of view, extracellular electron transfer mechanisms (EET-MIC) through pili or electron transfer compounds cannot be ruled out. Various MIC mitigating methods have been demonstrated to be effective in short term, but long term evaluations are necessary before clinical applications can be considered. Currently most in-vitro studies fail to simulate the complexity of intraoral physiological conditions which may either reduce or exacerbate corrosion risk, which must be addressed in future studies. STATEMENT OF SIGNIFICANCE: A thorough analysis on literature regarding oral MIC (microbiologically influenced corrosion) of biomedical metallic materials has been carried out, including characteristics of oral environment, MIC mechanisms, corrosion behaviors in the presence of typical oral microorganisms and potential mitigating methods (materials design and surface design). There is currently a lack of mechanistic understanding of oral MIC which is very important not only to corrosion researchers but also to dentists and clinicians. This paper discusses the significance of biofilms from a biocorrosion perspective and summarizes several aspects of MIC mechanisms which could be caused by oral microorganisms. Oral MIC has been closely associated with not only the materials research but also the dental/clinical research fields in this work.

Biomaterials science and surface engineering strategies for dental peri-implantitis management

Peri-implantitis is a bacterial infection that causes soft tissue inflammatory lesions and alveolar bone resorption, ultimately resulting in implant failure. Dental implants for clinical use barely have antibacterial properties, and bacterial colonization and biofilm formation on the dental implants are major causes of peri-implantitis. Treatment strategies such as mechanical debridement and antibiotic therapy have been used to remove dental plaque. However, it is particularly important to prevent the occurrence of peri-implantitis rather than treatment. Therefore, the current research spot has focused on improving the antibacterial properties of dental implants, such as the construction of specific micro-nano surface texture, the introduction of diverse functional coatings, or the application of materials with intrinsic antibacterial properties. The aforementioned antibacterial surfaces can be incorporated with bioactive molecules, metallic nanoparticles, or other functional components to further enhance the osteogenic properties and accelerate the healing process. In this review, we summarize the recent developments in biomaterial science and the modification strategies applied to dental implants to inhibit biofilm formation and facilitate bone-implant integration. Furthermore, we summarized the obstacles existing in the process of laboratory research to reach the clinic products, and propose corresponding directions for future developments and research perspectives, so that to provide insights into the rational design and construction of dental implants with the aim to balance antibacterial efficacy, biological safety, and osteogenic property.

Incorporating versus coating antimicrobials for polymethyl methacrylate: A systematic review

STATEMENT OF PROBLEM

Incorporating and coating with antimicrobials are techniques that can confer antimicrobial action on polymethyl methacrylate (PMMA) denture bases, which can accumulate microorganisms and promote oral and systemic disease.

PURPOSE

The purpose of this systematic review was to answer the question: "Do techniques for incorporating and coating antimicrobial agents in PMMA promote antimicrobial action?"

MATERIAL AND METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist guidelines were followed, and the SCOPUS, PubMed/Medline, EMBASE, and Science Direct databases searched. The studies were selected in 2 stages, reading the titles and abstracts and then reading the selected studies in full. The risk of bias was analyzed by adapting the quasi-experimental studies tool by the Joanna Briggs Institute (JBI).

RESULTS

A total of 970 articles were found in the databases; 71 were duplicates and, after reading the abstracts, 38 were selected for full reading. From these, 6 were excluded because they did not fulfill the inclusion criteria, and 32 studies were included in this review. Autopolymerizing, heat- polymerizing, and light-polymerizing resins were evaluated, with the incorporating technique prevailing over the coating, but both techniques effectively promoted antimicrobial activity.

CONCLUSIONS

Incorporating and coating antimicrobial agents are effective methods of promoting antimicrobial activity in PMMA. Combining the 2 methods led to increased antimicrobial activity compared with each individually.

Impact of multiscale surface topography characteristics on Candida albicans biofilm formation: From cell repellence to fungicidal activity

