Silver Nanoparticles on Chitosan/Silica Nanofibers: Characterization and Antibacterial Activity

Abstract

A simple, low-cost, and reproducible method for creating materials with even silver nanoparticles (AgNP) dispersion was established. Chitosan nanofibers with silica phase (CS/silica) were synthesized by an electrospinning technique to obtain highly porous 3D nanofiber scaffolds. Silver nanoparticles in the form of a well-dispersed metallic phase were synthesized in an external preparation step and embedded in the CS/silica nanofibers by deposition for obtaining chitosan nanofibers with silica phase decorated by silver nanoparticles (Ag/CS/silica). The antibacterial activity of investigated materials was tested using Gram-positive and Gram-negative bacteria. The results were compared with the properties of the nanocomposite without silver nanoparticles and a colloidal solution of AgNP. The minimum inhibitory concentration (MIC) of obtained AgNP against Staphylococcus aureus (S. aureus) ATCC25923 and Escherichia coli (E. coli) ATCC25922 was determined. The physicochemical characterization of Ag/CS/silica nanofibers using various analytical techniques, as well as the applicability of these techniques in the characterization of this type of nanocomposite, is presented. The resulting Ag/CS/silica nanocomposites (Ag/CS/silica nanofibers) were characterized by small angle X-ray scattering (SAXS), X-ray diffraction (XRD), and atomic force microscopy (AFM). The morphology of the AgNP in solution, both initial and extracted from composite, the properties of composites, the size, and crystallinity of the nanoparticles, and the characteristics of the chitosan fibers were determined by electron microscopy (SEM and TEM).

Small AgNP in the Biopolymer Nanocomposite System

“…Presumably, the reason why the smaller particles had a greater antibacterial effect is that they release more ions than the larger particles per unit mass. These suggestions were confirmed by an experimental test of the biostatic properties of the BP/AgP sample and previously investigated antibacterial properties of BP and BP/AgNP samples [ 41 ].…”

“…When the same amount of AgNP (1 µL of AgNP dropped on the composite discs and 1 µL used directly) was used, the better activity of AgNP stabilized on the biopolymer was observed (the synergy between biopolymer and silver nanoparticles). The detailed biostatic activity of BP alone, AgNPs alone, and BP/AgNPs are presented in our previous work [ 41 ] and should be compared with a significantly more active BP/AgP system.…”

“…Aqueous acetic acid (≥99.7%) was purchased from POCH (Avantor Performance Materials Poland S.A, Gliwice, Poland). The biopolymer scaffold was prepared from a biopolymer solution according to the procedure presented in a previous paper [ 41 ]. All solutions were prepared with MilliQ standard water.…”

“…Well-defined, monodisperse silver nanoparticles with a diameter less than 10 nm were prepared also through silver nitrate reduction by aniline and dodecylbenzene sulfonic acid (DBSA) as reducing and stabilizing agents respectively [ 36 ]. Looking at scientific works on this subject, the vast majority of systems containing silver nanoparticles concern dimensions above 10 nm [ 37 , 38 , 39 , 40 , 41 ]. In this work, we propose the synthesis of biopolymer systems with silver nanoparticles with dimensions significantly below 10 nm using a non-complex procedure that does not require the use of reducing agents.…”

“…In this work, the CS nanofibers as an example of a biofunctional matrix decorated by AgNP were prepared and characterized. Regardless of the effectiveness in the antibacterial effect of silver nanoparticles deposited on the biopolymer surface in a reduced form (as in the work preceding the current research [ 41 ]), extensive efforts were made to strengthen and stabilize the biopolymer surface by trying to miniaturize metallic particles for creating a reservoir of silver ions, investigation of the nature of the interaction between AgNP and biopolymer surface, and building an improved homogeneity of the nanometallic layer on the surface of biopolymer fibers.…”