Chitosan Bio‐Based Organic–Inorganic Hybrid Aerogel Microspheres

Biopolymer-based beads for the adsorptive removal of organic pollutants from wastewater: Current state and future perspectives

Among biopolymer-based adsorbents, composites in the form of beads have shown promising results in terms of high adsorption capacity and ease of separation from the effluents. This review addresses the potential of biopolymer-based beads to remediate wastewaters polluted with emerging organic contaminants, for instance dyes, active pharmaceutical ingredients, pesticides, phenols, oils, polyaromatic hydrocarbons, and polychlorinated biphenyls. High adsorption capacities up to 2541.76 mg g-1 for dyes, 392 mg g-1 for pesticides and phenols, 1890.3 mg g-1 for pharmaceuticals, and 537 g g-1 for oils and organic solvents have been reported. The review also attempted to convey to its readers the significance of wastewater treatment through adsorption by providing an overview on decontamination technologies of organic water contaminants. Various preparation methods of biopolymer-based gel beads and adsorption mechanisms involved in the process of decontamination have been summarized and analyzed. Therefore, we believe there is an urge to discuss the current state of the application of biopolymer-based gel beads for the adsorption of organic pollutants from wastewater and future perspectives in this regard since it is imperative to treat wastewater before releasing into freshwater bodies.

Preparation and application of the thermo-/pH-/ ion-sensitive semi-IPN hydrogel based on chitosan

Chitosan based hydrogels with multiple stimulus responses have broad application prospects in many fields. Considering the advantages of semi interpenetrating network (IPN) technology and the special temperature and ion responsiveness of polymers containing zwitterionic groups, a semi-IPN hydrogel was prepared through in situ free radical polymerization of N,N-dimethyl acrylamide and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide with polyethylene glycol dimethacrylate as a crosslinker and carboxymethyl chitosan as filler. The gel mass fraction and swelling ratio were measured, and the preparation conditions were optimized. The result indicated that the hydrogel possessed a unique thermo-/pH-/ ion-sensitive behavior. The swelling ratio increased with the increase of temperature and ion concentration, and showed a decreasing trend with the increase in pH. In addition, the hydrogel was stable when the stimuli changed. Adsorption behavior of the hydrogel to Eosin Y (EY) was systematically investigated. The adsorption process can be described well by the pseudo-second-order kinetic model and Langmuir isotherm model, indicating that it was a chemical adsorption. The experiments indicated that the hydrogel exhibited good antifouling and reusability features. Therefore, the semi-IPN hydrogel with antifouling properties and thermo-/pH-/ion-sensitivity can be easily manufactured is expected to find applications in water treatment fields.

Bio-based functionalized adsorptive polymers for sustainable water decontamination: A systematic review of challenges and real-world implementation

The overwhelming concerns of water pollution, industrial discharges and environmental deterioration by various organic and inorganic substances, including dyes, heavy metals, pesticides, pharmaceuticals, and detergents, intrinsically drive the search for urgent and efficacious decontamination techniques. This review illustrates the various approaches to remediation, their fundamentals, characteristics and demerits. In this manner, the advantageous implementation of nature-based adsorbents has been outlined and discussed. Different types of lignocellulosic compounds (cellulose, lignin, chitin, chitosan, starch) have been introduced, and the most used biopolymeric materials in bioremediation have been highlighted; their merits, synthesis methods, properties and performances in aqueous medium decontamination have been described. The literature assessment reveals the genuine interest and dependence of academic and industrial fields to valorize biopolymers in the adsorption of various hazardous substances. Yet, the full potential of this approach is still confined by certain constraints, such as the lack of reliable, substantial, and efficient extraction of biopolymers, as well as their modest and inconsistent physicochemical properties. The futuristic reliance on such biomaterials in all fields, rather than adsorption, is inherently reliable on in-depth investigations and understanding of their features and mechanisms, which can guarantee a real-world application and green technologies.

