Comparison activity of pure and chromium-doped nickel oxide nanoparticles for the selective removal of dyes from water.

The current study involves a synthesis of a composite of nickel oxide nanoparticles (NiONPs) with a chromium dopant to yield (Cr/NiONPs). Synthesis of nickel oxide was performed by the co-precipitation method. The synthesis of the composite was conducted by the impregnation method. FTIR, EDX, SEM, and XRD were used to characterize the synthesized materials. The synthesised materials' point zero charges (PZC) were performed using the potentiometric titration method. The obtained results show that the PZC for neat nickel oxide was around 5, and it was around 8 for Cr/NiONPs. The adsorption action of the prepared materials was examined by applying them to remove Reactive Red 2 (RR2) and Crystal Violate (CV) dyes from solutions. The outcomes demonstrated that Cr/NiONPs were stronger in the removal of dyes than NiONPs. Cr/NiONPs achieved 99.9% removal of dyes after 1 h. Adsorption isotherms involving Freundlich and Langmuir adsorption isotherms were also conducted, and the outcomes indicated that the most accurate representation of the adsorption data was offered by Langmuir adsorption isotherms. Additionally, it was discovered that the adsorption characteristics of the NiONPs and Cr/NiONPs correspond well with the pseudo-second-order kinetic model. Each of the NiONPs and Cr/NiONPs was reused five times, and the results display that the effectiveness of the removal of RR2 dye slightly declined with the increase in reuse cycles; it lost only 5% of its original efficiency after the 5 cycles. Generally, Cr/NiONPs showed better reusability than NiONPs under the same conditions.

High-performance photocatalytic degradation and antifungal activity of chromium-doped nickel oxide nanoparticles.

The elimination of pollutants such as dyes and fungi has become a tedious process hence there is a need for multifunctional materials that can be used for the removal or degradation of various pollutants from wastewater. Here, a nickel oxide nanoparticle (NiONPs) was synthesized by the co-precipitation method. In the current study, a composite of nickel oxide nanoparticles (NiONPs) was synthesized using nitrogen and chromium as dopants to create (N/NiONPs) and (Cr/N/NiONPs), respectively and used for the removal of dyes and fungi. The synthesized nanocomposites were characterized using zeta potential (ZP), scanning electron microscopy (SEM), X-rays diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The NiONPs, N/NiONPs and Cr/N/NiONPs were tested for the degradation of two dye pollutants, Reactive blue 13 (RB13) and eosin dye. The obtained results showed that Cr/N/NiONPs were more efficient than NiONPs and N/NiONPs for dye degradation by applying the same irradiation conditions. The Cr/N/NiONPs nanocomposites showed very good degradation efficiency of dye up to 94.2% for the RB13 and 90.8% for the eosin. We also examined the antifungal action of the NiONPs, N/NiONPs and Cr/N/NiONPs against Trichoderma fungus. The results showed that the Cr/N/NiONPs have an extremely strong antifungal impact on Trichoderma. This could be explained by the strong adhesion of Cr/N/NiONPs to the Trichoderma surface due to electrostatic attraction. This work has demonstrated that it is possible to create environmentally safe materials that can be used for the degradation of different dyes and the improvement of more effective antifungal treatments with lower active agent doses for fungus control with potential big economic benefits.

Fabrication of graded porous structure of hydroxypropyl cellulose hydrogels via temperature-induced phase separation.

A novel hydroxypropyl cellulose (gHPC) hydrogel with graded porosity has been fabricated, in which pore size, shape, and mechanical properties vary across the material. The graded porosity was achieved by cross-linking different parts of the hydrogel at temperatures below and above 42 °C, which was found to be the temperature of turbidity onset (lower critical solution temperature, LCST) for the HPC and divinylsulfone cross-linker mixture. Scanning electron microscopy imaging revealed a decreasing pore size along the cross-section of the HPC hydrogel from the top to the bottom layer. HPC hydrogels demonstrate graded mechanical properties whereby the top layer, Zone 1, cross-linked below LCST, can be compressed by about 50% before fracture, whereas the middle and bottom layers (Zone 2 and 3, respectively) cross-linked at 42 °C, can withstand 80% compression before failure. This work demonstrates a straightforward, yet novel, concept of exploiting a graded stimulus to incorporate a graded functionality into porous materials that can withstand mechanical stress and minor elastic deformations.