While there has been significant research conducted on bacterial colonization on implant materials, with a focus on developing surface modifications to prevent the formation of bacterial biofilms, the study of Candida albicans biofilms on implantable materials is still in its infancy, despite its growing relevance in implant-associated infections. C. albicans fungal infections represent a significant clinical concern due to their severity and associated high fatality rate. Pathogenic yeasts account for an increasing proportion of implant-associated infections, since Candida spp. readily form biofilms on medical and dental device surfaces. In addition, these biofilms are highly antifungal-resistant, making it crucial to explore alternative solutions for the prevention of Candida implant-associated infections. One promising approach is to modify the surface properties of the implant, such as the wettability and topography of these substrata, to prevent the initial Candida attachment to the surface. This review summarizes recent research on the effects of surface wettability, roughness, and architecture on Candida spp. attachment to implantable materials. The nanofabrication of material surfaces are highlighted as a potential method for the prevention of Candida spp. attachment and biofilm formation on medical implant materials. Understanding the mechanisms by which Candida spp. attach to surfaces will allow such surfaces to be designed such that the incidence and severity of Candida infections in patients can be significantly reduced. Most importantly, this approach could also substantially reduce the need to use antifungals for the prevention and treatment of these infections, thereby playing a crucial role in minimizing the possibility contributing to instances of antimicrobial resistance. STATEMENT OF SIGNIFICANCE: In this review we provide a systematic analysis of the role that surface characteristics, such as wettability, roughness, topography and architecture, play on the extent of C. albicans cells attachment that will occur on biomaterial surfaces. We show that exploiting bioinspired surfaces could significantly contribute to the prevention of antimicrobial resistance to antifungal and chemical-based preventive measures. By reducing the attachment and growth of C. albicans cells using surface structure approaches, we can decrease the need for antifungals, which are conventionally used to treat such infections.

Research progress on antibacterial activity of medical titanium alloy implant materials

Titanium and its alloys are the preferred materials for medical implants. However, easy infection is a fatal shortcoming of Ti implants. Fortunately, the ongoing development of antibacterial implant materials is a promising solution, and Ti alloys with antibacterial properties hold immense potential for medical applications. In this review, we briefly outline the mechanisms of bacterial colonization and biofilm formation on implants; discuss and classify the major antimicrobials currently in use and development, including inorganic and organic antimicrobials; and describe the important role of antimicrobials in the development of implant materials for clinical applications. Strategies and challenges related to improving the antimicrobial properties of implant materials as well as the prospects of antibacterial Ti alloys in the medical field are also discussed.

Can Graphene Pave the Way to Successful Periodontal and Dental Prosthetic Treatments? A Narrative Review

Graphene, as a promising material, holds the potential to significantly enhance the field of dental practices. Incorporating graphene into dental materials imparts enhanced strength and durability, while graphene-based nanocomposites offer the prospect of innovative solutions such as antimicrobial dental implants or scaffolds. Ongoing research into graphene-based dental adhesives and composites also suggests their capacity to improve the quality and reliability of dental restorations. This narrative review aims to provide an up-to-date overview of the application of graphene derivatives in the dental domain, with a particular focus on their application in prosthodontics and periodontics. It is important to acknowledge that further research and development are imperative to fully explore the potential of graphene and ensure its safe use in dental practices.

Antibiofilm activity of LAE (ethyl lauroyl arginate) against food-borne fungi and its application in polystyrene surface coating

Several filamentous fungi species as Fusarium oxysporum or Cladosporium sp. can form biofilms by themselves or by participating in polymicrobial biofilms with bacteria. However, despite the high impact of biofilm on the food industry and the high efforts done to control biofilm produced by bacteria in the food area, there has been little study of strategies to control fungal biofilm in this area. In this study, the antibiofilm activity of the safe antimicrobial compound ethyl lauroyl arginate (LAE) was investigated against food spoilage fungi (Cladosporium cladosporioides, Aspergillus ochraceus, Penicillium italicum, Botrytis cynerea and Fusarium oxyspoum). Finally, the efficacy of a varnish-based coating incorporating LAE and coated onto polystyrene microtiter plates has been evaluated as a strategy to reduce fungal biofilm formation. The results of the 2,3-bis-(2-metoxi-4-nitro-5-sulfofenil)-2H-tetrazoilo-5-carboxanilida (XTT) assay, which measure the biofilm metabolic activity of moulds, demonstrated that LAE reduced significantly the formation of fungal biofilm at concentrations from 6 to 25 mg/L. This reduction was confirmed by the micrographs obtained by scanning electronic microscopy (SEM). In addition, LAE also showed antifungal activity against established biofilms. Particularly, it reduced their metabolic activity and viability at concentrations from 6 to 25 mg/L according to results obtained in the XTT assay and observations made by confocal laser scanning microscopy (CLSM). Finally, active coating incorporating from 2% of LAE proved to reduce significantly the biofilm formation in C. cladosporioides, B. cynerea and F. oxyspoum according to the results obtained in the XTT assay. However, the released studies indicated that the retention of LAE in the coating should be improved to prolong their activity.