Aerogels based on cationically modified chitosan and poly(vinyl alcohol) for efficient capturing of viruses

In this study, we developed a new filtering bioaerogel based on linear polyvinyl alcohol (PVA) and the cationic derivative of chitosan (N-[(2-hydroxy-3-trimethylamine) propyl] chitosan chloride, HTCC) with a potential antiviral application. A strong intermolecular network architecture was formed thanks to the introduction of linear PVA chains, which can efficiently interpenetrate the glutaraldehyde(GA)-crosslinked HTCC chains. The morphology of the obtained structures was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The aerogels and modified polymers' elemental composition (including the chemical environment) was determined using X-ray photoelectron spectroscopy (XPS). New aerogels with more than twice as much developed micro- and mesopore space and BET-specific surface area were obtained concerning the starting sample chitosan aerogel crosslinked by glutaraldehyde (Chit/GA). The results obtained from the XPS analysis showed the presence of cationic 3-trimethylammonium groups on the surface of the aerogel, which can interact with viral capsid proteins. No cytotoxic effect of HTCC/GA/PVA aerogel was also observed on fibroblast cells of the NIH3T3 line. Furthermore, the HTCC/GA/PVA aerogel has been shown that efficiently traps mouse hepatitis virus (MHV) from suspension. The presented concept of aerogel filters for virus capture based on modified chitosan and polyvinyl alcohol has a high application potential.

Chitosan-Based Biomaterials: Insights into Chemistry, Properties, Devices, and Their Biomedical Applications

Chitosan is a marine-origin polysaccharide obtained from the deacetylation of chitin, the main component of crustaceans’ exoskeleton, and the second most abundant in nature. Although this biopolymer has received limited attention for several decades right after its discovery, since the new millennium chitosan has emerged owing to its physicochemical, structural and biological properties, multifunctionalities and applications in several sectors. This review aims at providing an overview of chitosan properties, chemical functionalization, and the innovative biomaterials obtained thereof. Firstly, the chemical functionalization of chitosan backbone in the amino and hydroxyl groups will be addressed. Then, the review will focus on the bottom-up strategies to process a wide array of chitosan-based biomaterials. In particular, the preparation of chitosan-based hydrogels, organic–inorganic hybrids, layer-by-layer assemblies, (bio)inks and their use in the biomedical field will be covered aiming to elucidate and inspire the community to keep on exploring the unique features and properties imparted by chitosan to develop advanced biomedical devices. Given the wide body of literature that has appeared in past years, this review is far from being exhaustive. Selected works in the last 10 years will be considered.

Photothermal Aerogel Beads Based on Polysaccharides: Controlled Fabrication and Hybrid Applications in Solar-Powered Interfacial Evaporation, Water Remediation, and Soil Enrichment

Solar-powered interfacial evaporation has emerged as an innovative and sustainable technology for clean water production. However, the rapid, mass and shape-controlled fabrication of three-dimensional (3D) steam generators (SGs) for versatile hybrid applications remains challenging. Herein, composite aerogel beads with self-contained properties (i.e., hydrophilic, porous, photothermal, and durable) are developed and demonstrated for threefold hybrid applications including efficient solar-powered interfacial evaporation, water remediation, and controlled soil enrichment. The rational incorporation of selected polysaccharides enables us to fabricate bead-like aerogels with rapid gelation, continuous processing, and enhanced ion adsorption. The composite beads can attain a high water evaporation rate of 1.62 kg m-2 h-1 under 1 sun. Meanwhile, high phosphate adsorption capacity of over 120 mg g-1 is achieved in broad pH (2.5-12.4) and concentration (200-1000 mg L-1) ranges of phosphate solutions. Gratifyingly, we demonstrate the first example of recycling biomaterials from interfacial SGs for controlled nutrient release, soil enrichment, and sustainable agriculture. The phosphate-saturated beads can be gradually broken down in the soil. Macronutrients (N, P, and K) can be slowly released in 50 days, sustaining the plant germination and growth in a whole growth stage. This work shines light on the mass and controlled fabrication of aerogel beads based on double-network biopolymers, not merely scaling up solar-powered interfacial evaporation but also considering water remediation, waste material disposal, and value-added conversion.

