Design strategies for antiviral coatings and surfaces: A review

The routine disinfection and sanitization of surfaces, objects, and textiles has become a time-consuming but necessary task for managing the COVID-19 pandemic. Nonetheless, the excessive use of sanitizers and disinfectants promotes the development of antibiotic-resistant microbes. Moreover, that improper disinfection could lead to more virus transfer, which leads to more viral mutations. Recently developed antiviral surface coatings can reduce the reliance on traditional disinfectants. These surfaces remain actively antimicrobial between periods of active cleaning of the surfaces, allowing a much more limited and optimized use of disinfectants. The novel nature of these surfaces has led, however, to many inconsistencies within the rapidly growing literature. Here we provide tools to guide the design and development of antimicrobial and antiviral surfaces and coatings. We describe how engineers can best choose testing options and propose new avenues for antiviral testing. After defining testing protocols, we summarize potential inorganic and organic materials able to serve as antiviral surfaces and present their antiviral mechanisms. We discuss the main limitations to their application, including issues related to toxicity, antimicrobial resistance, and environmental concerns. We propose solutions to counter these limitations and highlight how the context of specific use of an antiviral surface must guide material selection. Finally, we discuss how the use of coatings that combine multiple antimicrobial mechanisms can avoid the development of antibiotic resistance and improve the antiviral properties of these surfaces

Surface disinfections: present and future

The propagation of antibiotic resistance increases the chances of major infections for patients during hospitalization and the spread of health related diseases. Therefore finding new and effective solutions to prevent the proliferation of pathogenic microorganisms is critical, in order to protect hospital environment, such as the surfaces of biomedical devices. Modern nanotechnology has proven to be an effective countermeasure to tackle the threat of infections. On this note, recent scientific breakthroughs have demonstrated that antimicrobial nanomaterials are effective in preventing pathogens from developing resistance. Despite the ability to destroy a great deal of bacteria and control the outbreak of infections, nanomaterials present many other advantages. Moreover, it is unlikely for nanomaterials to develop resistance due to their multiple and simultaneous bactericidal mechanisms. In recent years, science has explored more complex antimicrobial coatings and nanomaterials based on graphene have shown great potential in antibacterial treatment. The purpose of this article is to deepen the discussion on the threat of infections related to surface disinfection and to assess the state of the art and potential solutions, with specific focus on disinfection procedures using nanomaterials

Electrical, mechanical and electromechanical properties of graphene-thermoset polymer composites produced using acetone-DMF solvents

Recently, graphene-polymer composites gained a central role in advanced stress and strain sensing. A fundamental step in the production of epoxy-composites filled with graphene nanoplatelets (GNPs) consists in the exfoliation and dispersion of expanded graphite in a proper solvent, in the mixing of the resulting GNP suspension with the polymer matrix, and in the final removal of the solvent from the composite before curing through evaporation. The effects of traces of residual solvent on polymer curing process are usually overlooked, even if it has been found that even a small amount of residual solvent can affect the mechanical properties of the final composite. In this paper, we show that residual traces of N,N′-Dimethylformamide (DMF) in vinylester epoxy composites can induce relevant variations of the electrical, mechanical and electromechanical properties of the cured GNP-composite. To this purpose, a complete analysis of the morphological and structural characteristics of the composite samples produced using different solvent mixtures (combining acetone and DMF) is performed. Moreover, electrical, mechanical and electromechanical properties of the produced composites are assessed. In particular, the effect on the piezoresistive response of the use of DMF in the solvent mixture is analyzed using an experimental strain dependent percolation law to fit the measured electromechanical data. It is shown that the composites realized using a higher amount of DMF are characterized by a higher electrical conductivity and by a strong reduction of Young’s Modulus

Electromagnetic and electromechanical applications of graphene-based materials

This volume contains the extended abstracts of the contributions presented at the workshop Nanoscale Excitations in Emergent Materials (NEEM 2015) held in Rome from 12 to 14 October 2015, an event organized and supported in the framework of the Bilateral Cooperation Agreement between Italy and India within the project of major relevance "Investigating local structure and magnetism of cobalt nano-structures", funded by the Italian Ministry of Foreign Affairs and the Department of Science and Technology in India

Graphene-based dental adhesive with anti-biofilm activity

BACKGROUND: Secondary caries are considered the main cause of dental restoration failure. In this context, anti-biofilm and bactericidal properties are desired in dental materials against pathogens such as Streptococcus mutans. To this purpose, graphene based materials can be used as fillers of polymer dental adhesives. In this work, we investigated the possibility to use as filler of dental adhesives, graphene nanoplatelets (GNP), a non toxic hydrophobic nanomaterial with antimicrobial and anti-biofilm properties. RESULTS: Graphene nanoplatelets have been produced starting from graphite intercalated compounds through a process consisting of thermal expansion and liquid exfoliation. Then, a dental adhesive filled with GNPs at different volume fractions has been produced through a solvent evaporation method. The rheological properties of the new experimental adhesives have been assessed experimentally. The adhesive properties have been tested using microtensile bond strength measurements (µ-TBS). Biocidal activity has been studied using the colony forming units count (CFU) method. The anti-biofilm properties have been demonstrated through FE-SEM imaging of the biofilm development after 3 and 24 h of growth. CONCLUSIONS: A significantly lower vitality of S. mutans cells has been demonstrated when in contact with the GNP filled dental adhesives. Biofilm growth on adhesive-covered dentine tissues demonstrated anti-adhesion properties of the produced materials. µ-TBS results demonstrated no significant difference in µ-TBS between the experimental and the control adhesive. The rheology tests highlighted the necessity to avoid low shear rate regimes during adhesive processing and application in clinical protocol, and confirmed that the adhesive containing the 0.2%wt of GNPs possess mechanical properties comparable with the ones of the control adhesive