Graphene and its derivatives: "one stone, three birds" strategy for orthopedic implant-associated infections

Orthopedic implants provide an avascular surface for microbial attachment and biofilm formation, impeding the entry of immune cells and the diffusion of antibiotics. The above is an important cause of dental and orthopedic implant-associated infection (IAI). For the prevention and treatment of IAI, the drawbacks of antibiotic resistance and surgical treatment are increasingly apparent. Due to their outstanding biological properties such as biocompatibility, immunomodulatory effects, and antibacterial properties, graphene-based nanomaterials (GBNs) have been applied to bone tissue engineering to deal with IAI, and in particular have great potential application in drug/gene carriers, multi-functional platforms, and coating forms. Here we review the latest research progress and achievements in GBNs for the prevention and treatment of IAI, mainly including their biomedical applications for antibacterial and immunomodulation effects, and for inducing osteogenesis. Furthermore, the biosafety of graphene family materials in bone tissue regeneration and the feasibility of clinical application are critically analyzed and discussed.

Graphene on dentistry: A bibliometric and scientometric analysis

Background

Today, the development of dental materials is a very important issue. Graphene has been used in dentistry to strengthen many materials.

Aim

The aim of this study was to analyze leading countries and to identify the preferred journals, the most commonly used keywords, and the most productive authors in the field of graphene.

Materials and Methods

The search keyword was "graphene" on the Web of Science database; the search was restricted to before 2022. The selected search from the Web of Science database included the title of articles, authors, year of publication, country, citation count, and keywords. An analysis was performed regarding citations and documents, authors, journals, and keywords using a bibliometric software program. All articles were evaluated and subjected to scientometric analysis.

Results

Twenty six articles were included in the study. There has been a remarkable increase in published articles from past to present, and a regular increase is observed in the number of citations. Dental Materials has highest number of publications among the articles included in the present study. Dr. Rosa, who had the highest number of citations, is also the most effective author. Graphene has many studies in dentistry with different materials. As per the data obtained, graphene, graphene oxide, and peri-implantitis are the most used keywords and Singapore and China are at the forefront of the countries where the articles are published.

Conclusion

This bibliometric analysis reveals the progress and trend of research on graphene in dentistry and extensive collaborations between authors, countries, and institutions. The findings of this study can help inspire researchers to plan new studies and collaborate on graphene.

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.

Graphene materials: Armor against nosocomial infections and biofilm formation - A review

Graphene has revolutionized the field of energy and storage sectors. Out of the total number of nosocomial infections diagnosed all around the world, the majority of the cases (around 70%) are found to be due to the medical device or assistance utilized while treating the patient. Combating these diseases is vital as they cause a nuisance to the patients and medical practitioners. Coatings of graphene and its derivatives hold the key to the formation of special surfaces that can rupture microbial cells using their sharp edges, ultimately leading to nuclear and cellular fragmentation. Their incorporation as a whole or as a part in the hospital apparel and the medical device has aided medical practitioners to combat many nosocomial diseases. Graphene is found to be highly virulent with broad-spectrum antimicrobial activity against nosocomial strains and biofilm formation. Their alternate mode of action like trapping and charge transfer has also been discussed well in the present review. The various combinational forms of graphene with its conjugates as a suitable agent to combat nosocomial infections and a potential coating for newer challenges like COVID-19 infections has also been assessed in the current study. Efficiency of graphene sheets has been found to be around 89% with a reaction time as less as 3 h. Polymers with graphene seem to have a higher potency against biofilm formation. When combined with graphene oxide, silver nanoparticles provide 99% activity against nosocomial pathogens. In conclusion, this review would be a guiding light for scientists working with graphene-based coatings to unfold the potentials of this marvelous commodity to tackle the present and future pandemics to come.

Antimicrobial-free graphene nanocoating decreases fungal yeast-to-hyphal switching and maturation of cross-kingdom biofilms containing clinical and antibiotic-resistant bacteria

Candida albicans and methicillin-resistant Staphylococcus aureus (MRSA) synergize in cross-kingdom biofilms to increase the risk of mortality and morbidity due to high resistance to immune and antimicrobial defenses. Biomedical devices and implants made with titanium are vulnerable to infections that may demand their surgical removal from the infected sites. Graphene nanocoating (GN) has promising anti-adhesive properties against C. albicans. Thus, we hypothesized that GN could prevent fungal yeast-to-hyphal switching and the development of cross-kingdom biofilms. Herein, titanium (Control) was coated with high-quality GN (coverage > 99%). Thereafter, mixed-species biofilms (C. albicans combined with S. aureus or MRSA) were allowed to develop on GN and Control. There were significant reductions in the number of viable cells, metabolic activity, and biofilm biomass on GN compared with the Control (CFU counting, XTT reduction, and crystal violet assays). Also, biofilms on GN were sparse and fragmented, whereas the Control presented several bacterial cells co-aggregating with intertwined hyphal elements (confocal and scanning electronic microscopy). Finally, GN did not induce hemolysis, an essential characteristic for blood-contacting biomaterials and devices. Thus, GN significantly inhibited the formation and maturation of deadly cross-kingdom biofilms, which can be advantageous to avoid infection and surgical removal of infected devices.

