Influence of Ag, Au and Pd noble metals doping on structural, optical and antimicrobial properties of zinc oxide and titanium dioxide nanomaterials

Comparative study of zinc oxide nanocomposites with different noble metals synthesized by biological method for photocatalytic disinfection of Escherichia coli present in hospital wastewater

Binary zinc oxide (ZnO) nanocomposites with different noble metals, silver (Ag) and ruthenium (Ru), were prepared from an aqueous leaf extract of Callistemon viminalis. The biosynthesized photocatalysts were characterized and examined for their photocatalytic disinfection against Escherichia coli isolated from hospital wastewater. The influence of the different noble metals showed a difference in physicochemical characteristics and photocatalytic efficiency between Ag-ZnO and Ru-ZnO. The photocatalytic degradation of methylene blue and photocatalytic disinfection were found to be in the order Ag-ZnO > Ru-ZnO > ZnO. The photocatalytic disinfection of Ag-ZnO reached a 75% reduction in 60 min, compared to 34 and 9% reductions of Ru-ZnO and ZnO, respectively. The kinetic reaction rate for the photocatalytic disinfection of Ag-ZnO was found to be 2.8 times higher than that of Ru-ZnO. The outstanding photocatalytic activity of Ag-ZnO over Ru-ZnO was attributed to higher crystallinity, greater UVA adsorption capacity, smaller particle size, and the additional antimicrobial effect of Ag itself. The C. viminalis-mediated Ag-ZnO nanocomposites can be a potential candidate for photocatalytic disinfection of drug-resistant E. coli in hospital wastewater.

Photocatalytic and Antimicrobial Properties of Electrospun TiO2-SiO2-Al2O3-ZrO2-CaO-CeO2 Ceramic Membranes

In this study, TiO₂-based ceramic nanofiber membranes in the system of TiO₂-SiO₂-Al₂O₃-ZrO₂-CaO-CeO₂ were synthesized by combining sol-gel and electrospinning processes. In order to investigate the thermal treatment temperature effect, the obtained nanofiber membranes were calcined at different temperatures ranging from 550 to 850 °C. Different characterization methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), and high-resolution transmission electron microscopy (HR-TEM) were conducted on the obtained membranes to investigate the structural and morphological properties of the nanofibers. The Brunauer-Emmett-Teller surface area of the nanofiber membranes was very high (46.6-149.2 m²/g) and decreased with increasing calcination temperature as expected. Photocatalytic activity investigations were determined using methylene blue (MB) as a model dye under UV and sunlight irradiation. High degradation performances were achieved with the calcination temperatures of 650 and 750 °C because of the high specific surface area and the anatase structure of the nanofiber membranes. Moreover, the ceramic membranes showed antibacterial activity against Escherichia coli as a Gram-negative bacterium and Staphylococcus aureus as a Gram-positive bacterium. The superior properties of the novel TiO₂-based multi-oxide nanofiber membranes proved as a promising candidate for various industries, especially the removal of textile dyes from wastewater.

Surface functionalized silver-doped ZnO nanocatalyst: a sustainable cooperative catalytic, photocatalytic and antibacterial platform for waste treatment

The different dyes used and discharged in industrial settings and microbial pathogenic issues have raised serious concerns about the content of bodies of water and the impact that dyes and microbes have on the environment and human health. Efficient treatment of contaminated water is thus a major challenge that is of great interest to researchers around the world. In the present work, we have fabricated functionalized silver-doped ZnO nanoparticles (Ag-doped ZnO NPs) via a hydrothermal method for wastewater treatment. X-ray photoelectron spectroscopy analysis confirmed the doping of Ag with ZnO NPs, and X-ray diffractometry analysis showed a decreasing trend in the crystallite size of the synthesized ZnO NPs with increased Ag concentration. Field emission scanning electron microscopy study of pure ZnO NPs and Ag-doped ZnO NPs revealed nanocrystal aggregates with mixed morphologies, such as hexagonal and rod-shaped structures. Distribution of Ag on the ZnO lattice is confirmed by high-resolution transmission electron microscopy analysis. ZnO NPs with 4 wt% Ag doping showed a maximum degradation of ∼95% in 1.5 h of malachite green dye (80 mg L-1) under visible light and ∼85% in 4 h under dark conditions. Up to five successive treatment cycles using the 4 wt% Ag-doped ZnO NP nanocatalyst confirmed its reusability, as it was still capable of degrading ∼86% and 82% of the dye under visible light and dark conditions, respectively. This limits the risk of nanotoxicity and aids the cost-effectiveness of the overall treatment process. The synthesized NPs showed antibacterial activity in a dose-dependent manner. The zone of inhibition of the Ag-doped ZnO NPs was higher than that of the pure ZnO NPs for all doping content. The studied Ag-doped ZnO NPs thus offer a significant eco-friendly route for the effective treatment of water contaminated with synthetic dyes and fecal bacterial load.

