This study aimed to synthesize and characterize juglone-entrapped poly(d,l-lactic-co-glycolic acid) (PLGA) nanoparticles and compare the antifungal properties of free juglone with its PLGA nanoparticle formulation for the first time. The juglone-loaded nanoparticles prepared using the oil-in-water (o/w) single-emulsion solvent evaporation method were characterized by the reaction yield (RY), encapsulation efficiency (EE), polydispersity index (PDI), particle size, zeta potential (ZP), FT-IR, and in vitro release properties and evaluated for their morphological features using SEM. The nanoparticle formulation had size, RY, ZP, EE, and PDI values of 212 nm, 66.91 ± 2.4%, -16.3 ± 0.7 mV, 70.66 ± 3.1%, and 0.083 ± 0.024, respectively. In vitro release showed a triphasic pattern with initial burst followed by sustained release and dormant phase over the study period, releasing about 72.8% in total after 42 days. The antifungal studies against Aspergillus flavus, Candida albicans, and Fusarium spp. using agar dilution and top agar dilution methods indicated that the juglone-encapsulated nanoparticle was more effective than free juglone. This study showed that the top agar method, which was applied for the first time on antifungal activity, is more suitable for the nanoparticular system based on sustained release. Therefore, PLGA nanoparticle formulations may be an important tool for application in many areas for the effective and beneficial use of hydrophobic compounds such as juglone.

The use of nanoparticle formulations of juglone in biological systems and applications could be more beneficial than its free form due to its toxicity.

The use of quercetin as a bioflavonoid is becoming increasingly common in food industries even though poor water solubility, instability, absorption, and permeability have limited its application. The oil-in-water single-emulsion solvent evaporation method to synthesize highly stable and soluble quercetin-encapsulated nanoparticles (NPs), in which the reaction yield, particle size, and polydispersity of the NPs are varied greatly within the process parameters of the synthesis method, has been optimized. NPs with different initial quercetin amounts were used to determine how the quercetin amount affected nanoparticle properties and antimicrobial efficiency. Listeria monocytogenes, Salmonella typhimurium, Escherichia coli, and Staphylococcus aureus were chosen as model bacteria due to their being foodborne pathogens. The results of antimicrobial activity evaluated by three different methods showed that the antimicrobial activity of both quercetin NPs and free quercetin was effective on gram-positive strains (L. monocytogenes and S. aureus). Additionally, it was detected that Q31 NPs have more effective antimicrobial activity than other synthesized quercetin nanoparticles depending on the amount of substance and release. Furthermore, on the basis of assessing the antibacterial effects by scanning electron microscopy, it was detected that bacteria cells lost their integrity and became pale with the release of cytoplasm and decomposed after treatment with Q31 NPs.

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