Preparation of capped silver nanoparticles using sunlight and cationic surfactants and their biological activity

L-tryptophan-titanium oxide nanoparticles showed selective anti-Toxoplasma gondii activity and improved host biocompatibility

Toxoplasma gondii, the etiological agent of toxoplasmosis, currently affects nearly one-third of the human population. Treatment options for toxoplasmosis are limited, which underscores the need for new drugs. In the present study, we screened nanoparticles (NPs) of titanium dioxide (TiO₂) and molybdenum (Mo) for their potential to inhibit the growth of T. gondii in vitro. NPs of TiO₂ and Mo showed non-dose-dependent anti-T. gondii activity with EC₅₀ values of 157.6 and 253 µg/mL, respectively. Previously, we showed that amino acid modification of NPs enhances their selective anti-parasite toxicity. Therefore, to enhance the selective anti-parasitic action of TiO₂, we modified the NP surface using alanine, aspartate, arginine, cysteine, glutamate, tryptophan, tyrosine, and bovine serum albumin. The bio-modified TiO₂ showed anti-parasite activity with EC₅₀ values ranging from 45.7 to 286.4 µg/mL. At effective anti-parasite concentrations, modified-TiO₂ showed no appreciable host cytotoxicity. Of the eight bio-modified TiO₂, tryptophan-TiO₂ showed the most promising anti-T. gondii specificity and improved host biocompatibility with a selectivity index (SI) of 49.1 versus 7.5 for TiO₂ (note, pyrimethamine, a standard drug for toxoplasmosis, has an SI of 2.3). Furthermore, our data indicate that redox modulation may be part of the anti-parasite action of these NPs. Indeed, augmentation with trolox and l-tryptophan reversed the growth restriction caused by the tryptophan-TiO₂ NPs. Collectively, these findings suggest that the parasite toxicity was selective and not a result of general cytotoxic action. Furthermore, surface modification with amino acids such as l-tryptophan not only enhanced the anti-parasitic action of TiO₂ but also improved the host biocompatibility. Overall, our findings indicate that the nutritional requirements of T. gondii represent a viable target for the development of new and effective anti-T. gondii agents.

Green Synthesis, Characterization, Antioxidant, Antibacterial and Enzyme Inhibition Effects of Chestnut (Castanea sativa) Honey-Mediated Silver Nanoparticles

In this study, chestnut honey-based silver nanoparticles (CH-AgNPs) were synthesized at different temperatures (30, 60 and 90 °C) and these nanoparticles were characterized by different techniques such as UV-vis spectrophotometer, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). The DPPH free radical scavenging assay was used to determine the antioxidant activity of the obtained nanoparticles. The inhibition effects of these nanoparticles for some clinically important enzymes such as myeloperoxidase and collagenase were investigated. In addition, the disk diffusion method (DDM), agar well diffusion (AWD), and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) techniques were used to determine the antibacterial activity of CH-AgNPs. In honey-based silver nanoparticle production processes using green synthesis, it was determined that the nanoparticle sizes decreased from 55 to 27 nm with an increase in temperature. In addition, it was determined that the rate of inhibition of myeloperoxidase (36.4% to 34.0%) and collagenase enzymes (74.2% to 68.7%) increased with a decrease in particle size. As a result of the antibacterial activity tests, it was observed that CH-AgNPs have antibacterial activity against all target pathogens including Gram-positive and Gram-negative bacteria. The obtained results show that CH-AgNPs produced using chestnut honey have the potential to be used in fields such as medicine, pharmacy and cosmetic technology.

