Leucas aspera mediated multifunctional CeO2 nanoparticles: Structural, photoluminescent, photocatalytic and antibacterial properties

Multifunctional scaffolds for bone repair following age-related biological decline: Promising prospects for smart biomaterial-driven technologies

The repair of large bone defects due to trauma, disease, and infection can be exceptionally challenging in the elderly. Despite best clinical practice, bone regeneration within contemporary, surgically implanted synthetic scaffolds is often problematic, inconsistent, and insufficient where additional osteobiological support is required to restore bone. Emergent smart multifunctional biomaterials may drive important and dynamic cellular crosstalk that directly targets, signals, stimulates, and promotes an innate bone repair response following age-related biological decline and when in the presence of disease or infection. However, their role remains largely undetermined. By highlighting their mechanism/s and mode/s of action, this review spotlights smart technologies that favorably align in their conceivable ability to directly target and enhance bone repair and thus are highly promising for future discovery for use in the elderly. The four degrees of interactive scaffold smartness are presented, with a focus on bioactive, bioresponsive, and the yet-to-be-developed autonomous scaffold activity. Further, cell- and biomolecular-assisted approaches were excluded, allowing for contemporary examination of the capabilities, demands, vision, and future requisites of next-generation biomaterial-induced technologies only. Data strongly supports that smart scaffolds hold significant promise in the promotion of bone repair in patients with a reduced osteobiological response. Importantly, many techniques have yet to be tested in preclinical models of aging. Thus, greater clarity on their proficiency to counteract the many unresolved challenges within the scope of aging bone is highly warranted and is arguably the next frontier in the field. This review demonstrates that the use of multifunctional smart synthetic scaffolds with an engineered strategy to circumvent the biological insufficiencies associated with aging bone is a viable route for achieving next-generation therapeutic success in the elderly population.

A neoteric antibacterial ceria-silver nanozyme for abiotic surfaces

Community-associated and hospital-acquired infections caused by bacteria continue to yield major global challenges to human health. Bacterial contamination on abiotic surfaces is largely spread via high-touch surfaces and contemporary standard disinfection practices show limited efficacy, resulting in unsatisfactory therapeutic outcomes. New strategies that offer non-specific and broad protection are urgently needed. Herein, we report our novel ceria-silver nanozyme engineered at a molar ratio of 5:1 and with a higher trivalent (Ce3+) surface fraction. Our results reveal potent levels of surface catalytic activity on both wet and dry surfaces, with rapid, and complete eradication of Pseudomonas aeruginosa, Staphylococcus aureus, and methicillin resistant S. aureus, in both planktonic and biofilm form. Preferential electrostatic adherence of anionic bacteria to the cationic nanozyme surface leads to a catastrophic loss in both aerobic and anaerobic respiration, DNA damage, osmodysregulation, and finally, programmed bacterial lysis. Our data reveal several unique mechanistic avenues of synergistic ceria-Ag efficacy. Ag potentially increases the presence of Ce3+ sites at the ceria-Ag interface, thereby facilitating the formation of harmful H2O2, followed by likely permeation across the cell wall. Further, a weakened Ag-induced Ce-O bond may drive electron transfer from the Ec band to O2, thereby further facilitating the selective reduction of O2 toward H2O2 formation. Ag destabilizes the surface adsorption of molecular H2O2, potentially leading to higher concentrations of free H2O2 adjacent to bacteria. To this end, our results show that H2O2 and/or NO/NO2-/NO3- are the key liberators of antibacterial activity, with a limited immediate role being offered by nanozyme-induced ROS including O2•- and OH•, and likely other light-activated radicals. A mini-pilot proof-of-concept study performed in a pediatric dental clinic setting confirms residual, and continual nanozyme antibacterial efficacy over a 28-day period. These findings open a new approach to alleviate infections caused by bacteria for use on high-touch hard surfaces.