In Vitro Antimicrobial and Anticancer Peculiarities of Ytterbium and Cerium Co-Doped Zinc Oxide Nanoparticles

Zinc oxide nanoparticles (ZnO NPs) are a promising platform for their use in biomedical research, especially given their anticancer and antimicrobial activities. This work presents the synthesis of ZnO NPs doped with different amounts of rare-earth ions of ytterbium (Yb) and cerium (Ce) and the assessment of their anticancer and antimicrobial activities. The structural investigations indicated a hexagonal wurtzite structure for all prepared NPs. The particle size was reduced by raising the amount of Ce and Yb in ZnO. The anticancer capabilities of the samples were examined by the cell viability MTT assay. Post 48-h treatment showed a reduction in the cancer cell viability, which was x = 0.00 (68%), x = 0.01 (58.70%), x = 0.03 (80.94%) and x = 0.05 (64.91%), respectively. We found that samples doped with x = 0.01 and x = 0.05 of Yb and Ce showed a better inhibitory effect on HCT-116 cancer cells than unadded ZnO (x = 0.00). The IC₅₀ for HCT-116 cells of Ce and Yb co-doped ZnO nanoparticles was calculated and the IC₅₀ values were x = 0.01 (3.50 µg/mL), x = 0.05 (8.25 µg/mL), x = 0.00 (11.75 µg/mL), and x = 0.03 (21.50 µg/mL). The treatment-doped ZnO NPs caused apoptotic cell death in the HCT-116 cells. The nanoparticles showed inhibitory action on both C. albicans and E. coli. It can be concluded that doping ZnO NPs with Yb and Ce improves their apoptotic effects on cancer and microbial cells.

Synthesis of ZnO/Au Nanocomposite for Antibacterial Applications

Annually, antimicrobial-resistant infections-related mortality worldwide accelerates due to the increased use of antibiotics during the coronavirus pandemic and the antimicrobial resistance, which grows exponentially, and disproportionately to the current rate of development of new antibiotics. Nanoparticles can be an alternative to the current therapeutic approach against multi-drug resistance microorganisms caused infections. The motivation behind this work was to find a superior antibacterial nanomaterial, which can be efficient, biocompatible, and stable in time. This study evaluated the antibacterial activity of ZnO-based nanomaterials with different morphologies, synthesized through the solvothermal method and further modified with Au nanoparticles through wet chemical reduction. The structure, crystallinity, and morphology of ZnO and ZnO/Au nanomaterials have been investigated with XRD, SEM, TEM, DLS, and FTIR spectroscopy. The antibacterial effect of unmodified ZnO and ZnO/Au nanomaterials against Escherichia coli and Staphylococcus aureus was investigated through disc diffusion and tetrazolium/formazan (TTC) assays. The results showed that the proposed nanomaterials exhibited significant antibacterial effects on the Gram-positive and Gram-negative bacteria. Furthermore, ZnO nanorods with diameters smaller than 50 nm showed better antibacterial activity than ZnO nanorods with larger dimensions. The antibacterial efficiency against Escherichia coli and Staphylococcus aureus improved considerably by adding 0.2% (w/w) Au to ZnO nanorods. The results indicated the new materials' potential for antibacterial applications.

