Gums as Macromolecular Crowding Agents in Human Skin Fibroblast Cultures

Even though tissue-engineered medicines are under intense academic, clinical, and commercial investigation, only a handful of products have been commercialised, primarily due to the costs associated with their prolonged manufacturing. While macromolecular crowding has been shown to enhance and accelerate extracellular matrix deposition in eukaryotic cell culture, possibly offering a solution in this procrastinating tissue-engineered medicine development, there is still no widely accepted macromolecular crowding agent. With these in mind, we herein assessed the potential of gum Arabic, gum gellan, gum karaya, and gum xanthan as macromolecular crowding agents in WS1 skin fibroblast cultures (no macromolecular crowding and carrageenan were used as a control). Dynamic light scattering analysis revealed that all macromolecules had negative charge and were polydispersed. None of the macromolecules affected basic cellular function. At day 7 (the longest time point assessed), gel electrophoresis analysis revealed that all macromolecules significantly increased collagen type I deposition in comparison to the non-macromolecular crowding group. Also at day 7, immunofluorescence analysis revealed that carrageenan; the 50 µg/mL, 75 µg/mL, and 100 µg/mL gum gellan; and the 500 µg/mL and 1000 µg/mL gum xanthan significantly increased both collagen type I and collagen type III deposition and only carrageenan significantly increased collagen type V deposition, all in comparison to the non-macromolecular crowding group at the respective time point. This preliminary study demonstrates the potential of gums as macromolecular crowding agents, but more detailed biological studies are needed to fully exploit their potential in the development of tissue-engineered medicines.

Hydraulic conductivity and microscopic properties of polyanionic cellulose and microscale zero-valent iron amended sand/bentonite backfills exposed to dichloromethane solution

Leachate comprising organic contaminants such as dichloromethane is frequently discharged into groundwater at contaminated sites and unlined landfills. Soil-bentonite backfills in vertical cutoff walls are extensively employed to contain the flow of contaminated groundwater, thereby safeguarding the downstream groundwater environmental quality and ecosystem. This study presented a comprehensive evaluation of effects of dichloromethane-impacted groundwater on hydraulic conductivity and microscopic characteristics of soil-bentonite backfills amended with polymer namely polyanionic cellulose and microscale zero-valent iron. The results showed the amended backfills exhibited lower hydraulic conductivity than the unamended backfill regardless of the permeant type, i.e., tap water and dichloromethane solution. Scanning electron microscopy coupled with energy-dispersive spectrometry analyses demonstrated that polyanionic cellulose hydrogel could effectively coat sand, bentonite, and microscale zero-valent iron particles, providing protection of bentonite particles against attacks imposed by the dichloromethane and multivalent iron ions, and diminish aggregation of microscale zero-valent iron particles in the amended backfills. X-ray diffraction results indicated there was no intercalation of polyanionic cellulose and microscale zero-valent iron into the montmorillonite platelets of bentonite particles. Based on the Fourier Transform Infrared Spectroscopy Spectra analysis, a new functional group (-CH2) was identified on the polyanionic cellulose amended bentonite particles. The results demonstrated that amendment with polyanionic cellulose and microscale zero-valent iron is a promising approach to improve the performance of soil-bentonite backfills in containing flow of dichloromethane-impacted groundwater.

Sustained activation of persulfate by slow release of Fe(II) from silica-coated nanosized zero-valent iron for in situ chemical oxidation