In situ fabrication of lanthanum-doped nickel oxide nanostructures using sol-gel for the degradation of rhodamine B

Nanoscale science represents a thriving field of research for environmental applications within materials science. This study focuses on the fabrication of pure and La-doped nickel oxide (NiO) nanostructures with varying concentrations (1.0, 2.0, 3.0, and 4.0 wt%) of lanthanum using a facile sol-gel technique. This study explores the structural, morphological, chemical composition, and optical characteristics of the resulting pure and La-doped NiO nanostructures. Techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, UV-visible spectroscopy, and photoluminescence (PL) spectroscopy were used for material analysis. The observed trend in the energy band gap (Eg) values demonstrates a continuous decrease up to a La-doping concentration of 3 wt% in NiO. However, after this concentration (at 4.0 wt%), there is a noticeable increase in the energy band gap. At lower La-doping concentrations (up to 3 wt%), the incorporation of La ions into the NiO lattice may result in the formation of defects and oxygen vacancies. The presence of these imperfections may lead to new energy levels into the band gap, resulting in partial filling and a subsequent reduction in the band gap. Beyond a specific doping concentration (e.g., 3 wt%), excess La atoms may aggregate or cluster inside the NiO lattice. This agglomeration may cause structural distortions, strain, and disturbances in the crystal lattice, resulting in an increase in the band gap. The 3 wt% La-doped NiO sample demonstrated a notable 84% degradation efficiency of the synthesized nanomaterials coupled with its inherent stability, highlighting its dual attributes of effective pollutant removal and sustained performance. Furthermore, the cyclic stability of the optimized nanostructure is anticipated to be ∼77.42% after six cycles, suggesting promising future applications in photocatalysis.

Tailoring the Structural and Optical Properties of Cerium Oxide Nanoparticles Prepared by an Ecofriendly Green Route Using Plant Extracts

The present study explores an environmentally friendly green approach to obtain cerium oxide nanoparticles via a biomediated route using Mellisa officinalis and Hypericum perforatum plant extracts as reducing agents. The as-prepared nanoparticles were studied for their structural and morphological characteristics using XRD diffractometry, scanning electron microscopy, Raman, fluorescence and electronic absorption spectra, and X-ray photoelectron spectroscopy (XPS). The XRD pattern has shown the centered fluorite crystal structure of cerium oxide nanoparticles with average crystallite size below 10 nm. These observations were in agreement with the STEM data. The cubic fluorite structure of the cerium oxide nanoparticles was confirmed by the vibrational mode around 462 cm-1 due to the Ce-08 unit. The optical band gap was estimated from UV-Vis reflectance spectra, which was found to decrease from 3.24 eV to 2.98 eV. A higher specific area was determined for the sample using M. officinalis aqueous extract. The EDX data indicated that only cerium and oxygen are present in the green synthesized nanoparticles.

Highly Conductive Peroxidase-like Ce-MoS2 Nanoflowers for the Simultaneous Electrochemical Detection of Dopamine and Epinephrine

The accurate and simultaneous detection of neurotransmitters, such as dopamine (DA) and epinephrine (EP), is of paramount importance in clinical diagnostic fields. Herein, we developed cerium-molybdenum disulfide nanoflowers (Ce-MoS2 NFs) using a simple one-pot hydrothermal method and demonstrated that they are highly conductive and exhibit significant peroxidase-mimicking activity, which was applied for the simultaneous electrochemical detection of DA and EP. Ce-MoS2 NFs showed a unique structure, comprising MoS2 NFs with divalent Ce ions. This structural design imparted a significantly enlarged surface area of 220.5 m2 g-1 with abundant active sites as well as enhanced redox properties, facilitating electron transfer and peroxidase-like catalytic action compared with bare MoS2 NFs without Ce incorporation. Based on these beneficial features, Ce-MoS2 NFs were incorporated onto a screen-printed electrode (Ce-MoS2 NFs/SPE), enabling the electrochemical detection of H2O2 based on their peroxidase-like activity. Ce-MoS2 NFs/SPE biosensors also showed distinct electrocatalytic oxidation characteristics for DA and EP, consequently yielding the highly selective, sensitive, and simultaneous detection of target DA and EP. Dynamic linear ranges for both DA and EP were determined to be 0.05~100 μM, with detection limits (S/N = 3) of 28 nM and 44 nM, respectively. This study shows the potential of hierarchically structured Ce-incorporated MoS2 NFs to enhance the detection performances of electrochemical biosensors, thus enabling extensive applications in healthcare, diagnostics, and environmental monitoring.

