Green polymeric nanomaterials for the photocatalytic degradation of dyes: a review

Extremophilic Exopolysaccharides: Biotechnologies and Wastewater Remediation

Various microorganisms thrive under extreme environments, like hot springs, hydrothermal vents, deep marine ecosystems, hyperacid lakes, acid mine drainage, high UV exposure, and more. To survive against the deleterious effect of these extreme circumstances, they form a network of biofilm where exopolysaccharides (EPSs) comprise a substantial part. The EPSs are often polyanionic due to different functional groups in their structural backbone, including uronic acids, sulfated units, and phosphate groups. Altogether, these chemical groups provide EPSs with a negative charge allowing them to (a) act as ligands toward dissolved cations as well as trace, and toxic metals; (b) be tolerant to the presence of salts, surfactants, and alpha-hydroxyl acids; and (c) interface the solubilization of hydrocarbons. Owing to their unique structural and functional characteristics, EPSs are anticipated to be utilized industrially to remediation of metals, crude oil, and hydrocarbons from contaminated wastewaters, mines, and oil spills. The biotechnological advantages of extremophilic EPSs are more diverse than traditional biopolymers. The present review aims at discussing the mechanisms and strategies for using EPSs from extremophiles in industries and environment bioremediation. Additionally, the potential of EPSs as fascinating biomaterials to mediate biogenic nanoparticles synthesis and treat multicomponent water contaminants is discussed.

Ecofriendly biopolymers and composites: Preparation and their applications in water-treatment

Over the past few decades, the term polymer has been repeatedly used in several industries for their immense characteristics in different applications. Polymers and their composites which were prepared from chemical monomer sources turned out to be potentially harmful to the environment due to their tedious degradation process. Biopolymers are natural substitutes for synthetic polymers which can be efficiently extricated from natural sources. They are predominantly available as polymeric units as well as monomeric units that are linked covalently. These environment-friendly biopolymers and their composites can be categorized based on their numerous sources, different methods of preparation and their potential form of usage. They were found to be biocompatible and biodegradable which make them exceptionally useful in environment based applications, mainly in the process of water treatment, both potable and wastewater. Further, the biopolymer and biopolymer composites easily fit into different parts of the treatment process by acting as filtration media, adsorbents, coagulants and as flocculants. The primary focus of this review is to provide a comprehensive information of biopolymers and biopolymer composites from synthesis to their usefulness for their productive application in water treatment processes. On the whole, it can be substantiated that the biopolymers were identified to play a notable adversary to the synthetic polymers in treating waters with an indispensable need for an elaborative study in the production of the biopolymers.

Recent progress in green and biopolymer based photocatalysts for the abatement of aquatic pollutants

Enormous research studies on the abatement of anthropogenic aquatic pollutants including organic dyes, pesticides, cosmetics, antibiotics and inorganic species by using varieties of semiconductor photocatalysts have been reported in recent decades. Besides, many of these photocatalysts suffer in real applications owing to their high production cost and low stability. In many cases, the photocatalysts themselves are being considered as secondary pollutants. To eliminate these drawbacks, the green synthesized photocatalysts and the use of biopolymers as photocatalyst supports are considered in recent years. In this context, recent developments in green synthesized metals, metal oxides, other metal compounds, and carbon based photocatalysts in water purification are critically reviewed. Furthermore, the pivotal role of biopolymers including chitin, chitosan, cellulose, natural gum, hydroxyapatite, alginate in photocatalytic removal of aquatic pollutants is comprehensively reviewed. The presence of functional groups, electron trapping ability, biocompatibility, natural occurrence, and low production cost are the major reasons for using biopolymers in photocatalysis. Finally, the summary and conclusion are presented along with existing challenges in this research area.