Sustained activation of persulfate through the slow release of Fe(II) from silica-coated nanosized zero-valent iron (nZVI) particles (nZVI@SiO2) was investigated. Slow release of Fe(II) prevented radical scavenging by excess Fe(II) and increased the radical yield, which improved the stoichiometric efficiency of phenol degradation. Sulfate and hydroxyl radicals were found to be the main oxidative species produced during phenol degradation and were found to make comparable contributions to oxidation. The nZVI@SiO2 particle silica shell thickness controlled the release of Fe(II) and therefore the sustained activation of persulfate and was strongly affected by the synthesis conditions, including the [Si]/[Fe] ratio and silica supply rate. Optimal sustained phenol degradation was achieved when nZVI@SiO2 particles were synthesized using a [Si]/[Fe] ratio of 0.5 and a tetraethyl orthosilicate supply rate of 0.5 mL/min, and this was attributed to the nZVI@SiO2 particles giving an optimal Fe(II) release rate and therefore a high persulfate activation rate and a high phenol removal efficiency. Sustained persulfate activation induced by Fe(II) being slowly released was described well by single-stage first-order kinetics rather than two-stage first-order kinetics typical of unmodified nZVI/persulfate systems. Persulfate was found still to be activated by iron (oxyhydr)oxides minerals after the nZVI@SiO2 particles had been exhausted but the persulfate sustained activation induced by the slow release of Fe(II) played a crucial role in determining the overall degradation efficiency. The results highlight the importance of the slow release of Fe(II) from nZVI-based materials for in situ chemical oxidation through sustained persulfate activation.

Recent Advances and Prospects for Plant Gum-Based Drug Delivery Systems: A Comprehensive Review

This work is an effort to first introduce plant-based gums and discussing their drug delivery applications. The composition of these plant gums and their major characteristics, which make them suitable as pharmaceutical excipients are also described in detail. The various modifications methods such as physical and chemical modifications of gums and polysaccharides have been discussed along with their applications in different fields. Consequently, plant-based gums modification such as etherification and grafting is attracting much scientific attention to satisfy industrial demand. The evaluation tests to characterize gum-based drug delivery systems have been summarized. The release behavior of drug from plant-gum-based drug delivery is being discussed. Thus, this review is an attempt to critically summarize different aspect of plant-gum-based polysaccharides to be utilized in drug delivery systems having potential industrial applications.

Green Synthesis of Silver Nanoparticles from Diospyros villosa Extracts and Evaluation of Antioxidant, Antimicrobial and Anti-Quorum Sensing Potential

The biosynthesis of silver nanoparticles (AgNPs) from Diospyros villosa leaves and stem bark extracts is described. The stem bark AgNPs of D. villosa synthesized at 80 °C (S80) showed good scavenging activity with a lower IC50 value of 8.75 µg·mL−1 compared to ascorbic acid (9.58 µg·mL−1). The total phenol content of the S80 AgNPs was measured and found to be 10.22 ± 0.14 mg.g−1 gallic acid equivalence (GAE). Bacterial growth inhibition (% GI) and violacein inhibition (% VI) of 10.08% and 58.83%, respectively, was observed against C.subtsugae CV017 with leaf AgNPs synthesized at 80 °C (L80) at 80 μg·mL−1. Stem bark AgNPs synthesized at room temperature (SRT) also indicated % GI of 13.83% and % VI of 65.97% against C. subtsugae CV017 at 160 μg·mL−1. Leaf AgNPs of D. villosa synthesized at room temperature (LRT), showed % GI of 29.07% and % VI of 56.53%, respectively, against C. violaceum ATCC 12472 at 320 μg·mL−1. The L80 and SRT at 160 μg·mL−1 and LRT at 320 μg·mL−1 may be considered as potential QS inhibitors following their activity against C. subtsugae CV017 and C. violaceum ATCC 12472, respectively. Therefore, D. villosa represents a potential source of antioxidants as well as an anti-quorum sensing therapeutic candidate for the control of Gram-negative bacterial infections.

Experimental study on in situ remediation of Cr(VI) contaminated groundwater by sulfidated micron zero valent iron stabilized with xanthan gum