Synthesis of Poly(ethylene furanoate) Based Nanocomposites by In Situ Polymerization with Enhanced Antibacterial Properties for Food Packaging Applications

Poly(ethylene 2,5-furandicarboxylate) (PEF)-based nanocomposites containing Ce-bioglass, ZnO, and ZrO2 nanoparticles were synthesized via in situ polymerization, targeting food packaging applications. The nanocomposites were thoroughly characterized, combining a range of techniques. The successful polymerization was confirmed using attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, and the molecular weight values were determined indirectly by applying intrinsic viscosity measurements. The nanocomposites' structure was investigated by depth profiling using time-of-flight secondary ion mass spectrometry (ToF-SIMS), while color measurements showed a low-to-moderate increase in the color concentration of all the nanocomposites compared to neat PEF. The thermal properties and crystallinity behavior of the synthesized materials were also examined. The neat PEF and PEF-based nanocomposites show a crystalline fraction of 0-5%, and annealed samples of both PEF and PEF-based nanocomposites exhibit a crystallinity above 20%. Furthermore, scanning electron microscopy (SEM) micrographs revealed that active agent nanoparticles are well dispersed in the PEF matrix. Contact angle measurements showed that incorporating nanoparticles into the PEF matrix significantly reduces the wetting angle due to increased roughness and introduction of the polar -OH groups. Antimicrobial studies indicated a significant increase in inhibition of bacterial strains of about 9-22% for Gram-positive bacterial strains and 5-16% for Gram-negative bacterial strains in PEF nanocomposite films, respectively. Finally, nanoindentation tests showed that the ZnO-based nanocomposite exhibits improved hardness and elastic modulus values compared to neat PEF.

Phytomediated-Assisted Preparation of Cerium Oxide Nanoparticles Using Plant Extracts and Assessment of Their Structural and Optical Properties

Cerium oxide nanoparticles were obtained using aqueous extracts of Chelidonium majus and Viscum album. X-ray diffractometry analysis confirmed the crystalline structure of the synthesized cerium oxide nanoparticles calcined at 600 °C. Scanning electron microscopy, UV-Vis reflectance and Raman spectroscopy, XPS, and fluorescence studies were utilized to interpret the morphological and optical properties of these nanoparticles. The STEM images revealed the spherical shape of the nanoparticles and that they were predominantly uniform in size. The optical band gap of our cerium nanoparticles was determined to be 3.3 and 3.0 eV from reflectance measurements using the Tauc plots. The nanoparticle sizes evaluated from the Raman band at 464 cm^-1 due to the F2g mode of the cubic fluorite structure of cerium oxide are close to those determined from the XRD and STEM data. The fluorescence results showed emission bands at 425, 446, 467, and 480 nm. The electronic absorption spectra have exhibited an absorption band around 325 nm. The antioxidant potential of the cerium oxide nanoparticles was estimated by DPPH scavenging assay.

Influence of Ag on the Structural, Electrochemical, Antibacterial, and Photocatalytic Performance of the (CuO-Cu2O)Cu Nanocomposite

The cost-effective novel Ag-doped (1-7%) (CuO-Cu₂O)Cu (C3) heterostructured nanocomposites are successfully synthesized by the facile solution combustion process using the Leucas aspera extract as a green fuel. The structural properties of fabricated nanocomposites were well-characterized by specific spectral techniques for enhanced electrochemical sensor detection, antibacterial activities, and sunlight-driven photocatalytic dye decoloration studies. The existence of Ag⁺ ions has been confirmed by the appearance of two peaks of Ag 3d_5/2 (367.9 eV) and Ag 3d_3/2 (373.9 eV), with the chemical binding nature and exchange of the Ag⁺ state in the nanocomposite lattice as revealed by X-ray photoelectron spectroscopy analysis. The energy band gap value of the doped nanocomposite decreases from 2.2 to 1.8 eV, as measured by the UV-visible absorption spectral technique, hindering the recombination of electron-holes pairs by trapping e^- and h⁺. This result supports that the C3Ag5 nanocomposite has a great potential as a sunlight photocatalyst toward the Alizarin Red (AR) dye, for which an excellent degradation activity of 98% at 180 min was achieved compared to that of the host nanocomposite (78% at 180 min). The variation of redox peak potentials of the prepared graphite nanocomposite working electrode is an effective tool for paracetamol sensing activity in 0.1 M KCl using electrochemical spectral studies. In addition, the antibacterial activities of the C3Ag5 nanocomposite against Escherichia coli and Staphylococcus aureus were successfully studied. The C3Ag5 nanocomposite exhibited a better performance than C3. The increase in activity is attributed to the presence of Ag as a dopant.

