Recent advances in nanoscience and nanotechnology radically changed the way we diagnose, treat, and prevent various diseases in all aspects of human life. Silver nanoparticles (AgNPs) are one of the most vital and fascinating nanomaterials among several metallic nanoparticles that are involved in biomedical applications. AgNPs play an important role in nanoscience and nanotechnology, particularly in nanomedicine. Although several noble metals have been used for various purposes, AgNPs have been focused on potential applications in cancer diagnosis and therapy. In this review, we discuss the synthesis of AgNPs using physical, chemical, and biological methods. We also discuss the properties of AgNPs and methods for their characterization. More importantly, we extensively discuss the multifunctional bio-applications of AgNPs; for example, as antibacterial, antifungal, antiviral, anti-inflammatory, anti-angiogenic, and anti-cancer agents, and the mechanism of the anti-cancer activity of AgNPs. In addition, we discuss therapeutic approaches and challenges for cancer therapy using AgNPs. Finally, we conclude by discussing the future perspective of AgNPs.

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Silver Nanoparticles: Synthesis, Characterization, Properties, Applications, and Therapeutic Approaches

Role of nanomaterials in water treatment applications: a review.

Functional graphene nanomaterials (FGNs) are fast emerging materials with extremely unique physical and chemical properties and physiological ability to interfere and/or interact with bioorganisms; as a result, FGNs present manifold possibilities for diverse biological applications. Beyond their use in drug/gene delivery, phototherapy, and bioimaging, recent studies have revealed that FGNs can significantly promote interfacial biointeractions, in particular, with proteins, mammalian cells/stem cells, and microbials. FGNs can adsorb and concentrate nutrition factors including proteins from physiological media. This accelerates the formation of extracellular matrix, which eventually promotes cell colonization by providing a more beneficial microenvironment for cell adhesion and growth. Furthermore, FGNs can also interact with cocultured cells by physical or chemical stimulation, which significantly mediate their cellular signaling and biological performance. In this review, we elucidate FGNs–bioorganism int...

Functional Graphene Nanomaterials Based Architectures: Biointeractions, Fabrications, and Emerging Biological Applications

Complications related to infectious diseases have significantly decreased due to the availability and use of a wide variety of antibiotics and antimicrobial agents. However, excessive use of antibiotics and antimicrobial agents over years has increased the number of drug resistant pathogens. Microbial multidrug resistance poses serious risks and consequently research attention has refocused on finding alternatives for antimicrobial treatment. Among the various approaches, the use of engineered nanostructures is currently the most promising strategy to overcome microbial drug resistance by improving the remedial efficiency due to their high surface-to-volume ratio and their intrinsic or chemically incorporated antibacterial activity. Graphene, a two-dimensional ultra-thin nanomaterial, possesses excellent biocompatibility, putting it in the forefront for different applications in biosensing, drug delivery, biomedical device development, diagnostics and therapeutics. Graphene-based nanostructures also hold great promise for combating microbial infections. Yet, several questions remain unanswered such as the mechanism of action with the microbial entities, the importance of size and chemical composition in the inhibition of bacterial proliferation and adhesion, cytotoxicity, and other issues when considering future clinical implementation. This review summarizes the current efforts in the formulation of graphene-based nanocomposites with antimicrobial and antibiofilm activities as new tools to tackle the current challenges in fighting against bacterial targets. Furthermore, the review describes the features of graphene–bacterial interactions, with the hope to shed light on the range of possible mode of actions, serving the goal to develop a better understanding of the antibacterial capabilities of graphene-based nanostructures.

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Antibacterial activity of graphene-based materials

Stable reduced graphene oxide-cuprous oxide (rGO-Cu2O) nanocomposites with long-term antibacterial activities were prepared by reducing copper sulfate supported on GO using ascorbic acid as reducing agent in the presence of polyethylene glycol (PEG) and sodium hydroxide at room temperature. The rGO provided a protective barrier for Cu2O, preventing Cu2O from reacting with external solution to leach copper ions too quickly. Meanwhile, the rGO also promoted the separation of photoexcited charge carriers of Cu2O nanoparticles to enhance the oxidative stress reactive and protected Cu2O from falling apart in the phosphate buffered solution (PBS) solution to prolong the generation time of reactive oxygen species (ROS). More importantly, the large specific surface area of rGO improved the dispersibility of Cu2O by electrostatic interaction. The synergistic effect of sustained release of copper ions, elevated ROS production ability and uniform dispersion of rGO-Cu2O nanocomposites resulted in the excellent antibacterial activities of rGO-Cu2O nanocomposites against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) which were maintained around 70% and 65% and were increased by 40% and 35% compared with free Cu2O after immersing 30 days in PBS solutions.