Micron zero valent iron (mZVI) was an underground remediation material, which had great application potential to replace nano zero valent iron (nZVI) from the perspective of economic and health benefits. However, mZVI was highly prone to gravitational settling, which limited its wide application for in situ remediation of contaminated groundwater. This paper was devoted to develop an efficient and economical groundwater remediation material based on mZVI, which should possess excellent stability, reactivity, and transportability. Thereby xanthan gum (XG) stabilized and Na₂S₂O₄ sulfidated mZVI (XG-S-mZVI) was synthesized and characterized with SEM, XRD, XPS, and FTIR techniques. In terms of stability, the adsorbed XG and the dispersed XG worked together to resist the sedimentation of S-mZVI. In terms of reactivity, sulfidation enhanced the electron transfer rate and electron selectivity of XG-S-mZVI, thereby improved the reactivity of XG-S-mZVI. The hexavalent chromium (Cr(VI)) removal rate constant by XG-S-mZVI was determined to be 832.4 times than bare mZVI. In terms of transportability, the transportability of XG-S-mZVI was greatly improved (~80 cm in coarse sand and ~50 cm in medium sand). Straining was the main mechanism of XG-S-mZVI retention in porous media. XG-S-mZVI in situ reactive zone (XG-S-mZVI-IRZ) was only suitable to the media with a grain size larger than 0.25 mm. This study could provide theoretical support and guidance for the implementation of IRZ technology based on mZVI.

In situ nanoremediation of soils and groundwaters from the nanoparticle's standpoint: A review

Anthropogenic pollution coming from industrial processes, agricultural practices and consumer products, results in the release of toxic substances into rural and urban environments. Once released, these chemicals migrate through the atmosphere and water, and find their way into matrices such as sediments and groundwaters, thus making large areas potentially uninhabitable. Common pollutants, including heavy metal(loid)s, radionuclides, aliphatic hydrocarbons and halogenated organics, are known to adversely affect physiological systems in animal species. Pollution can be cleaned up using techniques such as coagulation, reverse osmosis, oxidation and biological methods, among others. The use of nanoparticles (NPs) extends the range of available technologies and offers particular benefits, not only by degrading, transforming and immobilizing contaminants, but also by reaching inaccessible areas and promoting biotic degradation. The development of NPs is understandably heralded as an environmentally beneficial technology; however, it is only now that the ecological risks associated with their use are being evaluated. This review presents recent developments in the use of engineered NPs for the in situ remediation of two paramount environmental matrices: soils and groundwaters. Emphasis will be placed on (i) the successful applications of nano-objects for environmental cleanup, (ii) the potential safety implications caused by the challenging requirements of [high reactivity toward pollutants] vs. [none reactivity toward biota], with a thorough view on their transport and evolution in the matrix, and (iii) the perspectives on scientific and regulatory challenges. To this end, the most promising nanomaterials will be considered, including nanoscale zerovalent iron, nano-oxides and carbonaceous materials. The purpose of the present review is to give an overview of the development of nanoremediators since they appeared in the 2000s, from their chemical modifications, mechanism of action and environmental behavior to an understanding of the problematics (technical limitations, economic constraints and institutional precautionary approaches) that will drive their future full-scale applications.

Confining polyacrylic acid on the surface of nanoscale zero-valent iron by aluminum hydroxide for in-situ anti-passivation

Aggregation and surface passivation of nanoscale zero-valent iron (NZVI) particles have limited their reactivity and application for environmental remediation. In this study, an aluminum hydroxide/polyacrylic acid (Al(OH)₃/PAA) hybrid shell was homogeneously coated on the NZVI surface to overcome the limitations. PAA molecules were confined onto the NZVI surface by hydration of Al(III) cations. The Al(OH)₃/PAA coating shell provided more electrostatic repulsion forces between NZVI particles to hinder the particle aggregation and preserve the NZVI reactivity. On the other hand, the surface-anchored PAA provided a thickened reactive layer for Cr(VI) reduction. Besides, XPS and TEM results showed that the surface carboxylic groups bound produced Cr(III) and Fe(III) cations and inhibited the precipitation of hydroxides on the NZVI surface. The reduced passivation layer increased the longevity of NZVI for surface reactions. As a result, the 24-h Cr(VI) reduction capacity of NZVI particles was improved from 49.4 to 92.6 mg/g with a 2 wt% (Al/Fe) Al(OH)₃/PAA coating shell. Overall, this study presented a promising strategy to effectively tune the surface properties of nanoparticles and improve the feasibility of NZVI for environmental remediation.