The solvent-free mechano-chemical grinding of a bifunctional P25-graphene oxide adsorbent-photocatalyst and its configuration as porous beads

Owing to their use in water-cleaning technology, titanium-dioxide-based nanomaterials have dominated the photocatalysis scene, with so-called Degussa (P25) being the most promising under UV light. However, this is not the case under visible light, where it is necessary to combine titanium dioxide with other photosensitising nanomaterials. Unfortunately, most of the strategies aimed in this direction are chemically non-facile, energy-intensive, economically expensive, and not suitable for large-scale production. We herein describe a straightforward solvent-free approach for accessing visible-light-activated titanium-dioxide-based photocatalysts via the mechanochemical grinding of Degussa P25 with a second solid partner. Upon comparing several solid-material benchmarks, P25-graphene oxide is the best combination. The resulting material showed efficient performance for the adsorption and photodegradation of different dye pollutants, namely methylene blue, malachite green, Congo red, and methyl orange. The recorded performance was nearly comparable to that reached using sol-gel materials, with the ultimate advantage of being more sustainable and industrially scalable. The recyclability can be improved through a porous-bead configuration using biomass waste chitosan hydrogel, an approach that can further fulfill the requirement for more sustainable photocatalyst designs.

A high-performance solid electrolyte assisted with hybrid biomaterials for lithium metal batteries

The demand for high safety lithium batteries has led to the rapid development of solid electrolytes. However, some inherent limitations of solid polymer electrolytes (SPEs) impede them achieving commercial value. In this work, a novel polyethylene oxide (PEO)-based solid electrolyte is reported. For the first time, biomaterial-based chitosan-silica (CS) hybrid particles serve as fillers, which can interact with polymer matrix to significantly improve the electrochemical performance. The optimized polymer electrolyte exhibits a maximum ion conductivity of 1.91 × 10^-4 S·cm^-1 at 30 °C when the mass ratio of PEO and CS is 4:1 (PCS4). All-solid-state LiFePO₄|PCS4|Li cells deliver a high coulombic efficiency and stable cycling performance, remaining an excellent capacity of more than 96.2 % after 150 cycles. Furthermore, the wide electrochemical window (5.4 V) and steady interfacial stability provide the possibility for high-voltage batteries applications. NCM811|| Li cells are assembled and display reliable charge and discharge cycle properties.

Novel Chitosan-Silica Hybrid Hydrogels for Cell Encapsulation and Drug Delivery

Hydrogels constructed from naturally derived polymers provide an aqueous environment that encourages cell growth, however, mechanical properties are poor and degradation can be difficult to predict. Whilst, synthetic hydrogels exhibit some improved mechanical properties, these materials lack biochemical cues for cells growing and have limited biodegradation. To produce hydrogels that support 3D cell cultures to form tissue mimics, materials must exhibit appropriate biological and mechanical properties. In this study, novel organic-inorganic hybrid hydrogels based on chitosan and silica were prepared using the sol-gel technique. The chemical, physical and biological properties of the hydrogels were assessed. Statistical analysis was performed using One-Way ANOVAs and independent-sample t-tests. Fourier transform infrared spectroscopy showed characteristic absorption bands including amide II, Si-O and Si-O-Si confirming formation of hybrid networks. Oscillatory rheometry was used to characterise the sol to gel transition and viscoelastic behaviour of hydrogels. Furthermore, in vitro degradation revealed both chitosan and silica were released over 21 days. The hydrogels exhibited high loading efficiency as total protein loading was released in a week. There were significant differences between TC₂G and C₂G at all-time points (p < 0.05). The viability of osteoblasts seeded on, and encapsulated within, the hydrogels was >70% over 168 h culture and antimicrobial activity was demonstrated against Pseudomonas aeruginosa and Enterococcus faecalis. The hydrogels developed here offer alternatives for biopolymer hydrogels for biomedical use, including for application in drug/cell delivery and for bone tissue engineering.

Co-Fe Nanoparticles Wrapped on N-Doped Graphitic Carbons as Highly Selective CO2 Methanation Catalysts

Pyrolysis of chitosan containing various loadings of Co and Fe renders Co-Fe alloy nanoparticles supported on N-doped graphitic carbon. Transmission electron microscopy (TEM) images show that the surface of Co-Fe NPs is partially covered by three or four graphene layers. These Co-Fe@(N)C samples catalyze the Sabatier CO₂ hydrogenation, increasing the activity and CH₄ selectivity with the reaction temperature in the range of 300-500 °C. Under optimal conditions, a CH₄ selectivity of 91% at an 87% CO₂ conversion was reached at 500 °C and a space velocity of 75 h^-1 under 10 bar. The Co-Fe alloy nanoparticles supported on N-doped graphitic carbon are remarkably stable and behave differently as an analogous Co-Fe catalyst supported on TiO₂.

