Enhanced Inactivation of Escherichia coli and MS2 Coliphage by Cupric Ion in the Presence of Hydroxylamine: Dual Microbicidal Effects

Abstract

The inactivation of Escherichia coli and MS2 coliphage by Cu(II) is found to be significantly enhanced in the presence of hydroxylamine (HA). The addition of a small amount of HA (i.e., 5-20 μM) increased the inactivation efficacies of E. coli and MS2 coliphage by 5- to 100-fold, depending on the conditions. Dual effects were anticipated to enhance the biocidal activity of Cu(II) by the addition of HA, viz. (i) the accelerated reduction of Cu(II) into Cu(I) (a stronger biocide) and (ii) the production of reactive oxidants from the reaction of Cu(I) with dissolved oxygen (evidenced by the oxidative transformation of methanol into formaldehyde). Deaeration enhanced the inactivation of E. coli but slightly decreased the inactivation efficacy of MS2 coliphage. The addition of 10 μM hydrogen peroxide (H2O2) greatly enhanced the MS2 inactivation, whereas the same concentration of H2O2 did not significantly affect the inactivation efficacy of E. coli Observations collectively indicate that different biocidal actions lead to the inactivation of E. coli and MS2 coliphage. The toxicity of Cu(I) is dominantly responsible for the E. coli inactivation. However, for the MS2 coliphage inactivation, the oxidative damage induced by reactive oxidants is as important as the effect of Cu(I).

Bacterial Disinfection by CuFe2O4 Nanoparticles Enhanced by NH2OH: A Mechanistic Study

“…It has been previously reported that NH 2 OH was able to efficiently transform Cu(II) ion into Cu(I) ion, which shows approximately 100-1000-fold enhancement in terms of antibacterial activity [7,33] reductive action of NH2OH. Besides, CuFe2O4/NH2OH reaction also mediated a significant change in O 1s electronic property.…”

“…The results showed that, at a concentration of 0.1, 0.2, 0.4, and 1 g/L CuFe 2 O 4 nanoparticles, the E. coli inactivation rate was 0.27-, 2.71-, 3.55-, and 4.74-log, respectively (Figure 5a), suggesting a dose-dependent CuFe 2 O 4 nanoparticle-induced reduction of bacterial viability. This is presumably because more exposed Cu(I) species mediated by NH 2 OH reduction acted as a highly potent antibacterial agent [32,33]. We subsequently evaluated the effect of NH 2 OH concentration.…”

“…It has been previously reported that NH2OH was able to efficiently transform Cu(II) ion into Cu(I) ion, which shows approximately 100-1000-fold enhancement in terms of antibacterial activity [7,33]. Because CuFe2O4 also owns Cu(II) species exposed onto the nanoparticle surface, we thus explored if the highly bactericidal Cu(I) species was formed by NH2OH reduction.…”

“…These two synergistic functions of Cu(I) lead to its bacteria inactivation performance with hundreds of times higher efficiency than Cu(II) and Cu(0). It has been previously reported that Cu(II) could be reduced by hydroxylamine (NH 2 OH) to produce Cu(I) with a high efficiency [32,33], but Cu(II) ion should be prohibited from drinking water because of its strong toxicity to human beings [34,35]. Specifically, the U.S. Environmental Protection Agency (EPA)-permitted copper ion concentration in drinking water is 1.3 ppm [36].…”

A Novel Copper-Binding Peptide That Self-Assembles Into a Transparent Antibacterial and Antiviral Coating

“…The burdens of both the viral outbreaks and the bacterial infections could be mitigated via a single coating with the dual functionality of being antiviral and antibacterial. Different materials were used as a coating that combines antiviral and antibacterial functions, such as silver nanoparticles, TiO 2 , small-molecule organics, polymers, and Cu-containing surfaces ( Kim et al, 2015 ; Si et al, 2018 ; Gurunathan et al, 2020 ; Balasubramaniam et al, 2021 ). The antiviral and antimicrobial mechanism of these materials involves different pathways, such as reactive oxygen species (ROS) production, contact killing, and membrane depolarization by the dissolution of metal ions.…”