Influence of catalyst zeta potential on the activation of persulfate

The effect of the zeta potential of nano zero-valent iron (nZVI) and carbocatalyst on the activation of persulfate was investigated. The oxidation experiments were performed on three different compounds, with variously modified nZVI and three distinct carbocatalysts. From the obtained results, an evident linear correlation between nanoparticles' zeta potential and reaction rate constants of these three compounds oxidation may be observed. This phenomenon is not mechanism-specific and occurs for the radical and non-radical processes. The present work indicates the critical influence of the surface charge of nZVI and carbocatalysts on the persulfate catalytic activation.

Polysaccharide-based (nano)materials for Cr(VI) removal

Chromium is a potentially poisonous and carcinogenic species, which originates from human activities and various industries such as leather, steel, iron, and electroplating industries. Chromium is present in various oxidation states, among which hexavalent chromium (Cr(VI)) is highly toxic as a natural contaminant. Therefore, chromium, particularly Cr(VI), must be eliminated from the environment, soil, and water to overcome significant problems due to its accumulation in the environment. There are different approaches such as adsorption, ion exchange, photocatalytic reduction, etc. for removing Cr(VI) from the environment. By converting Cr(VI) to Cr(III), its toxicity is reduced. Cr(III) is essential for the human diet, even in small amounts. Today, biopolymers such as alginate, cellulose, gum, pectin, starch, chitin, and chitosan have received much attention for the removal of environmental pollutants. Biopolymers, particularly polysaccharides, are very useful compounds due to their OH and NH₂ functional groups and some advantages such as biodegradability, biocompatibility, and accessibility. Therefore, they can be widely applied in catalytic applications and as efficient adsorbents for the removal of toxic compounds from the environment. This review briefly investigates the application of polysaccharide-based (nano)materials for efficient Cr(VI) removal from the environment using adsorption/reduction, photocatalytic, and chemical reduction mechanisms.

Remediation of soil contaminated with organic compounds by nanoscale zero-valent iron: A review

In recent years, nanoscale zero-valent iron (nZVI) has been gradually applied in soil remediation due to its strong reducing ability and large specific surface area. Compared to conventional remediation solutions, in situ remediation using nZVI offers some unique advantages. In this review, respective merits and demerits of each approach to nZVI synthesis are summarized in detail, particularly the most commonly used aqueous-phase reduction method featuring surface modification. In order to overcome undesired oxidation and agglomeration of fresh nZVI due to its high reactivity, modifications of nZVI have been developed such as doping with transition metals, stabilization using macromolecules or surfactants, and sulfidation. Mechanisms underlying efficient removal of organic pollutants enabled by the modified nZVI lie in alleviative oxidation and agglomeration of nZVI and enhanced electron utilization efficiency. In addition to chemical modification, other assisting methods for further improving nZVI mobility and reactivity, such as electrokinetics and microbial technologies, are evaluated. The effects of different remediation technologies and soil physicochemical properties on remediation performance of nZVI are also summarized. Overall, this review offers an up-to-date comprehensive understanding of nZVI-driven soil remediation from scientific and practical perspectives.

The enhanced reduction of bromate by highly reactive and dispersive green nano-zerovalent iron (G-NZVI) synthesized with onion peel extract

In this study, novel green nano-zerovalent iron (G-NZVI) is synthesized for the first time using onion peel extract for the prevention of rapid surface oxidation and the enhancement of particle dispersibility with a high reductive capacity. The results from various surface analyses revealed that the spherical shape of G-NZVI was fully covered by the onion peel extract composed of polyphenolic compounds with C[double bond, length as m-dash]C-C[double bond, length as m-dash]C unsaturated carbon, C[double bond, length as m-dash]C, C-O, and O-H bonds, resulting in high mobility during column chromatography. Furthermore, the obtained G-NZVI showed the complete removal of 50 mg L-1 of bromate (BrO3 -) in 2 min under both aerobic (k = 4.42 min-1) and anaerobic conditions (k = 4.50 min-1), showing that G-NZVI had outstanding oxidation resistance compared to that of bare NZVI. Moreover, the observed performance of G-NZVI showed that it was much more reactive than other well-known reductants (e.g., Fe and Co metal organic frameworks), regardless of whether aerobic or anaerobic conditions were used. The effects of G-NZVI loading, the BrO3 - concentration, and pH on the BrO3 - removal kinetics using G-NZVI were also investigated in this study. The results provide the novel insight that organic onion peel waste can be reused to synthesize highly reactive anti-oxidative nanoparticles for the treatment of inorganic chemical species and heavy metals in water and wastewater.

