Small AgNP in the Biopolymer Nanocomposite System.

Małgorzata Zienkiewicz-Strzałka,Anna Deryło-Marczewska

doi:10.3390/ijms21249388

Małgorzata Zienkiewicz-Strzałka, Anna Deryło-Marczewska

Open Access

https://doi.org/10.3390/ijms21249388

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Abstract

In this work, ultra-small and stable silver nanoparticles (AgNP) on chitosan biopolymer (BP/AgP) were prepared by in situ reduction of the diamminesilver(I) complex ([Ag(NH3)2]+) to create a biostatic membrane system. The small AgNP (3 nm) as a stable source of silver ions, their crystal form, and homogeneous distribution in the whole solid membrane were confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The X-ray photoelectron spectroscopy (XPS) and Auger analysis were applied to investigate the elemental composition, concentration, and chemical state of surface atoms. It was found that ultra-small metallic nanoparticles might form a steady source of silver ions and enhance the biostatic properties of solid membranes. Ultra-small AgNP with disturbed electronic structure and plasmonic properties may generate interaction between amine groups of the biopolymer for improving the homogeneity of the nanometallic layer. In this work, the significant differences between the typical way (deposition of ex-situ-prepared AgNP) and the proposed in-situ synthesis approach were determined. The improved thermal stability (by thermogravimetry and differential scanning calorimetry (TG/DSC) analysis) for BP/AgP was observed and explained by the presence of the protective layer of a low-molecular silver phase. Finally, the antibacterial activity of the BP/AgP nanocomposite was tested using selected bacteria biofilms. The grafted membrane showed clear inhibition properties by destruction and multiple damages of bacteria cells. The possible mechanisms of biocidal activity were discussed, and the investigation of the AgNP influence on the bacteria body was illustrated by AFM measurements. The results obtained concluded that the biopolymer membrane properties were significantly improved by the integration with ultra-small Ag nanoparticles, which added value to its applications as a biostatic membrane system for filtration and separation issues.

Highlights

The nanoworld of the ultra-small structures is a rich source of new, functional materials and inspiration for science and solutions to everyday problems
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
The increase in the silver content in the surface layer for the ionic way and their in-situ reduction suggests the greater probability of obtaining the homogeneous silver layer and confirms the better efficiency in incorporation the silver phase onto the biopolymer surface compared to the ex-situ procedure despite the similar amounts of introduced silver (The silver concentration in reference solution of AgNP prepared by reduction the same amount of [Ag(NH3)2]+ as for BP/AgP was determined as 43.5 mg/L by atomic absorption spectrometry)

Summary

Introduction

The nanoworld of the ultra-small structures is a rich source of new, functional materials and inspiration for science and solutions to everyday problems. Nanomaterials are an inescapable part of modern technology and the subject of heated debates and intensive research [1,2,3,4]. Their importance in this field cause formation of new products such as metallic nanoparticles, polymer particles, and polymer nanocomposites, silica-based materials, ceramics, and clays [5,6,7,8]. In this rich world, the nanocomposites based on metallic nanoparticles remain the most important. One or more phases with nanoscale dimensions (0-D, 1-D, and 2-D) such as noble metal nanoparticles are located on the surface or embedded in a matrix [9,10]

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