Effect of Texturing Environment on Wetting of Biomimetic Superhydrophobic Surfaces Designed by Femtosecond Laser Texturing

Inspired by Euphorbia leaves, micrometric pillars are designed on 316L stainless steel surfaces using a femtosecond laser to achieve superhydrophobicity. In this study, we focus on wetting behavior evolution as a function of time and chemical environment. Two types of texturing designs are performed: the laser texturing of micrometric square pillars, and the laser texturing of micrometric square pillars whose tops were irradiated using various fluences to obtain a different topography on the nanometric scale. Two laser texturing environments are considered in both cases: a CO₂ flow and ambient air. The main result is that 250 days after laser texturing, steady-state contact angles (SSCA) were above 130° no matter what the environment was. We also study the effect of regular wetting over time. Comparing the results of surfaces for which wetting over time was conducted and that of the undisturbed surfaces for 250 days demonstrates that performing wetting measurements when the surface is not stable led to major changes in droplet behavior. Our surfaces have a unique wettability in which droplets are in an intermediate state. Finally, using a CO₂ flow did not help reach higher SSCA, but it limited the effect of regular wetting measurements.

Physical-chemical and microbiological performances of graphene-doped PMMA for CAD/CAM applications before and after accelerated aging protocols

OBJECTIVES

Innovative, nanotechnologies-featuring dental materials for CAD/CAM applications are becoming available. However, the interaction with the oral environment poses critical challenges to their longevity. The present study evaluated specific physical-chemical properties and antimicrobial potential of a CAD/CAM graphene-doped resin before and after accelerated aging protocols.

METHODS

Graphene nanofibers (GNF)-doped (<50 ppm) PMMA (GPMMA) and control PMMA CAD/CAM discs were used. Specimens underwent aging procedures of their bulk (thermo- and load-cycling) and surface (24 h-immersion in absolute ethanol), then they were tested for flexural strength, ultimate tensile strength, sorption/solubility, and methyl-methacrylate elution. Surface characterization included x-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, surface roughness, microhardness, and scanning electron microscopy (SEM). Adherence of Streptococcus mutans and Candida albicans, and biofilm formation (continuous-flow bioreactor) by the same strains and an artificial oral microcosm were investigated.

RESULTS

GNF-doping improved the physical-chemical bulk properties of the PMMA resin. Surface aging reduced microhardness and increased the roughness of both test and control materials. Surfaces displayed signs of swelling and degradation at SEM. Microbiological data of non-aged surfaces showed that GNF-doping significantly reduced biofilm formation by all tested strains despite having no impact on microbial adherence. After aging, microbial adherence was higher on GPMMA surfaces, while biofilm formation was not promoted.

SIGNIFICANCE

GNF-doping improved the material's performance and influenced its antimicrobial potential. This strategy seems a valuable option to overcome the effects of surface degradation induced by aging on the antimicrobial potential of PMMA resin.

On the interface between biomaterials and two-dimensional materials for biomedical applications

Two-dimensional (2D) materials have garnered significant attention due to their ultrathin 2D structures with a high degree of anisotropy and functionality. Reliable manipulation of interfaces between 2D materials and biomaterials is a new frontier for biomedical nanoscience and combining biomaterials with 2D materials offers a promising way to fabricate innovative 2D biomaterials composites with distinct functionality for biomedical applications. Here, we focus exclusively on a summary of the current work in the interface investigation of 2D biomaterials. Specifically, we highlight extraordinary features that make 2D materials so desirable, as well as the molecular level interactions between 2D materials and biomaterials that have been studied thus far. Furthermore, the approaches for investigating the interface characteristics of 2D biomaterials are presented and described in depth. To capture the emerging trend in mass manufacturing of 2D materials, we review the research progress on biomaterial-assisted exfoliation. Finally, we present a critical assessment of newly developed 2D biomaterials in biomedical applications.

Graphene-Based Nanomaterials for Dental Applications: Principles, Current Advances, and Future Outlook

With the development of nanotechnology, nanomaterials have been used in dental fields over the past years. Among them, graphene and its derivatives have attracted great attentions, owing to their excellent physicochemical property, morphology, biocompatibility, multi-differentiation activity, and antimicrobial activity. In our review, we summarized the recent progress about their applications on the dentistry. The synthesis methods, structures, and properties of graphene-based materials are discussed. Then, the dental applications of graphene-based materials are emphatically collected and described. Finally, the challenges and outlooks of graphene-based nanomaterials on the dental applications are discussed in this paper, aiming at inspiring more excellent studies.