Molecular Bottom-Up Approaches for the Synthesis of Inorganic and Hybrid Nanostructures

Chemical routes for the synthesis of nanostructures are fundamental in nanoscience. Among the different strategies for the production of nanostructures, this article reviews the fundamentals of the bottom-up approaches, focusing on wet chemistry synthesis. It offers a general view on the synthesis of different inorganic and hybrid organic–inorganic nanostructures such as ceramics, metal, and semiconductor nanoparticles, mesoporous structures, and metal–organic frameworks. This review article is especially written for a wide audience demanding a text focused on the basic concepts and ideas of the synthesis of inorganic and hybrid nanostructures. It is styled for both early researchers who are starting to work on this topic and also non-specialist readers with a basic background on chemistry. Updated references and texts that provide a deeper discussion and describing the different synthesis strategies in detail are given, as well as a section on the current perspectives and possible future evolution.

High performance biocatalyst based on β-d-galactosidase immobilized on mesoporous silica/titania/chitosan material

A new support for the immobilization of β-d-galactosidase from Kluyveromyces lactis was developed, consisting of mesoporous silica/titania with a chitosan coating. This support presents a high available surface area and adequate pore size for optimizing the immobilization efficiency of the enzyme and, furthermore, maintaining its activity. The obtained supported biocatalyst was applied in enzyme hydrolytic activity tests with o-NPG, showing high activity 1223 Ug^-1, excellent efficiency (74%), and activity recovery (54%). Tests of lactose hydrolysis in a continuous flow reactor showed that during 14 days operation, the biocatalyst maintained full enzymatic activity. In a batch system, after 15 cycles, it retained approximately 90% of its initial catalytic activity and attained full conversion of the lactose 100% (±12%). Additionally, with the use of the mesoporous silica/titania support, the biocatalyst presented no deformation and fragmentation, in both systems, demonstrating high operational stability and appropriate properties for applications in food manufacturing.

Polysaccharide-Based Aerogel Production for Biomedical Applications: A Comparative Review

A comparative analysis concerning bio-based gels production, to be used for tissue regeneration, has been performed in this review. These gels are generally applied as scaffolds in the biomedical field, thanks to their morphology, low cytotoxicity, and high biocompatibility. Focusing on the time interval 2015-2020, the production of 3D scaffolds of alginate, chitosan and agarose, for skin and bone regeneration, has mainly been investigated. Traditional techniques are critically reviewed to understand their limitations and how supercritical CO2-assisted processes could overcome these drawbacks. In particular, even if freeze-drying represents the most widespread drying technique used to produce polysaccharide-based cryogels, supercritical CO2-assisted drying effectively allows preservation of the nanoporous aerogel structure and removes the organic solvent used for gel preparation. These characteristics are essential for cell adhesion and proliferation.

Preparation of aerogel beads and microspheres based on chitosan and cellulose for drug delivery: A review

Spherical aerogels are not easily broken during use and are easier to transport and store which can be used as templates for drug delivery. This review summarizes the possible approaches for the preparation of aerogel beads and microspheres based on chitosan and cellulose, an overview to the methods of manufacturing droplets is presented, afterwards, the transition mechanisms from sol to a spherical gel are reviewed in detail followed by different drying processes to obtain spherical aerogels with porous structures. Additionally, a specific focus is given to aerogel beads and microspheres to be regarded as drug delivery carriers. Furthermore, a core/shell architecture of aerogel beads and microspheres for controlled drug release is described and subjected to inspire readers to create novel drug release system. Finally, the conclusions and outlooks of aerogel beads and microspheres for drug delivery are summarized.