Preparation of zwitterionic ionic surfactants-based sulphonyl for steel protections: Experimental and theoretical insights

Designating an organic inhibitor with a specific chemical structure that actively participates in steel protection by increasing adsorption on the steel surface. Based on that, we synthesized three zwitterionic surfactants based on azomethine with different hydrophobic chain lengths labeled ZWSO, ZWSD, and ZWSH. The presence of azomethine group, electrons, and heteroatoms in the zwitterionic surfactant’s amphipathic structure helped to improve C-steel protection. Their inhibitory activity toward steel corrosion was investigated utilizing electrochemical impedance spectroscopy (EIS), gravimetrical, and potentiodynamic polarization techniques. Importantly, the surfactant tail influenced corrosion inhibition performance; as surfactant tail length increased, so did inhibition efficiency due to increased adsorption affinity. The inhibition efficiencies of ZWSO, ZWSD, and ZWSH are 87.15, 89.82, and 91.36%, respectively. Tafel data clarified that ZWSO, ZWSD, and ZWSH inhibitors behave as mixed-type inhibitors following the modified Langmuir isotherm. The inhibitors can adsorb physiochemically on the steel surface with ∆G ads ranges from −38.48 to −44.6 kJ mol−1. The SEM confirms that the morphology of C-steel becomes smoother because of inhibitor adsorption. The DFT and MCs output data supported the experimental performance of the tested ZWSO, ZWSD, and ZWSH inhibitors and especially their dependence on surfactant tail length.

Effect of phenolic compounds-capped AgNPs on growth inhibition of Aspergillus niger

An exponential increase of scientific works dealing with the use of polyphenol-rich 'natural products' for the synthesis of bioactive AgNPs is in progress. However, a lack of fundamental studies on phytochemical compounds involved, and their role is evident. In this work, a comprehensive study of the antifungal performances of silver nanoparticles (AgNPs) synthesized exclusively with phenolic compounds (PCs) with different structures and different antioxidant capacity is presented. The experimental hypothesis is that AgNPs@PCs produced with different PCs can exert different toxicity. In particular, di-hydroxylic and tri-hydroxylic phenolic acids (caffeic acid and gallic acid) and flavonoids (catechin and myricetin) were compared. A room temperature rapid and simple AgNPs synthesis was carefully optimized, obtaining stable and reproducible colloids. AgNPs@PCs suspensions were characterized by UV-vis spectroscopy, ς-potential, dynamic light scattering and transmission electron microscopy. AgNPs@PCs radical scavenging capacity was also assessed. Finally, the AgNPs@PCs antifungal effect was tested against Aspergillus niger, particularly on spore germination and mycelial growth. The different antifungal activity was attributed to the different PCs' ability to generate/stabilize AgNPs with different shells, residual antioxidant capacity, and capacity to interact and aggregate during their 'attack' to A. niger hyphae. This work paves the way for the rational use of PCs and PCs rich-products for AgNPs-based applications.

Aggregation kinetics and mechanisms of silver nanoparticles in simulated pollution water under UV light irradiation

This paper investigated the effect mechanism of complex components (fulvic acid [FA], sodium dodecylbenzene sulfonate [SDBS], and sodium nitrate [NaNO₃ ]) on the aggregation kinetics of polyvinylpyrrolidone-modified silver nanoparticles (PVP-AgNPs) under UV irradiation. The results showed that FA and NaNO₃ alone did not cause aggregation due to the high steric hindrance and/or electrostatic repulsive forces. In high concentration of SDBS solution (20-50 mM), the stability of PVP-AgNPs was reduced by adsorbing SDBS on nanoparticle surface and replacing their PVP coatings. A mixed system of two pollutants had a synergistic effect on PVP-AgNPs aggregation. In the mixed system of SDBS and FA, the interaction of SDBS and PVP-AgNPs dominated the aggregation of PVP-AgNPs. NaNO₃ significantly improved the aggregation rate of PVP-AgNPs in SDBS solution due to the charge neutralization effect of electrolyte. In 20 mg/L FA solution, the aggregation rate increased slightly with increasing NaNO₃ concentration from 50 to 200 mM due to the charge neutralization effect, while the hydrodynamic diameters of PVP-AgNPs increased linearly and rapidly to micrometer size because the spatial conformation of adsorbed FA became compact in high-salinity solution. The calculation results of eDLVO theory were basically consistent with most of the experimental results. PRACTITIONER POINTS: PVP-AgNPs was uniformly dispersed in NaNO₃ or FA solution under UV irradiation. PVP-AgNPs formed aggregates in SDBS solutions under UV irradiation. A system with two mixed pollutants had a synergistic effect on promoting aggregation of PVP-AgNPs. eDLVO theory could explain the aggregation results in different chemical conditions except in NaNO₃ solution.