Graphene for Antimicrobial and Coating Application

Graphene is a versatile compound with several outstanding properties, providing a combination of impressive surface area, high strength, thermal and electrical properties, with a wide array of functionalization possibilities. This review aims to present an introduction of graphene and presents a comprehensive up-to-date review of graphene as an antimicrobial and coating application in medicine and dentistry. Available articles on graphene for biomedical applications were reviewed from January 1957 to August 2020) using MEDLINE/PubMed, Web of Science, and ScienceDirect. The selected articles were included in this study. Extensive research on graphene in several fields exists. However, the available literature on graphene-based coatings in dentistry and medical implant technology is limited. Graphene exhibits high biocompatibility, corrosion prevention, antimicrobial properties to prevent the colonization of bacteria. Graphene coatings enhance adhesion of cells, osteogenic differentiation, and promote antibacterial activity to parts of titanium unaffected by the thermal treatment. Furthermore, the graphene layer can improve the surface properties of implants which can be used for biomedical applications. Hence, graphene and its derivatives may hold the key for the next revolution in dental and medical technology.

Biological Effects of the Novel Mulberry Surface Characterized by Micro/Nanopores and Plasma-Based Graphene Oxide Deposition on Titanium

Purpose

This paper presents a technique for developing a novel surface for dental implants using a combination of nitriding and anodic oxidation, followed by the deposition of graphene oxide using atmospheric plasma. The effects of various surface treatments on bacterial adhesion and osteoblast activation were also evaluated.

Methods

CP titanium (control) was processed into disk-shaped specimens. Nitriding was conducted using vacuum nitriding, followed by anodic oxidation, which was performed in an electrolyte using a DC power supply, to form the novel “mulberry surface.” Graphene oxide deposition was performed using atmospheric plasma with an inflow of carbon sources. After analyzing the sample surfaces, antibacterial activity was evaluated using Streptococcus mutans and Porphyromonas gingivalis bacteria. The viability, adhesion, proliferation, and differentiation of osteoblasts were also assessed. Analysis of variance (ANOVA) with Tukey’s post-hoc test was used to calculate statistical differences.

Results

We observed that the mulberry surface was formed on samples treated with nitriding and anodic oxidation, and these samples exhibited more effective antibacterial activity than the control. We also found that the samples with additional graphene oxide deposition exhibited better biocompatibility, which was validated by osteoblast adhesion, proliferation, and differentiation.

Conclusion

The development of the mulberry surface along with graphene oxide deposition inhibits bacterial adhesion to the implant and enhances the adhesion, proliferation, and differentiation of osteoblasts. These results indicate that the mulberry surface and graphene oxide deposition together can inhibit peri-implantitis and promote osseointegration.

Osteoinductive and antimicrobial mechanisms of graphene-based materials for enhancing bone tissue engineering

Graphene-based materials (GMs) have great application prospects in bone tissue engineering due to their osteoinductive ability and antimicrobial activity. GMs induce osteogenic differentiation through several mechanisms and pathways in bone tissue engineering. First of all, the surface and high hardness of the porous folds of graphene or graphene oxide (GO) can generate mechanical stimulation to initiate a cascade of reactions that promote osteogenic differentiation without any chemical inducers. In addition, change of the extracellular matrix (ECM), regulation of macrophage polarization, the oncostatin M (OSM) signaling pathway, the MAPK signaling pathway, the BMP signaling pathway, the Wnt/β-catenin signaling pathway, and other pathways are involved in GMs' regulation of osteogenesis. In bone tissue engineering, GMs prevent the formation of microbial biofilms mainly through preventing microbial adhesion and killing them. The former is mainly achieved by reducing surface free energy (SFE) and increasing hydrophobicity. The latter mainly includes oxidative stress and photothermal/photodynamic effects. Graphene and its derivatives (GDs) are mainly combined with bioactive ceramic materials, metal materials and macromolecular polymers to play an antimicrobial effect in bone tissue engineering. Concentration, number of layers, and type of GDs often affect the antimicrobial activity of GMs. In this paper, we reviewed relevant osteoinductive and antimicrobial mechanisms of GMs and their applications in bone tissue engineering.

Graphene Nanocoating: High Quality and Stability upon Several Stressors

Titanium implants present 2 major drawbacks-namely, the long time needed for osseointegration and the lack of inherent antimicrobial properties. Surface modifications and coatings to improve biomaterials can lose their integrity and biological potential when exposed to stressful microenvironments. Graphene nanocoating (GN) can be deposited onto actual-size dental and orthopedic implants. It has antiadhesive properties and can enhance bone formation in vivo. However, its ability to maintain structural integrity and quality when challenged by biologically relevant stresses remains largely unknown. GN was produced by chemical vapor deposition and transferred to titanium via a polymer-assisted transfer technique. GN has high inertness and did not increase expression of inflammatory markers by macrophages, even in the presence of lipopolysaccharides. It kept high coverage at the top tercile of tapered dental implant collars after installation and removal from bone substitute and pig maxilla. It also resisted microbiologically influenced corrosion, and it maintained very high coverage area and quality after prolonged exposure to biofilms and their removal by different techniques. Our findings show that GN is unresponsive to harsh and inflammatory environments and that it maintains a promising level of structural integrity on the top tercile of dental implant collars, which is the area highly affected by biofilms during the onset of implant diseases. Our findings open the avenues for the clinical studies required for the use of GN in the development of implants that have higher osteogenic potential and are less prone to implant diseases.