Effect of sonication on morphology and dc electrical conductivity of graphene nanoplatelets-thick films

Graphene and its derivatives are nowadays gaining an ever increasing attention for diverse applications, such as supercapacitors, flexible screens and nanocomposites. One of the main challenges still limiting the wide spreading use of graphene-based nanomaterials in electrical and electromagnetic applications consists in the capability of controlling their morphological properties and electrical conductivity through the proper setting of the synthesis route and production process. In this paper graphene nanoplatelets (GNPs) are produced via thermochemical exfoliation of graphite intercalated compound (GIC). The crucial phase of the exfoliation process consists in the tip sonication of the solution containing thermally reduced GIC. The study presented here aims at evaluating the effect of several synthesis parameters, such as the sonication duty cycle and suspension temperature, on the DC conductivity of GNP thick films and on the morphological properties of GNPs

PVDF composite films including graphene/ZnO nanostructures and their antimicrobial activity

Poly(vinylidene fluoride) (PVDF) is a biocompatible polymer commonly used for biomedical applications, food packaging and hygiene products. Within these contexts, the polymer surface is typically exposed to microorganisms and bacteria, with consequent biofilm formation. In this paper, self-standing flexible composite poly(vinylidene fluoride) (PVDF) films with antimicrobial properties were prepared by simple solution casting method. We investigated the effect of three different types of nanofillers, namely graphene nanoplatelets (GNPs), zinc oxide nanorods (ZnO-NRs) and ZnO-NR-decorated GNPs (ZNGs), on the antimicrobial activity of PVDF composite films against Pseudomonas aeruginosa. ZnO-NRs were also grown directly over the surface of PVDF composite films filled with ZnO nanoparticles, acting as nucleation seeds. In all cases, vitality tests performed in static conditions demonstrated a strong antimicrobial property of the produced specimens. This effect can be mainly ascribed to the bacteria/nanomaterials strong surface interaction, which results in the biofilm integrity disruption

Application of nanotechnology in pediatric dentistry

BACKGROUND: The aim of this work was to study and pro- duce a dental adhesive with antibacterial properties through the use of micro and nanometric fillers based on graphene. METHODS: Graphene is the name given to a flat monolayer of carbon atoms tightly packed into a two-dimensional (2D) honeycomb lattice, and is a basic building block for graphitic materials of all other dimensionalities. It is extremely durable and hard (100 times more than steel), transparent and flexible. In addition, it present, at room temperature, an electrical conductivity superior to any other sub- stance and in recent years he has shown raised interest also in the biomedical field. In the present study it was developed and produced an den- tin/enamel adhesive with antibacterial properties thanks to the introduction of the graphene nanoplatelets (GNP) used as filler, starting from a common commercial adhesive used in dentistry and its widely-known properties. The GNP have been made from expanded graphite (EG), which in turn was produced from graphite intercalation compounds via rapid evaporation of the intercalant at elevated temperatures. The GNP thus obtained, have been incorporated into the commercial adhesive with the technique of solution processing. Antibacterial tests were carried out treating our experimental adhesive with bacterial strains of Streptococcus mutans. The antimicrobic effects of the adhesive were analyzed at both zero time 0 and after aging (1 week). Furthermore, tests of resistance to microtensile were carried out. RESULTS: Tests have shown that GNP present toxicity on microorganisms, thanks to mechanic interaction by wrapping and trapping bacteria. Furthermore, they show also an antibiofilm effect causing fractures in the structure of the same biofilm. The produced material shows a high efficacy the first days of application in which the bacteria mortality was detected by 100% and then the stoppage of biofilm growth. After the aging of the material concordant results were obtained, with a slight decrease of bacteria mortality as the hours passed. The mechanical tests analysis, in order to study the binding strength in the adhesive by GNP introduction, has shown a value by 29,1 MPa, slightly inferior to the value shown by the corresponding commercial adhesive. The given testing value is anyway included within the average of values referred to dental adhesives currently on the market. CONCLUSIONS: The undertook study permitted to develop an enamel dentinal adhesive with innovative antimicrobic properties. The main component of such properties is GNP, which has shown also a high biocompatibility on both human and animal cells. By analyzing bacterial cells in suspension by the method of Colony Forming Units (CFU), it was observed that GNP not only have toxicity on single cells, but also an antibiofilm effect interfering with the vital cycle of the same, thus inhibiting its development. Mechanical tests have shown excellent characteristics of the experimental adhesive so much that it can be considered virtually competitive