Surface modification of zero-valent iron nanoparticles with β-cyclodextrin for 4-nitrophenol conversion

Environmental pollution causes irreversible damage to ecosystems and their structure. Therefore, the development of novel remedial techniques is a must for an effective response to emerging contaminants and those already persisting in the environment. The nanosized zero-valent iron (nZVI) is considered as an important nanostructure for the degradation of toxic compounds. Furthermore, the degradative potential of nZVI may be improved by surface modification. In this work nZVI was functionalized with β-cyclodextrin (β-CD), which is considered to be an environmentally-friendly and cheap adsorbent for toxic pollutants. Such a 'green' improvement not only enhances the activity of nZVI but also enables the conversion of 4-nitrophenol to 4-aminophenol, which under standard conditions is persistent and does not significantly react with bare nZVI. This research may help to find a solution to treat persistent organic pollutants (POPs) in aqueous environment.

Sustainable Synthesis of Nanoscale Zerovalent Iron Particles for Environmental Remediation

Nanoscale zerovalent iron (nZVI) particles represent an important material for diverse environmental applications because of their exceptional electron-donating properties, which can be exploited for applications such as reduction, catalysis, adsorption, and degradation of a broad range of pollutants. The synthesis and assembly of nZVI by using biological and natural sustainable resources is an attractive option for alleviating environmental contamination worldwide. In this Review, various green synthesis pathways for generating nZVI particles are summarized and compared with conventional chemical and physical methods. In addition to describing the latest environmentally benign methods for the synthesis of nZVI, their properties and interactions with diverse biomolecules are discussed, especially in the context of environmental remediation and catalysis. Future prospects in the field are also considered.

Effect of pH on hexavalent and total chromium removal from aqueous solutions by avocado shell using batch and continuous systems

Solution pH appears to be the most important regulator of the biosorptive removal of chromium ions from aqueous solutions. This work presents a kinetic study of the effects of solution pH on Cr(VI) and total chromium removal from aqueous solution by Hass avocado shell (HAS) in batch and continuous packed bed column systems. Different Cr(VI) and total chromium removal performances of HAS were obtained in pH-shift batch, pH-controlled batch, and continuous systems. These results emphasize the great importance of determining the most appropriate pH for Cr(VI) and total chromium removal, considering the operational mode of the proposed large-scale treatment system. Total chromium biosorption batch kinetics was well described by the Elovich model, whereas in the continuous system, the fitness of the kinetic models to the experimental data was pH dependent. X-ray photoelectron spectroscopy and kinetic studies clearly indicated that the reaction mechanism of Cr(VI) with HAS was the reductive biotransformation of Cr(VI) to Cr(III), which was partially released to the aqueous solution and partially biosorbed onto HAS.

Designing biocompatible sterile organogel–bigel formulations for drug delivery applications using green protocol

Present article discusses the formation of a bigel formulation for drug delivery applications via a newly developed green approach using gamma radiation induced crosslinking.

