The Safety of Cold-Chain Food in Post-COVID-19 Pandemic: Precaution and Quarantine

Since the outbreak of coronavirus disease-19 (COVID-19), cold-chain food contamination caused by the pathogenic severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has attracted huge concern. Cold-chain foods provide a congenial environment for SARS-CoV-2 survival, which presents a potential risk for public health. Strengthening the SARS-CoV-2 supervision of cold-chain foods has become the top priority in many countries. Methodologically, the potential safety risks and precaution measures of SARS-CoV-2 contamination on cold-chain food are analyzed. To ensure the safety of cold-chain foods, the advances in SARS-CoV-2 detection strategies are summarized based on technical principles and target biomarkers. In particular, the techniques suitable for SARS-CoV-2 detection in a cold-chain environment are discussed. Although many quarantine techniques are available, the field-based quarantine technique on cold-chain food with characteristics of real-time, sensitive, specific, portable, and large-scale application is urgently needed

Effects of Crystallite Sizes of Pt/HZSM-5 Zeolite Catalysts on the Hydrodeoxygenation of Guaiacol

Herein, Pt/HZSM-5 zeolite catalysts with different crystallite sizes ranging from nanosheet (~2 nm) to bulk crystals (~1.5 μm) have been prepared for the hydrodeoxygenation of guaiacol, and their effects on the reaction pathway and product selectivity were explored. HZSM-5 zeolites prepared by seeding (Pt/Z-40: ~40 nm) or templating (Pt/NS-2: ~2 nm) fabricated intra-crystalline mesopores and thus enhanced the reaction rate by promoting the diffusion of various molecules, especially the bulky ones such as guaiacol and 2-methoxycyclohexanol, leading to a higher cyclohexane selectivity of up to 80 wt % (both for Pt/Z-40 and Pt/NS-2) compared to 70 wt % for bulky HZSM-5 (Pt/CZ: ~1.5 μm) at 250 °C and 120 min. Furthermore, decreased crystallite sizes more effectively promoted the dispersion of Pt particles than bulky HZSM-5 (Pt/Z-400: ~400 nm and Pt/CZ). The relatively low distance between Pt and acidic sites on the Pt/Z-40 catalyst enhanced the metal/support interaction and induced the reaction between the guaiacol molecules adsorbed on the acidic sites and the metal-activated hydrogen species, which was found more favorable for deoxygenation than for hydrogenation of oxygen-containing molecules. In addition, Pt/NS-2 catalyst with a highly exposed surface facilitated more diverse reaction pathways such as alkyl transfer and isomerization

Adsorption–Desorption Behavior of Black Phosphorus Quantum Dots on Mucin Surface

Black phosphorus quantum dots (BPQDs) as novel nanomaterials have many potential applications in biomedicine. However, the interaction of BPQDs with proteins and their biological effects and potential risks are still unclear. Here, mucin, which serves biologically as a physical barrier against foreign substances entering tissues, was chosen as a model substrate for studying the adsorption–desorption behavior of BPQDs using surface plasmon resonance sensing and a quartz crystal microbalance with dissipation monitoring. We found that the surface modification of BPQDs with poly­(ethylene glycol)-amine (PEG-NH₂) reduces the adsorption rate of the quantum dots but increases their adsorbed amount on the mucin surface. The pH value, ionic strength, and ionic valence also had significant effects on the adsorption behavior of BPQDs. Upon increasing the pH from 2 to 7, the amount of BPQD adsorption decreased from 14.1 to 3.2 ng/cm². A high ionic strength and ionic valence (e.g., Mg²⁺, Al³⁺) also inhibit the surface adsorption of BPQDs. Furthermore, the adsorption–desorption mechanisms of BPQDs on the mucin surface were proposed. The adsorption–desorption behavior under different conditions may be attributed to the steric hindrance of PEG, the electrostatic interaction, and/or charge screening. These findings provide useful insights into the interfacial behavior of BPQDs before they enter the tissues

Synergy between zwitterionic polymers and hyaluronic acid enhances antifouling performance

Challenges associated with nonspecific adsorption of proteins on sensor surfaces have steered the development of novel antifouling materials and strategies. Inspired by human synovial fluid composition and structure, we designed synergistic antifouling coatings with mixtures of hyaluronic acid (HA) and a zwitterionic bottlebrush polymer (BB). Using a fast and convenient online surface modification method, the polymers were immobilized on the Au surface, significantly increasing its hydrophilicity. Using surface plasmon resonance (SPR), a 10:1 ratio of HA to BB was found optimal to provide the best antifouling performance. Bovine serum albumin (BSA) adsorption on HA-BB coated surfaces was 0.2 ng/cm2, which was 60 times lower than BB or HA alone and 25 times lower than the commonly accepted ultralow adsorption limit (<5 ng/cm2), demonstrating the synergistic effect of HA and BB against nonspecific protein adsorption. This was found to be independent of BSA concentration up to physiological concentrations. Furthermore, the antifouling performance of HA-BB coated surfaces was tested against milk and serum, showing almost 92% lower protein adsorption than that on bare surfaces, suggesting the potential efficacy of this antifouling coating in real life settings

Biomimetic bottle-brush polymer coatings for fabrication of ultra-low fouling surfaces

The increasing demand for long lasting antifouling surfaces has steered the development of accessible, novel, biocompatible and environmentally-friendly materials. Inspired by lubricin (LUB), a component of mammalian synovial fluid with excellent antifouling properties, we designed three block polymers with bottle-brush structures and outstanding stability, efficacy, and ease of use. By a simple drop casting or online exposure, the polymers strongly adsorbed on silica surfaces in less than 10 min and were found to be stable in extremely high-salinity solutions and under an unprecedented wide range of pH. The polymers antifouling properties against proteins and bacteria were evaluated using different techniques, demonstrating ultralow fouling properties. With serum albumin and lysozyme adsorption < 0.2 ng/cm2, the polymers were found to be 50 and 25 times more effective than LUB and the known ultralow fouling coatings. The antifouling properties were also successfully tested under MPa compression pressures by direct force measurements using the surface forces apparatus (SFA). The findings of this study suggest that these polymers are amongst the most robust and efficient antifouling agents known today