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Zeolite, as an intricate microporous material with redox sites, has been widely examined in many chemical industries. However, zeolite is not available everywhere, and it is expensive considering the price of raw materials from which it can be synthesized. In this study, ZSM-5 zeolite, as a local silica source with the high crystallinity, was synthesized, based on diatomite exploited from a mine in the north-west of Iran. The diatomite was employed as the only source of silica, and underwent hydrothermal transformation in a Teflon-lined autoclave operating at 170 °C without any alkaline post-treatment. The effects of the reaction pH and the reaction time on the properties of the synthesized MFI-type zeolite were monitored. The hydrothermal reaction time was optimized and hierarchical ZSM-5 hexagonal crystals were obtained. Furthermore, the effect of Si/Al ratio on the crystallinity of the resulting zeolite was investigated. The XRD, SEM, TEM, BET, FTIR, TPD, TGA, and DSC analyses were carried out to characterize the synthesized zeolites. The results confirmed the creation of MFI-type zeolites from diatomite applying hydrothermal process at an optimized pH and reaction time. In addition, the synthesized ZSM-5 zeolites exhibited a narrow pore size distribution resembling the mesoporous structure of standard ZSM-5 zeolites. Plenty of regularly arranged pores with diameters of 300–500 nm were observed inside the round circle-like sections of diatomite. For zeolites in which Si/Al ratio was higher (55 compared to 37), a relatively narrower pore size distribution similar to that of the standard ZSM-5 zeolite was detected. Comparably, the synthesized zeolites also contained stronger acid sites, rendering it as an excellent catalyst for the conversion of methanol to gasoline.

Agarose is a prominent marine polysaccharide representing reversible thermogelling behavior, outstanding mechanical properties, high bioactivity, and switchable chemical reactivity for functionalization. As a result, agarose has received particular attention in the fabrication of advanced delivery systems as sophisticated carriers for therapeutic agents. The ever-growing use of agarose-based biomaterials for drug delivery systems resulted in rapid growth in the number of related publications, however still, a long way should be paved to achieve FDA approval for most of the proposed products. This review aims at a classification of agarose-based biomaterials and their derivatives applicable for controlled/targeted drug delivery purposes. Moreover, it attempts to deal with opportunities and challenges associated with the future developments ahead of agarose-based biomaterials in the realm of advanced drug delivery. Undoubtedly, this class of biomaterials needs further advancement, and a lot of critical questions have yet to be answered.

Poloxamers, also called Pluronic, belong to a unique class of synthetic tri-block copolymers containing central hydrophobic chains of poly(propylene oxide) sandwiched between two hydrophilic chains of poly(ethylene oxide). Some chemical characteristics of poloxamers such as temperature-dependent self-assembly and thermo-reversible behavior along with biocompatibility and physiochemical properties make poloxamer-based biomaterials promising candidates for biomedical application such as tissue engineering and drug delivery. The microstructure, bioactivity, and mechanical properties of poloxamers can be tailored to mimic the behavior of various types of tissues. Moreover, their amphiphilic nature and the potential to self-assemble into the micelles make them promising drug carriers with the ability to improve the drug availability to make cancer cells more vulnerable to drugs. Poloxamers are also used for the modification of hydrophobic tissue-engineered constructs. This article collects the recent advances in design and application of poloxamer-based biomaterials in tissue engineering, drug/gene delivery, theranostic devices, and bioinks for 3D printing. STATEMENT OF SIGNIFICANCE: Poloxamers, also called Pluronic, belong to a unique class of synthetic tri-block copolymers containing central hydrophobic chains of poly(propylene oxide) sandwiched between two hydrophilic chains of poly(ethylene oxide). The microstructure, bioactivity, and mechanical properties of poloxamers can be tailored to mimic the behavior of various types of tissues. Moreover, their amphiphilic nature and the potential to self-assemble into the micelles make them promising drug carriers with the ability to improve the drug availability to make cancer cells more vulnerable to drugs. However, no reports have systematically reviewed the critical role of poloxamer for biomedical applications. Research on poloxamers is growing today opening new scenarios that expand the potential of these biomaterials from "traditional" treatments to a new era of tissue engineering. To the best of our knowledge, this is the first review article in which such issue is systematically reviewed and critically discussed in the light of the existing literature.

