Electrocatalytic Generation of Singlet Oxygen via ROS-Mediated Redox Chain Reaction for Efficient Disinfection.

The risk of harmful microorganisms to ecosystems and human health has stimulated exploration of singlet oxygen (1O2)-based disinfection. It can be potentially generated via an electrocatalytic process, but is limited by the low production yield and unclear intermediate-mediated mechanism. Herein, we designed a two-site catalyst (Fe/Mo-N/C) for the selective 1O2 generation. The Mo sites enhance the generation of 1O2 precursors (H2O2), accompanied by the generation of intermediate •HO2/•O2-. The Fe site facilitates activation of H2O2 into •OH, which accelerates the •HO2/•O2- into 1O2. A possible mechanism for promoting 1O2 production through the ROS-mediated chain reaction is reported. The as-developed electrochemical disinfection system can kill 1 × 107 CFU mL-1 of E. coli within 8 min, leading to cell membrane damage and DNA degradation. It can be effectively applied for the disinfection of medical wastewater. This work provides a general strategy for promoting the production of 1O2 through electrocatalysis and for efficient electrochemical disinfection.

Highly selective nanozyme-based glucose sensing platform via construction of artificial recognition sites on gold nanospheres.

Nanozymes have been regarded as the ideal alternatives to natural enzymes in bioassays due to their good stability and low cost. However, their applications in sensing usually suffer from poor selectivity. For example, Au-based nanozymes, as a kind of classical glucose oxidase mimic enzyme, could catalyze diverse monosaccharides. Therefore, it is of great necessity and urgency to endow the Au-based nanozymes with enhanced selectivity for the construction of specific glucose sensing platform. In our study, easily recyclable polydopamine (PDA)-supported Au-based nanozymes (PDA@Au NPs) were successfully prepared and could catalyze diverse monosaccharides including glucose, xylose, mannose, and sucrose. To enhance the selectivity of PDA@Au NPs, molecularly imprinted polymers (MIPs) were constructed on the surface of PDA@Au NPs using glucose and boronic acid derivatives as template and functional monomer. Impressively, the catalytic activity of the obtained molecularly imprinted nanozyme (PDA@Au NPs-MIPs) only shows a slight decrease (6.3%) while their selectivity is obviously enhanced (≥230%). Accordingly, the as-prepared sensor achieved the sensitive and selective detection of glucose in the concentration range of 10 µM-1 mM and a low detection limit (LOD) of 0.227 µM (S/N = 3), avoiding the influence of other monosaccharides exited in the sensing solutions to a great extent. As expected, the as-prepared sensors also showed good recovery, and long-term stability.

Nanozyme with tailored selectivity and highly catalytic activity for efficient sensing of endotoxin and sourcing gram-negative bacteria.

Endotoxin detection is important for determining bacterial contamination and infection in fields of food, pharmaceutical and clinical disease diagnosis. The horseshoe crab deformed cell lysate analysis is regarded as the gold-standard method, but the endangered and high-cost horseshoe crab animals required in sensing process further raise animal ethical issues and hinder their applications. The colorimetric methods based on nanozymes are simple and economical, but the low selectivity and sensitivity are still the bottleneck for their further application. Herein, we successfully developed a phenylboronic acid functionalized iron-based nanozyme with higher selectivity and highly catalytic activity for endotoxin sensing. The as-prepared colorimetric sensor using the obtained nanozyme as sensing probes shows a good linear relationship for endotoxin sensing in the range of 1-20 µg mL-1, with a LOD = 0.42 µg mL-1, along with good selectivity and reproducibility. The sensor can also be well applied to detecting endotoxin in practical samples such as beer and serum. Moreover, the parameters including time and temperature which could affect the endotoxin release from E. coli were also studied and optimized, based on the relationship between endotoxin and Gram-negative bacteria, the as-prepared sensor achieves the qualitative and quantification of E. coli.

MoOxNWs with mechanical damage - oriented synergistic photothermal / photodynamic therapy for highly effective treating wound infections.