Emerging nanotechnologies for targeting antimicrobial resistance.

Antimicrobial resistance is a leading cause of mortality worldwide. Without newly approved antibiotics and antifungals being brought to the market, resistance is being developed to the ones currently available to clinicians. The reason is the applied evolutionary pressure to bacterial and fungal species due to the wide overuse of common antibiotics and antifungals in clinical practice and agriculture. Biofilms harbour antimicrobial-resistant subpopulations, which make their antimicrobial treatment even more challenging. Nanoparticle-based technologies have recently been shown to successfully overcome antimicrobial resistance in both planktonic and biofilms phenotypes. This results from the combination of novel nanomaterial research and classic antimicrobial therapies which promise to deliver a whole new generation of high-performance active nanocarrier systems. This review discusses the latest developments of promising nanotechnologies with applications against resistant pathogens and evaluates their potential and feasibility for use in novel antimicrobial therapies.

Enhanced Antimould Action of Surface Modified Copper Oxide Nanoparticles with Phenylboronic Acid Surface Functionality.

Antimould agents are widely used in different applications, such as specialty paints, building materials, wood preservation and crop protection. However, many antimould agents can be toxic to the environment. This work aims to evaluate the application of copper oxide nanoparticles (CuONPs) surface modified with boronic acid (BA) terminal groups as antimould agents. We developed CuONPs grafted with (3-glycidyloxypropyl) trimethoxysilane (GLYMO), coupled with 4-hydroxyphenylboronic acid (4-HPBA), which provided a strong boost of their action as antimould agents. We studied the antimould action of the 4-HPBA-functionalized CuONPs against two mould species: Aspergillus niger (A. niger) and Penicillium chrysogenum (P. chrysogenum). The cis-diol groups of polysaccharides expressed on the mould cell walls can form reversible covalent bonds with the BA groups attached on the CuONPs surface. This allowed them to bind strongly to the mould surface, resulting in a very substantial boost of their antimould activity, which is not based on electrostatic adhesion, as in the case of bare CuONPs. The impact of these BA-surface functionalized nanoparticles was studied by measuring the growth of the mould colonies versus time. The BA-functionalized CuONPs showed significant antimould action, compared to the untreated mould sample at the same conditions and period of time. These results can be applied for the development of more efficient antimould treatments at a lower concentration of active agent with potentially substantial economic and environmental benefits.

"Ghost" Silica Nanoparticles of "Host"-Inherited Antibacterial Action.

We fabricated surface-rough mesoporous silica nanoparticles ("ghost" SiO2NPs) by using composite mesoporous copper oxide nanoparticles ("host" CuONPs) as templates, which allowed us to mimic their surface morphology. The "host" CuONPs used here as templates, however, had a very high antibacterial effect, with or without functionalization. To evaluate the surface roughness effect on the "ghost" SiO2NPs antibacterial action, we functionalized them with (3-glycidyloxypropyl)trimethoxysilane (GLYMO) to permit additional covalent coupling of 4-hydroxyphenylboronic acid (4-HPBA). The diol groups on the bacterial membrane can form reversible covalent bonds with boronic acid (BA) groups on the "ghost" SiO2NPs surface and bind to the bacteria, resulting in a very strong amplification of their antibacterial activity, which does not depend on electrostatic adhesion. The BA-functionalized "ghost" SiO2NPs showed a very significant antibacterial effect as compared to smooth SiO2NPs of the same surface coating and particle size. We attribute this to the "ghost" SiO2NPs mesoporous surface morphology, which mimics to a certain extent those of the original mesoporous CuONPs used as templates for their preparation. We envisage that the "ghost" SiO2NPs effectively acquire some of the antibacterial properties from the "host" CuONPs, with the same functionality, despite being completely free of copper. The antibacterial effect of the functionalized "ghost" SiO2NPs/GLYMO/4-HPBA on Rhodococcus rhodochrous (R. rhodochrous) and Escherichia coli (E. coli) is much higher than that of the nonfunctionalized "ghost" SiO2NPs or the "ghost" SiO2NPs/GLYMO. The results indicate that the combination of rough surface morphology and strong adhesion of the particle surface to the bacteria can make even benign material such as silica act as a strong antimicrobial agent. Additionally, our BA-functionalized nanoparticles ("ghost" SiO2NPs/GLYMO/4-HPBA) showed no detectable cytotoxic impact against human keratinocytes at particle concentrations, which are effective against bacteria.