Endosomal pH-Responsive Fe-Based Hyaluronate Nanoparticles for Doxorubicin Delivery

In this study, we report pH-responsive metal-based biopolymer nanoparticles (NPs) for tumor-specific chemotherapy. Here, aminated hyaluronic acid (aHA) coupled with 2,3-dimethylmaleic anhydride (DMA, as a pH-responsive moiety) (aHA-DMA) was electrostatically complexed with ferrous chloride tetrahydrate (FeCl₂/4H₂O, as a chelating metal) and doxorubicin (DOX, as an antitumor drug model), producing DOX-loaded Fe-based hyaluronate nanoparticles (DOX@aHA-DMA/Fe NPs). Importantly, the DOX@aHA-DMA/Fe NPs improved tumor cellular uptake due to HA-mediated endocytosis for tumor cells overexpressing CD44 receptors. As a result, the average fluorescent DOX intensity observed in MDA-MB-231 cells (with CD44 receptors) was ~7.9 × 10² (DOX@HA/Fe NPs, without DMA), ~8.1 × 10² (DOX@aHA-DMA_0.36/Fe NPs), and ~9.3 × 10² (DOX@aHA-DMA_0.60/Fe NPs). Furthermore, the DOX@aHA-DMA/Fe NPs were destabilized due to ionic repulsion between Fe²⁺ and DMA-detached aHA (i.e., positively charged free aHA) in the acidic environment of tumor cells. This event accelerated the release of DOX from the destabilized NPs. Our results suggest that these NPs can be promising tumor-targeting drug carriers responding to acidic endosomal pH.

Amelioration of Pterostilbene Antiproliferative, Proapoptotic, and Oxidant Potentials in Human Breast Cancer MCF7 Cells Using Zein Nanocomposites

Purpose

This study aimed to explain the influence of zein nanosphere (ZN NS) formulation on the pharmacotherapeutic profile of PTS in MCF7 cells.

Methods

Liquid–liquid phase separation was used to formulate PTS-ZN NSs. The formulations developed were evaluated for particle-size analysis, encapsulation efficiency, and in vitro diffusion. Also, assays of cytotoxicity, uptake, cell-cycle progression, annexin V, apoptotic gene mRNA expression and biochemical assays were carried out.

Results

The PTS-ZN NS formulation selected showed 104.5±6.2 nm, 33.4±1.8 mV, 95.1%±3.6%, and 89.1%±2.65% average particle size, zeta-potential, encapsulation efficiency and in vitro diffusion, respectively. With MCF7 cells, IC₅₀ was reduced approximately 15-fold, with increased cellular uptake, accumulation in the G₂/M phase, increased percentage of cells in the pre-G₁ phase, amelioration of early and late apoptosis, raised mRNA expression of CASP3 and CASP7, lower expression of cyclin-CDK1, and enhanced oxidant potential through decreased glutathione reductase (GR) activity, and enhanced reactive oxygen–species generation and lipid-peroxidation products.

Conclusion

PTS-ZN NSs indicated enhanced antiproliferative, proapoptotic, and oxidant potential toward MCF7 cells compared to free PTS. Ameliorated results of nanosized carriers, cellular uptake, and sustained diffusion may contribute to these outcomes.

COVID-19 transmission, vulnerability, persistence and nanotherapy: a review

End 2019, the zoonotic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), named COVID-19 for coronavirus disease 2019, is the third adaptation of a contagious virus following the severe acute respiratory syndrome coronavirus in 2002, SARS-CoV, and the Middle East respiratory syndrome virus in 2012, MERS-CoV. COVID-19 is highly infectious and virulent compared to previous outbreaks. We review sources, contagious routes, preventive measures, pandemic, outbreak, epidemiology of SARS-CoV, MERS-CoV and SARS-CoV-2 from 2002 to 2020 using a Medline search. We discuss the chronology of the three coronaviruses, the vulnerability of healthcare workers, coronaviruses on surface and in wastewater, diagnostics and cures, and measures to prevent spreading.