Eco-Friendly Synthesis of Water-Glass-Based Silica Aerogels via Catechol-Based Modifier

Silica aerogels have attracted much attention owing to their excellent thermal insulation properties. However, the conventional synthesis of silica aerogels involves the use of expensive and toxic alkoxide precursors and surface modifiers such as trimethylchlorosilane. In this study, cost-effective water-glass silica aerogels were synthesized using an eco-friendly catechol derivative surface modifier instead of trimethylchlorosilane. Polydopamine was introduced to increase adhesion to the SiO₂ surface. The addition of 4-tert-butyl catechol and hexylamine imparted hydrophobicity to the surface and suppressed the polymerization of the polydopamine. After an ambient pressure drying process, catechol-modified aerogel exhibited a specific surface area of 377 m²/g and an average pore diameter of approximately 21 nm. To investigate their thermal conductivities, glass wool sheets were impregnated with catechol-modified aerogel. The thermal conductivity was 40.4 mWm⁻¹K⁻¹, which is lower than that of xerogel at 48.7 mWm⁻¹K⁻¹. Thus, by precisely controlling the catechol coating in the mesoporous framework, an eco-friendly synthetic method for aerogel preparation is proposed.

A novel electrochemical platform based on mesoporous silica/titania and gold nanoparticles for simultaneous determination of norepinephrine and dopamine

An amorphous and mesoporous silica/titania (SiTi) material was synthesized by sol-gel method and its surface was modified with gold nanoparticles (AuNP) previously stabilized in a chitosan solution. The presence of small AuNP, with diameter lower than 10 nm was confirmed by transmission electron microscopy (TEM) and UV-Vis spectroscopy. Carbon paste electrodes were prepared to test the electrochemical properties by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in [Fe(CN)₆]^3-/4- solution probe whereby the material silica-titania/gold nanoparticles (SiTi/AuNP) showed a huge improvement in the redox peak current and low charge transfer resistance. This electrode presented a good response for both norepinephrine and dopamine by means of square wave voltammetry (SWV) measurements; great sensitivity for both analytes, in an extensive linear range, was obtained. The limits of detection were 0.35 μmol L^-1 and 0.57 μmol L^-1 for norepinephrine and dopamine, respectively. Additionally, this electrode showed high selectivity for both analytes and it was applied in the simultaneous determination of norepinephrine and dopamine. The sensor was also tested in simulated biological fluids presenting a good recovery. The SWV electrochemical response of norepinephrine was also investigated in the presence of possible interferers such as uric acid, ascorbic acid and glucose and there was no significant interference. The prepared electrode also exhibits good reproducibility for norepinephrine detection, with relative standard deviation of 5.19%.

New Trends in Bio-Based Aerogels

(1) Background: The fascinating properties of currently synthesized aerogels associated with the flexible approach of sol-gel chemistry play an important role in the emergence of special biomedical applications. Although it is increasingly known and mentioned, the potential of aerogels in the medical field is not sufficiently explored. Interest in aerogels has increased greatly in recent decades due to their special properties, such as high surface area, excellent thermal and acoustic properties, low density and thermal conductivity, high porosity, flame resistance and humidity, and low refractive index and dielectric constant. On the other hand, high manufacturing costs and poor mechanical strength limit the growth of the market. (2) Results: In this paper, we analyze more than 180 articles from recent literature studies focused on the dynamics of aerogels research to summarize the technologies used in manufacturing and the properties of materials based on natural polymers from renewable sources. Biomedical applications of these bio-based materials are also introduced. (3) Conclusions: Due to their complementary functionalities (bioactivity, biocompatibility, biodegradability, and unique chemistry), bio-based materials provide a vast capability for utilization in the field of interdisciplinary and multidisciplinary scientific research.

Strong, Machinable, and Insulating Chitosan-Urea Aerogels: Toward Ambient Pressure Drying of Biopolymer Aerogel Monoliths

