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.

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.

A novel electrochemical sensing platform for nitrobenzene has been developed using silver nanoparticles (AgNPs) embedded in the poly(amic) acid (PAA) polymer matrix (PAA–AgNPs). PAA was synthesized via the polycondensation reaction of para-phenylenediamine and benzene-1,2,4,5-tetracarboxylic dianhydride. PAA–AgNP nanocomposites were synthesized by the in situ reduction of a silver precursor by the polymer at room temperature in a one-step approach without using an extraneous reducing or capping agent. The composite was subsequently characterized in solution and as a thin film. The X-ray diffraction technique revealed the crystalline nature of the PAA films with the embedded AgNPs. Unlike conventional polymers, the synthesized PAA membrane exhibits significant UV/Vis spectroscopic response. The sequestered nanoparticles also show the characteristic surface plasmon resonance (SPR) peaks confirming the presence of AgNPs. Integrated charge areas were 4.826 mC and 2.176 C for PAA/GC and PAA–AgNPs/GC respectively. The charge at the PAA–AgNP/GC electrode is 451 times greater than that at the PAA/GC electrode suggesting that the AgNP composite exhibits higher electroactivity. When tested as a sensor for nitrobenzene, the PAA–AgNP modified GC electrode showed promising potential as an electrochemical sensor. The electrochemical sensors exhibit a wide linear dynamic range (10–600 μM) with a correlation coefficient of 0.9735, a detection limit of 1.68 μM and a sensitivity of 7.88 μA μM⁻¹. The sensor also exhibited minimal interference effects on structurally-similar nitroaromatic compounds and metal species such as 4-nitroaniline (4-NA), 2-nitrophenol (2-NP), dinitrobenzene (DNB), Pb²⁺ and Cd²⁺.