Metal nanoparticles produced by plants with antibacterial properties against Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a pathogenic bacteria that causes a variety of potentially fatal infections. The emergence of antibiotic-resistant strains of S. aureus has made treatment even more difficult. In recent years, nanoparticles have been used as an alternative therapeutic agent for S. aureus infections. Among various methods for the synthesis of nanoparticles, the method utilizing plant extracts from different parts of a plant, such as root, stem, leaf, flower, seeds, etc. is gaining widespread usage. Phytochemicals present in plant extract are an inexpensive, eco-friendly, natural material that act as reducing and stabilization agent for the nanoparticle synthesis. The utilization of plant-fabricated nanoparticles against S. aureus is currently in trend. The current review discusses recent findings in the therapeutic application of phytofabricated metal-based nanoparticles against Staphylococcus aureus.

Green synthesis of metal-based nanoparticles for sustainable agriculture

The large-scale use of conventional pesticides and fertilizers has put tremendous pressure on agriculture and the environment. In recent years, nanoparticles (NPs) have become the focus of many fields due to their cost-effectiveness, environmental friendliness and high performance, especially in sustainable agriculture. Traditional NPs manufacturing methods are energy-intensive and harmful to environment. In contrast, synthesizing metal-based NPs using plants is similar to chemical synthesis, except the biological extracts replace the chemical reducing agent. This not only greatly reduces the used of traditional chemicals, but also produces NPs that are more economical, efficient, less toxic, and less polluting. Therefore, green synthesized metal nanoparticles (GS-MNPs) are widely used in agriculture to improve yields and quality. This review provides a comprehensive and detailed discussion of GS-MNPs for agriculture, highlights the importance of green synthesis, compares the performance of conventional NPs with GS-MNPs, and highlights the advantages of GS-MNPs in agriculture. The wide applications of these GS-MNPs in agriculture, including plant growth promotion, plant disease control, and heavy metal stress mitigation under various exposure pathways, are summarized. Finally, the shortcomings and prospects of GS-MNPs in agricultural applications are highlighted to provide guidance to nanotechnology for sustainable agriculture.

Nanocomposites Based on Cerium, Lanthanum, and Titanium Oxides Doped with Silver for Biomedical Application

Nanosized composites CeO2–Ag, La2O3–Ag, and TiO2–Ag are a class of nanomaterials suitable for photocatalysis, optical devices, and photoelectrochemical elements. Further, nanocomposites with several wt.% of silver can be used as creating materials for pathogenic virus inactivation with pandemic-neutralizing potential. Thus, CeO2–Ag, La2O3–Ag, and TiO2–Ag nanocomposites are prospective materials due to their optical and biological activity. In the present work, CeO2–Ag, La2O3–Ag, and TiO2–Ag nanocomposites were synthesized by the co-precipitation method. The morphological and optical properties and the structure of the prepared nanocomposites were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) with EDX, and nitrogen adsorption-desorption based on BET, Raman spectroscopy, and photoluminescence (PL). Both oxide matrixes corresponded to the cubic crystal lattice with the inclusion of argentum into the crystal lattice of oxides at relative low c(Ag) and reduction of silver on particle surface at 5 wt.% Ag and greater. The CeO2, TiO2, and La2O3 with a concentration of 4 wt.% Ag inhibited the growth processes of prokaryotic cells of E. coli, Bacillus sp., and S. aureus compared to pure oxides. Influenza A virus and herpes completely suppressed reproduction by nanocomposites of CeO2–Ag (2, 5 wt.%) and La2O3–Ag (2, 5 wt.%) action.

