Preparation, Characterization, and Photocatalytic Applications of MWCNTs/TiO2 Composite

The multiwall carbon nanotubes (MWCNTs)/titanium dioxide (P25) composite in different ratios was prepared using simple evaporation and drying process. The composite was characterized by Raman spectroscopy, X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy, and scanning electron microscopy (SEM). The photocatalytic activity of this composite was investigated using degradation of the Bismarck brown R dye (BBR). An optimal MWCNTs/TiO2 ratio of 0.5% (w/w) was found to achieve the maximum rate of BBR degradation. It was observed that the composite exhibits enhanced photocatalytic activity compared with TiO2. The enhancement in photocatalytic activity performance of the MWCNTs/P25 composite is explained in terms of recombination of photogenerated electron-hole pairs. In addition, MWCNTs act as a dispersing support to control the morphology of TiO2 particles in the MWCNTs/TiO2 composite

Novel nanoparticle formulations for antimicrobial action

Colloidal particles are being extensively studied in various antimicrobial applications due to their small size, enormous surface area to volume ratio and ability to exhibit a wide spectrum of antibacterial, antifungal, antialgal and antiviral action. This thesis aims to develop novel nanoparticle formulations for antimicrobial action. The present work focuses on various nanoparticles (NPs) of inorganic materials and discusses some of the methods for their preparation as well as mechanisms of their antimicrobial action. The antimicrobial applications of metal oxide nanoparticles (zinc oxide and copper oxide) and metal hydroxide nanoparticles such as magnesium hydroxide were studied. Recent advances in the functionalization of nanoparticles and their potential antimicrobial applications were also studied as a viable alternative of conventional antibiotics and antiseptic agents which can help to tackle antimicrobial resistance.The synthesis and characterisation of a range of surface modified zinc oxide (ZnONPs, Chapter 3 and 4), magnesium hydroxide Mg(OH)2NPs (Chapter 5 and 6) and copper oxide (CuONPs, Chapter 7 and 8) have been described including particle size distribution, crystallite size, zeta potential, isoelectric point, X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), etc. The antibacterial, anti-algal and anti-yeast activity of the modified nanoparticles on microalgae (C. reinhardtii), yeast (S. cerevisiae) and Escherichia coli (E.coli) were explored. The viability of these cells was evaluated for various concentrations and exposure times with nanoparticles. It was discovered that the antimicrobial activity of uncoated nanoparticles on the viability of C. reinhardtii occurred at considerably lower particle concentrations than for S. cerevisiae and E.coli. The results indicate that the antimicrobial activity of polyelectrolyte-coated nanoparticles alternates with their surface charge. The anionic nanoparticles (ZnONPs/PSS, ZnONPs/ZnS, ZnONPs/SiO2, CuONPs/PSS and Mg(OH)2NPs/PSS) have much lower antibacterial activity than the cationic ones (NPs/PSS/PAH and uncoated NPs). These findings have been explained by the lower adhesion of the anionic nanoparticles to the cell wall because of electrostatic repulsion and the enhanced particle-cell adhesion due to electrostatic attraction in the case of cationic nanoparticles. The results can potentially be applied to control the cytotoxicity and the antimicrobial activity of other inorganic nanoparticles.A novel type of antimicrobial formulation of CuONPs has been developed and tested. This has been achieved by functionalizing CuONPs with (3-glycidyloxypropyl)- trimethoxysilane (GLYMO) and subsequent 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, anti-algal and anti-yeast action which is not based on electrostatic adhesion. This work (Chapter 8) demonstrates that the CuONPs with boronic acid surface functionality are far superior antibacterial agents compared to bare CuONPs. The results showed that the antibacterial, anti-algal and anti-yeast impact of the 4-HPBA-functionalized CuONPs on Rhodococcus rhodochrous (R. rhodochrous), E.coli, C. reinhardtii and S. cerevisiae is one order of magnitude higher than that of bare CuONPs or CuONPs/GLYMO. It was 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, the results 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. The experiments with human keratinocyte cell line exposure to CuONPs/GLYMO/4-HPBA indicated lack of measurable cytotoxicity at particle concentrations which are effective as an antibacterial agent for both R. rhodochrous, E. coli, C. reinhardtii and S. cerevisiae. This suggests 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.The role of surface roughness in the antimicrobial activity of oxide nanoparticles has been studied (Chapter 9). This has been achieved by comparing the antimicrobial action of non-porous silica nanoparticles (SiO2NPs) with smooth surface and mesoporous surfacerough SiO2NPs, both functionalized with GLYMO and 4-HPBA. Surface-rough mesoporous silica nanoparticles (‘ghost’ SiO2NPs) have been fabricated by using composite mesoporous copper oxide nanoparticles (‘host’ CuONPs) as templates which allowed the SiO2NPs to copy their surface morphology. It was demonstrated that the functionalized ‘ghost’ SiO2NPs with GLYMO and 4-HPBA (SiO2NPs/GLYMO/4-HPBA) show a very significant antibacterial effect compared to smooth SiO2NPs of the same surface coating and particle size. This was attributed to the ‘ghost’ SiO2NPs surface morphology which mimics to certain extent the surface of the original CuONPs used as templates for their preparation. It can be envisaged 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. Antibacterial tests showed that the ‘ghost’ SiO2NPs/GLYMO/4-HPBA have much higher antibacterial action than the nonfunctionalized ‘ghost’ SiO2NPs or GLYMO functionalized ‘ghost’ SiO2NPs for R. rhodochrous. 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 as silica act as a strong antimicrobial

"Ghost" silica nanoparticles of "host"-inherited antibacterial action

Copyright © 2019 American Chemical Society. 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.

