Dry Heat as a Potential Decontamination Method on the Filtration Efficiency of Filtering Facepiece Respirators.

Filtering facepiece respirators have been widely used in the fields of occupational health and public hygiene, especially during the COVID-19 pandemic. In particular, disposable respirators have been in high demand, and the waste generated from these disposable products poses a problem for the environment. Here, we aimed to test a practical decontamination method to allow for the reuse of KN95 respirators. In this study, three types of KN95 respirators were heated at 80 °C and 90 °C for different durations (15 min, 30 min, 45 min, 1 h, 2 h, 3 h, 4 h, 6 h, 8 h, 10 h, and 24 h). The filtration efficiencies of the tested KN95 respirators before and after heating were measured, and the changes in microstructure were imaged with a scanning electron microscope (SEM). In addition, a neural network model based on the nonlinear autoregressive with external input (NARX) to predict the filtration efficiency of the KN95 respirator was established. The results show that the temperature and time of dry heating affected particle prevention. The higher the temperature and the longer the heating time, the more obvious the decline in the filtration efficiency of the respirators. When the heating temperature reached 100 °C, the respirator may be no longer suitable for reuse. These results show that a dry heat temperature between 70 °C and 90 °C, and a heating time between 30 min and 2 h is assumed to be a suitable and effective decontamination method for respirators.

Comparative Genomic and Physiological Analyses of a Superoxide Dismutase Mimetic (SODm-123) for Its Ability to Respond to Oxidative Stress in Tomato Plants.

Superoxide dismutases (SODs) are a group of enzymes that have a crucial role in controlling oxidative stress in plants. Here, we synthesized an environmentally friendly SOD mimic, SODm-123, from L-aspartic acid and manganese oxide. SODm-123 showed similar enzymatic activity to Mn-SOD. To gain insights into the role of SODm-123 in oxidative stress tolerance, a series of experiments were conducted to assess the physiological and molecular responses of tomato plants when treated with SODm-123. The results showed that the levels of O2-• and H2O2 in tomato cells were affected by SODm-123 treatment, indicating that SODm-123 can control oxidative stress like Mn-SOD. The results also exhibited that SODm-123 increased the contents of photosynthetic pigments. However, it was noted that SODm-123 resulted in a reduction in the content of soluble sugar and MDA. These results indicate that SODm-123 promoted the efficiency of photosynthesis by regulating the content of H2O2. To further investigate the role of SODm-123 in controlling oxidative stress, a transcriptome analysis was used to identify differentially expressed genes (DEGs) associated with SODm-123 treatment. The results indicated that SODm-123 treatment resulted in 341 differentially expressed genes (DEGs) in treated tomato leaves at 96 h after treatment. Kyoto encyclopedia of genes and genomes (KEGG) revealed that DEGs were involved in pathways such as photosynthetic pigment biosynthesis, ABC transporters, sugar metabolism, and MAPK signaling, which further confirmed a positive role of SODm-123 in improving stress tolerance in plants. Overall, the results of this study suggest that SODm-123 promotes the growth and development of tomato seedlings and therefore can be used as a potential growth-promoting agent for plants.