Physico-mechanical properties, antimicrobial activities, and anti-biofilm potencies of orthodontic adhesive containing cerium oxide nanoparticles against Streptococcus mutans

Introduction: White spot lesions around orthodontic brackets may lead to the formation of dental caries during and following fixed orthodontic treatment.

Aim: This study aimed to evaluate the physico-mechanical properties and antimicrobial potencies of orthodontic adhesive doped with cerium oxide nanoparticles (CeO2-NPs) against Streptococcus mutans.

Materials and methods: After synthesis and conformation of CeO2-NPs by transmission electron microscope (TEM), shear bond strength (SBS) and adhesive remnant index (ARI) of modified orthodontic adhesive containing different concentrations of CeO2-NPs (0, 1, 2, 5, and 10 wt%) were measured. The antimicrobial effects of modified orthodontic adhesive were evaluated by disk agar diffusion method and biofilm formation inhibition assay.

Results: The pseudo-spherical shapes of CeO2-NPs were observed in TEM micrographs. The physico-mechanical finding showed that 5 wt% CeO2-NPs showed the highest concentration of CeO2-NPs and SBS value (18.21±9.06 MPa, p<0.05) simultaneously with no significant differences in ARI compared with the control group (p>0.05). There was a significant reduction in cell viability of S. mutans with increasing CeO2-NPs concentration. The 3.1 Log10 and 4.6 Log10 reductions were observed in the count of treated S. mutans with 5 and 10 wt% CeO2-NPs, respectively (p<0.05).

Conclusions: Overall, an orthodontic adhesive containing 5 wt% CeO2-NPs had antimicrobial properties against S. mutans without adverse effects on SBS and ARI.

The Use of Cerium Compounds as Antimicrobials for Biomedical Applications

Cerium and its derivatives have been used as remedies for wounds since the early 20th century. Cerium nitrate has attracted most attention in the treatment of deep burns, followed later by reports of its antimicrobial properties. Its ability to mimic and replace calcium is presumed to be a major mechanism of its beneficial action. However, despite some encouraging results, the overall data are somewhat confusing with seemingly the same compounds yielding opposing results. Despite this, cerium nitrate is currently used in wound treatment in combination with silver sulfadiazine as Flammacérium. Cerium oxide, especially in nanoparticle form (Nanoceria), has lately captured much interest due to its antibacterial properties mediated via oxidative stress, leading to an increase of published reports. The properties of Nanoceria depend on the synthesis method, their shape and size. Recently, the green synthesis route has gained a lot of interest as an alternative environmentally friendly method, resulting in production of effective antimicrobial and antifungal nanoparticles. Unfortunately, as is the case with antibiotics, emerging bacterial resistance against cerium-derived nanoparticles is a growing concern, especially in the case of bacterial biofilm. However, diverse strategies resulting from better understanding of the biology of cerium are promising. The aim of this paper is to present the progress to date in the use of cerium compounds as antimicrobials in clinical applications (in particular wound healing) and to provide an overview of the mechanisms of action of cerium at both the cellular and molecular level.

Structural and Functional Behaviour of Ce-Doped Wide-Bandgap Semiconductors for Photo-Catalytic Applications

Increasing the photocatalytic efficiency of earth-abundant wide-bandgap semiconductors is of high interest for the development of cheap but effective light-driven chemical conversion processes. In this study, the coupling of ZnO and TiO2 with low contents of the rare-earth Ce species aimed to assess the photo-catalytic performance of the two semiconductors (SC). Structural and optical characterizations were performed to estimate the effect of the different interactions between Zn2+, Ti4+ and Ce4+ ions, and how the photo-responsive behaviour of Ce-Ti and Ce-Zn composites was affected. Therefore, photo-catalytic tests were performed for all Ce-modified SC to assess both their photo-oxidative and photo-reductive properties. Amongst all the tested materials, only Zn-based samples resulted in being suitable for the photo-oxidation of the methylene blue (MB) organic pollutant in a synthetic-dependent fashion.

