Inhibitory effects of fucoidan from Laminaria japonica against some pathogenic bacteria and SARS-CoV-2 depend on its large molecular weight.

Fucoidan is a highly sulfated polysaccharide with a wide range of bioactivities, including anti-pathogenic activity. However, the relationship between structure and activity of fucoidan in inhibiting pathogen infections remains unclear. Here, different-molecular-weight fucoidans were prepared by photocatalytic degradation followed by membrane ultrafiltration, and their chemical structures and anti-pathogenic microbiota activity were compared. Results showed that photocatalytic degradation could effectively degrade fucoidan while its structure block and sulfate groups were not destroyed obviously. Fucoidan (90.8 kDa) of 5 mg/mL could inhibit the growth of S. aureus, S. typhimurium and E. coli, but its degradation products, Dfuc1 (19.2 kDa) and Dfuc2 (5.5 kDa), demonstrated lower inhibitory effect. In addition, compared to Dfuc1 and Dfuc2, fucoidan showed stronger capability to prevent the adhesion of S. aureus, L. monocytogenes, V. parahaemolyticus and S. typhimurium to HT-29 cells. Moreover, the inhibitory effect against SARS-CoV-2 and the binding activity to S protein were also positively correlated to molecular weight. These results indicate that natural fucoidan with higher molecular weight are more effective to inhibit these pathogenic bacteria and SARS-CoV-2, providing a better understanding of the relationship between structure and activity of fucoidan against pathogenic microbiota.

Evaluation of the multifunctional activity of silver bionanocomposites in environmental remediation and inhibition of the growth of multidrug-resistant pathogens

Synthesis of bio-based environmental remedial and antimicrobial products is an urgent need of the 21st century in the COVID-19 pandemic world. Keeping this in mind, cellulose-supported Ag bionanocomposites (AGC NCs) were synthesized by using cellulose as a reducing and stabilizing agent. AGC NCs showed potential antimicrobial activity against Candida albicans, Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Bacillus subtilis with a MIC of 15, 15, 35, 15, and 30 mu g ml(-1) respectively. AGC NCs efficiently degraded harmful dyes, Orange G, Phenol red, Brilliant blue FCF, Giemsa stain, Neutral red, and 2-nitro aniline in the presence of sunlight with a rate constant of 0.229 x 10(-2) min(-1), 1.147 x 10(-2) L mol(-1) min(-1), 0.447 x 10(-2) L mol(-1) min(-1), 4.144 x 10(-2) mol L-1 min(-1), 0.317 x 10(-2) L mol(-1) min(-1), and 0.785 x 10(-2) L mol(-1) min(-1) in 60 min respectively. AGC NCs also showed efficient antioxidant activity in DPPH assay with an IC50 value of 52.67 mu g ml(-1). Formation of Ag NPs was confirmed by observing the UV-Visible absorption peak at 418 nm. The FCC structure of AGC NCs was confirmed by the X-ray diffraction (XRD) pattern with well-defined peaks at angles 38.24 degrees, 44.40 degrees, 64.64 degrees, and 77.28 degrees corresponding to the planes 111, 200, 220, and 311, with a d-spacing of 2.35, 2.04, 1.44, and 1.23 (JCPDS no. 00-001-1164). The presence of cellulose in AGC NCs was determined by Fourier transform infrared spectroscopy (FTIR) with bands at 3421.90 cm(-1) and 2899.3 cm(-1) due to O-H stretching and the methylene (-CH2-) group respectively and at 1076-1023 cm(-1) and 903 cm(-1) due to -C-O-C- pyranose ring skeletal vibration and beta-glycosidic linkages. The morphology, shape and size (13.21 nm), and elemental composition of the nanocomposites were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS) respectively. The thermal properties (exothermic peaks appear at 335 degrees C and 440 degrees C due to the thermal degradation of Ag NPs and cellulose respectively), surface area (13.892 m(2) g(-1)), stability (-18.43 +/- 0.850 mV), and hydrodynamic diameter (399.10 +/- 30.49 nm) and polydispersity index (PDI) value (0.565 +/- 0.193) of the composites were determined by thermogravimetric analysis (TGA) and differential thermal analysis (DTA), Brunauer-Emmett-Teller (BET) method, Zeta potential studies, and dynamic light scattering (DLS) respectively.

Photocatalytic Degradation of Plastic Waste: A Mini Review.

Plastic waste becomes an immediate threat to our society with ever-increasing negative impacts on our environment and health by entering our food chain. Sunlight is known to be the natural energy source that degrades plastic waste at a very slow rate. Mimicking the role of sunlight, the photocatalytic degradation process could significantly accelerate the degradation rate thanks to the photocatalyst that drastically facilitates the photochemical reactions involved in the degradation process. This mini review begins with an introduction to the chemical compositions of the common plastic waste. The mechanisms of photodegradation of polymers in general were then revisited. Afterwards, a few photocatalysts were introduced with an emphasis on titanium dioxide (TiO2), which is the most frequently used photocatalyst. The roles of TiO2 photocatalyst in the photodegradation process were then elaborated, followed by the recent advances of photocatalytic degradation of various plastic waste. Lastly, our perspectives on the future research directions of photocatalytic plastic degradation are present. Herein, the importance of catalytic photodegradation is emphasized to inspire research on developing new photocatalysts and new processes for decomposition of plastic waste, and then to increase its recycling rate particularly in the current pandemic with the ever-increasing generation of plastic waste.

Antibacterial, Antiviral, and Self-Cleaning Mats with Sensing Capabilities Based on Electrospun Nanofibers Decorated with ZnO Nanorods and Ag Nanoparticles for Protective Clothing Applications.

The COVID-19 pandemic has clearly shown the importance of developments in fabrication of advanced protective equipment. This study investigates the potential of using multifunctional electrospun poly(methyl methacrylate) (PMMA) nanofibers decorated with ZnO nanorods and Ag nanoparticles (PMMA/ZnO-Ag NFs) in protective mats. Herein, the PMMA/ZnO-Ag NFs with an average diameter of 450 nm were simply prepared on a nonwoven fabric by directly electrospinning from solutions containing PMMA, ZnO nanorods, and Ag nanoparticles. The novel material showed high performance with four functionalities (i) antibacterial agent for killing of Gram-negative and Gram-positive bacteria, (ii) antiviral agent for inhibition of corona and influenza viruses, (iii) photocatalyst for degradation of organic pollutants, enabling a self-cleaning protective mat, and (iv) reusable surface-enhanced Raman scattering substrate for quantitative analysis of trace pollutants on the nanofiber. This multi-functional material has high potential for use in protective clothing applications by providing passive and active protection pathways together with sensing capabilities.