Long-term antibacterial stable reduced graphene oxide nanocomposites loaded with cuprous oxide nanoparticles.

In this work, we report a facile and green approach to prepare a uniform silver nanoparticles (AgNPs) decorated graphene oxide (GO) nanocomposite (GO-Ag). The nanocomposite was fully characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra, ultraviolet–visible (UV–vis) absorption spectra, and X-ray photoelectron spectroscopy (XPS), which demonstrated that AgNPs with a diameter of approximately 22 nm were uniformly and compactly deposited on GO. To investigate the silver ion release behaviors, HEPES buffers with different pH (5.5, 7, and 8.5) were selected and the mechanism of release actions was discussed in detail. The cytotoxicity of GO-Ag nanocomposite was also studied using HEK 293 cells. GO-Ag nanocomposite displayed good cytocompatibility. Furthermore, the antibacterial properties of GO-Ag nanocomposite were studied using Gram-negative E. coli ATCC 25922 and Gram-positive S. aureus ATCC 6538 by both the plate count method and disk diffusion method. The nanoc...

Preparation, Characterization, and Antibacterial Activity of Silver Nanoparticle-Decorated Graphene Oxide Nanocomposite

Bacterial adhesion on the surfaces of medical devices, food processing equipment, heat exchangers and ship hulls has been recognized as a widespread problem. Bacterial adhesion on a surface is influenced by surface physical and chemical properties of the surface. In this paper, polyethyleneimine (PEI) grafted graphene oxide (GO) nanosheets were incorporated into Ni–P coatings by an electroless plating technique to modify the surface energy, and therefore to influence the interactions between the prepared surfaces and the tested bacteria. Ni–P–GO coatings were investigated by SEM, AFM, Raman spectrum and XPS. Contact angles of Ni–P–GO coatings with different GO loadings were tested and the surface free energies and their dispersive and polar components were calculated using the van Oss acid–base approach. The results showed that the surface free energies of the coatings had a significant influence on S. aureus adhesion. The Ni–P–GO coatings showed excellent antibacterial adhesion activity. Extended DLVO theory is used to explain the antibacterial adhesion behavior. The novel coatings reported here can be used in controlling bacterial adhesion and biofilm formation for various applications.

Graphene oxide reinforced Ni–P coatings for bacterial adhesion inhibition

CO2-Assisted Water-Washing Process of Municipal Solid Waste Incineration Fly Ash for Chloride Removal

Utilization of municipal solid waste incineration fly ash (MSWI-FA) can avoid land occupation and environmental risks of landfill. In this paper, MSWI-FA was used to prepare alkali activated cementitious materials (AACMs) after two-step pretreatment. The ash calcination at 450 °C removed 93% of dioxins. The alkali washing with 0.2 g NaOH/g ash removed 89% of chlorine and retained almost 100% of calcium. The initial setting time of AACMs was too short to detect for 20% of MSWI-FA addition, and the prepared block had extensive cracks and expansion for CaClOH and CaSO4 inside. Alkaline washing pretreatment increased the initial setting time by longer than 3 min with 30% ash addition and eliminated the cracks and expansion. The significance of the factors for compressive strength followed the modulus of alkali activator > silica fume amount > alkaline washing MSWI fly ash (AW-MSWI-FA) amount. When the activator modulus was 1.2, 1.4 and 1.6, the blocks with 30% of AW-MSWI-FA had a compressive strength of up to 36.73, 32.61 and 16.06 MPa, meeting MU15 grade. The leaching test shows that these AACM blocks were not hazardous waste and almost no Zn, Cu, Cd, Pb, Ba, Ni, Be and Ag were released in the leaching solution.

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Guanghui Dong

Papers

Preparation, Characterization, and Antibacterial Activity of Silver Nanoparticle-Decorated Graphene Oxide Nanocomposite

Graphene oxide reinforced Ni–P coatings for bacterial adhesion inhibition

CO2-Assisted Water-Washing Process of Municipal Solid Waste Incineration Fly Ash for Chloride Removal

Preparation of Alkali Activated Cementitious Material by Upgraded Fly Ash from MSW Incineration