Plant-mediated synthesis of nanoparticles and their antimicrobial activity against phytopathogens

Nanotechnology is an emerging science with a wide array of applications involving the synthesis and manipulation of materials with dimensions in the range of 1-100 nm. Nanotechnological applications include diverse fields such as pharmaceuticals, medicine, the environment, food processing and agriculture. Regarding the latter, applications are mainly focused on plant growth and crop protection against plagues and diseases. In recent years, the biogenic reduction of elements such as Ag, Au, Cu, Cd, Al, Se, Zn, Ce, Ti and Fe with plant extracts has become one of the most accepted techniques for obtaining nanoparticles (NPs), as it is considered an ecological and cost-effective process without the use of chemical contaminants. The objective of this work was to review NPs synthesized by green chemistry using vegetable extracts, as well as their use as antimicrobial agents against phytopathogenic fungi and bacteria. Given the need for alternatives to control and integrate management of phytopathogens, this review is relevant to agriculture, although this technology is barely exploited in this field. © 2020 Society of Chemical Industry.

Effect of CeO2-ZnO Nanocomposite for Photocatalytic and Antibacterial Activities

The impact of a CeO2-ZnO nanocomposite on the photocatalytic and antibacterial properties compared to bare ZnO was investigated. A CeO2-ZnO nanocomposite was synthesized using Acacia nilotica fruit extract as a novel fuel by a simple solution combustion method. The obtained CeO2-ZnO nanocomposite was confirmed structurally by XRD, FTIR, Raman and UV-DRS and morphologically by SEM/TEM analysis. The XRD pattern indicates the presence of both hexagonal Wurtzite-structured ZnO (major) and cubic-phase CeO2 (minor). FTIR shows the presence of a Ce-O-Ce vibration at 468 cm−1 and Zn-O vibration at 445 cm−1. The existence of a band at 460 cm−1 confirmed the F2g Raman-active mode of the fluorite cubic crystalline structure for CeO2. Diffused reflectance spectroscopy was used to estimate the bandgap (Eg) from Kubelka–Munk (K–M) theory which was found to be 3.4 eV. TEM analysis shows almost spherical-shaped particles, at a size of about 10–15 nm. The CeO2-ZnO nanocomposite shows a good BET specific surface area of 30 m2g−1. The surface defects and porosity of the CeO2-ZnO nanocomposite caused methylene blue (MB) dye to degrade under sunlight (88%) and UV light (92%). The CeO2-ZnO nanocomposite also exhibited considerable antibacterial activity against a pathogenic bacterial strain.

Green Synthesis of Cerium Oxide Nanoparticles (CeO2 NPs) and Their Antimicrobial Applications: A Review

During the last decade green synthesized cerium oxide nanoparticles (CeO2 NPs) attracted remarkable interest in various fields of science and technology. This review, explores the vast array of biological resources such as plants, microbes, and other biological products being used in synthesis of CeO2 NPs. It also discusses their biosynthetic mechanism, current understandings, and trends in the green synthesis of CeO2 NPs. Novel therapies based on green synthesized CeO2 NPs are illustrated, in particular their antimicrobial potential along with attempts of their mechanistic elucidation. Overall, the main objective of this review is to provide a rational insight of the major accomplishments of CeO2 NPs as novel therapeutics agents for a wide range of microbial pathogens and combating other diseases.

Biogenic Ceria Nanoparticles (CeO2 NPs) for Effective Photocatalytic and Cytotoxic Activity

Ceria nanoparticles (CeO₂ NPs) are generally considered in various functional applications, such as catalysts in fuel cells, sensors, and antioxidant and oxidase-like enzymes in the biological environment. The CeO₂ NPs were synthesized using the E. globulus leaf extract-mediated hydrothermal technique. The synthesized NPs were characterized by various analytical instruments including powder X-ray diffractometer (PXRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and dynamic light scattering (DLS) analysis. The XRD results showed an average NPs sizes of 13.7 nm. Cytotoxic study results showed an IC₅₀ value of 45.5 µg/L for A549 and 58.2 µg/L for HCT 116, indicating that CeO₂ NPs are more toxic to A549 compared to HCT116 cell lines. The generation of ROS was responsible for its cytotoxic activity against cancer cell lines. Specific surface area (40.96 m²/g) and pore diameter (7.8 nm) were measured using Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption isotherms. CeO₂ NPs with a high surface area were used as photocatalyst in degrading sunset yellow (SY) dye under UV-irradiation and 97.3% of the dye was degraded within 90 min. These results suggest that the synthesized CeO₂ NPs could be used as a good photocatalyst as well as a cytotoxic agent against human cancer cell lines.