The biodegradability and mechanical properties of polysaccharides are dependent on their architecture (linear or branched) as well as their crystallinity (size of crystals and crystallinity percent). The amount of crystalline zones in the polysaccharide significantly governs their ultimate properties and applications (from packaging to biomedicine). Although synthesis, characterization, and properties of polysaccharides have been the subject of several review papers, the effects of crystallization kinetics and crystalline domains on the properties and application have not been comprehensively addressed. This review places focus on different aspects of crystallization of polysaccharides as well as applications of crystalline polysaccharides. Crystallization of cellulose, chitin, chitosan, and starch, as the main members of this family, were discussed. Then, application of the aforementioned crystalline polysaccharides and nano-polysaccharides as well as their physical and chemical interactions were overviewed. This review attempts to provide a complete picture of crystallization-property relationship in polysaccharides.

The necessity of research on flame retardancy has directed attentions toward development of advanced coating systems in order to meet requirements of competitive markets. As a result, a wide range of organic coating materials were developed in the quest of higher flame retardancy performance. Polyaniline (PANI) as a promising conductive polymer has been widely considered for various applications, and it quite frequently took credit for the success. This article deals with the benefits expecting from PANI in advanced flame retardant systems in view of its extraordinary fire retardancy performance. The necessity of study on potentially high thermal stability and flame retardancy of advanced coating systems containing PANI was also discussed. There is a belief that identifying the worth of PANI as the most famous member of conductive polymers may help determine the locus of PANI in an inevitable shift from general-purpose to advanced flame retardant (FR) systems in which PANI plays a dual role. Harmoniously, ongoing progress in the knowledge and technology of FR coating systems would enliven emerging technologies for utilizing organic materials in response to increasing demand for PANI-based systems with an additional flame retardancy mission in the near future.

The ability of mesenchymal stem cells (MSCs) to enhance cutaneous wound healing has been well established. Extensive expansion of cells to reach sufficient cell numbers for regenerating tissues has always limited cell-based therapies. An ingenious solution to address this challenge is to develop a strategy to increase the immunomodulatory effects of MSCs without expanding them. In this study, we employed a simple characteristic of cells. It was observed that an optimized three-dimensional (3D) MSC culture in spheroid forms significantly improved their paracrine effects. An electrospray (ES) encapsulation apparatus was used to encapsulate individual or 3D spheroid MSCs into microscale alginate beads (microbeads). Furthermore, alginate microbeads were embedded in an injectable thermosensitive hydrogel matrix, which gels at skin temperature. The hydrogel fills and seals the wounds cavities, maintains high humidity at the wound area, absorbs exudate, and fixes microbeads, protecting them from direct contact with the harsh wound environment. In vitro investigations revealed that secretion of interleukin 10 (IL-0) and transforming growth factor β1 (TGF-β1) gene was gradually enhanced, providing a delivery platform for prolonged release of bioactive molecules. In vivo study on full-thickness wounds showed granulation and re-epithelialization, only after 7 days. Moreover, increased expression of α-smooth muscle actin (α-SMA) in the first 14 days after treatment ensured wound contraction. Besides, a gradual decrease in α-SMA secretion resulted in reduced scar formation. Well-organized collagen fibrils and high expression of the angiogenesis biomarker CD31 confirmed the promoting effect of the hydrogel on the wound-healing process. The proposed wound-dressing system would potentially be used in scalable and effective cell-based wound therapies.

Polysaccharides are the most abundant naturally available carbohydrate polymers; composed of monosaccharide units covalently connected together. Chitosan is the most widely used polysaccharides because of its exceptional biocompatibility, mucoadhesion, and chemical versatility. However, it suffers from a few drawbacks, e.g. poor mechanical properties and antibacterial activity for biomedical applications. Blending chitosan with natural or synthetic polymers may not merely improve its physicochemical and mechanical properties, but may also improve its bioactivity-induced properties. This review paper summarizes progress in chitosan blends with biodegradable polymers and polysaccharides and their biomedical applications. Blends of chitosan with alginate, starch, cellulose, pectin and dextran and their applications were particularly addressed. The critical and challenging aspects as well as the future ahead of the use of chitosan-based blends were eventually enlightened.

Hydrogel membranes (HMs) are defined and applied as hydrated porous media constructed of hydrophilic polymers for a broad range of applications. Fascinating physiochemical properties, unique porous architecture, water-swollen features, biocompatibility, and special water content dependent transport phenomena in semi-permeable HMs make them appealing constructs for various applications from wastewater treatment to biomedical fields. Water absorption, mechanical properties, and viscoelastic features of three-dimensional (3D) HM networks evoke the extracellular matrix (ECM). On the other hand, the porous structure with controlled/uniform pore-size distribution, permeability/selectivity features, and structural/chemical tunability of HMs recall membrane separation processes such as desalination, wastewater treatment, and gas separation. Furthermore, supreme physiochemical stability and high ion conductivity make them promising to be utilised in the structure of accumulators such as batteries and supercapacitors. In this review, after summarising the general concepts and production processes for HMs, a comprehensive overview of their applications in medicine, environmental engineering, sensing usage, and energy storage/conservation is well-featured. The present review concludes with existing restrictions, possible potentials, and future directions of HMs.

