Scheme 1
The interest of this research consists in using inorganic natural alumino-silicates such as clay minerals, known to be harmless for human health and biodiversity. Among these, smectite-type sodium montmorillonite (NaMt) could be an interesting host matrice for metals due to its natural abundance, cost effectiveness, non-toxicity, chemical inertness, sorptive capabilities, large specific surface area (Komadel, 2016) and even beneficial medicinal effects (Carretero, 2002; Nadziakiewicza, Kehoe, & Micek, 2019). .
To overcome this problem, inorganic carriers such as clay minerals for metal nanoparticles have been investigated (Kim et al., 2007). Successful attempts against bacteria were already achieved using other clay minerals such as allophane and imogolite doped with metals like Ag, Cu, Co, Zn (Stavitskaya et al., 2019; Williams et al., 2011). Attempts were also achieved using functionalized clay minerals and vegetal fibers for the dispersion of silver and copper ions (Joshi, Purwar, Udakhe, & Sreedevi, 2015).
High adsorptive capabilities for metal nanoparticles in NaMt are largely responsible for the antimicrobial properties of the metal-clays. The adsorptive properties in NaMt are governed by a large specific surface area with increased net negative charges on the sheets that can be obtained by intercalation of NaMt with dendritic polyols like BoltornTM H20 (Vdović, Jurina, Škapin, & Sondi, 2010). Reportedly, eco-friendly and cost-effective cotton fabric–based composite materials doped with copper oxide showed antibacterial action against Staphylococcus epidermis and Escherichia coli(Nabil, Christine, Julien, & Abdelkrim, 2018). The aim of this work was to prepare organoclays and/or natural polymers for hosting metal nanoparticles with long-term antibacterial effects.
Deeper insights in metal-matrice interaction will allow tailoring optimal interactions with MNPs by modifying the type and number of chemical functions of the organic moiety. This is expected to influence the metal to be released, the release velocity and desired antibacterial activity. This concept allows envisaging diverse applications for controlled release of a wide variety and drugs and other medicinal molecules.