Metal-phenolic networks derived CN-FeC hollow nanozyme with robust peroxidase-like activity for total antioxidant capacity detection.

A tannate-iron network-derived peroxidase-like catalyst loaded with Fe ions on carbon nitride (C3N4) was reported for detection of total antioxidant capacity (TAC) in food in this study. Metal-phenolic networks (MPNs) was employed to form a low coordination compound on C3N4, and calcined catalyst formed hollow structure with abundant and uniform Fe sites and surface folds. CN-FeC exhibited significant peroxidase-like activity and high substrate affinity. The homogeneous distribution of amorphous Fe elements on the C3N4 substrate provides more active sites, resulting in provided excellent catalytic activity to activate H2O2 to ·OH, 1O2 and O2·-. The established CN-FeC/TMB/H2O2 colorimetric system can detect AA in the concentration range of 5-40 µM, with the detection limits of 1.40 µM, respectively. It has good accuracy for the detection of vitamin C tablets, beverages. Taken together, this work shows that metal-phenolic networks can be an effective way to achieve efficient utilization of metal atoms and provides a promising idea for metal-phenolic networks in nanoparticle enzyme performance enhancement.

Tannic acid-derived selective capture of bacteria from apple juice.

Given the enormous burden pathogens pose on human health, rapid capture and removal of bacteria for sterilization or further bacterial detection is essential. Herein, tannic acid-functionalized virus-like Fe3O4 (vFe3O4-TA) was established for bacterial enrichment. We investigated the ability of vFe3O4-TA to capture Gram-negative bacteria (E. coli, S. flex and S. typhi) and Gram-positive bacteria (S. aureus, MRSA and LM), respectively. Compared to the capture efficiency of <15 % for Gram-negative bacteria, vFe3O4-TA showed excellent selectivity and efficiency in isolating Gram-positive bacteria with >87 % removal efficiency. GFN-xTB semiempirical quantum chemical calculations revealed that the selective recognition originates from the high affinity between TA and peptidoglycan. Without impacting ingredients, the TA-mediated trapper also shows excellent ability to distinguish Gram-positive bacteria in juice samples. These results are expected to reveal the interaction of TA with bacteria, and inaugurate a potential natural safe tool for food safety control, medical treatment and environmental remediation.

A high-efficient and stable artificial superoxide dismutase based on functionalized melanin nanoparticles from cuttlefish ink for food preservation.

Natural superoxide dismutase (SOD), consisting of proteins and metal cofactors, is widely used in food preservation because of its good antioxidant activity. However, due to the poor stability of SOD enzyme, its activity was reduced in the process of moving into the film, resulting in limited application. Based on the structure of the active site of the natural enzyme, Cu2+ was used to functionalize the melanin nanoparticles (NMPs) in ink of cuttlefish, and an SOD-like nanozyme (Cu-NMPs) with high stability, high activity and strong free radical scavenging capacity was constructed. In order to apply the constructed simulated enzyme to food preservation, the simulated enzyme was embedded into carrageenan (Carr) films to prepare the composite film for food packaging. The results showed that when the concentration of Cu-NMPs was 10 µg/mL, the ·O2- rate could reach more than 80 %, the activity exceeded that of 60 U/mL natural SOD. In addition, the fresh-keeping test of cherry tomatoes showed that Carr/Cu-NMPs composite film extended the storage time of cherry tomatoes by more 3 days. Therefore, the present work showed that nanozymes with advanced catalytic capabilities can be constructed by metal ions and NMPs, thus successfully combined with food packaging for food preservation.

Natural melanin nanoparticle-based photothermal film for edible antibacterial food packaging.

