Study On The Optimization Of DNA Hydrolase-like Activities Of MOF-based Nanomaterials And Their Applications For The Removal Of Antibiotic-resistance Genes From Aquatic Environment

With the increased usage of antibiotics,antibiotic-resistant genes(ARGs)are now ubiquitous in various natural environments,including municipal solid waste leachate,sludge,sediments,wastewater,and even drinking water.Moreover,the spread of ARGs in the environment by horizontal gene transfer has seriously threatened ecological environment and human health.The traditional treatment methods for the removal of ARGs mainly includes phyiscal adsorption and oxidation.However,the treatment technology based on adsorption is difficult to degrade ARGs and cannot fundamentally block the spread of bacteria resistance to antibiotic;the treatment technology based on oxidation also has problems such as low efficiency and secondary pollution.Therefore,it is urgent to develop new treatment technologies with high efficiency and low pollution.In recent years,various nanomaterials,such as carbon-based nanomaterials,cerium oxide-based nanomaterials and metal oxides-based nanomaterials,have been reported to degrade DNA.Among them,MOF-based nanomaterials are widely used in the degradation of a series of phosphoester bond-based environmental pollutants,such as organophosphorus pesticides and chemical warfare agents due to their unique advantages such as being able to mimic natural phosphatase active sites.Therefore,the development of MOF-based DNA hydrolases that catalyze the hydrolysis of phosphodiester bonds with high efficiency is expected to provide a new strategy for eliminating resistant genes.However,the activity of MOF-based nanomaterilas catalyzing the hydrolysis of phosphoester bonds is very limited.Therefore,we proposed an atomic engineering strategy to achieve the optimization of the DNA hydrolase activity of MOF-based nanomaterials by regulating the position of the introduced metal atoms,and further investigate the degradation effect of MOFs on ARGs and the ability to inhibit the spread of ARGs.Firstly,we prepared three UiO-type MOFs loaded with single-atom copper at different doping sites.It was found that the Cu species was introduced in form of single atom.Combined with the analysis of the fine local structure of the Cu atoms,the location of the incorperated Cu atoms was further confirmed,including attachment on the missing-linker defects(Cu/UiO-66),occupying metal node sites(Cuex-UiO-66),and attachment to organic ligands(UiO-67-CuN).Secondly,the hydrolysis activity of the three types of MOFs toward phosphoester bonds were evaluated.According to the reaction kinetics,the introduction of Cu atoms promoted the hydrolysis activity of MOFs,and their catalytic hydrolysis activities were highly depended on the location of incorporated Cu atoms,suggesting that tuning the location of incorporated metal atoms is an important modulation strategy to improve the catalytically hydrolysis activity of MOF-based nanomaterials.Among them,UiO-67-CuN,where Cu was anchored to ligands displayed the highest activity.Further analysis of the valence state of Cu species and the surface defects of MOFs revealed that the excellent catalytic activity of UiO-67-CuN may originate from its higher oxygen vacancy concentration and stronger Lewis acidity.Finally,the cleavage effect of UiO-67-CuN on ARGs was investigated and the effect on its horizontal transfer was evaluated.Through gel electrophoresis and atomic force microscopy,it was found that UiO-67-CuN can efficiently catalyze the cleavage of DNA,acting as DNA hydrolases.As a result,UiO-67-CuN effectively inhibited the transformation of drug resistance genes and further eliminated bacterial resistance to antibiotic.