Microbicidal Dispersions and Coatings from Hybrid Nanoparticles of Poly (Methyl Methacrylate), Poly (Diallyl Dimethyl Ammonium) Chloride, Lipids, and Surfactants.

Rodrigo Tadeu Ribeiro,Carolina Nascimento Galvão,Beatriz Ideriha Mathiazzi,Ana Maria Carmona-Ribeiro,Yunys Pérez Betancourt

doi:10.3390/ijms20246150

Rodrigo Tadeu Ribeiro, Carolina Nascimento Galvão + Show 3 more

Open Access

https://doi.org/10.3390/ijms20246150

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Abstract

Hybrid and antimicrobial nanoparticles (NPs) of poly (methyl methacrylate) (PMMA) in the presence of poly (diallyl dimethyl ammonium) chloride (PDDA) were previously obtained by emulsion polymerization in absence of surfactant with low conversion. In the presence of amphiphiles such as cetyl trimethyl ammonium bromide (CTAB), dioctadecyl dimethyl ammonium bromide (DODAB) or soybean lecithin, we found that conversion increased substantially. In this work, the effect of the amphiphiles on the NPs core-shell structure and on the antimicrobial activity of the NPs was evaluated. NPs dispersions casted on silicon wafers, glass coverslips or polystyrene substrates were also used to obtain antimicrobial coatings. Methods for characterizing the dispersions and coatings were based on scanning electron microscopy, dynamic light scattering, determination of thickness, rugosity, and wettability for the coatings and determination of colony-forming unities (log CFU/mL) of microbia after 1 h interaction with the coatings or dispersions. The amphiphiles used during PMMA/PDDA/amphiphile NPs synthesis reduced the thickness of the NPs PDDA shell surrounding each particle. The antimicrobial activity of the dispersions and coatings were due to PDDA—the amphiphiles were either washed out by dialysis or remained in the PMMA polymeric core of the NPs. The most active NPs and coatings were those of PMMA/PDDA/CTAB—the corresponding coatings showed the highest rugosity and total surface area to interact with the microbes. The dispersions and coatings obtained by casting of the NPs dispersions onto silicon wafers were hydrophilic and exhibited microbicidal activity against Escherichia coli, Staphylococcus aureus, and Candida albicans. In addition, a major effect of reduction in particle size revealed the suitability of nanometric and cationic NPs (sizes below 100 nm) represented by PMMA/PDDA/CTAB NPs to yield maximal microbicidal activity from films and dispersions against all microbia tested. The reduction of cell viability by coatings and dispersions amounted to 6–8 logs from [PDDA] ≥ minimal microbicidal concentration.

Highlights

Several hybrid materials can exhibit antimicrobial activity [1,2,3]
SEM micrographs for the dried PMMA/poly (diallyl dimethyl ammonium) chloride (PDDA)/amphiphile dispersions after dialysis revealed uniform spherical NPs as synthesized in the presence of cetyl trimethyl ammonium bromide (CTAB) (Figure 1a), dioctadecyl dimethyl ammonium bromide (DODAB) (Figure 1b) or lecithin (Figure 1c)
The zeta-potentials (ζ) after dialysis remained positive, high and very similar to the ζ values for the PMMA/PDDA NPs obtained in absence of amphiphiles

Summary

Introduction

In restorative dentistry, inorganic antibacterial nanoparticles (NPs) incorporated to resin composites effectively reduce microorganism biofilm formation [4]. Examples of inorganic NPs with intrinsic antimicrobial activity are those made of ZnO, MgO, CuO, metallic silver, or gold, metal hydroxides such as Mg(OH)2 [5]. The other class of hybrid nanomaterials encompasses the biomimetic antimicrobial NPs and coatings obtained from the assembly of polymers, surfactants, or lipids [8,9] or from the use of virus-like, bacteria-like, or biological structure-like nanomaterials carrying antimicrobials [10]. The very useful NPs can yield a variety of nanostructures. NPs may form hybrid antimicrobial coatings and films [8,14,15,16,17,18]

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