Biopolymer aerogels are an emerging class of materials with potential applications in drug delivery, thermal insulation, separation, and filtration. Chitosan is of particular interest as a sustainable, biocompatible, and abundant raw material. Here, we present urea-modified chitosan aerogels with a high surface area and excellent thermal and mechanical properties. The irreversible gelation of an acidic chitosan solution is triggered by the thermal decomposition of urea at 80 °C through an increase in pH and, more importantly, the formation of abundant ureido terminal groups. The hydrogels are dried using either supercritical CO₂ drying (SCD) or ambient pressure drying (APD) methods to elucidate the influence of the drying process on the final aerogel properties. The hydrogels are exchanged into ethanol prior to SCD, and into ethanol and then heptane prior to APD. The surface chemistry and microstructure are monitored by solid-state NMR and Fourier transform infrared spectroscopy, scanning electron microscopy, and nitrogen sorption. Surprisingly, large monolithic aerogel plates (70 × 70 mm²) can be produced by APD, albeit at a somewhat higher density (0.17-0.42 g/cm³). The as prepared aerogels have thermal conductivities of ∼24 and ∼31 mW/(m·K) and surface areas of 160-170 and 85-230 m²/g, for SCD and APD, respectively. For a primarily biopolymer-based material, these aerogels are exceptionally stable at elevated temperature (TGA) and char and self-extinguish after direct flame exposure. The urea-modified chitosan aerogels display superior mechanical properties compared to traditional silica aerogels, with no brittle rupture up to at least 80% strain, and depending on the chitosan concentration, relatively high E-moduli (1.0-11.6 MPa), and stress at 80% strain values (σ₈₀ of 3.5-17.9 MPa). Remarkably, the aerogel monoliths can be shaped and machined with standard tools, for example, drilling and sawing. This first demonstration to produce monolithic and machinable, mesoporous aerogels from bio-sourced, renewable, and nontoxic precursors, combined with the potential for reduced production cost by means of simple APD, opens up new opportunities for biopolymer aerogel applications and marks an important step toward commercialization of biopolymer aerogels.

Chitosan-Functionalized Graphene Nanocomposite Films: Interfacial Interplay and Biological Activity

Graphene oxide (GO) has recently captured tremendous attention, but only few functionalized graphene derivatives were used as fillers, and insightful studies dealing with the thermal, mechanical, and biological effects of graphene surface functionalization are currently missing in the literature. Herein, reduced graphene oxide (rGO), phosphorylated graphene oxide (PGO), and trimethylsilylated graphene oxide (SiMe3GO) were prepared by the post-modification of GO. The electrostatic interactions of these fillers with chitosan afforded colloidal solutions that provide, after water evaporation, transparent and flexible chitosan-modified graphene films. All reinforced chitosan-graphene films displayed improved mechanical, thermal, and antibacterial (S. aureus, E. coli) properties compared to native chitosan films. Hemolysis, intracellular catalase activity, and hemoglobin oxidation were also observed for these materials. This study shows that graphene functionalization provides a handle for tuning the properties of graphene-reinforced nanocomposite films and customizing their functionalities.

Luminescence properties of the Ln-EDTA complexes covalently linked to the chitosan biopolymers containing β-diketonate as antenna ligands

This paper reports on the preparation, characterization, and photoluminescence properties of novel hybrid materials, in which the EDTA-Ln-L complexes (where L: H₂ O, acac, bzac, dbm, and tta ligands, and Ln: Eu, Gd, and Tb) were covalently linked to the precursor medium molecular weight chitosan surface (CS) matrices or on the chitosan surfaces previously crosslinked with epichlorohydrin (CSech). The emission spectra of these materials were characterized by intraconfigurational-4fN transitions centred on the Eu³⁺ and Tb³⁺ ions. Some broad bands from the polymeric matrix were also observed in the emission spectra, however the relative intensities of the intraconfigurational bands increased significantly for systems containing diketonate ligands when the antenna effect became more efficient. The values of the radiative rates (A_rad ) were higher for crosslinked hybrid systems with epichlorohydrin, while nonradiative rates (A_nrad ) presented the opposite behaviour. These data contributed to an increase in the values of emission quantum efficiency (η) for crosslinked materials. The effect of the modification process and antenna ligand on the values of intensities, intensity parameters Ω₂ e Ω₄ of the Eu³⁺ complexes were also investigated. The results showed that the crosslinked biopolymer surfaces have great potential for applications in molecular devices light converters.

Phosphorylation triggered growth of metal phosphate on halloysite and sepiolite nanoparticles: preparation, entrapment in chitosan hydrogels and application as recyclable scavengers

Surprising growth of crystalline metal phosphate during clay phosphorylation. When entangled in chitosan beads, good adsorption performance could be reached.