Although nanocomposite films had shown excellent potential in antibacterial food packaging, their potential harmful impact limits their further application in reality. Therefore, exploring a Generally Recognized As Safe (GRAS) nanomaterial that has antibacterial ability is the pioneer for the fabrication of a real edible nanocomposite-based antibacterial packaging film. Herein, for the first time by using the natural nanostructure extracted from cuttlefish ink, an edible antibacterial food packaging with high safety were constructed. The natural melanin nanoparticles (NMPs) in cuttlefish ink have good photothermal conversion ability. As such, by incorporating with natural pectin (PC) film and with near infrared (NIR) irradiation triggering, the results show that PC/NMPs films perform high-efficiency and short-term bactericidal activity against foodborne pathogenic bacteria, including thermotolerant Listeria monocytogenes. The sterilization rate could reach more than 90 % within only 5 min. Also, this nanocomposite film showed better mechanical properties, thermal stability and barrier properties than the neat pectin film. Antibacterial test on food sample also proved the good antibacterial ability of the PC/NMPs films. Therefore, exploring GRAS natural functional nanocomposite film is expected to be the effective way to promote edible nano-antibacterial packaging.

"From food waste to food supervision"-Cuttlefish Ink Natural Nanoparticles-Driven Dual-mode Lateral Flow Immunoassay for Advancing Point-of-Care Tests.

Apart from the obvious benefit of "trash-to-treasure", the acquisition of natural nanomaterials from cheap and renewable waste has been intensively researched because of various bioactivities and physical-chemical features. Herein, for the first time, we employed natural cuttlefish ink nanoparticles (CINPs) as a multifunctional label and designed colorimetric-photothermal dual-mode lateral flow immunoassays (CINPs-mediated CPLFIA) for sensitive detection of clenbuterol (CL). The accessibility and renewability of CINPs overcome barriers that artificial nanomaterials face, such as complex manufacturing and relatively high costs. Additionally, inspired by the mussel adhesion, the bio-affinity of CINPs, such as antibody coupling and preservation, was investigated and showed to be considerably superior to Au NPs, leading to significantly increased immunosensor sensitivity. Meanwhile, CINPs exhibit excellent photothermal conversion efficiency for dual-signal production, avoiding the effect of environmental elements (particularly light) for colorimetric mode. Besides, the biosensor was integrated with a smartphone and a thermal imager for portable sensing. After optimization, the detection limit of CINPs-mediated CPLFIA was 0.179 ng mL-1 (colorimetric mode) and 0.076 ng mL-1 (photothermal mode), which were significantly lower than traditional gold nanoparticles-based LFIA (0.786 ng mL-1). This research attempted to explain the rise in sensitivity. From food waste to food supervision, this research explores the hidden value of natural resources.

Magnetic Nanoseparation Technology for Efficient Control of Microorganisms and Toxins in Foods: A Review.

Outbreaks of foodborne diseases mediated by food microorganisms and toxins remain one of the leading causes of disease and death worldwide. It not only poses a serious threat to human health and safety but also imposes a huge burden on health care and socioeconomics. Traditional methods for the removal and detection of pathogenic bacteria and toxins in various samples such as food and drinking water have certain limitations, requiring a rapid and sensitive strategy for the enrichment and separation of target analytes. Magnetic nanoparticles (MNPs) exhibit excellent performance in this field due to their fascinating properties. The strategy of combining biorecognition elements with MNPs can be used for fast and efficient enrichment and isolation of pathogens. In this review, we describe new trends and practical applications of magnetic nanoseparation technology in the detection of foodborne microorganisms and toxins. We mainly summarize the biochemical modification and functionalization methods of commonly used magnetic nanomaterial carriers and discuss the application of magnetic separation combined with other instrumental analysis techniques. Combined with various detection techniques, it will increase the efficiency of detection and identification of microorganisms and toxins in rapid assays.

Glucose Oxidase-Integrated Metal-Polyphenolic Network as a Microenvironment-Activated Cascade Nanozyme for Hyperglycemic Wound Disinfection.

The high systemic blood glucose concentration of hyperglycemic wound microenvironment (WME) severely impedes the disinfection and healing of infected skin wounds. Herein, a WME-activated smart natural product, integrated GOx-GA-Fe nanozyme (GGFzyme), is engineered, which combines a nanozyme and natural enzyme to promote reactive oxygen species (ROS) generation in situ for hyperglycemic wound disinfection. GGFzyme can consume a high concentration of glucose in hyperglycemia wounds and generate H2O2. The conversion of glucose into gluconic acid not avails starvation treatment but reduces the pH of WME to elevate the catalytic activities of both the nanozyme (GA-Fe) and natural enzyme (GOx). And H2O2 is then high efficiently catalyzed into •OH and O2•- in situ to combat pathogenic bacteria and promote wound disinfection. The high catalytic antibacterial capacity and superior biosafety, combined with beneficial WME modulation, demonstrate that GGFzyme is a promising therapeutic agent for hyperglycemic wounds.

