Exploring the Control in Antibacterial Activity of Silver Triangular Nanoplates by Surface Coating Modulation.

Jamila Djafari,Javier Fernández-Lodeiro,José Luis Capelo,Carlos Fernández-Lodeiro,Patrícia Poeta,Vanessa Silva,Carlos Lodeiro,Gilberto Igrejas,Adrián Fernández-Lodeiro

doi:10.3389/fchem.2018.00677

Abstract

In the present work, the synthesis and characterization of silver triangular nanoplates (AgNTs) and their silica coating composites are reported. Engineering control on the surface coating has demonstrated the possibility to modulate the antibacterial effect. Several AgNT-coated nanomaterials, such as PVP (Polyvinylpyrrolidone) and MHA (16-mercaptohexadecanoic acid) as a stable organic coating system as well as uniform silica coating (≈5 nm) of AgNTs, have been prepared and fully characterized. The antibacterial properties of the systems reported, organic (MHA) and inorganic (amine and carboxylic terminated SiO2) coating nanocomposites, have been tested on Gram-positive and Gram-negative bacteria strains. We observed that the AgNTs' organic coating improved antimicrobial properties when compared to other spherical silver colloids found in the literature. We have also found that thick inorganic silica coating decreases the antimicrobial effect, but does not cancel it. In addition, the effect of surface charge in AgNTs@Si seems to play a crucial role toward S. aureus ATCC 25923 bacteria, obtaining MIC/MBC values compared to the AgNTs with an organic coating.

Highlights

Silver nanoparticles (AgNPs) have attracted much attention as a result of their particular optoelectronic (Kelly et al, 2003; Wei, 2011), catalytic (Jiang et al, 2005; Köhler et al, 2008), or antibacterial properties (Morones et al, 2005; Rai et al, 2009).Engineering modifications of AgNPs’ size and shape represent a fascinating synthetic challenge that allow modification of the final nanomaterial’s properties
All the experiments have been conceived to determine the antibacterial effects of AgNTs as a function of the surface coating
A variety of works that report the synthesis of different triangular nanoplates or nanoprisms with an organic coating to explore their antibacterial properties can be found, but to the best of our knowledge only two works report the controlled silica deposition on AgNTs, and none of them explores the antibacterial properties of the resulting product (Xue et al, 2007; Brandon et al, 2014)

Summary

Introduction

Engineering modifications of AgNPs’ size and shape represent a fascinating synthetic challenge that allow modification of the final nanomaterial’s properties. These structural modifications at the nanoscale level strongly affect the macroscopic properties of the silver colloidal solutions. Silver Triangular Nanoplates SCM by adjusting the size and/or the shape of the NPs, allowing a spectral tuning that ranges from the visible to the near-IR region. This is true for anisotropic structures such as nanoprisms or nanoplates, among others (Pastoriza-Santos and Liz-Marzán, 2008; Millstone et al, 2009)

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