Structural Evolution of Palygorskite as the Nanocarrier of Silver Nanoparticles for Improving Antibacterial Activity

Abstract

The carrier performance of palygorskite (Pal) can be significantly affected by its structure, morphology, and activity, which was regulated by controlling the dissolution degree of the metal-oxygen octahedron of raw Pal (RPal) under the action of oxalic acid (OA) in this study. The RPal and OA-leached RPal (OPal) then served as supports for immobilizing silver nanoparticles (AgNPs) to form RPal/AgNPs and OPal/AgNPs antibacterial nanocomposites. The structural and morphological characterizations were used to confirm the dispersion uniformity of AgNPs on the RPal and OPal nanorods, and antibacterial experiments were conducted to evaluate the performance of as-prepared composites and also investigate their antibacterial mechanism. The results showed that OPal-48h (OA leaching for 48 h) loaded with AgNPs (OPal-48h/AgNPs) possesses the most excellent and broad-spectrum antibacterial properties, where its minimum inhibitory concentration values against E. coli, S. aureus, ESBL-E. coli, and MRSA reached 0.25, 0.125, 0.25, and 0.5 mg/mL, respectively, which are mainly attributed to the optimal balance between surface activity and structural stability of OPal-48h that maximally increased its dispersibility and active sites, therefore contributing to the in situ formation of monodisperse AgNPs on the nanorods of OPal-48h.

Antifungal Properties of Nanosilver Clay Composites Against Fungal Pathogens of Agaricus bisporus

“…[43] Although AgNP-zeolite showed similar peaks, slight alterations are observed in bands located on the 3700-3100 range cm À 1 and regions from 1020 to 600 cm À 1 affected by metal cations' interaction with the zeolite surface. A noticeable difference was the appearance of a peak at 1384 cm À 1 , which indicated the existence of Ag in the composite, and this result agreed with that reported by Zhang et al [44] The FT-IR spectra demonstrated the inflexibility of the silicate structure and the non-bond chemical interface between the silicate structure and AgNPs in the composite. [42] The structural modification of montmorillonite after AgNP incorporation is revealed by the increase in the intensity of OÀ H stretching (3620 cm À 1 ), 1628 cm À 1 (OÀ H bending) in plane SiÀ O stretching (997 cm À 1 ), AlÀ O stretching (914 cm À 1 ) [45] associated with the aluminosilicate structure (Figure 2B).…”

“…The differences in silver loading on the different clays could be attributed to the fact that surface area (especially the internal pore surface), pore size distribution, and the degree of ionization at the surface of absorbents (such as clays) influence the extent of absorption or ion carrying capacity of a matrix [44] . The low Ag content on palygorskite can be attributed to its fibrous rod‐like morphology and porous channels parallel to the long axis of palygorskite crystals (where most ion exchange reactions occur) [40,44] . These characteristics cause palygorskite clays to have less surface area for binding NPs and a low ion exchange capacity compared to the flatter surfaces of materials such as zeolite and montmorillonite [46] …”

“…The alteration of the band intensity could be attributed to the presence of AgNPs on the defects on the octahedral sheets. [28,43] The appearance of an additional band at 1334 cm À 1 and the downward shift in the characteristic vibrations, namely SiÀ O stretch (997 cm À 1 ), in comparison to the unmodified clay mineral, indicates a disturbance in the bonding in the structure of the aluminosilicate [40,44,45] and hence a more ordered structure due to the presence of AgNPs.…”

The nanocomposites of modified attapulgite with vitamin E and mannan oligosaccharide regulated the intestinal epithelial barrier and improved intestinal microbiota composition to prevent diarrhea in weaned piglets

“…Propionate regulated intestinal inflammation and improved intestinal barrier function. Spearman analysis showed that colon propionate content was significantly positively correlated with the relative abundance of Phascolarctobacterium , and a previous study also showed that Phascolarctobacterium can utilized succinate and produced propionate 5,7,8 . These data indicated that dietary supplementation with SLK5 enriched Phascolarctobacterium to produce propionate.…”

“…APT is widely used as a feed additive, which can absorb various toxins and bacteria, as well as regulate the intestinal microbiota community and intestinal epithelial barrier function 2–4 . A previous study also showed the antibacterial ability and biocompatibility of modified attapulgite was better than that of APT 5–9 . Quaternized chitosan/ZnO/APT nanocomposites effectively inhibit the growth of Escherichia coli and Staphylococcus aureus , and also demonstrated good biocompatibility 5 .…”