Antimicrobial Activity of Cerium Oxide Nanoparticles on Opportunistic Microorganisms: A Systematic Review

An evaluation of studies of biologically active nanoparticles provides guidance for the synthesis of nanoparticles with the goal of developing new antibiotics/antifungals to combat microbial resistance. This review article focuses on the physicochemical properties of cerium oxide nanoparticles (CeNPs) with antimicrobial activity. Method. This systematic review followed the Guidelines for Transparent Reporting of Systematic Reviews and Meta-Analyses. Results. Studies have confirmed the antimicrobial activity of CeNPs (synthesized by different routes) using nitrate or chloride salt precursors and having sizes less than 54 nm. Conclusion. Due to the lack of standardization in studies with respect to the bacteria and CeNP concentrations assayed, comparisons between studies to determine more effective routes of synthesis are difficult. The mechanism of CeNP action likely occurs through oxidative stress of components in the cell membrane of the microorganism. During this process, a valence change occurs on the CeNP surface in which an electron is gained and Ce⁴⁺ is converted to Ce³⁺.

Facile green fabrication of nanostructure ZnO plates, bullets, flower, prismatic tip, closed pine cone: Their antibacterial, antioxidant, photoluminescent and photocatalytic properties

Green synthesis of multifunctional Zinc oxide nanoparticles (NPs) with a variety of morphologies were achieved by low temperature solution combustion route employing neem (Azadirachta indica) extract as fuel. The nanoparticles were characterized by PXRD, FTIR, XPS, Raman and UV-Visible spectroscopic studies. The Morphologies were studied by SEM and TEM analysis. The NPs were subjected for photoluminescence, photocatalytic, antibacterial and antioxidant activity studies. PXRD pattern confirmed the hexagonal wurtzite structure of the product. SEM images indicated the transformation of mushroom like hexagonal disks to bullets, buds, cones, bundles and closed pine cone structured NPs with increase in the concentration of neem extract in reaction mixture. The NPs exhibited prominent green emission due to the presence of intrinsic defect centers. The as-formed bullet shaped ZnO with 4ml of neem extract was found to decolorize Methylene blue (MB) under Sunlight and UV light irradiation. The antibacterial studies indicated that ZnO NPs of concentration 500, 750 and 1000μg resulted in significant antibacterial activity on Klebsiella aerogenes and Staphylococcus aureus but not against Escherichia coli and Pseudomonas aeruginosa in agar well diffusion method. Further, ZnO NPs exhibited significant antioxidant activity against scavenging DPPH free radicals. The current investigation demonstrated green engineering method for the synthesis of multifunctional ZnO NPs with interesting morphologies using neem extract.

Bio-mediated route for the synthesis of shape tunable Y₂O₃: Tb³⁺ nanoparticles: Photoluminescence and antibacterial properties

The study reports green mediated combustion route for the synthesis of Tb(3+) ion activated Y2O3 nanophosphors using Aloe Vera gel as fuel. The concentration of Tb(3+) plays a key role in controlling the morphology of Y2O3 nanostructures. The formation of different morphologies of Y2O3: Tb(3+) nanophosphors were characterized by PXRD, SEM, TEM and HRTEM. PXRD data and Rietveld analysis evident the formation of single phase Y2O3 with cubic crystal structure. The influence of Tb(3+) ion concentration on structural morphology, UV-visible absorption and PL emission were investigated systematically. The PL emission of Y2O3: Tb(3+) (1-11 mol%) nanophosphors were studied in detail under 271 and 304nm excitation wavelengths. The CIE coordinates lies well within green region and correlated color temperature values were found to be 6221 and 5562K under different excitations. Thus, the present phosphor can serve as an excellent candidate for LEDs. Further, prismatic Y2O3: Tb(3+) (3 mol%) nanophosphor showed significant antibacterial activity against Pseudomonas desmolyticum and Staphylococcus aureus. The present study successfully demonstrates Y2O3: Tb(3+) nanophosphors can be used for display applications as well as in medical applications for controlling pathogenic bacteria.