Graphene nanocoating provides superb long-lasting corrosion protection to titanium alloy

OBJECTIVE

The presence of metallic species around failed implants raises concerns about the stability of titanium alloy (Ti-6Al-4V). Graphene nanocoating on titanium alloy (GN) has promising anti-corrosion properties, but its long-term protective potential and structural stability remains unknown. The objective was to determine GN's anti-corrosion potential and stability over time.

METHODS

GN and uncoated titanium alloy (Control) were challenged with a highly acidic fluorinated corrosive medium (pH 2.0) for up to 240 days. The samples were periodically tested using potentiodynamic polarization curves, electrochemical impedance spectroscopy and inductively coupled plasma-atomic emission spectroscopy (elemental release). The integrity of samples was determined using Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy. Statistical analyses were performed with one-sample t-test, paired t-test and one-way ANOVA with Tukey post-hoc test with a pre-set significance level of 5%.

RESULTS

There was negligible corrosion and elemental loss on GN. After 240 days of corrosion challenge, the corrosion rate and roughness increased by two and twelve times for the Control whereas remained unchanged for GN. The nanocoating presented remarkably high structural integrity and coverage area (>98%) at all time points tested.

SIGNIFICANCE

Graphene nanocoating protects titanium alloy from corrosion and dissolution over a long period while maintaining high structural integrity. This coating has promising potential for persistent protection of titanium and potentially other metallic alloys against corrosion.

Biofilm inhibition and bactericidal activity of NiTi alloy coated with graphene oxide/silver nanoparticles via electrophoretic deposition

Biofilm formation on medical devices can induce complications. Graphene oxide/silver nanoparticles (GO/AgNPs) coated nickel-titanium (NiTi) alloy has been successfully produced. Therefore, the aim of this study was to determine the anti-bacterial and anti-biofilm effects of a GO/AgNPs coated NiTi alloy prepared by Electrophoretic deposition (EPD). GO/AgNPs were coated on NiTi alloy using various coating times. The surface characteristics of the coated NiTi alloy substrates were investigated and its anti-biofilm and anti-bacterial effect on Streptococcus mutans biofilm were determined by measuring the biofilm mass and the number of viable cells using a crystal violet assay and colony counting assay, respectively. The results showed that although the surface roughness increased in a coating time-dependent manner, there was no positive correlation between the surface roughness and the total biofilm mass. However, increased GO/AgNPs deposition produced by the increased coating time significantly reduced the number of viable bacteria in the biofilm (p < 0.05). Therefore, the GO/AgNPs on NiTi alloy have an antibacterial effect on the S. mutans biofilm. However, the increased surface roughness does not influence total biofilm mass formation (p = 0.993). Modifying the NiTi alloy surface using GO/AgNPs can be a promising coating to reduce the consequences of biofilm formation.

Fighting viruses with materials science: Prospects for antivirus surfaces, drug delivery systems and artificial intelligence

OBJECTIVE

Viruses on environmental surfaces, in saliva and other body fluids represent risk of contamination for general population and healthcare professionals. The development of vaccines and medicines is costly and time consuming. Thus, the development of novel materials and technologies to decrease viral availability, viability, infectivity, and to improve therapeutic outcomes can positively impact the prevention and treatment of viral diseases.

METHODS

Herein, we discuss (a) interaction mechanisms between viruses and materials, (b) novel strategies to develop materials with antiviral properties and oral antiviral delivery systems, and (c) the potential of artificial intelligence to design and optimize preventive measures and therapeutic regimen.

RESULTS

The mechanisms of viral adsorption on surfaces are well characterized but no major breakthrough has become clinically available. Materials with fine-tuned physical and chemical properties have the potential to compromise viral availability and stability. Emerging strategies using oral antiviral delivery systems and artificial intelligence can decrease infectivity and improve antiviral therapies.

SIGNIFICANCE

Emerging viral infections are concerning due to risk of mortality, as well as psychological and economic impacts. Materials science emerges for the development of novel materials and technologies to diminish viral availability, infectivity, and to enable enhanced preventive and therapeutic strategies, for the safety and well-being of humankind.

