Diminishing biofilm resistance to antimicrobial nanomaterials through electrolyte screening of electrostatic interactions

TY - JOUR

T1 - Diminishing biofilm resistance to antimicrobial nanomaterials through electrolyte screening of electrostatic interactions

AU - Harper, Robert

PY - 2019/1/1

Y1 - 2019/1/1

N2 - The extracellular polymer substances (EPS) generated by biofilms confers resistance to antimicrobial agents through electrostatic and steric interactions that hinder molecular diffusion. This resistance mechanism is particularly evident for antibacterial nanomaterials, which inherently diffuse more slowly compared to small organic antibacterial agents. The aim of this study was to determine if a biofilm’s resistance to antibacterial nanomaterial diffusion could be diminished using electrolytes to screen the EPS’s electrostatic interactions. Anionic (+) alpha-tocopherol phosphate (α-TP) liposomes were used as the antimicrobial nanomaterials in the study. They self-assembled into 700 nm sized structures with a zeta potential of −20 mV that were capable of killing oral bacteria (S. oralis growth inhibition time of 3.34 ± 0.52 h). In a phosphate (-ve) buffer the -ve α-TP liposomes did not penetrate multispecies oral biofilms, but in a Tris (hydroxymethyl)aminomethane (+ve) buffer they did (depth - 12.4 ± 3.6 μm). The Tris did not modify the surface charge of the α-TP nanomaterials, rather it facilitated the α-TP-biofilm interactions through electrolyte screening (Langmuir modelled surface pressure increase of 2.7 ± 1.8 mN/ m). This data indicated that EPS resistance was mediated through charge repulsion and that this effect could be diminished through the co-administration of cationic electrolytes.

AB - The extracellular polymer substances (EPS) generated by biofilms confers resistance to antimicrobial agents through electrostatic and steric interactions that hinder molecular diffusion. This resistance mechanism is particularly evident for antibacterial nanomaterials, which inherently diffuse more slowly compared to small organic antibacterial agents. The aim of this study was to determine if a biofilm’s resistance to antibacterial nanomaterial diffusion could be diminished using electrolytes to screen the EPS’s electrostatic interactions. Anionic (+) alpha-tocopherol phosphate (α-TP) liposomes were used as the antimicrobial nanomaterials in the study. They self-assembled into 700 nm sized structures with a zeta potential of −20 mV that were capable of killing oral bacteria (S. oralis growth inhibition time of 3.34 ± 0.52 h). In a phosphate (-ve) buffer the -ve α-TP liposomes did not penetrate multispecies oral biofilms, but in a Tris (hydroxymethyl)aminomethane (+ve) buffer they did (depth - 12.4 ± 3.6 μm). The Tris did not modify the surface charge of the α-TP nanomaterials, rather it facilitated the α-TP-biofilm interactions through electrolyte screening (Langmuir modelled surface pressure increase of 2.7 ± 1.8 mN/ m). This data indicated that EPS resistance was mediated through charge repulsion and that this effect could be diminished through the co-administration of cationic electrolytes.

KW - (+) Alpha tocopheryl phosphate

KW - Antimicrobial

KW - Biological interactions

KW - Electrolyte screening

KW - Nanomaterial

KW - Oral biofilm

KW - Penetration

KW - Resistance

KW - Tooth enamel

UR - http://www.scopus.com/inward/record.url?scp=85054617065&partnerID=8YFLogxK

U2 - 10.1016/j.colsurfb.2018.09.018

DO - 10.1016/j.colsurfb.2018.09.018

M3 - Article

VL - 173

SP - 392

EP - 399

JO - Colloids and Surfaces B: Biointerfaces

JF - Colloids and Surfaces B: Biointerfaces

SN - 0927-7765

ER -