Controlling the Antimicrobial Action of Surface Modified Magnesium Hydroxide Nanoparticles.

Magnesium hydroxide nanoparticles (Mg(OH)2NPs) have recently attracted significant attention due to their wide applications as environmentally friendly antimicrobial nanomaterials, with potentially low toxicity and low fabrication cost. Here, we describe the synthesis and characterisation of a range of surface modified Mg(OH)2NPs, including particle size distribution, crystallite size, zeta potential, isoelectric point, X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). We explored the antimicrobial activity of the modified Mg(OH)2NPs on the microalgae (C. reinhardtii), yeast (S. cerevisiae) and Escherichia coli (E. coli). The viability of these cells was evaluated for various concentrations and exposure times with Mg(OH)2NPs. It was discovered that the antimicrobial activity of the uncoated Mg(OH)2NPs on the viability of C. reinhardtii occurred at considerably lower particle concentrations than for S. cerevisiae and E. coli. Our results indicate that the antimicrobial activity of polyelectrolyte-coated Mg(OH)2NPs alternates with their surface charge. The anionic nanoparticles (Mg(OH)2NPs/PSS) have much lower antibacterial activity than the cationic ones (Mg(OH)2NPs/PSS/PAH and uncoated Mg(OH)2NPs). These findings could be explained by the lower adhesion of the Mg(OH)2NPs/PSS to the cell wall, because of electrostatic repulsion and the enhanced particle-cell adhesion due to electrostatic attraction in the case of cationic Mg(OH)2NPs. The results can be potentially applied to control the cytotoxicity and the antimicrobial activity of other inorganic nanoparticles.

Strongly Enhanced Antibacterial Action of Copper Oxide Nanoparticles with Boronic Acid Surface Functionality.

Copper oxide nanoparticles (CuONPs) have been widely recognized as good antimicrobial agents but are heavily regulated due to environmental concerns of their postuse. In this work, we have developed and tested a novel type of formulation for copper oxide (CuONPs) which have been functionalized with (3-glycidyloxypropyl)trimethoxysilane (GLYMO) to allow further covalent coupling of 4-hydroxyphenylboronic acid (4-HPBA). As the boronic acid (BA) groups on the surface of CuONPs/GLYMO/4-HPBA can form reversible covalent bonds with the diol groups of glycoproteins on the bacterial cell surface, they can strongly bind to the cells walls resulting in a very strong enhancement of their antibacterial action which is not based on electrostatic adhesion. Scanning electron microscopy and transmission electron microscopy imaging revealed that 4-HPBA-functionalized CuO nanoparticles could accumulate more on the cell surface than nonfunctionalized ones. We demonstrate that the CuONPs with boronic acid surface functionality are far superior antibacterial agents compared to bare CuONPs. Our results showed that the antibacterial impact of the 4-HPBA-functionalized CuONPs on Rhodococcus rhodochrous and Escherichia coli is 1 order of magnitude higher than that of bare CuONPs or CuONPs/GLYMO. We also observed a marked increase of the 4-HPBA-functionalized CuONPs antibacterial action on these microorganisms at shorter incubation times compared with the bare CuONPs at the same conditions. Significantly, we show that the cytotoxicity of CuONPs functionalized with 4-HPBA as an outer layer can be controlled by the concentration of glucose in the media, and that the effect is reversible as glucose competes with the sugar residues on the bacterial cell walls for the BA-groups on the CuONPs. Our experiments with human keratinocyte cell line exposure to CuONPs/GLYMO/4-HPBA indicated lack of measurable cytotoxicity at particle concentration which are effective as an antibacterial agent for both R. rhodochrous and E. coli. We envisage that formulations of CuONPs/GLYMO/4-HPBA can be used to drastically reduce the overall CuO concentration in antimicrobial formulations while strongly increasing their efficiency.