Aqueous Acetamiprid Degradation Using Combined Ultrasonication and Photocatalysis Under Visible Light

Acetamiprid (ACE), a neonicotinoid pesticide widely used in pest control, was found in high concentrations in soils, rivers, and lakes. In the present study, ACE degradation was investigated using visible light driven photocatalysis over nitrogen-graphene oxide (N-GO) and palladium-graphene oxide (Pd-GO)-doped ZnO photocatalysts combined with ultrasonication implemented either as a pretreatment (sonolysis) or operated simultaneously with photocatalysis (sonophocatalysis). The effectiveness of the two ACE degradation processes was determined separately. The sonolysis pretreatment allowed reaching almost 40% acetamiprid conversion within 30 min of reaction. Pursuing with the photodegradation reaction in the presence of N-GO-ZnO and Pd-GO-ZnO resulted in a maximum conversion of 98% of ACE within 5 h. As for the sonophotocatalysis process, the reaction time was shortened from 5 to 2 h with 100% acetamiprid conversion. In addition, the photocatalysts were shown to keep their activity even after 5 sonophotocatalytic cycles, thus proving their reusability.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11270-022-05867-4.

Synthesis of Metal-Loaded Carboxylated Biopolymers with Antibacterial Activity through Metal Subnanoparticle Incorporation

Carboxymethyl starch (CMS) and carboxymethyl cellulose (CMC) loaded by highly dispersed metal subnanoparticles (MSNPs) showed antibacterial activity against E. coli and B. subtilis strains. Copper and silver were found to act in both cationic and zero-valence forms. The antibacterial activity depends on the metal species content but only up to a certain level. Silver cation (Ag⁺) showed higher antibacterial activity as compared to Ag⁰, which was, however, more effective than Cu⁰, due to weaker retention. The number of carboxyl groups of the biopolymers was found to govern the material dispersion in aqueous media, the metal retention strength and dispersion in the host-matrices. Cation and metal retention in both biopolymers was found to involve interactions with the oxygen atoms of both hydroxyl and carboxyl groups. There exists a ternary interdependence between the Zeta potential (ZP), pH induced by the biocidal agent and its particle size (PS). This interdependence is a key factor in the exchange processes with the surrounding species, including bacteria. Clay mineral incorporation was found to mitigate material dispersion, due to detrimental competitive clay:polymer interaction. This knowledge advancement opens promising prospects for manufacturing metal-loaded materials for biomedical applications.

Impact of metallic coating on the retention of 225Ac and its daugthers within core-shell nanocarriers

Currently, alpha-emitting radionuclide 225Ac is one of the most promising isotopes in alpha therapy due to its high linear energy transfer during four sequential alpha decays. However, the main obstacle preventing the full introduction of 225Ac into clinical practice is the lack of stable retention of radionuclides, leading to free circulation of toxic isotopes in the body. In this work, the surface of silica nanoparticles (SiO2 NPs) has been modified with metallic shells composed of titanium dioxide (TiO2) and gold (Au) nanostructures to improve the retention of 225Ac and its decay products within the developed nanocarriers. In vitro and in vivo studies in healthy mice show that the metallic surface coating of SiO2 NPs promotes an enhanced sequestering of radionuclides (225Ac and its daughter isotopes) compared to non-modified SiO2 NPs for a prolonged period of time. Histological analysis reveals that for the period of 3-10 d after the injections, the developed nanocarriers have no significant toxic effects in mice. At the same time, almost no accumulation of leaked radionuclides can be detected in non-target organs (e.g., in the kidneys). In contrast, non-modified carriers (SiO2 NPs) demonstrate the release of free radionuclides, which are distributed over the whole animal body with the consequent morphological changes in the lung, liver and kidney tissues. These results highlight the potential of the developed nanocarriers to be utilized as radionuclide delivery systems and offer an insight into design rules for the fabrication of new nanotherapeutic agents.

Chitosan nanofiber biocomposites for potential wound healing applications: Antioxidant activity with synergic antibacterial effect

Bacterial wound infection is one of the most common nosocomial infections. The unnecessary employment of antibiotics led to raising the growth of antibiotic-resistant bacteria. Accordingly, alternative armaments capable of accelerating wound healing along with bactericidal effects are urgently needed. Considering this, we fabricated chitosan (CS)/polyethylene oxide (PEO) nanofibers armed with antibacterial silver and zinc oxide nanoparticles. The nanocomposites exhibited a high antioxidant effect and antibacterial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Besides, based on the results of the cell viability assays, the optimum concentration of ZnONPs and AgNPs in the nanofibrous mats is 0.2% w/v and 0.08% w/v respectively and had no cytotoxicity on fibroblast cells. The scaffold also showed good blood compatibility according to the effects of coagulation time. As well as significant fibroblast migration and proliferation on the wound margin, according to wound-healing assay. All in all, the developed biocompatible, antioxidant, and antibacterial Ag-ZnO NPs incorporated CS/PEO nanofibrous mats showed their potential as an effective wound dressing.