High-Strength Physically Multi-Cross-Linked Chitosan Hydrogels and Aerogels for Removing Heavy-Metal Ions

With the goal of improving the mechanical strength of chitosan hydrogels, gallic acid modified carboxymethyl chitosan/iron ion (GA-CMCS/Fe^III) complex hydrogels were initially prepared via noncovalent interactions and metal coordination. ¹H NMR, ¹³C NMR, and Fourier trantsform infrared spectra analysis confirmed the covalent reactions between CMCS and GA. The formation of GA-CMCS hydrogel occurred through electrostatic interactions, hydrogen bonds, and hydrophobic interactions. GA-CMCS/Fe^III hydrogel (380 kPa) exhibited higher compressive strength than GA-CMCS hydrogel (315 kPa). In addition, GA-CMCS/Fe^III aerogel displayed satisfactory mechanical strength (1.59 MPa) and high-efficiency adsorption capacities up to 97.15 mg/g for Pb²⁺, 99.75 mg/g for Cd²⁺, and 98.50 mg/g for Cu²⁺, respectively. In addition, both of the GA-CMCS and GA-CMCS/Fe^III aerogel adsorbents exhibited satisfactory recyclability. The design of GA-CMCS and GA-CMCS/Fe^III hydrogels and aerogels offers a new opportunity for the construction of physically multi-cross-linked systems with excellent mechanical properties.

Aldehyde-conjugated chitosan-graphene oxide glucodynamers: Ternary cooperative assembly and controlled chemical release

Simultaneous condensation of aromatic aldehydes (Ar_xCHO; x = 1-4) on chitosan biopolymer (CS) affords, after water-evaporation, structurally-conjugated aryl-functionalized CS-Ar_x-f films. Similarly, cooperative assembly of two-dimensional nanometric graphene oxide (GO), aromatic aldehyde and chitosan provides transparent, flexible and crack-free aldehyde-functionalized, ternary-reinforced CS-Ar_x-GO-f nanocomposite films. Homogenous films were obtained using ortho-hydroxybenzaldehyde Ar₁ while the para-hydroxybenzaldehyde Ar₄ was prone to packing inside. Textural and mechanical properties were investigated and expectedly, significant improvement was found for CS-Ar₁-GO-f because of the great dispersion of the aromatic and the presence of the filler. The sensitivity of unsaturated CN imine bond to hydrolysis was explored for triggering controlled release of aromatics from the as-prepared films. All of them were found to induce a time-dependent aromatic release. It has been moreover observed that the release was significantly delayed in CS-Ar_x-GO-f compared to CS-Ar_x-f, a fact attributed to the interplay of the ring with the basal and edges of graphene oxide, through π-π stacking and additional hydrogen bonding interactions. This finding shows that beyond the conventional wisdom using fillers for improving thermal and mechanical properties, the tiny carbon sheets can act as a regulator for aldehyde release, thereby providing a way for more controlled chemical delivery from confined nanocomposites.

Cross-linked chitosan aerogel modified with Pd(II)/phthalocyanine: Synthesis, characterization, and catalytic application

Palladium(II) phthalocyanine (PdPc) tetrasulfonate was chemically bonded to an amine moiety of chitosan aerogel. The reaction was promoted by the transformation of sulfonic acid groups of PdPc to sulfonyl chloride, which is highly active for amination. The porous composite showed good catalytic activity in the oxidation reaction of some alkylarenes, aliphatic and benzylic alcohols, and cyclohexanol. High conversions and excellent selectivities were obtained for the solvent-free reactions under aerobic conditions at 80 °C during 24 h. While many oxidation reactions have been reported catalysed with palladium phthalocyanine, this is the first reported oxidation of alkylarenes via this catalyst. The organometallic compound is applicable as a heterogeneous catalyst having high chemical stability with recyclability up to six times.

