Green synthesis-assisted copper nanoparticles using Aegle marmelos leaves extract: physical, optical, and antimicrobial properties

In the present report, Aegle marmelos leaf powder was used to synthesize copper nanoparticles (CuNPs) using a simple and cost-effective method. A. marmelos leaves have various medicinal uses including for the treatment of diarrhoea, constipation, diabetes, cholera, skin diseases, earache, blood purification, heart problems, and so on. The plant biomolecules induce the reduction of Cu2+ ions to CuNPs and also act as a capping and stabilizing agent. The formation of CuNPs was confirmed using photoluminescence (PL) excitation and emission spectra on a Shimadzu RF-5301 PC spectrofluorophotometer and the absorbance spectra of a UV-visible spectrophotometer at different stages during the synthesis process. In addition, other properties of synthesized CuNPs were also investigated using X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy techniques. The average size of the synthesized CuNPs was in the range 20-40 nm. Furthermore, the synthesized NPs were also considered for an antimicrobial study against Gram-positive Staphylococcus aureus and Proteus, and Gram-negative Escherichia coli and Salmonella spp. using the agar well diffusion method. The zone of inhibition against the Gram-positive bacteria was greater than the zone of inhibition against the Gram-negative bacteria. These investigation results suggest that synthesized NPs are promising nanomaterials for use as antimicrobial agents.

Effect of Size and Concentration of Copper Nanoparticles on the Antimicrobial Activity in Escherichia coli through Multiple Mechanisms

Metal and metal oxide nanoparticles, including copper nanoparticles (CuNPs), display antimicrobial activities and are regarded as promising microorganism inhibitors. Here, we explored the antimicrobial activity of CuNPs in Escherichia coli (E. coli) using two particle sizes (20 and 60 nm) and five concentrations (1, 5, 10, 50 and 100 μg/mL). The result showed a concentration-dependent trend of bactericidal activities for both size groups, with 20 nm particles more effective than 60 nm particles at low concentrations. The membrane disruption caused by CuNPs was confirmed by electron microscopy, PI staining and protein leaking analysis. However, the results of reactive oxygen species generation and genomic DNA damage revealed that the size and concentration of CuNPs were factors affecting the induction of multiple bactericidal mechanisms simultaneously on different scales. Further results of annexin V-PI staining supported this hypothesis by showing the shifting composition of the early-, late- and non-apoptotic dead cells across the CuNP groups. Many CuNP treatment groups were rescued when four mammalian modulators-wortmannin, necrosulfonamide, Z-VAD-FMK, and SBI-0206965-were applied separately. The results suggest the possible existence of bacterial programmed cell death pathways in E. coli which could be triggered by CuNP treatments.

Synergistic Antifungal Study of PEGylated Graphene Oxides and Copper Nanoparticles against Candida albicans

The coupling reactions of polyethylene glycol (PEG) with two different nano-carbonaceous materials, graphene oxide (GO) and expanded graphene oxide (EGO), were achieved by amide bond formations. These reactions yielded PEGylated graphene oxides, GO-PEG and EGO-PEG. Whilst presence of the newly formed amide links (NH-CO) were confirmed by FTIR stretches observed at 1732 cm⁻¹ and 1712 cm⁻¹, the associated Raman D- and G-bands resonated at 1311/1318 cm⁻¹ and 1584/1595 cm⁻¹ had shown the carbonaceous structures in both PEGylated products remain unchanged. Whilst SEM images revealed the nano-sheet structures in all the GO derivatives (GO/EGO and GO-PEG/EGO-PEG), TEM images clearly showed the nano-structures of both GO-PEG and EGO-PEG had undergone significant morphological changes from their starting materials after the PEGylated processes. The successful PEGylations were also indicated by the change of pH values measured in the starting GO/EGO (pH 2.6–3.3) and the PEGylated GO-PEG/EGO-PEG (pH 6.6–6.9) products. Initial antifungal activities of selective metallic nanomaterials (ZnO and Cu) and the four GO derivatives were screened against Candida albicans using the in vitro cut-well method. Whilst the haemocytometer count indicated GO-PEG and copper nanoparticles (CuNPs) exhibited the best antifungal effects, the corresponding SEM images showed C. albicans had, respectively, undergone extensive shrinkage and porosity deformations. Synergistic antifungal effects all GO derivatives in various ratio of CuNPs combinations were determined by assessing C. albicans viabilities using broth dilution assays. The best synergistic effects were observed when a 30:70 ratio of GO/GO-PEG combined with CuNPs, where MIC₅₀ 185–225 μm/mL were recorded. Moreover, the decreased antifungal activities observed in EGO and EGO-PEG may be explained by their poor colloidal stability with increasing nanoparticle concentrations.

Comparison Between Insecticidal Activity of <i>Lantana camara</i> Extract and its Synthesized Nanoparticles Against Anopheline mosquitoes

BACKGROUND AND OBJECTIVE

Malaria is still a severe health problem especially in developing countries which occur and young children are the most affected. The present study was designed to compare the insecticidal potential of Lantana camara leaves extract alone and its synthesized nanoparticles against Anopheles multicolor.

MATERIALS AND METHODS

Copper nanoparticles CuNPs were synthesized by green bio-reduction method using aqueous extract of leaves of Lantana camara plant. The CuNPs formation was confirmed by ultraviolet visible spectrophotometer (UV-VIS) and Transitional Electron Microscopy (TEM). The application of L. camara extract and its synthesized CuNPs on different stages of A. multicolor were adopted.

RESULTS

The biosynthesized CuNPs were spherical with the average sizes of 11-17.8 nm. The highest insecticidal effect (100% of larval mortality) achieved at high dose (140 ppm) of L. camara leaves extract alone comparing with that occur at low dose (20 ppm) of CuNPs synthesized L. camara leaves. The LC50 and LC90 for the 4 instar larvae were 63.5 and 119.9 ppm for plant extract alone compared to 12.6 and 18.4 ppm for CuNPs preparation.

CONCLUSION

So, this study proved that CuNPs preparation of L. camara leaves is highly efficient compared to the plant extract alone and more economic as less quantities were used. Also, awareness against invasion of Anopheles mosquito vectors with effective preventive measures to protect from malaria infection.