Recent advancements in cellulose-based biomaterials for management of infected wounds

INTRODUCTION

Chronic wounds are a substantial burden on the healthcare system. Their treatment requires advanced dressings, which can provide a moist wound environment, prevent bacterial infiltration, and act as a drug carrier. Cellulose is biocompatible, biodegradable, and can be functionalized according to specific requirements, which makes it a highly versatile biomaterial. Antimicrobial cellulose dressings are proving to be highly effective against infected wounds.

AREAS COVERED

This review briefly addresses the mechanism of wound healing and its pathophysiology. It also discusses wound infections, biofilm formation, and progressive emergence of drug-resistant bacteria in chronic wounds and the treatment strategies for such types of infected wounds. It also summarizes the general properties, method of production, and types of cellulose wound dressings. It explores recent studies and advancements regarding the use of cellulose and its derivatives in wound management.

EXPERT OPINION

Cellulose and its various functionalized derivatives represent a promising choice of wound dressing material. Cellulose-based dressings loaded with antimicrobials are very useful in controlling infection in a chronic wound. Recent studies showing its efficacy against drug-resistant bacteria make it a favorable choice for chronic wound infections. Further research and large-scale clinical trials are required for better clinical evidence of its efficiency.

Recent progress on Ag/TiO2 photocatalysts: photocatalytic and bactericidal behaviors

For many decades, titanium dioxide (TiO₂) semiconductor has been extensively applied in several environmental applications due to its higher photocatalytic performances toward different organic pollutants, pharmaceutical compounds, and bacteria. However, its shortfall response to visible light, and the expeditious recombination rate of the photogenerated electron-hole pairs, hampers its utilization. Doping TiO₂ semiconductor with silver nanoparticles is a sound strategy to (1) extend its photocatalytic activity to visible light, (2) prevent the electron/holes pairs recombination due to the formation of the Schottky barrier at the interfaces with TiO₂ that act as an electron-trapping center, and (3) enhance its bactericide performances. This review focuses on the recent progress on silver-doped titanium dioxide (Ag/TiO₂)-based photocatalysts. It addresses a wide range of Ag/TiO₂ synthesis techniques, their physicochemical properties and discusses thoroughly the important role of silver (Ag) nanoparticles in enhancing the removal capacity and antibacterial performances of the Ag/TiO₂ photocatalysts.

Recent advances in functionalized nanomaterials for the diagnosis and treatment of bacterial infections

The growing problem of resistant infections due to antibiotic misuse is a worldwide concern that poses a grave threat to healthcare systems. Thus, it is necessary to discover new strategies to combat infectious diseases. In this review, we provide a selective overview of recent advances in the use of nanocomposites as alternatives to antibiotics in antimicrobial treatments. Metals and metal oxide nanoparticles (NPs) have been associated with inorganic and organic supports to improve their antibacterial activity and stability as well as other properties. For successful antibiotic treatment, it is critical to achieve a high drug concentration at the infection site. In recent years, the development of stimuli-responsive systems has allowed the vectorization of antibiotics to the site of infection. These nanomaterials can be triggered by various mechanisms (such as changes in pH, light, magnetic fields, and the presence of bacterial enzymes); additionally, they can improve antibacterial efficacy and reduce side effects and microbial resistance. To this end, various types of modified polymers, lipids, and inorganic components (such as metals, silica, and graphene) have been developed. Applications of these nanocomposites in diverse fields ranging from food packaging, environment, and biomedical antimicrobial treatments to diagnosis and theranosis are discussed.