Novel Structures and Applications of Graphene-Based Semiconductor Photocatalysts: Faceted Particles, Photonic Crystals, Antimicrobial and Magnetic Properties

Graphene, graphene oxide, reduced graphene oxide and their composites with various compounds/materials have high potential for substantial impact as cheap photocatalysts, which is essential to meet the demands of global activity, offering the advantage of utilizing “green” solar energy. Accordingly, graphene-based materials might help to reduce reliance on fossil fuel supplies and facile remediation routes to achieve clean environment and pure water. This review presents recent developments of graphene-based semiconductor photocatalysts, including novel composites with faceted particles, photonic crystals, and nanotubes/nanowires, where the enhancement of activity mechanism is associated with a synergistic effect resulting from the presence of graphene structure. Moreover, antimicrobial potential (highly needed these days), and facile recovery/reuse of photocatalysts by magnetic field have been addresses as very important issue for future commercialization. It is believed that graphene materials should be available soon in the market, especially because of constantly decreasing prices of graphene, vis response, excellent charge transfer ability, and thus high and broad photocatalytic activity against both organic pollutants and microorganisms.

Antibacterial and antibiofilm properties of graphene and its derivatives

Infections resulting from bacteria and biofilms have become a huge problem threatening human health. In recent years, the antibacterial and antibiofilm effects of graphene and its derivatives have been extensively studied. However, there continues to be some controversy over whether graphene and its derivatives can resist infection and biofilms. Moreover, the antibacterial mechanism and cytotoxicity of graphene and its derivatives are unclear. In the present review, antibacterial and antibiofilm abilities of graphene and its derivatives in solution, on the surface are reviewed, and their toxicity and possible mechanisms are also reviewed. Furthermore, we propose possible future development directions for graphene and its derivatives in antibacterial and antibiofilm applications.

Persistent inhibition of Candida albicans biofilm and hyphae growth on titanium by graphene nanocoating

OBJECTIVES

Candida albicanscolonizes biomaterial surfaces and are highly resistant to therapeutics. Graphene nanocoating on titanium compromises initial biofilm formation. However, its sustained antibiofilm potential is unknown. The objective of this study was to investigate the potential of graphene nanocoating to decrease long-term fungal biofilm development and hyphae growth on titanium.

METHODS

Graphene nanocoating was deposited twice (TiGD) or five times (TiGV) on grade 4 titanium with vacuum assisted technique and characterized with Raman spectroscopy and atomic force microscope. The biofilm formation and hyphae growth of C. albicans was monitored for seven days by CFU, XTT, confocal, mean cell density and scanning electronic microscopy (SEM). Uncoated titanium was the Control. All tests had three independent biological samples and were performed in independent triplicates. Data was analyzed with one- or two-way ANOVA and Tukey's HSD (α = 0.05).

RESULTS

Both TiGD and TiGV presented less biofilms at all times points compared with Control. The confocal and SEM images revealed few adhered cells on graphene coated samples, absence of hyphae and no features of a mature biofilm architecture. The increase in number of layers of graphene nanocoating did not improve its antibiofilm potential.

SIGNIFICANCE

The graphene nanocoating exerted a long-term persistent inhibitory effect on the biofilm formation on titanium. The fewer cells that were able to attach on graphene coated titanium were scattered and unable to form a mature biofilm with hyphae elements. The findings open opportunities to prevent microbial attachment and proliferation on implantable materials without the use of antibiotics.

Graphene: An Antibacterial Agent or a Promoter of Bacterial Proliferation?

Graphene materials (GMs) are being investigated for multiple microbiological applications because of their unique physicochemical characteristics including high electrical conductivity, large specific surface area, and robust mechanical strength. In the last decade, studies on the interaction of GMs with bacterial cells appear conflicting. On one side, GMs have been developed to promote the proliferation of electroactive bacteria on the surface of electrodes in bioelectrochemical systems or to accelerate interspecies electron transfer during anaerobic digestion. On the other side, GMs with antibacterial properties have been synthesized to prevent biofilm formation on membranes for water treatment, on medical equipment, and on tissue engineering scaffolds. In this review, we discuss the mechanisms and factors determining the positive or negative impact of GMs on bacteria. Furthermore, we examine the bacterial growth-promoting and antibacterial applications of GMs and debate their practicability.