Development of Pomegranate Peel Extract and Nano ZnO Co-Reinforced Polylactic Acid Film for Active Food Packaging.

The multifunctional packaging used for fresh food, such as antioxidant and antimicrobial packaging, can reduce food waste. In this work, a polylactic acid (PLA)-based composite film with antioxidant and antibacterial properties was prepared by using nano-zinc oxide (ZnONPs) and pomegranate peel extract (PEE) via the solvent-casting method. Different amounts of PEE (0.5, 1, 1.5 and 2 wt%) and 3 wt% ZnONPs were added to PLA to produce the active films. The results of various characterizations (SEM, XRD, etc.) showed that ZnONPs and PEE were uniformly dispersed in PLA film. Compared to PLA films, the PLA/ZnONPs/PEE films showed an increased UV barrier, water vapor permeability and elongation at break, and decreased transparency and tensile strength. In addition, the antioxidant activity of the composite film was evaluated based on DPPH and ABTS. The maximum DPPH and ABTS scavenging activities of PLA/ZnONPs/PEE were 96.2 ± 0.8% and 93.1 ± 0.5%. After 24 h, PLA/ZnONPs/PEE composite film inhibited 1.4 ± 0.05 Log CFU/mL of S. aureus and 8.2 ± 0.35 Log CFU/mL of E. coli, compared with the blank group. The results showed that PLA/ZnONPs/PEE composite film had good antibacterial and antioxidant activities. Therefore, the composite film showed great potential for food packaging.

Food-borne melanoidin-based nanozyme mimics natural peroxidase for efficient catalytic disinfection.

Nanozymes show great potential as broad-spectrum antibacterial agents in the field of anti-infection. Their feasibility of application has received great hindrance due to low catalytic performance, insufficient reactive oxygen species (ROS), complex material design, and biosafety issues. Herein, we discovered an Fe3+-centered Melanoidin/Fe3+ nanozyme that exhibited superior reaction rate and catalytic activity to horseradish peroxidase (HRP) through the carboxyl, nitrogenous structure of Melanoidin. Melanoidin/Fe3+ catalyzed the formation of hydrogen peroxide (H2O2) into highly toxic superoxide anion (O2-•), which promoted the antibacterial ability of H2O2. The results showed that Melanoidin/Fe3+ had an excellent antibacterial effect against methicillin-resistant Staphylococcus aureus (MRSA) in low concentration H2O2 system. Both the infection wound model experiment and the biocompatibility experiment showed that the Melanoidin/Fe3+ promoted wound healing and had impressive biosafety. Thus, Melanoidin/Fe3+ shows ideal promise for the design of artificial enzymes with catalytic properties comparable to those of natural enzymes and clinical antibacterial therapy.

Micro/nanomotor technology: the new era for food safety control.

Food poisoning caused by eating contaminated food remains a threat to global public health. Making the situation even worse is the aggravated global environmental pollution, which poses a major threat to the safety of agricultural resources. Food adulteration has been rampant owing to negligent national food safety regulations. The speed at which contaminated food is detected and disposed of determines the extent to which consumers' lives are safeguarded and agricultural economic losses are prevented. Micro/nanomotors offer a high-speed mobile loading platform that substantially increases the chemical reaction rates and, accordingly, exhibit great potential as alternatives to conventional detection and degradation techniques. This review summarizes the propulsion modes applicable to micro/nanomotors in food systems and the advantages of using micro/nanomotors, highlighting examples of their potential use in recent years for the detection and removal of food contaminants. Micro/nanomotors are an emerging technology for food applications that is moving toward mass production, simple preparation, and important functions.

Dimensionality reduction boosts the peroxidase-like activity of bimetallic MOFs for enhanced multidrug-resistant bacteria eradication.