Functionalized graphene oxide (FGO)/epoxy nanocomposite coatings were prepared through a cathodic electrophoretic deposition (C-EPD) process for anti-corrosion applications. The C-EPD process was carried out at different voltages, for 5 min to create uniform coatings of different thicknesses (i.e., 5−10 μm). Electrochemical impedance spectroscopy (EIS) and salt spray tests showed that nanocomposite coatings containing 0.1 wt. % FGO possess outstanding corrosion resistance properties. It was concluded that the incorporation of FGO act equivalent to thickness increase in terms of retarding corrosive agents to diffuse into the coating. However, at higher loadings, FGO aggregates may adversely affect anti-corrosion properties.

Since drinkable water resources are not infinite, the most plausible solution to address the forthcoming water scarcity is to treat the polluted water streams. This state-of-the-art review highlights the prime role of conductive polymers (CPs), widely known as intrinsically conductive polymers (ICPs), in wastewater treatment through reviewing very recent studies conducted on the elimination of noxious contaminations. Herein, after a brief introduction to the characteristics of conductive polymers, we tried to give a more comprehensive overview of the decontamination of polluted water based on different prevailing water treatment processes. The first section belonged to the adsorptive removal of pollutants is well-featured on various heavy-metal ions capture along with a comprehensive discussion on the governing uptake mechanism. After that, diversified types of CP-based composites applied for sorptive elimination of other types of pollutants, especially organic dyes, and their possible adsorption mechanism was also reviewed in detail. Next, recent publications related to CP-based photocatalysts utilized for the degradation of aquatic contamination were adequately summarized. The applicability and efficiency of the CP-based membrane for water purification through different membrane filtration techniques were underscored. Moreover, In the last section of the current study, a conclusion and perspective are provided, in which we discussed what one could discern from the remaining distinctive challenges, limitations, and, more importantly, the envisaged future directions of CP-based materials toward water treatment.

Due to population growth and subsequent growing energy demand, clean energy generation is one of the major challenges today and in the future. Dye-sensitized solar cells (DSSCs) is one of the new approaches to producing clean, endless energy. In this review, the primary function, structure, performance parameters, and key elements of DSSCs are analyzed first, with a focus on the photosensitizer as the crucial part due to electron production. Photosensitizers based on natural resources recently attracted attention because of their economic and environmental advantages, but there are substantial challenges such as low conversion efficiency and long term stability. Also, diverse and, in some cases, contradictory results presented in the literature make conclusions difficult. Here, different challenges about DSSCs based on natural dyes are categorized and discussed according to the published papers, and possible solutions are presented, which could shed light on future investigations. Furthermore, according to different factors, such as average solar radiation and economic/technological aspects, DSSCs based on natural dyes are proposed to be the most promising renewable energy technology for arid to semi-arid, sunny countries like Iran in the future. Accordingly, the performance of DSSCs based on natural dyes manufactured using dye extract of different plants grow in Iranian is summarized then. In recent years, many DSSCs based on natural dyes have been manufactured using different plants grown in different parts of the country. Interestingly, it is possible to extract many natural dyes for DSSCs based on natural dyes from agricultural wastes such as saffron petals and walnut shells, of which thousand tons them are disposed every year.

In this paper, chemical polymerization of aniline and aniline/multi-walled carbon nanotubes (MWCNTs) is investigated, and a modified polymerization model is proposed based on the obtained experimental results. In the experimental section, the variation in temperature of the reaction mixture was measured during the polymerization reaction. According to the obtained thermographs, it was concluded that the polymerization of aniline or aniline/MWCNTs takes place in three different steps. In the first step, some nuclei of phenazine-type trimers are formed for pure aniline while for aniline/MWCNTs, aniline molecules are adsorbed on the nanotubes surfaces. In the second step, cation-radical polymerization occurs at a high speed where there are a significant number of monomers around the growing chains. It is proposed that in the third step a new polymerization reaction begins on the pre-synthesized polymers. For pure PANI, it seems that only oligomers are created in this step while for PANI/MWCNTs, long chain polymers can also grow. Experimental results show that the enthalpy of polymerization reduces while polymerization yield increases with the weight percent of MWCNTs, which can be explained by the new observed polymerization model.