The surge of resistant food pathogens is a major threat worldwide. Previous research conducted on phytochemicals has shown their antibacterial activity against pathogenic bacteria. The design of antimicrobial agents to curb pathogenic disease remains a challenge demanding critical attention. Flavonoids such as apigenin and quercetin were evaluated against Gram-positive and Gram-negative bacteria. The results indicated that the antibacterial activity of each flavonoid occurred at a different minimum inhibitory concentration. However, the antimicrobial activity results of the modified flavonoids were also reported, and it was observed that the Gram-positive bacteria were more susceptible in comparison to the Gram-negative bacteria. The cell wall structure of the Gram-positive and Gram-negative bacteria could be the main reason for the bacteria susceptibility. Modified flavonoids could be used as a suitable alternative antimicrobial agent for the treatment of infectious diseases. Our results indicated 100% inhibition of Listeria monocytogenes , Pseudomonas aeruginosa , and Aeromonas hydrophila with modified flavonoids.

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We report for the first time, the aqueous-based synthesis of multibranched, monodispersed gold nanoflowers (AuNFs) using pyromellitic dianhydride-p-phenylene diamine - PPDDs at room temperature. AuNF synthesis was achieved using PPDDs that converts Au precursor (Au) into AuNFs while serving as both the reducing and directional agent. The resulting branched AuNFs exhibited different degrees of anisotropy and protuberance lengths obtained by modulating the ratio of PPDDs and HAuCl·3HO. The surface roughness obtained ranged from small bud-like protuberances to elongated spikes, which enabled the tuning of the optical properties of the nanoparticles from ∼450 to 1100 nm. Systematic analysis revealed that the generation of urchin-like particles as well as their size depended on the PPDDs/HAuCl·3HO ratio. At a medium concentration of the precursor, spherical nanoparticles were formed. Whereas at lower precursor concentrations, urchin-like nanoparticles were obtained with their size and protuberances length increasing at even lower HAuCl·3HO concentration. Increasing the temperature to 100 °C resulted in the enhancement of the anisotropy of the AuNFs. The resulting gold nanoflowers exhibited an enhanced performance in surface-enhanced Raman scattering (SERS). This work provides a unique approach for anisotropic particle synthesis using water soluble polymer and greener approaches. The fabricated AuNFs exhibited variable UV-vis absorption and SERS enhancement as a function of branch morphology, indicating their potential application in biolabeling, biosensing, imaging, and therapeutic applications.

We hereby present a novel approach for the synthesis of gold nanoparticles (AuNPs) using water soluble, naturally-derived flavonoids.

Plant-based pathogenic microbes hinder the yield and quality of food production. Plant diseases have caused an increase in food costs due to crop destruction. There is a need to develop novel methods that can target and mitigate pathogenic microbes. This study focuses on investigating the effects of luteolin tetraphosphate derived silver nanoparticles (LTP-AgNPs) and gold nanoparticles (LTP-AuNPs) as a therapeutic agent on the growth and expression of plant-based bacteria and fungi. In this study, the silver and gold nanoparticles were synthesized at room temperature using luteolin tetraphosphate (LTP) as the reducing and capping agents. The synthesis of LTP-AgNPs and LTP-AuNP was characterized by Transmission Electron Microscopy (TEM) and size distribution. The TEM images of both LTP-AgNPs and LTP-AuNPs showed different sizes and shapes (spherical, quasi-spherical, and cuboidal). The antimicrobial test was conducted using fungi: Aspergillus nidulans, Trichaptum biforme, Penicillium italicum, Fusarium oxysporum, and Colletotrichum gloeosporioides, while the class of bacteria employed include Pseudomonas aeruginosa, Aeromonas hydrophila, Escherichia coli, and Citrobacter freundii as Gram (−) bacteria, and Listeria monocytogenes and Staphylococcus epidermidis as Gram (+) bacterium. The antifungal study demonstrated the selective size and shape-dependent capabilities in which smaller sized spherical (9 nm) and quasi-spherical (21 nm) AgNPs exhibited 100% inhibition of the tested fungi and bacteria. The LTP-AgNPs exhibited a higher antimicrobial activity than LTP-AuNPs. We have demonstrated that smaller sized AgNPs showed excellent inhibition of A. nidulans growth compared to the larger size nanoparticles. These results suggest that LTP-AuNP and LTP-AgNPs could be used to address the detection and remediation of pathogenic fungi, respectively.

This study presents for the first time the use of environment-friendly Poly (amic) acid (PAA) to synthesize polymer-supported gold (AuNPs) and silver nanoparticles (AgNPs). PAA shows great potential as both reductant and stabilizer of AuNPs and AgNPs, with the resultant nanoparticles retaining their catalytic and antimicrobial activity. This environment-friendly approach utilizing the tunable properties of PAA opens a new frontier for nanomaterials that can be used for catalysis, filtration, sensors and other applications. ABSTRACTWe hereby report a rapid, simple, and one pot synthesis of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) using conductive, electroactive and biodegradable. Poly (amic)acid (PAA) polymer as both the reductant and stabilizer. The synthesized AgNPs and AuNPs were characterized using transmission electron microscopy (TEM), High resolution HRTEM, energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and ultra-violet visible spectroscopy (UV-Vis). UV-VIS spectra exhibit major peaks at 440nm and 535nm for AgNPs and AuNPs respectively. The XRD patterns revealed four diffraction peaks at 38.12 , 44.07˚, 64.27 , and 77.22 ͦ that can be indexed to the (111), (200), (220), and (311) planes of face-centered cubic (fcc) silver crystallites respectively. The size of the crystallites along the [111] direction was estimated to be 4.2±0.5nm, which is in agreement with the TEM result. The effect of temperature on the formation of AgNPs in the presence of PAA was investigated and found to be significant at 100 C, resulting in silver-polyamic acid nanocomposite without altering the fcc crystal pattern.The prepared AuNPs and AgNPs were found to exhibit catalytic activity towards 4-nitrophenol and methylene blue with a rate constant of 5.2 ×10 -3 S -1 and 1.09×10 -2 S -1 respectively. Finally, the synthesized AgNPs exhibit excellent antibacterial activity against Gram negative (E coli DH5 Alpha, E.coli 25922, Aeromonas hydrophilia & Pseudomonas aeruginosa) and gram positive (Listeria monocytogenes strains F2365 and HCC7 and S. epidermidis) bacteria in addition to modest cytotoxicity against non-cancerous immortalized IEC-6 and cancerous Caco-2 cell lines.

We hereby present a novel greener and ecofriendly synthesis of anisotropic silver nanoparticles (AgNPs) using water soluble quercetin diphosphate (QDP). QDP was employed as a reducing, capping and stabilizing agent at room temperature without any extraneous reagents.