A nanostructured anti-biofilm surface widens the efficacy against spindle-shaped and chain-forming rod-like bacteria

Current control of pathogenic bacteria at all biomaterial interfaces is poorly attuned to a broad range of disease-causing pathogens. Leading antimicrobial surface functionalization strategies with antimicrobial peptides (AMPs), defensins, have not shown their promised efficacy. One of the main problems is the lack of stability and swift clearance from the surface. Surface nanotopography bearing sharp protrusions is a non-chemical solution that is intrinsically stable and long-lasting. Previously, the geometrically ordered arrays of nanotipped spines repelled or rapidly ruptured bacteria that come into contact. The killing properties so far work on cocci and rod-like bacteria, but there is no validation of the efficacy of protrusional surfaces on pathogenic bacteria with different sizes and morphologies, thus broadening the utility of such surfaces to cover increasingly more disease entities. Here, we report a synthetic analogue of nanotipped spines with a pyramidal shape that show great effectiveness on species of bacteria with strongly contrasting shapes and sizes. To highlight this phenomenon in the field of dental applications where selective bacterial control is vital to the clinical success of biomaterial functions, we modified the poly(methyl)-methacrylate (PMMA) texture and tested it against Streptococcus mutans, Enterococcus faecalis, Porphyromonas gingivalis, and Fusobacterium nucleatum. These nanopyramids performed effectively at levels well above those of normal and roughened PMMA biomaterials for dentistry and a model material for general use in medicine and disease transmission in hospital environments.

Screening effect of CVD graphene on the surface free energy of substrates

The wettability of graphene has been a topic under constant discussion in the literature since 2012. In this work we measured the contact angle (CA) of six different types of substrates (glass, quartz, Si₃N₄, Si/SiO₂, sapphire and Si) with varying dielectric constants and surface roughnesses in order to calculate the surface free energy of graphene films to evaluate how the wetting properties of graphene-coated substrates are changed according to the underlying substrate. We used a residual-free transfer process to remove the high-quality graphene (CVD-Gr) grown onto copper foil. Afterwards, we performed an inert thermal treatment (Ar, at 300 °C for 30 minutes) to remove airborne contaminants from the graphene surface and evaluate the roughness of substrates by atomic force microscopy, the advancing and receding contact angles of two liquids (water and ethylene glycol), hysteresis, and surface free energy (polar and dispersive components) calculations. The presence of high-quality monolayer graphene (free of any air contaminants, polymer residues, etc.) led to a common wettability behaviour for all coated surfaces, regardless of the nature of the underlying substrate. This result can be understood in terms of the screening of van der Waals and dipole interactions by the electrons in graphene.

The Effectiveness of Nafion-Coated Stainless Steel Surfaces for Inhibiting Bacillus Subtilis Biofilm Formation

Stainless steel is one of most commonly used materials in the world; however, biofilms on the surfaces of stainless steel cause many serious problems. In order to find effective methods of reducing bacterial adhesion to stainless steel, and to investigate the role of electrostatic effects during the formation of biofilms, this study used a stainless steel surface that was negatively charged by being coated with Nafion which was terminated by sulfonic groups. The results showed that the roughness of stainless steel discs coated with 1% Nafion was similar to an uncoated surface; however the hydrophobicity increased, and the Nafion-coated surface reduced the adhesion of Bacillus subtilis by 75% compared with uncoated surfaces. Therefore, a facile way to acquire antibacterial stainless steel was found, and it is proved that electrostatic effects have a significant influence on the formation of biofilms.

Inhibiting Corrosion of Biomedical-Grade Ti-6Al-4V Alloys with Graphene Nanocoating

The identification of metal ions and particles in the vicinity of failed implants has raised the concern that biomedical titanium alloys undergo corrosion in healthy and infected tissues. Various surface modifications and coatings have been investigated to prevent the deterioration and biocorrosion of titanium alloys but so far with limited success. Graphene is a cytocompatible atom-thick film made of carbon atoms. It has a very high surface area and can be deposited onto metal objects with complex shapes. As the carbon lattice has a very small pore size, graphene has promising impermeability capacity. Here, we show that graphene coating can effectively protect Ti-6Al-4V from corrosion. Graphene nanocoatings were produced on Ti-6Al-4V grade 5 and 23 discs and subjected to corrosive challenge (0.5M NaCl supplemented with 2-ppm fluoride, pH of 2.0) up to 30 d. The linear polarization resistance curves and electrochemical impedance spectroscopy analysis showed that the graphene-coated samples presented higher corrosion resistance and electrochemical stability at all time points. Moreover, the corrosion rate of the graphene-coated samples was very low and stable (~0.001 mm/y), whereas that of the uncoated controls increased up to 16 and 5 times for grade 5 and 23 (~0.091 mm/y) at the end point, respectively. The surface oxidation, degradation (e.g., crevice defects), and leaching of Ti, Al, and V ions observed in the uncoated controls were prevented by the graphene nanocoating. The Raman mappings confirmed that the graphene nanocoating presented high structural stability and resistance to mechanical stresses and chemical degradation, keeping >99% of coverage after corrosion challenge. Our findings open the avenues for the use of graphene as anticorrosion coatings for metal biomedical alloys and implantable devices.