Nanoparticles (NPs) are increasingly used to target bacteria as an alternative to antibiotics. Nanotechnology may be particularly advantageous in treating bacterial infections. Examples include the utilization of NPs in antibacterial coatings for implantable devices and medicinal materials to prevent infection and promote wound healing, in antibiotic delivery systems to treat disease, in bacterial detection systems to generate microbial diagnostics, and in antibacterial vaccines to control bacterial infections. The antibacterial mechanisms of NPs are poorly understood, but the currently accepted mechanisms include oxidative stress induction, metal ion release, and non-oxidative mechanisms. The multiple simultaneous mechanisms of action against microbes would require multiple simultaneous gene mutations in the same bacterial cell for antibacterial resistance to develop; therefore, it is difficult for bacterial cells to become resistant to NPs. In this review, we discuss the antibacterial mechanisms of NPs against bacteria and the factors that are involved. The limitations of current research are also discussed.

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The antimicrobial activity of nanoparticles: present situation and prospects for the future

A systematic and complete antibacterial study on well-designed and well-characterized microparticle (micro), nanoparticle (nano), and capped nano ZnO has been carried out in both dark and light conditions with the objective of arriving at the mechanism of the antibacterial activity of ZnO, particularly in the dark. The present systematic study has conclusively proved that reactive oxygen species (ROS) such as •OH, •O2–, and H2O2 are significantly produced from aqueous suspension of ZnO even in the dark and are mainly responsible for the activity in the dark up to 17%, rather than Zn2+ ion leaching as proposed earlier. This work further confirms that surface defects play a major role in the production of ROS both in the presence and absence of light. In the dark, superoxide (•O2–) radical mediated ROS generation through singly ionized oxygen vacancy is proposed for the first time, and it is confirmed by EPR and scavenger studies. ROS such as •O2–, H2O2, and •OH have been estimated by UV–visible spectroscop...

Insight into the Mechanism of Antibacterial Activity of ZnO: Surface Defects Mediated Reactive Oxygen Species Even in the Dark

The efficient handling of wastewater pollutants is a must, since they are continuously defiling limited fresh water resources, seriously affecting the terrestrial, aquatic, and aerial flora and fauna. Our vision is to undertake an exhaustive examination of current research trends with a focus on nanomaterials (NMs) to considerably improve the performance of classical wastewater treatment technologies, e.g. adsorption, catalysis, separation, and disinfection. Additionally, NM-based sensor technologies are considered, since they have been significantly used for monitoring water contaminants. We also suggest future directions to inform investigators of potentially disruptive NM technologies that have to be investigated in more detail. The fate and environmental transformations of NMs, which need to be addressed before large-scale implementation of NMs for water purification, are also highlighted.

Recent advances in nanomaterials for water protection and monitoring.

Synthesis, properties and applications of ZnO nanomaterials with oxygen vacancies: A review

Plant-extract mediated synthesis of ZnO nanoparticles using Pongamia pinnata and their activity against pathogenic bacteria

The production of H2O2 has been taken for a crucial reason for antimicrobial activity of ZnO without light irradiation. However, how the H2O2 generates in ZnO suspension is not clear. In the presen...

Antimicrobial Mechanism Based on H2O2 Generation at Oxygen Vacancies in ZnO Crystals

Evaluation of photocatalytic production of active oxygen and decomposition of phenol in ZnO suspensions

In view of their super capacity of adsorbing microbial, the carbon nanotubes (CNTs) were used as the carriers for in situ synthesizing well-dispersed and small-sized silver nanodots (AgND), to prepare a new type of antibacterial agent with remarkably improved activity. Polyethyleneimine (PEI) was introduced as a linkage for guaranteeing the as-generated AgND to be anchored onto the CNTs and to prevent them from agglomeration. The obtained hybridizing materials were characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, and the results showed that the AgND with an average size of 2.6 nm were uniformly loaded on surfaces of CNTs. There existed special interactions between silver atoms and CNTs. The antibacterial activities of the as-prepared hybrids against Escherichia coli were evaluated by disk diffusion assay method and minimal inhibitory concentration measurements. The results showed that the as-prepared hybrids displayed a remarkable improvement in antibacterial activity as compared to CNTs, acidified-CNTs and even the identical silver amount of AgNO3 solution, which was mainly attributed to the small size of AgND and the hybridizing effect between AgND and CNTs.

Remarkably Improvement in Antibacterial Activity of Carbon Nanotubes by Hybridizing with Silver Nanodots.

Method for improving antibacterial property of tetrapod-like zinc oxide whisker

Cu doping zinc oxides (ZnOs) were prepared by a post doping process with CuCl2 at high temperature With the increase of the dopant loading, the lattice constant c decreased firstly and then increased, which indicated that the doped Cu atoms substituted for Zn atoms at lower loading and extra dopant of the Cu atoms existed as interstitial atoms UV-Vis diffuse reflectance spectra (UV-DRS) illustrated that the energy band gap was effectively narrowed after Cu doping The photocatalytic production of hydroxyl radical (•OH) and superoxide anion (O2-) were determined by terephthalic acid with fluorescence spectrophotometer and nitroblue tetrazolium with UV-Vis spectrophotometer respectively, and the results showed that both the photocatalytic production of •OH and O2- were deceased with the increase of the dopant concentration, which indicated that the recombination centers were formed in the samples

Dan Chen

Papers

Antimicrobial Mechanism Based on H2O2 Generation at Oxygen Vacancies in ZnO Crystals

Evaluation of photocatalytic production of active oxygen and decomposition of phenol in ZnO suspensions

Remarkably Improvement in Antibacterial Activity of Carbon Nanotubes by Hybridizing with Silver Nanodots.

Method for improving antibacterial property of tetrapod-like zinc oxide whisker

Post-Doping of ZnO with Cu and its Effect on their Photocatalytic Production of Active Oxygen Species