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

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

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

Boosting the antimicrobial action of vancomycin formulated in shellac nanoparticles of dual-surface functionality

We report a strong amplification of the antimicrobial action of vancomycin (VCM) encapsulated in shellac nanoparticles (NPs) with dual surface functionalisation. These shellac nanocarriers for VCM were produced in two steps: (i) a pH drop from aqueous ammonium shellac solution containing Poloxamer 407 (P407) as a steric stabilising polymer in solution of vancomycin hydrochloride, and (ii) subsequent doping with the insoluble cationic surfactant octadecyltrimethylammonium bromide (ODTAB) though a solvent change to yield cationic surface functionality. We evaluated the encapsulation efficiency of VCM and its release profiles from these nanocarriers. This study explored the antibiotic action of these VCM nanocarriers at the various stages of their preparation which helped us to evaluate how they could be made to work efficiently, to adapt their design and demonstrate the role of the nanocarrier dual functionalisation on its antibiotic action and delivery. The antibiotic effect of VCM loaded in such versatile functionalised shellac nanocarriers was tested on three different proxy microorganisms, C. reinhardtii, S. cerevisiae and E. coli. We also compared the antibiotic effect of free VCM with non-coated VCM-loaded nanocarriers at the same overall concentrations. The ODTAB coating of the shellac NPs strongly enhanced the antibiotic action of the encapsulated VCM across all tested microorganisms. The enhanced VCM action is explained with the increased electrostatic adhesion between the ODTAB-coated VCM-loaded shellac NPs and the negatively charged surface of the microbial cell walls which allows local delivery of VCM with a high concentration directly on the cell membrane. This nanocarrier-mediated boost of the antibiotic action may potentially breathe new life into old antibiotics and help to fight off antibiotic resistance by making them more effective

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

© 2019 The Royal Society of Chemistry. 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

ANTIMOULD ACTION OF ZIRAM AND IPBC LOADED IN FUNCTIONALISED NANOGELS AGAINST ASPERGILLUS NIGER AND PENICILLIUM CHRYSOGENUM

We explore the antimould action of zinc bis(dimethyldithiocarbamate) (Ziram) and 3-iodo-2-propynyl N-butylcarbamate (IPBC) encapsulated into nanogel particles with and without surface functionalization with a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDAC). The antimould nanocarriers were based on commercially available polyacrylic copolymeric nanogel. The antimould agents were loaded into the nanogel particles in their swollen state in alkaline media followed by collapsing of the nanogel particles at acidic pH. We treated Aspergillus niger and Penicillium chrysogenum cultures at different concentrations of the nanocarrier-loaded antimould agent. The effect of the surface charge of the antimould agent-loaded nanocarriers was examined in order to gain better understanding of how the electrostatic interaction of the nanocarrier with the cell walls of the mould hyphae and spores impacts its antimould action. Non-coated nanocarriers proved more efficient than PDAC-coated ones in their antimould action for both Ziram and IPBC formulations. Four different methods of application of the antimould nanocarriers were also explored. We found that the application method of the nanogel carrier is crucial for its efficiency and sustained antimould delivery. Pre-mixing the nanogel-formulated Ziram or IPBC with culture media generally produced much better antimould action. Such a strategy can potentially bypass this antimould resistance and lead to novel formulations with highly sustained antimould activity at similar concentrations of the antimould agent. These insights may lead to the development of more efficient antimould treatments at lower concentration of active agent for mould control with potentially substantial economic and environmental benefits

Preparation and Characterization of Activated Carbon from Iraqi Khestawy Date Palm

This work includes a synthesis of three types of the activated carbon (AC) from three different positions from the same Iraqi Khestawy date palm. These three positions are the palm fronds (AC1), the date palm seeds (AC2), and the palm fiber (AC3). These three types of AC were synthesized by a physiochemical activation method using the same activator which was H3PO4. These materials were investigated using different techniques such as Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The adsorption activity of the synthesized AC samples was investigated by following the removal of both Bismarck brown G (BBG) and reactive yellow dye 145 (RY145). Both the kinetics of adsorption and the removal percentage of these dyes were investigated from the batch tests in this study. Different reaction parameters and conditions for adsorption processes were investigated. Also an investigation of both Langmuir and Freundlich adsorption isotherms was considered. The different physical properties of these materials were undertaken such as the point zero charges of the synthesized samples (PZCs), the percentage of humidity, and the adsorption capacity also being investigated. The activity of these materials in the removal of BBG from the aqueous solution was as follows: AC1>AC2>AC3