Bioactive ZnO Nanoparticles: Biosynthesis, Characterization and Potential Antimicrobial Applications

Plant-engineered ZnO and CuO nanoparticles exhibit pesticidal activity and mitigate Fusarium infestation in soybean: A mechanistic understanding

Herein, CuO and ZnO nanoparticles (NPs) were biogenically synthesized using plant (Artemisia vulgaris) extracts. The biogenic NPs were subsequently evaluated in vitro for antifungal activity (200 mg/L) against Fusarium virguliforme (FV; the cause of soybean sudden death), and for crop protection (200-500 mg/L) in FV-infested soybean. ZnONPs exhibited 3.8-, 2.5-, and 4.9 -fold greater in vitro antifungal activity, compared to Zn or Cu acetate salt, the Artemisia extract, and a commercial fungicide (Medalion Fludioxon), respectively. The corresponding CuONP values were 1.2-, 1.0-, and 2.2 -fold, respectively. Scanning electron microscopy (SEM) revealed significant morpho-anatomical damage to fungal mycelia and conidia. NP-treated FV lost their hyphal turgidity and uniformity and appeared structurally compromised. ZnONP caused shriveled and broken mycelia lacking conidia, while CuONP caused collapsed mycelia with shriveled and disfigured conidia. In soybean, 200 mg/L of both NPs enhanced growth by 13%, compared to diseased controls, in both soil and foliar exposures. Leaf SEM showed fungal colonization of different infection sites, including the glandular trichome, palisade parenchyma, and vasculature. Foliar application of ZnONP resulted in the deposition of particulate ZnO on the leaf surface and stomatal interiors, likely leading to particle and ion entry via several pathways, including ion diffusion across the cuticle/stomata. SEM also suggested that ZnO/CuO NPs trigger structural reinforcement and anatomical defense responses in both leaves and roots against fungal infection. Collectively, these findings provide important insights into novel and effective mechanisms of crop protection against fungal pathogens by plant-engineered metal oxide nanoparticles, thereby contributing to the sustainability of nano-enabled agriculture.

Comparative evaluation of biologically and chemically synthesized zinc oxide nanoparticles for preventing Candida auris biofilm

Candidozyma auris (formerly Candida auris) is a multidrug-resistant yeast that poses a significant global health threat due to its ability to form biofilms and resist various antifungal treatments. This study evaluates and compares the antifungal efficacy of biologically synthesized zinc oxide nanoparticles (ZnO-NP-B) and chemically synthesized ZnO nanoparticles (ZnO-NP-C1 and ZnO-NP-C2), developed using the dry-wet chemical method and sol-gel method, respectively. ZnO-NP-B was synthesized using Lactobacillus gasseri. The nanoparticles were characterized for size, charge, and morphology using Particle Size Analyzer, photon correlation spectroscopy with a 90 Plus Zetasizer, and scanning electron microscopy (SEM), respectively. The antifungal activity was assessed through minimum inhibitory concentration (MIC50) determination, biofilm inhibition assays by XTT assay, and gene expression analysis. ZnO-NP-C1 exhibited the highest antifungal activity against C. auris planktonic cells, with a MIC50 value of 61.9 ± 3.3 µg/ml, followed by ZnO-NP-C2 (151 ± 7.83 µg/ml), whereas ZnO-NP-B showed limited efficacy (MIC50 = 1 mg/ml). Chemically synthesized ZnO-NPs, particularly ZnO-NP-C2, did not induce overexpression of resistance genes (CDR1, MDR1, ERG2, ERG11, FKS1, CHS1), whereas ZnO-NP-B triggered their upregulation, potentially promoting resistance. ZnO-NP-C1 was the most effective in preventing biofilm formation, reducing C. auris adhesion by 67.9 ± 2.35% at 150 µg/ml, while ZnO-NP-B exhibited negligible inhibition. Gene expression analysis further confirmed that ZnO-NP-C1 significantly downregulated adhesive genes (ALS5, IFF4, CSA1) by up to 0.37 ± 0.006, 0.043 ± 0.002, and 0.06 ± 0.0004, respectively. These findings highlight the potential of ZnO-NP-C1 as a promising antifungal agent for preventing C. auris biofilms, emphasizing the critical role of synthesis methods in optimizing nanoparticle properties for antifungal applications.