Multifunctional Chitosan/Gold Nanoparticles Coatings for Biomedical Textiles

Gold nanoparticles (AuNPs), chemically synthesized by citrate reduction, were for the first time immobilized onto chitosan-treated soybean knitted fabric via exhaustion method. AuNPs were successfully produced in the form of highly spherical, moderated polydisperse, stable structures. Their average size was estimated at ≈35 nm. Successful immobilization of chitosan and AuNPs were confirmed by alterations in the fabric's spectrophotometric reflectance spectrum and by detection of nitrogen and gold, non-conjugated C=O stretching vibrations of carbonyl functional groups and residual N-acetyl groups characteristic bands by X-ray photoelectron spectroscopy (XPS) and Fourier-Transform Infrared Spectroscopy (FTIR) analysis. XPS analysis confirms the strong binding of AuNPs on the chitosan matrix. The fabrics' thermal stability increased with the introduction of both chitosan and AuNPs. Coated fabrics revealed an ultraviolet protection factor (UPF) of +50, which established their effectiveness in ultraviolet (UV) radiation shielding. They were also found to resist up to 5 washing cycles with low loss of immobilized AuNPs. Compared with AuNPs or chitosan alone, the combined functionalized coating on soy fabrics demonstrated an improved antimicrobial effect by reducing Staphylococcus aureus adhesion (99.94%) and Escherichia coli (96.26%). Overall, the engineered fabrics were confirmed as multifunctional, displaying attractive optical properties, UV-light protection and important antimicrobial features, that increase their interest for potential biomedical applications.

Bioaerogels: Synthesis approaches, cellular uptake, and the biomedical applications

Aerogels are a class of porous structures with promising physicochemical properties. Among aerogels with various origins, polysaccharide aerogels (e.g., cellulose, chitosan, alginate, starch, agar, and so on) have received more attention. This group of aerogels can be classified as bioaerogels, which are originated from natural, semi-synthetic, and synthetic sources with exceptional biomedical applications. This review focuses on bioaerogels from the viewpoints of synthesis approaches, cellular uptake, toxicity, biodegradability, and the biomedical application perspectives.

Review on the Production of Polysaccharide Aerogel Particles

A detailed study of the production of polysaccharide aerogel (bio-aerogel) particles from lab to pilot scale is surveyed in this article. An introduction to various droplets techniques available in the market is given and compared with the lab scale production of droplets using pipettes and syringes. An overview of the mechanisms of gelation of polysaccharide solutions together with non-solvent induced phase separation option is then discussed in the view of making wet particles. The main steps of particle recovery and solvent exchange are briefly described in order to pass through the final drying process. Various drying processes are overviewed and the importance of supercritical drying is highlighted. In addition, we present the characterization techniques to analyse the morphology and properties of the aerogels. The case studies of bio-aerogel (agar, alginate, cellulose, chitin, κ-carrageenan, pectin and starch) particles are reviewed. Potential applications of polysaccharide aerogel particles are briefly given. Finally, the conclusions summarize the prospects of the potential scale-up methods for producing bio-aerogel particles.

CHARMM Drude Polarizable Force Field for Glycosidic Linkages Involving Pyranoses and Furanoses

We present an extension of the CHARMM Drude polarizable force field to enable modeling of polysaccharides containing pyranose and furanose monosaccharides. The new force field parameters encompass 1↔2, 1→3, 1→4, and 1→6 pyranose-furanose linkages, 2→1 and 2→6 furanose-furanose linkages, 2→2, 2→3, and 2→4 furanose-pyranose, and 1↔1, 1→2, 1→3, 1→4, and 1→6 pyranose-pyranose linkages. For the glycosidic linkages, both simple model compounds and the full disaccharides with methylation at the reducing end were used for parameter optimization. The model compounds were chosen to be monomers or glycosidic-linked dimers of tetrahydropyran (THP) and tetrahydrofuran (THF). Target data for optimization included one- and two-dimensional potential energy scans of ω and the Φ/Ψ glycosidic dihedral angles in the model compounds and full disaccharides computed by quantum mechanical (QM) RIMP2/cc-pVQZ single point energies on MP2/6-31G(d) optimized structures. Also included in the target data are extensive sets of QM gas phase monohydrate water-saccharide interactions, dipole moments, and molecular polarizabilities for both model compounds and full disaccharides. The resulting polarizable model is shown to be in good agreement with a range of QM data, offering a significant improvement over the additive CHARMM36 carbohydrate force field, as well as experimental data including crystal structures and conformational properties of disaccharides and a trisaccharide in aqueous solution.