Tree gum-based renewable materials: Sustainable applications in nanotechnology, biomedical and environmental fields

The prospective uses of tree gum polysaccharides and their nanostructures in various aspects of food, water, energy, biotechnology, environment and medicine industries, have garnered a great deal of attention recently. In addition to extensive applications of tree gums in food, there are substantial non-food applications of these commercial gums, which have gained widespread attention due to their availability, structural diversity and remarkable properties as 'green' bio-based renewable materials. Tree gums are obtainable as natural polysaccharides from various tree genera possessing exceptional properties, including their renewable, biocompatible, biodegradable, and non-toxic nature and their ability to undergo easy chemical modifications. This review focuses on non-food applications of several important commercially available gums (arabic, karaya, tragacanth, ghatti and kondagogu) for the greener synthesis and stabilization of metal/metal oxide NPs, production of electrospun fibers, environmental bioremediation, bio-catalysis, biosensors, coordination complexes of metal-hydrogels, and for antimicrobial and biomedical applications. Furthermore, polysaccharides acquired from botanical, seaweed, animal, and microbial origins are briefly compared with the characteristics of tree gum exudates.

Removal of Cr (VI) from Simulated and Leachate Wastewaters by Bentonite-Supported Zero-Valent Iron Nanoparticles

Zero-valent iron (Fe⁰) nanoparticles (NPs) have shown excellent ability to remove contaminants hexavalent chromium (Cr(VI)) from aquatic systems. Use of support materials can help to prevent oxidation and aggregation of Fe⁰NPs, and thus enhance their remediation efficiency. However, most previous studies were conducted using artificially synthetic wastewater, and little is known on the remediation effects of supported Fe⁰NPs on actual wastewaters containing Cr(VI). Here, bentonite-supported Fe⁰NPs (BFe⁰NPs) with 1–5% of bentonite were prepared and characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. Batch experiments were performed to study Cr(VI) removal by the selected BFe⁰NPs from a simulated wastewater and a leachate wastewater originating from a Cr slag heap-polluted soil. The results show that Fe⁰NPs were uniformly dispersed on the bentonite, leading to a decreased aggregation of NPs, and the optimal mass ratio of bentonite was 4%. Batch experiment results show that lower pH values favored Cr(VI) removal by BFe⁰NPs. The removal percentage of Cr(VI) was higher than 90% for both wastewaters when the pH value was 2.0, but decreased significantly as pH value increased. Cr(VI) removal reaction was quite fast within the initial 10 min, and at least 85% of Cr(VI) was removed for both wastewaters. Cr(VI) removal percentage increased with increasing BFe⁰NPs dosages ranging from 30 to 60, but remained almost unchanged when the Fe/Cr mass ratio increased to above 60. The reaction of BFe⁰NPs to remove Cr(VI) followed the pseudo second-order reaction model. In most cases, the removal rates of Cr(VI) were higher in simulated wastewater than in leachate wastewater, but all approached 100% at the optimal conditions. Our present results show that BFe⁰NPs with 4% bentonite are efficient for treatment of Cr(VI)-containing wastewaters.

Green synthesis of gold nanoparticles using Artemisia dracunculus extract: control of the shape and size by varying synthesis conditions

In this study, selective green synthesis of gold nanoparticles (nAu) with the use of Tarragon extract (Artemisia dracunculus) was investigated. Characterization of the synthetized nAu was carried out using several techniques including: UV-Vis, SEM, zeta potential analysis, DLS, and ATR-FTIR. Based on measurements of Tarragon extract by HPLC-MS, significant chemical substances participating as reducing and stabilizing agents were identified. FTIR confirmed typical functional groups that could be found in these acids on the nAu surface, such as O-H, C=O and C-O. The effects of various parameters (concentration of Tarragon extract, Au precursor, and initial pH of the synthesis) on the shape and size of the nanoparticles have been investigated. UV-Vis and SEM confirmed the formation of nAu at various concentrations of the extract and Au precursor and showed correlation between the added extract concentration and shift in maximal absorbance towards higher frequencies, indicating the formation of smaller nanoplates. Zeta potential determined at various pH levels revealed that its value decreased with pH, but for all experiments in the pH range of 2.8 to 5.0, the value is below - 30 mV, an absolute value high enough for long-term nAu stability. In order to evaluate nAu catalytic activity, the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride was used as a model system. The reaction takes place 1.5 times faster on Au-triangles than on Au-spherical NPs.