Evaluation of Dermal Wound Healing Potential: Phytochemical Characterization, Anti-Inflammatory, Antioxidant, and Antimicrobial Activities of Euphorbia guyoniana Boiss. & Reut. Latex

This study investigates the wound-healing potential of Euphorbia guyoniana latex (EGL) in male Wistar rats, along with its biochemical composition and biological activities. Phytochemical analysis identified moderate levels of phenolics, flavonoids, and tannins, with HPLC revealing five phenolic compounds. EGL demonstrated strong antioxidant activity in DPPH assays, surpassing ascorbic acid in protecting red blood cells. Its performance in the ß-carotene-linoleic acid assay was robust, though its FRAP assay results were weaker. EGL also exhibited significant anti-inflammatory activity, comparable to Acetylsalicylic acid, and showed antibacterial effects against Listeria innocua. In Vivo, EGL-infused ointments accelerated wound healing, reducing epithelialization periods to 12-16 days, with a higher wound contraction rate compared to controls. The study concludes that EGL, rich in bioactive compounds, holds potential as a promising natural agent for wound healing, owing to its potent antioxidant, anti-inflammatory, and antibacterial properties.

Neuroprotective properties of zinc oxide nanoparticles: therapeutic implications for Parkinson's disease

Parkinson's disease (PD) significantly affects millions of people worldwide due to the progressive degeneration of dopamine-producing neurons in the substantia nigra pars compacta. Despite extensive research efforts, effective treatments that can halt or reverse the progression of PD remain elusive. In recent years, nanotechnology has emerged as a promising new avenue for addressing this challenge, with zinc oxide nanoparticles (ZnO-NPs) standing out for their extensive therapeutic potential. ZnO-NPs have shown remarkable promise in neuroprotection through several key mechanisms. The multifaceted properties of ZnO-NPs suggest that they could play a crucial role in intervening across various fundamental mechanisms implicated in PD. By targeting these mechanisms, ZnO-NPs offer new insights and potential strategies for managing and treating PD. This review aims to provide a thorough examination of the molecular mechanisms through which ZnO-NPs exert their neuroprotective effects. It highlights their potential as innovative therapeutic agents for PD and outlines directions for future research to explore and harness their full capabilities.

Plant extract-mediated biosynthesis of sulphur nanoparticles and their antibacterial and plant growth-promoting activity

This study reports green synthesis of sulphur nanoparticles using sodium thiosulfate pentahydrate (Na2S2O35H2O) and Cannabis sativa leaf extracts. X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM) was employed to examine the crystallinity of the particles and morphological characteristics, proved both spherical and rod-shaped morphology of the S NPs having porous nature. The FTIR spectra revealed the interaction of the synthesized SNPs with the biomolecules present in the leaf extract. UV-VIS spectral investigations confirmed the production of SNPs from C. sativa leaf extract and that these SNPs can be used for visible region photocatalysis for the removal of pollutants from wastewater. Energy dispersive X-ray (EDX) spectrum of the SNP shows a single peak around 2.4 keV, confirmed S NPs purity. TEM image revealed the formation of mainly nanorods having a width of ∼20-25 nm and a length of 50-100 nm. Furthermore, some spherical particles (∼20-30 nm) were also formed. HRTEM image of the rod-shaped particles clearly shows the crystal fringe spacing of 0.38 nm. Further, disc diffusion method (DDM) was used to check the antibacterial activity of S NPs against gram-positive S. aureus (MTCC737) 18 ± 0.12 mm and gram-negative bacteria against E. coli (MTCC443) 21.5 ± 0.12 mm, A. salmonicida (MTCC1522) 19.1 ± 0.12 mm, K. pneumoniae (MTCC3384) 17.8 ± 0.10 mm. Among all the strains of bacteria, E. coli (MTCC443) showed a maximum zone of inhibition of 21.5 ± 0.12 mm and its antibacterial activity is somewhat like streptomycin sulfate. These SNPs also promote growth of C. sativa in pot experiment, resulting in a 30 % increase in biomass, 90 cm in shoot length and 28 cm in root length and higher fresh and dry weight (50g and 20g, respectively) with 1.0 mg mL-1 NPs treatment. In addition, SEM-EDX confirmed the accumulation of nanomaterial in plant leaves. This environmentally friendly approach to SNP synthesis using C. sativa extracts demonstrates both potent antibacterial properties and plant growth-promoting effects, making it a promising solution for agriculture and biomedicine.