Reactive oxygen species (ROS)-based therapy has emerged as a promising antibacterial strategy. However, it faces the limitations of uncontrollable space-time release and excessive lipid peroxidation, which may lead to a series of metabolic disorders and decreased immune function. In this study, mechanical damage by molybdenum oxide nanowires (MoOxNWs) is introduced as a synergistic factor to enhance the photothermal and photodynamic effects for controllable and efficient antibacterial therapy. Through their sharp ends, the nanowires can effectively pierce and damage the bacterial cells, thus facilitating the entry of externally generated ROS into the cells. The ROS are generated via photodynamic effect of the nanowires under a mere 5 min of near-infrared light irradiation. This approach enhances the photothermal (by 27.3 %) and photodynamic properties of ROS generation. MoOxNWs (100 µg·mL-1) achieve sterilisation rates of 97.67 % for extended-spectrum ß-lactamase-producing E. coli and 96.34 % for methicillin-resistant Staphylococcus aureus, which are comparable or even exceeding the efficacy of most MoOx-based antibacterial agents. Moreover, they exhibit good biocompatibility and low in vivo toxicity.

Ultrafine particles exposure is associated with specific operative procedures in a multi-chair dental clinic.

Air quality in dental clinics is critical, especially in light of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic, given that dental professionals and patients are at risk of regular exposure to aerosols and bioaerosols in dental clinics. High levels of ultrafine particles (UFP) may be produced by dental procedures. This study aimed to quantify ultrafine particles (UFP) concentrations in a real multi-chair dental clinic and compare the levels of UFP produced by different dental procedures. The efficiency of a high-volume evacuator (HVE) in reducing the UFP concentrations during dental procedures was also assessed. UFP concentrations were measured both inside and outside of a dental clinic in Shanghai, China during a 12-day period from July to September 2020. Dental activities were recorded during working hours. The mean (±standard deviation) concentrations of indoor and outdoor UFP during the sampling period were 8,209 (±4,407) counts/cm3 and 15,984 (±7,977) counts/cm3, respectively. The indoor UFP concentration was much higher during working hours (10,057 ± 5,725 counts/cm3) than during non-working hours (7,163 ± 2,972 counts/cm3). The UFP concentrations increased significantly during laser periodontal treatment, root canal filling, tooth drilling, and grinding, and were slightly elevated during ultrasonic scaling or tooth extraction by piezo-surgery. The highest UFP concentration (241,136 counts/cm3) was observed during laser periodontal treatment, followed by root canal filling (75,034 counts/cm3), which showed the second highest level. The use of an HVE resulted in lower number concentration of UFP when drilling and grinding teeth with high-speed handpieces, but did not significantly reduce UFP measured during laser periodontal therapy. we found that many dental procedures can generate high concentration of UFP in dental clinics, which may have a great health impact on the dental workers. The use of an HVE may help reduce the exposure to UFP during the use of high-speed handpieces.

Berberine ameliorates the LPS-induced imbalance of osteogenic and adipogenic differentiation in rat bone marrow-derived mesenchymal stem cells.

Lipopolysaccharide (LPS) from oral pathogenic bacteria is an important factor leading to alveolar bone absorption and the implant failure. The present study aimed to evaluate the modulation of berberine hydrochloride (BBR) on the LPS-mediated osteogenesis and adipogenesis imbalance in rat bone marrow-derived mesenchymal stem cells (BMSCs). Cell viability, osteoblastic and adipogenic differentiation levels were measured using the Cell Counting Kit-8 assay, alkaline phosphatase (ALP) staining and content assay, and oil red O staining, respectively. Reverse transcription-quantitative PCR and immunoblotting were used to detect the related gene and protein expression levels. In undifferentiated cells, BBR increased the mRNA expression levels of the osteoblastic genes (Alp, RUNX family transcription factor 2, osteocalcin and secreted phosphoprotein 1) but not the adipogenic genes (fatty acid binding protein 4, Adipsin and peroxisome proliferator-activated receptorγ). LPS-induced osteoblastic gene downregulation, adipogenic gene enhancement and NF-κB activation were reversed by BBR treatment. In osteoblastic differentiated cells, decreased ALP production by LPS treatment was recovered with BBR co-incubation. In adipogenic differentiated cells, LPS-mediated lipid accumulation was decreased by BBR administration. The mRNA expression levels of the pro-inflammatory factors (MCP-1, TNF-α, IL-6 and IL-1ß) were increased by LPS under both adipogenic and osteoblastic conditions, which were effectively ameliorated by BBR. The actions of BBR were attenuated by compound C, suggesting that the role of BBR may be partly due to AMP-activated protein kinase activation. The results demonstrated notable pro-osteogenic and anti-adipogenic actions of BBR in a LPS-stimulated inflammatory environment. This indicated a potential role of BBR for bacterial infected-related peri-implantitis medication.