ABSTRACT
Objective The epidemic of COVID-19 and its variants is endangering human health. Wearing protective masks can effectively reduce the infection risk by resisting the inhalation of the polluted air containing the coronavirus. Electrospun polyamide nanofibers can be used as the core layer of protective masks and have lately received growing attention because of their high filtration performance and robust mechanical properties. However, existing electrospun polyamide nanofiber filters are usually prepared from toxic solvents which could cause severe environmental pollution and endanger workers' health, hence, their practical application should be restricted. Therefore, it is imperative to seek and develop green-solvent-based polyamide nanofiber filters. Method Innovative polyamide nanofiber filters were developed by direct electrospinning technique based on green solvents (Fig. 1). Ethanol as the solvent and water as the nonsolvent were adopted to prepare the green-solvent-based polyamide (GSPA) nanofibers by designing spinning solutions with different ethanol/water mass ratios (i.e., 10: 0, 9: 1, 8: 2, 7: 3, and 6: 4) . During electrospinning process, the working voltage, tip-to-collector distance, and solution extrusion speed were set as 30 kV, 15 cm and 1 mL/h, respectively. The nanofibers prepared with the different ethanol/water ratios were denoted as GSPA - 0, GSPA - 1, GSPA - 2, GSPA-3, and GSPA-4, respectively. Results It was found that water content had a great influence on the morphological structures of polyamide nanofibers (Fig. 2) - After introducing a small amount of water, the obtained GSPA - 1 nanofibers featuring thinner diameter of 332 nm were compared to the GSPA-0 nanofibers (499 nm). The enhanced conductivity (10. 5 μS/cm) of waterborne spinning solutions (Fig. 3) stimulated more charges on spinning jets and led to larger electrostatic force, thus greatly elongating the jets and thinning the fiber diameter. However, with the further increment of water concentrations from 20% to 40%, the obtained fibers exhibited an increased average diameter ranging from 443 to 1 553 nm, which was mainly attributed to the larger viscosity of spinning solutions. Although water cannot dissolve polyamide, homogenous waterborne polyamide/ethanol solutions can still be obtained with different ethanol/water mass ratios within a broad area in the stable region (Fig. 3) - The average pore size of GSPA -1 membranes decreased by 55% compared with that of GSPA-0 membranes, contributing to high filtration efficiency. Moreover, with different concentrations (10%, 20%, 30%) of water, the fluffy structure of GSPA nanofibers were achieved with a high porosity (> 80%), which would offer more passageways to transmit air rapidly. As the water concentration increased, the breaking strength of membranes increased at first and then decreased (Fig. 5), and the GSPA- 1 membranes exhibited the highest breaking strength of 5. 6 MPa, which was believed to be related to the enhanced entanglements and contacts among the adjacent fibers because of the small fiber diameter. The GSPA -1 membranes displayed the highest filtration efficiency (99. 02%) for the most penetration particles (PM0.3) by virtue of the small fiber diameter but suffered from poor permeability with a pressure drop of 158 Pa. Moreover, the GSPA- 1 membranes possessed the highest quality factor of 0. 029 3 Pa, suggesting the optimal filtration performance among different GSPA membranes. A high PM0.3 removal efficiency (>95%) was achieved for GSPA-1 filters under various airflow velocities ranging from 10 to 90 L/min (Fig. 7). Compared with conventional melt-blown fibers, the GSPA nanofibers featured a smaller diameter and higher Knudsen number (Fig. 8), and PM0.3 were captured mainly on the surfaces of green polyamide nanofibers (Fig. 9), demonstrating the higher adsorption ability benefiting from the larger specific surface area. Conclusion A cleaner production of polyamide nanofibers for air filtration was proposed by direct electrospinning based on green and sustaina le binary solvents of water and ethanol. For the first time, the structure including fiber diameter, porosity, and pore size of electrospun polyamide nanofibers were precisely tailored by manipulating water concentration in spinning solutions. The prepared environmentally friendly polyamide nanofiber filters feature the interconnected porous structure with the nanoscale ID building blocks (332 nm), mean pore size (0.7 μm), and porosity (84%), thus achieving efficient PM0.3 capture performance with the filtration efficiency of 99. 02% and pressure drop of 158 Pa, which could be comparable to previous toxic-solvent-processed nanofibers. Moreover, the GSPA nanofibers exhibit robust mechanical properties with an impressive breaking strength (5 . 6 MPa) and elongation (163. 9%), contributing to withstanding the external forces and deformation in the practical assembly and usage of resultant filters. It is envisaged that the green-solvent-based polyamide nanofibers could be used as promising candidates for next-generation air filters, and the proposed waterborne spinning strategy can provide valuable insights for cleaner production of advanced polyamide textiles. © 2023 China Textile Engineering Society. All rights reserved.
ABSTRACT
The remarkable success of messenger RNA vaccines against the ongoing coronavirus-2019 (COVID-19) pandemic renews attention toward nucleic acid therapeutics. While nucleic acid therapy using unmodified DNA or RNA is the primary focus in disease treatment, there is growing need to develop nucleic acid-based small molecules owing to their potential clinical benefits as drugs in terms of cost and scalability. While small molecules targeting protein-protein interactions are known to alter the transcriptional status of a cell, they can result in a transient effect and variation of bio-efficacy among patients. Small molecules targeting DNA and/or RNA are in demand in the precision medicine approach as they have consistent bioactivity among patients. This review details the progress of sequence-specific DNA-binding pyrrole-imidazole polyamides (PIPs) in modulating the transcriptional status of target gene(s) without altering the underlying DNA sequence. Here, the different versions of PIPs are listed, and also, how conjugating them with DNA alkylating agents, epigenetic modulators, and other drugs can improve their clinical utility as targeted transcription therapeutics. Owing to their specificity, functional diversity, and limited toxicity, PIP technology holds enormous promise as frontrunner in small-molecule-based nucleic acid drugs to precisely regulate therapeutically important genes on demand and treat intractable diseases.Copyright © 2023 Wiley-VCH GmbH.
ABSTRACT
During the COVID-19 pandemic, the increased use of plastic for personal protective equipment (PPE), single-use plastic bags, and food packaging raised significant environmental concerns. This study aimed to investigate the shape, abundance, and type of microplastics in the sediment of Jakarta Bay, specifically Tanjung Priok, Ancol Beach, and Sunda Kelapa Port. Sediment was collected using an Ekman sediment grab sampler and was extracted using the density separation method. The microplastics were counted and categorized according to the shape under a microscope. The differences in microplastic abundance in three different stations were determined using a one-way ANOVA. The polymer of microplastics was identified using Fourier Transform Infra-Red (FTIR). The results show that the abundance of the microplastics from coastal sediment was highest in the Sunda Kelapa Port (45066.67 ± 5205.13 particle/kg dry weight), which is significantly different (p<0.05) from Tanjung Priok (40533.33 ± 2444.04 particle/kg dry weight) and Ancol Beach (34666.67 ± 2444.04 particle/kg dry weight). Fragments dominated the shape of microplastic in Tanjung Priok, Ancol Beach, and Sunda Kelapa Post, comprising 36%, 40%, 38%, respectively, followed by fiber, film, and pellet. The FT-IR tests indicated that polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyamide are the most prevalent microplastic polymers.