Gold Nanozymes:From Concept to Biomedical Applications

In recent years,gold nanoparticles have demonstrated excellent enzyme-mimicking activities which resemble those of peroxidase,oxidase,catalase,superoxide dismutase or reductase.This,merged with their ease of synthesis,tunability,biocompatibility and low cost,makes them excellent candidates when compared with biological enzymes for applications in biomedicine or biochemical analyses.Herein,over 200 research papers have been systematically reviewed to present the recent progress on the fundamentals of gold nanozymes and their potential applications.The review reveals that the morphology and surface chemistry of the nanoparticles play an important role in their catalytic properties,as well as external parameters such as pH or temperature.Yet,real applications often require specific biorecognition elements to be immobilized onto the nanozymes,leading to unexpected positive or negative effects on their activity.Thus,rational design of efficient nanozymes remains a challenge of paramount importance.Different implementation paths have already been explored,including the application of peroxidase-like nanozymes for the development of clinical diagnostics or the regulation of oxidative stress within cells via their catalase and superoxide dismutase activities.The review also indicates that it is essential to understand how external parameters may boost or inhibit each of these activities,as more than one of them could coexist.Likewise,further toxicity studies are required to ensure the applicability of gold nanozymes in vivo.Current challenges and future prospects of gold nanozymes are discussed in this review,whose significance can be anticipated in a diverse range of fields beyond biomedicine,such as food safety,environmental analyses or the chemical industry.

A systematic review of global occurrence of emerging mycotoxins in crops and animal feeds,and their toxicity in livestock

Mycotoxins are the most frequently occurring natural contaminant in food and feed.Their occurrence in crops and animal feed represents an enormous challenge,particularly for livestock farmers in terms of increased production costs,reduced animal performance and profitability.This study investigates the scale of emerging mycotoxins contamination of crops and animal feeds globally,and evaluates their impacts on the health and performance of livestock,especially when they co-occur alongside regulated mycotoxins.Emerging mycotoxins including nivalenol,enniatins,beauvericin,diacetoxyscirpenol,fusaric acid,patulin,moniliformin and sterigmatocystin were found to be the most prevalent contaminants of cereals and other feed commodities worldwide.The pooled mean levels for beauvericin,nivalenol,enniatins,moniliformin,sterigmatocystin,diacetoxyscirpenol,fusaric acid,and patulin were 386,421,7,854,204,136,126,370 and 138 mg/kg,respectively.In terms of toxicity,co-occurrence of emerging mycotoxins with each other and also with regulated mycotoxins profoundly impacts livestock performance,even at low levels.Therefore,there is a need for cumulative risk assessments to evaluate the health risks associated with simultaneous exposure to emerging and regulated mycotoxins and also to develop effective mitigation strategies.

Unusual switchable peroxidase-mimicking nanozyme for the determination of proteolytic biomarker

Detection of enzyme biomarkers originating from either bio-fluids or contaminating microorganisms is of utmost importance in clinical diagnostics and food safety. Herein, we present a simple, low-cost and easy-to-use sensing approach based on the switchable peroxidase-mimicking activity of plasmonic gold nanoparticles (AuNPs) that can catalyse for the oxidation of 3,3’,5’5-tetramethylbenzidine (TMB) for the determination of protease enzyme. The AuNP surface is modified with casein, showing dual functionalities. The first function of the coating molecule is to suppress the intrinsic peroxidase-mimicking activity of AuNPs by up to 77.1%, due to surface shielding effects. Secondly, casein also functions as recognition sites for the enzyme biomarker. In the presence of protease, the enzyme binds to and catalyses the degradation of the coating layer on the AuNP surface, resulting in the recovery of peroxidase-mimicking activity. This is shown visually in the development of a blue colored product (oxidised TMB) or spectroscopically as an increase in absorbance at 370 and 650 nm. This mechanism allows for the detection of protease at 44 ng·mL^-1 in 90 min. The nanosensor circumvents issues associated with current methods of detection in terms of ease of use, compatibility with point-of-care testing, low-cost production and short analysis time. The sensing approach has also been applied for the detection of protease spiked in ultra-heat treated (UHT) milk and synthetic human urine samples at a limit of detection of 490 and 176 ng·mL^-1, respectively, showing great potential in clinical diagnostics, food safety and quality control.

Amalgamated gold-nanoalloys with enhanced catalytic activity for the detection of mercury ions(Hg^2+)in seawater samples

Mercury(Hg)is extremely toxic,and continues to cause major threats to aquatic life,human health and the environment.Hg^2+mainly derives from seawater as a product of atmospheric deposition,therefore there is great demand for sensing approaches that can detect Hg^2+in seawater samples.Herein,we demonstrate that the peroxidase-mimicking activity of gold nanoparticles(AuNPs)or so-called nanozymes,can be exploited for the detection of Hg^2+ions in various water samples.In a high electrolyte environment,the catalytic activity for the oxidation of 3,3’,5,5’-tetramethylbenzidine(TMB)was significantly diminished due to poor stability of the bare-AuNPs.This activity was reduced by-73.7%when the NaCl concentration was higher than 1.168%,which is much lower than that of seawater(-3.5%),thus presenting its unsuitability for detecting Hg^2+in harsh water matrices.To overcome this limitation,AuNPs were first functionalized with oligo-ethylene glycol(OEG),of which their colloidal form presented high stability in NaCl concentrations up to 20%and across a wide range of pHs from 1-14.Interestingly,the catalytic activity of OEG-AuNPs for the oxidation of TMB was strongly suppressed by the coating,but enhanced upon formation of Au-Hg amalgamation.This novel finding underlies a straightforward,sensitive,and highly selective detection platform for Hg^2+in water samples.The approach could detect the exposure limit level for Hg^2+in drinking water(i.e.,2 ppb for tap and bottled water)as set by the United States Environmental Protection Agency(EPA)and the World Health Organization(WHO).When Hg^2+was spiked into a 3.5%saline solution and a coastal seawater certified reference material(CRM),the detection limits were found to be 10 ancM 3 ppb,respectively,which exceed the Hg^2+concentrations commonly found within seawater(-60-80 ppb).The whole procedure takes less than 45 min to conduct,providing a highly innovative,rapid and low-cost approach for detecting Hg^2+in complex water matrices.

Food Safety Strategies:The One Health Approach to Global Challenges and China’s Actions

WORLD FOOD SAFETY DAY World Food Safety Day(WFSD)(1)celebrated on 7 June 2021 aims to draw attention and inspire action to help prevent,detect and manage foodborne risks,contributing to food security,human health,economic prosperity,agriculture,market access,tourism and sustainable development.The theme of 2021,“Safe food today for a healthy tomorrow”,stresses that production and consumption of safe food has immediate and long-term benefits for people,the planet and the economy.Recognizing the systemic connections between the health of people,animals,plants,the environment and the economy will help us meet the needs of the future.

Sino-EU Intergovernmental Collaboration in the Campaign Against the COVID-19 Pandemic on Food via EU-China-Safe Framework

The coronavirus disease 2019(COVID-19)pandemic has swept across the planet with more than 81 million confirmed cases and deaths surpassing 1.8 million in over 222 countries(1).Since the first outbreak found in Wuhan in late December 2019,the capital city in Hubei Province of China,healthcare workers and scientists having been working relentlessly to fight against this invisible enemy.It is very clear that starting from nowhere.