Facile production of three-dimensional chitosan fiber embedded with zinc oxide as recoverable photocatalyst for organic dye degradation

Herein we report on a facile and green strategy for continuous production of chitosan-zinc oxide fibers and then compare their photodegradation performance against three organic dyes (i.e., methylene blue (MB), methyl orange (MO) and Rhodamine B, respectively) under different lights. Chitosan-zinc hydrogel fibers (CS/Zn) with different zinc loadings are obtained by direct mixing of chitosan and zinc acetate solutions using a double-syringe injection device. The as-prepared CS/Zn fibers are then immersed into glutaraldehyde (GA) and sodium hydroxide solutions, respectively, and dried at T = 50 °C. The resultant CS/ZnO/GA fibers of ca. 617 μm in diameter are characterized using X-ray diffraction (XRD), thermogravimetric analysis and field emission scanning electron microscope (FE-SEM). XRD and FE-SEM data confirm that the CS/ZnO/GA fibers consist of a large amount of hexagonal wurtzite ZnO nanorods up to 550 nm in length, and exhibit three-dimensional interconnected macroporous architecture. Photodegradation results clearly show that the CS/ZnO/GA fibers are effective for the removal of organic dyes upon UV irradiation and can be easily recovered and reused for at least 6 consecutive cycles. Unlike most reported CS/ZnO nanocomposites, the current CS/ZnO/GA fiber shows a higher adsorption of cationic MB rather than anionic MO, the mechanism of which is proposed.

Application of Silver-Loaded Composite Track-Etched Membranes for Photocatalytic Decomposition of Methylene Blue under Visible Light

In this study, the use of composite track-etched membranes (TeMs) based on polyethylene terephthalate (PET) and electrolessly deposited silver microtubes (MTs) for the decomposition of toxic phenothiazine cationic dye, methylene blue (MB), under visible light was investigated. The structure and composition of the composite membranes were elucidated by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction technique. Under visible light irradiation, composite membrane with embedded silver MTs (Ag/PET) displayed high photocatalytic efficiency. The effects of various parameters such as initial dye concentration, temperature, and sample exposure time on the photocatalytic degradation process were studied. The decomposition reaction of MB was found to follow the Langmuir-Hinshelwood mechanism and a pseudo-first-order kinetic model. The degradation kinetics of MB accelerated with increasing temperature and activation energy, E a, was calculated to be 20.6 kJ/mol. The reusability of the catalyst was also investigated for 11 consecutive runs without any activation and regeneration procedures. The Ag/PET composite performed at high degradation efficiency of over 68% after 11 consecutive uses.

Characterization of biogenically synthesized silver nanoparticles for therapeutic applications and enzyme nanocomplex generation

The present study describes green synthesis of silver nanoparticles (AgNPs) and inulin hydrolyzing enzyme nanocomplexes (ENC) using Azadirachta indica (Ai) and Punica granatum (Pg) leaf extracts. Surface topology and physico-chemical characteristics of AgNPs were studied using surface plasmon resonance (SPR), FTIR, SEM, AFM and EDX analyses. Particle size analysis using dynamic light scattering and AFM studies revealed that Ai-AgNPs (76.4 nm) were spherical in shape having central bigger nano-regime with smaller surroundings while Pg-AgNPs (72.1 nm) and ENCs (Inulinase-Pg-AgNPs ~ 145 nm) were spherical particles having smooth surfaces. Pg-AgNPs exhibited significant photocatalysis of a thiazine dye, methylene blue. Both Ai- and Pg-AgNPs showed selective antibacterial action by inhibiting pathogenic Bacillus cereus, while the probiotic Lactobacillus strains remained unaffected. Ai-AgNPs showed potential anti-biofilm effect (30% viability) on B. cereus biofilms. Pg-AgNPs showed anti-cancer effect against human colon cancer cell lines (Caco-2) resulting in 40% cell death in 48 h. Enzymes (inulinase, L-asparaginase and glucose oxidase) were successfully immobilized onto nanoparticles together with the biogenic synthesis of AgNPs and recyclability of the Inulinase-Pg-AgNPs complex was demonstrated. The study elaborates characteristics of green synthesized nanoparticles and their potential applications as anti-cancer, antibacterial and antioxidant nano drugs that could be used in food and nutraceutical industries. Enzyme immobilization on AgNPs without any toxic cross-linker opens up newer possibilites in enzyme-nanocomplex research.