Alpinia calcarata: potential source for the fabrication of bioactive silver nanoparticles

In the present study silver nanoparticles fabricated by using leaf extract of Alpinia calcarata. We have also studied the effect of various experimental parameters viz., metal ion concentration, pH and incubation period on nanoparticle biosynthesis. Results of optimization showed that metal ion concentration of 1.5 mM, alkaline pH and incubation period of 12 h were the optimum conditions for metal nanoparticle biosynthesis. Synthesized silver nanoparticles were characterized by UV-Visible spectroscopy, Dynamic light scattering (DLS), Zeta potential analysis, Fourier transform infrared spectroscopy (FTIR), Inductively coupled plasma-optical emission spectrometry (ICP-OES), Transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The UV-visible spectrum shows a sharp peak at 420 nm which was due to the surface plasmon resonance of the silver nanoparticles. Effect of several phytochemicals present in A. calcarata, on synthesis of silver nanoparticles was studied by Fourier transform infrared spectroscopy. The results indicate that the flavonoids, phytosterol, quinones and phenolic compounds present in the plant extract plays a major role in formation of silver nanoparticles in their respective ions in solution. Results of TEM and XRD analysis showed that synthesized silver nanoparticles were mostly spherical in shape with an average diameter of 27.2 ± 0.2.5 nm and highly crystalline in nature. Moreover the synthesized silver nanoparticles were also evaluated for their potential antibacterial and antioxidant activities. It showed good antibacterial activity as well as antioxidant activity. Thus the obtained result provides a scientific support that leaf extract of A. calcarata can be used efficiently in the production of potential bioactive silver nanoparticles with several pharmaceutical applications.

Poly-L-arginine Coated Silver Nanoprisms and Their Anti-Bacterial Properties

The aim of this study was to test the effect of two different morphologies of silver nanoparticles, spheres, and prisms, on their antibacterial properties when coated with poly-L-arginine (poly-Arg) to enhance the interactions with cells. Silver nanoparticle solutions were characterized by UV-visible spectroscopy, transmission electron microscopy, dynamic light scattering, zeta potential, as well as antimicrobial tests. These ultimately showed that a prismatic morphology exhibited stronger antimicrobial effects against Escherichia coli, Pseudomonas aeruginosa and Salmonella enterica. The minimum bactericidal concentration was found to be 0.65 μg/mL in the case of a prismatic AgNP-poly-Arg-PVP (silver nanoparticle-poly-L-arginine-polyvinylpyrrolidone) nanocomposite. The anticancer cell activity of the silver nanoparticles was also studied, where the maximum effect against a HeLa cell line was 80% mortality with a prismatic AgNP-poly-Arg-PVP nanocomposite at a concentration of 11 μg/mL. The antimicrobial activity of these silver nanocomposites demonstrates the potential of such coated silver nanoparticles in the area of nano-medicine.

Studying the silver nanoparticles influence on thermodynamic behavior and antimicrobial activities of novel amide Gemini cationic surfactants

Three novels amide Gemini cationic surfactants with various alkyl chains and their silver nanohybrid with silver nanoparticles were synthesized and a confirmation study for surfactant and their nanoparticles formation has been established using IR, ¹HNMR, TEM and UV-Vis spectroscopy. The surface-active properties of these surfactants and their nanoform were investigated through surface tension and electrical conductivity measurements and a comparative study has been established. The thermodynamic parameters of micellization and adsorption were assessed at temperatures range from 25 to 65°C. The effect of silver particles on the surface behavior of the synthesized surfactant has been discussed. The aggregation behavior of silver nanoparticles with these synthesized Gemini surfactants in water were investigated using dynamic light scattering and transmission electron microscopy. Furthermore, the antimicrobial activities of these synthesized amide Gemini surfactants and their nanostructure with silver against both Gram positive and Gram negative bacteria were also investigated.

Catalytic removal of organic colorants from water using some transition metal oxide nanoparticles synthesized under sunlight

The novelty of the work lies in utilizing the sunlight irradiated, green synthesis of TMO nanoparticles, and their potential in simulated water treatment.