Benefits of Usage of Immobilized Silver Nanoparticles as Pseudomonas aeruginosa Antibiofilm Factors

Microwave Irradiation vs. Structural, Physicochemical, and Biological Features of Porous Environmentally Active Silver–Silica Nanocomposites

Heavy metals and other organic pollutants burden the environment, and their removal or neutralization is still inadequate. The great potential for development in this area includes porous, spherical silica nanostructures with a well-developed active surface and open porosity. In this context, we modified the surface of silica spheres using a microwave field (variable power and exposure time) to increase the metal uptake potential and build stable bioactive Ag2O/Ag2CO3 heterojunctions. The results showed that the power of the microwave field (P = 150 or 700 W) had a more negligible effect on carrier modification than time (t = 60 or 150 s). The surface-activated and silver-loaded silica carrier features like morphology, structure, and chemical composition correlate with microbial and antioxidant enzyme activity. We demonstrated that the increased sphericity of silver nanoparticles enormously increased toxicity against E. coli, B. cereus, and S. epidermidis. Furthermore, such structures negatively affected the antioxidant defense system of E. coli, B. cereus, and S. epidermidis through the induction of oxidative stress, leading to cell death. The most robust effects were found for nanocomposites in which the carrier was treated for an extended period in a microwave field.

The Release of Non-Extractable Ferulic Acid from Cereal By-Products by Enzyme-Assisted Hydrolysis for Possible Utilization in Green Synthesis of Silver Nanoparticles

The present work was undertaken to elucidate the potential contribution of biosynthetically produced ferulic acid (FA) via enzymatic hydrolysis (EH) of rye bran (RB) to the formation of silver nanoparticles (AgNPs) during green synthesis. An analytical approach accomplished by multiple reaction monitoring (MRM) using triple quadrupole mass selective detection (HPLC-ESI-TQ-MS/MS) of the obtained hydrolysate revealed a relative abundance of two isomeric forms of FA, i.e., trans-FA (t-FA) and trans-iso-FA (t-iso-FA). Further analysis utilizing high-performance liquid chromatography with refractive index (HPLC-RID) detection confirmed the effectiveness of RB EH, indicating the presence of cellulose and hemicellulose degradation products in the hydrolysate, i.e., xylose, arabinose, and glucose. The purification process by solid-phase extraction with styrene-divinylbenzene-based reversed-phase sorbent ensured up to 116.02 and 126.21 mg g^-1 of t-FA and t-iso-FA in the final eluate fraction, respectively. In the green synthesis of AgNPs using synthetic t-FA, the formation of NPs with an average size of 56.8 nm was confirmed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. The inclusion of polyvinylpyrrolidone (PVP-40) in the composition of NPs during synthesis favorably affected the morphological features, i.e., the size and shape of AgNPs, in which as big as 22.4 nm NPs were engineered. Meanwhile, nearly homogeneous round-shaped AgNPs with an average size of 16.5 nm were engineered using biosynthetically produced a mixture of t-FA and t-iso-FA and PVP-40 as a capping agent. The antimicrobial activity of AgNPs against Gram-positive and Gram-negative bacteria, including Pseudomonas aeruginosa, E. coli, Enterococcus faecalis, Bacillus subtilis, and Staphylococcus aureus was confirmed by the disk diffusion method and additionally supported by values of minimum inhibitory (MIC) and bactericidal (MBC) concentrations. Given the need to reduce problems of environmental pollution with cereal processing by-products, this study demonstrated a technological solution of RB rational use in the sustainable production of AgNPs during green synthesis. The AgNPs can be considered as active pharmaceutical ingredients (APIs) to be used for developing new antimicrobial agents and modifying therapies in treating multi-drug resistant (MDR) pathogens.

Hybrid Nanosystems Based on Nicotinate-Functionalized Mesoporous Silica and Silver Chloride Nanoparticles Loaded with Phenytoin for Preventing Pseudomonas aeruginosa Biofilm Development

Pseudomonas aeruginosa (PA) is one of the most common bacteria isolated from chronic wounds and burns. Its treatment is a challenge due to antimicrobial drug resistance and biofilm formation. In this context, this study aimed to perform the synthesis and full characterization of hybrid nanosystems based on mesoporous silica nanoparticles (MSNs) functionalized with a nicotinic ligand and silver chloride nanoparticles, both phenytoin sodium (Ph)-loaded and unloaded, to evaluate the antibacterial properties against three different strains of PA (including two clinical strains) in a planktonic state and as biofilms. Ph is a well-known proliferative agent, which was incorporated into the hybrid nanomaterials to obtain an effective material for tissue healing and prevention of infection caused by PA. The Ph-loaded materials promoted a quasi-complete inhibition of bacterial growth in wound-like medium and biofilm development, with values of 99% and 96%, respectively, with selectivity indices above the requirements for drugs to become promising agents for the topic preventive treatment of chronic wounds and burns.