The effects of interfacial potential on antimicrobial propensity of ZnO nanoparticle

Abstract

The work investigates the role of interfacial potential in defining antimicrobial propensity of ZnO nanoparticle (ZnONP) against different Gram positive and Gram negative bacteria. ZnONPs with positive and negative surface potential are tested against different bacteria with varying surface potentials, ranging −14.7 to −23.6 mV. Chemically synthesized ZnONPs with positive surface potential show very high antimicrobial propensity with minimum inhibitory concentration of 50 and 100 μg/mL for Gram negative and positive bacterium, respectively. On other hand, ZnONPs of the same size but with negative surface potential show insignificant antimicrobial propensity against the studied bacteria. Unlike the positively charged nanoparticles, neither Zn2+ ion nor negatively charged ZnONP shows any significant inhibition in growth or morphology of the bacterium. Potential neutralization and colony forming unit studies together proved adverse effect of the resultant nano-bacterial interfacial potential on bacterial viability. Thus, ZnONP with positive surface potential upon interaction with negative surface potential of bacterial membrane enhances production of the reactive oxygen species and exerts mechanical stress on the membrane, resulting in the membrane depolarization. Our results show that the antimicrobial propensity of metal oxide nanoparticle mainly depends upon the interfacial potential, the potential resulting upon interaction of nanoparticle surface with bacterial membrane.

Mode of Action of a Designed Antimicrobial Peptide: High Potency against Cryptococcus neoformans

“…For zeta-potential measurements of C. neoformans upon treatment with VG16KRKP a Nano S ZEN3690 (Malvern Instruments, Westborough, MA) was employed using a method described in Arakha et al (25). The details of the method can be found in the Supporting Material.…”

“…All stocks and solutions were prepared in 10 mM phosphate buffer of pH 7.2. The sample was excited at 280 nm and the emission spectrum was measured at a range of 300-400 nm at a temperature of 25 C. Both excitation and emission slits were set at 5 nm. DAPI fluorescence experiments were also performed to study minor groove binding of VG16KRKP to DNA (GG28).…”

“…Twenty micromolar of either GG28 or GC28 DNA alone in 10 mM phosphate buffer, pH 7.2 was scanned from a range of 320-210 nm at a scanning speed of 100 nm/min with data points collected at every nanometer, and for four repetitive scans that were finally averaged out. Titrations were carried out at 25 C with increasing concentrations of VG16KRKP starting from 20 to 100 mM. CD melting experiments were also carried out with DNA alone and in presence of VG16KRKP in a DNA/peptide ratio of 1:5 for both GG28 and GC28 sequences.…”

“…One-dimensional proton NMR spectra of VG16KRKP at 25 C was carried out on a Bruker Avance III 500 MHz NMR spectrometer (equipped with smart probe), followed by a series of 1D titrations using C. neoformans cell suspensions (OD 600 ¼ 1.0) in same buffer amounting to a final range of~10 7 cells. For live cell STD experiments, a 1 mM VG16KRKP solution was prepared in 10 mM deuterated phosphate buffer of pH 7.2 to rule out the possibility of peptide resonance suppression by water (33,34).…”

Characterisation and antimicrobial activity of silver nanoparticles derived from Vascellum pratense polysaccharide extract and sodium citrate

“…However, in the present study E. faecalis turned out to be the most resistant bacterial strain and a G-bacterium, Proteus mirabilis the most susceptible to AgNPs, although the exact zeta potential of the tested strains was not measured. Connection between the zeta potential and antimicrobial activity of various nanoparticles was earlier reported (Arakha et al, 2015;Tamara et al, 2018), however more studies are needed to establish such a connection for silver nanoparticles. The nature of the AgNPs coating may be more important than its charge, as bacteria can recognize some types of chemical species and possibly take up AgNPs via active transport as well.…”