Lyophilized Polyvinyl Alcohol and Chitosan Scaffolds Pre-Loaded with Silicon Dioxide Nanoparticles for Tissue Regeneration

Materials with a soft tissue regenerative capacity can be produced using biopolymer scaffolds and nanomaterials, which allow injured tissue to recover without any side effects or limitations. Four formulations were prepared using polyvinyl alcohol (PVA) and chitosan (CS), with silicon dioxide nanoparticles (NPs-SiO2) incorporated using the freeze-drying method at a temperature of -50 °C. TGA and DSC showed no change in thermal degradation, with glass transition temperatures around 74 °C and 77 °C. The interactions between the hydroxyl groups of PVA and CS remained stable. Scanning electron microscopy (SEM) indicated that the incorporation of NPs-SiO2 complemented the freeze-drying process, enabling the dispersion of the components on the polymeric matrix and obtaining structures with a small pore size (between 30 and 60 μm) and large pores (between 100 and 160 μm). The antimicrobial capacity analysis of Gram-positive and Gram-negative bacteria revealed that the scaffolds inhibited around 99% of K. pneumoniae, E. cloacae, and S. aureus ATCC 55804. The subdermal implantation analysis demonstrated tissue growth and proliferation, with good biocompatibility, promoting the healing process for tissue restoration through the simultaneous degradation and formation of type I collagen fibers. All the results presented expand the boundaries in tissue engineering and regenerative medicine by highlighting the crucial role of nanoparticles in optimizing scaffold properties.

A comprehensive review on crosslinked network systems of zinc oxide-organic polymer composites

In recent years, the synergistic crosslinked networks formed by zinc oxide (ZnO) particles and organic polymers have gained significant attention. This importance is ascribed due to the valuable combination of low band gap containing ZnO particles with responsive behavior containing organic polymers. These properties of both ZnO and organic polymers make a suitable system of crosslinked ZnO-organic polymer composite (CZOPC) for various applications in the fields of biomedicine, catalysis, and environmental perspectives. The literature extensively provided the diverse morphologies and structures of CZOPC, and these architectural structures play a crucial role in determining their efficiency across various applications. Consequently, the careful design of CZOPC shapes tailored to specific purposes has become a focal point. This comprehensive review provides insights into the classifications, synthetic approaches, characterizations, and applications of ZnO particles decorated in organic polymers with crosslinked network. The exploration extends to the adsorption, environmental, catalytic, and biomedical applications of ZnO-organic polymer composites. Adopting a tutorial approach, the review systematically investigates and elucidates the applications of CZOPC with a comprehensive understanding of their diverse capabilities and uses.

Advances in the Involvement of Metals and Metalloids in Plant Defense Response to External Stress

Plants, as sessile organisms, uptake nutrients from the soil. Throughout their whole life cycle, they confront various external biotic and abiotic threats, encompassing harmful element toxicity, pathogen infection, and herbivore attack, posing risks to plant growth and production. Plants have evolved multifaceted mechanisms to cope with exogenous stress. The element defense hypothesis (EDH) theory elucidates that plants employ elements within their tissues to withstand various natural enemies. Notably, essential and non-essential trace metals and metalloids have been identified as active participants in plant defense mechanisms, especially in nanoparticle form. In this review, we compiled and synthetized recent advancements and robust evidence regarding the involvement of trace metals and metalloids in plant element defense against external stresses that include biotic stressors (such as drought, salinity, and heavy metal toxicity) and abiotic environmental stressors (such as pathogen invasion and herbivore attack). We discuss the mechanisms underlying the metals and metalloids involved in plant defense enhancement from physiological, biochemical, and molecular perspectives. By consolidating this information, this review enhances our understanding of how metals and metalloids contribute to plant element defense. Drawing on the current advances in plant elemental defense, we propose an application prospect of metals and metalloids in agricultural products to solve current issues, including soil pollution and production, for the sustainable development of agriculture. Although the studies focused on plant elemental defense have advanced, the precise mechanism under the plant defense response still needs further investigation.