Self-grafting copper oxide nanoparticles show a strong enhancement of their anti-algal and anti-yeast action.

We have developed and tested copper oxide nanoparticles (CuONPs) grafted with (3-glycidyloxypropyl)trimethoxysilane (GLYMO) and coupled with 4-hydroxyphenylboronic acid (4-HPBA), which provides a very strong boost of their action as anti-algal and anti-yeast agents. The boronic acid terminal groups on the surface of the CuONPs/GLYMO/4-HPBA can form reversible covalent bonds with the diol groups of glycoproteins and carbohydrates expressed on the cell surface where they bind and accumulate, which is not based on electrostatic adhesion. Results showed that, the impact of the 4-HPBA grafted CuONPs on microalgae (C. reinhardtii) and yeast (S. cerevisiae) is several hundred percent higher than that of bare CuONPs and CuONPs/GLYMO at the same particle concentration. SEM and TEM imaging revealed that 4-HPBA-functionalized CuONPs nanoparticles can accumulate more on the cell walls than non-functionalized CuONPs. We found a marked increase of the 4-HPBA functionalized CuONPs action on these microorganisms at shorter incubation times compared with the bare CuONPs at the same conditions. We also showed that the anti-algal action of CuONPs/GLYMO/4-HPBA can be controlled by the concentration of glucose in the media and that the effect is reversible as glucose competes with the diol residues on the algal cell walls for the HPBA groups on the CuONPs. Our experiments with human cell lines incubated with CuONPs/GLYMO/4-HPBA indicated a lack of measurable loss of cell viability at particle concentrations which are effective as anti-algal agents. CuONPs/GLYMO/4-HPBA can be used to drastically reduce the overall CuO concentration in anti-algal and anti-yeast formulations while strongly increasing their efficiency.

Colloid particle formulations for antimicrobial applications.

Colloidal particles are being extensively studied in various antimicrobial applications due to their small size to volume ratio and ability to exhibit a wide spectrum of antibacterial, antifungal, antialgal and antiviral action. The present review focuses on various nanoparticles (NPs) of inorganic, organic and hybrid materials, and discusses some of the methods for their preparation as well as mechanisms of their antimicrobial action. We consider the antimicrobial applications of metal oxide nanoparticles (ZnO, MgO, CuO, Cu2O, Al2O3, TiO2, CeO2 and Y2O3), metal nanoparticles (NPs), such as copper, silver and gold, metal hydroxide NPs such as Mg(OH)2 as well as hybrid NPs made from biodegradable materials, such as chitosan, lignin and dextran, loaded with other antimicrobial agents. Recent developments for targeted delivery of antimicrobials by using colloid antibodies for microbial cell shape and surface recognition are also discussed. We also consider recent advances in the functionalization of nanoparticles and their potential antimicrobial applications as a viable alternative of conventional antibiotics and antiseptic agents which can help to tackle antimicrobial resistance. The review also covers the recently developed environmentally benign NPs (EbNPs) as a "safer-by-design" green chemistry solution of the post use fate of antimicrobial nanomaterials.