The antibacterial strategy using cutting-edge metal-organic framework (MOF)-based nanozymes can effectively solve the problem caused by antibiotic resistance to protect human health and the environment; however it has been significantly limited by the complicated modification method and non-ideal catalytic activity. Herein, we report a facile dimensionality-reduction strategy to improve the catalytic activity of MOF-based nanozymes. By reducing the dimensionality of two-dimensional Co-TCPP(Fe) (Co-Fe NSs) to zero-dimensional Co-TCPP(Fe) (Co-Fe NDs), the peroxidase-like activity of the prepared bimetallic Co-Fe NDs was almost tripled. Consequently, the bimetallic Co-Fe NDs can highly efficiently catalyze the lower-concentration H2O2 into reactive oxygen species (ROS), resulting in a favorable antibacterial effect against methicillin-resistant Staphylococcus aureus (MRSA). Meanwhile, Co-Fe NDs can effectively promote wound healing and water environment disinfection with good biocompatibility. This work reveals the potential of a zero-dimensional bimetallic MOF-based nanozyme in resisting drug-resistant bacteria and holds great promise for future clinical and environmental applications.

Natural Products Self-Assembled Nanozyme for Cascade Detection of Glucose and Bacterial Viability in Food.

Sugar content and bacterial contamination levels are important indicators for the health and safety of food, respectively. Therefore, it is important to construct a method that can detect both glucose and bacterial activity. Herein, natural compounds (gallic acid and glucose oxidase) were assembled into nanozyme (GOx@GA-Fe (ii)) for mild cascade detection. The nanozyme catalyzes glucose to produce hydrogen peroxide, which is then converted to ·OH and oxidized colorless TMB from blue oxidized TMB. Under the optimal conditions, the method has a good linear relationship in the glucose concentration range of 1-500 µM (R2 = 0.993) with minimum detection concentration of 0.43 µM. Based on the glucose consumption of bacteria metabolism, the cascade reaction was then applied to detect the viability of 5 common bacteria. As such, a cascade method based on a natural self-assembled nanozyme was fabricated to monitor the quality of food.

Lycium Barbarum Polysaccharide-Iron (III) Chelate as Peroxidase Mimics for Total Antioxidant Capacity Assay of Fruit and Vegetable Food.

Quantitative evaluation of the antioxidant capacity of foods is of great significance for estimating food's nutritional value and preventing oxidative changes in food. Herein, we demonstrated an easy and selective colorimetric method for the total antioxidant capacity (TAC) assay based on 3,3',5,5'-tetramethyl-benzidine (TMB), hydrogen peroxide (H2O2) and synthetic Lycium barbarum polysaccharide-iron (III) chelate (LBPIC) with high peroxidase (POD)-like activity. The results of steady-state kinetics study showed that the Km values of LBPIC toward H2O2 and TMB were 5.54 mM and 0.16 mM, respectively. The detection parameters were optimized, and the linear interval and limit of detection (LOD) were determined to be 2-100 µM and 1.51 µM, respectively. Additionally, a subsequent study of the determination of TAC in six commercial fruit and vegetable beverages using the established method was successfully carried out. The results implied an expanded application of polysaccharide-iron (III) chelates with enzymatic activity in food antioxidant analysis and other biosensing fields.

Fused multicyclic polyketides with a two-spiro-carbon skeleton from mangrove-derived endophytic fungus Epicoccum nigrum SCNU-F0002.

A pair of uncommon fused multicyclic polyketides with a two- spiro-carbon skeleton, (±)-isoepicolactone, (±)-1, and one new isobenzofuranone monomer (4), together with four other known biosynthetically related compounds were isolated from the fermentation of an endophytic fungus, Epicoccum nigrum SCNU-F0002, which was isolated from the fresh fruit of the mangrove plant Acanthus ilicifolius L. Comprehensive spectroscopic analysis, X-ray crystallography, together with calculated ECD, were employed to define the structures. The antibacterial and COX-2 inhibitory activities of the compounds (1-6) were evaluated. A possible biogenetic pathway of (±)-isoepicolactone was confirmed.