Ultrasensitive aptasensor for isolation and detection of circulating tumor cells based on CeO2@Ir nanorods and DNA walker

Herein, based on dual signal amplification by CeO₂@Ir nanorods (Ce@IrNRs) and enzyme-free DNA walker, a novel electrochemical aptasensor was developed for simultaneous isolation and detection of circulating tumor cells (CTCs). A membrane protein MUC1-targeting aptamer was used to specifically recognize and capture MCF-7 cells. Uracil DNA glycosylase could hydrolyze deoxyuracils of the aptamer to isolate the captured cells. Novel Ce@IrNRs with large surface area and high peroxidase activity were synthesized to amplify the signal, and the enzyme-free DNA walker was applied to release more signal probes combined with Ce@IrNRs. Furthermore, to reduce steric hindrance by cells, the signal probes rather than the target cells, were directly combined with the electrode. The aptasensor could detect CTCs in the range of 2 to 2 × 10⁶ cells mL^-1 with a limit of detection 1 cell mL^-1. The developed aptasensor, which can simultaneously isolate and detect CTCs, has great application potential in the early monitoring of tumor metastasis and in individualized treatment.

Cellulose from sources to nanocellulose and an overview of synthesis and properties of nanocellulose/zinc oxide nanocomposite materials

Recently, environmental and ecological concerns are increasing due to the usage of petroleum-based products so the synthesis of ultra-fine chemicals and functional materials from natural resources is drawing a tremendous level of attention. Nanocellulose, a unique and promising natural material extracted from native cellulose, may prove to be most ecofriendly materials that are technically and economically feasible in modern times, minimizing the pollution generation. Nanocellulose has gained tremendous attention for its use in various applications, due to its excellent special surface chemistry, physical properties, and remarkable biological properties (biodegradability, biocompatibility, and non-toxicity). Various types of nanocellulose, viz. cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial nanocellulose (BNC), are deeply introduced and compared in this work in terms of sources, production, structures and properties. The metal and metal oxides especially zinc oxide nanoparticles (ZnO-NPs) are broadly used in various fields due to the diversity of functional properties such as antimicrobial and ultraviolet (UV) properties. Thus, the advancement of nanocellulose and zinc oxide nanoparticles (ZnO-NPs)-based composites materials are summarized in this article in terms of the preparation methods and remarkable properties with the help of recent knowledge and significant findings (especially from the past six years reports). The nanocellulose materials complement zinc oxide nanoparticles, where they impart their functional properties to the nanoparticle composites. As a result hybrid nanocomposite containing nanocellulose/zinc oxide composite has shown excellent mechanical, UV barrier, and antibacterial properties. The nanocellulose based hybrid nanomaterials have huge potential applications in the area of food packaging, biopharmaceuticals, biomedical, and cosmetics. Thus the functional composite materials containing nanocellulose and zinc oxide will determine the potential biomedical application for nanocellulose.

The Antibiofilm Effect of a Medical Device Containing TIAB on Microorganisms Associated with Surgical Site Infection

Surgical site infections (SSIs) represent the most common nosocomial infections, and surgical sutures are optimal surfaces for bacterial adhesion and biofilm formation. Staphylococcus spp., Enterococcus spp., and Escherichia coli are the most commonly isolated microorganisms. The aim of this research was to evaluate the antibiofilm activity of a medical device (MD) containing TIAB, which is a silver-nanotech patented product. The antibacterial effect was evaluated against Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, and E. coli ATCC 25922 by assessing the minimum inhibitory concentration (MIC) by the Alamar Blue^® (AB) assay. The antibiofilm effect was determined by evaluation of the minimum biofilm inhibitory concentration (MBIC) and colony-forming unit (CFU) count. Subsequently, the MD was applied on sutures exposed to the bacterial species. The antimicrobial and antibiofilm effects were evaluated by the agar diffusion test method, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM). The MIC was determined for S. aureus and E. faecalis at 2 mg/mL, while the MBIC was 1.5 mg/mL for S. aureus and 1 mg/mL for E. faecalis. The formation of an inhibition zone around three different treated sutures confirmed the antimicrobial activity, while the SEM and CLSM analysis performed on the MD-treated sutures underlined the presence of a few adhesive cells, which were for the most part dead. The MD showed antimicrobial and antibiofilm activities versus S. aureus and E. faecalis, but a lower efficacy against E. coli. Surgical sutures coated with the MD have the potential to reduce SSIs as well as the risk of biofilm formation post-surgery.