Chitosan Monomer Research Articles

Solvation behavior of chitosan monomers in aqueous [Hmim]CL solutions. Experimental and DFT studies

This paper reports densities and viscosities for the mixtures of D-glucosamine hydrochloride (GlcN·HCl) and N-acetyl-D-glucosamine (GlcNAc) with aqueous solutions of 1-hexyl-3-methylimidazolium chloride, [Hmim]Cl, between 293.15 and 318.15 K in 5 K increments and atmospheric pressure. Leveraging this data, we calculated volumetric properties such as apparent molar volume, Vϕ, limiting partial molar volume, Vϕ0, and standard molar volume of transfer, ΔVϕ0. We handled viscosity data to compute the viscosity B-coefficient and several activation parameters of viscous flow. Some of these are relevant in discussing interactions between monosaccharides (solute) and [Hmim]Cl (co-solvent) in aqueous media. The solute–solvent interactions were discussed based on ionic/ hydrophilic/ hydrophobic interactions using the co-sphere overlap model. ΔVϕ0 > 0 indicates that ionic/hydrophilic interactions predominate in the studied systems and are stronger in GlcN·HCl solutions than in GlcNAc at low [Hmim]Cl molalities. At higher [Hmim]Cl concentrations, decreasing values of ΔVϕ0 suggest the dominance of hydrophobic interactions over hydrophilic/ionic ones. We discuss (using Hepler’s constant and viscosity B-coefficient) the ability of monosaccharides to act as structure maker/breaker in aqueous [Hmim]Cl solutions. This indicates that GlcNAc is a better structure promoter than GlcN⋅HCl in aqueous [Hmim]Cl solutions. Finally, density functional theory (DFT) was used to model the molecular structure and compute the solute–solvent interaction energies using the GAMESS 2016 software.

Optimized design of quaternary amino-functionalized chitosan fibers for ultra-high diclofenac adsorption from wastewater

The extraction of non-steroidal anti-inflammatory drugs (NSAIDs) from water bodies is imperative due to the potential harm to humans and the ecosystem caused by NSAID-contaminated water. Quaternary amino-functionalized epichlorohydrin cross-linked chitosan fibers (QECFs), an economical and eco-friendly adsorbent, were successfully prepared using a simple and gentle method for efficient diclofenac (DCF) adsorption. Additionally, the optimized factors for the preparation of QECFs included epichlorohydrin concentration, pH, temperature, and (3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHTAC) concentration. QECFs demonstrated excellent adsorption performance for DCF across a broad pH range of 7–12. The calculated maximum adsorption capacity and the amount of adsorbed DCF per adsorption site were determined to be 987.5 ± 20.1 mg/g and 1.2 ± 0.2, respectively, according to the D-R and Hill isotherm models, at pH 7 within 180 min. This performance surpassed that of previously reported adsorbents. The regeneration of QECFs could be achieved using a 0.5 mol/L NaOH solution within 90 min, with QECFs retaining their original fiber form and experiencing only a 9.18% reduction in adsorption capacity after 5 cycles. The Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy were used to study the characterization of QECFs, the preparation mechanism of QECFs, and the adsorption mechanism of DCF by QECFs. Quaternary ammonium groups (R4N+) were well developed in QECFs through the reaction between amino/hydroxyl groups on chitosan and CHTAC, and approximately 0.98 CHTAC molecule with 0.98 R4N+ group were immobilized on each chitosan monomer. Additionally, these R4N+ on QECFs played a crucial role in the removal of DCF.

Insight into a novel composite biosorbent by incorporating chitosan into electrolytic manganese residue for Cr(VI) removal from aqueous solutions

A novel adsorbent was obtained by using a typical solid waste electrolytic manganese residue (EMR) and a green material chitosan (CS) for the Cr(VI) removal from the aqueous environment. The tagged mineral phases and elements in the EMR were successfully detected in the synthesized composites according to the XRD and SEM-EDS results. Furthermore, the characteristic peak of metal and hydroxyl group binding appeared at 779 cm−1, and the Si-O bending vibration at 454 cm−1 in the FT-IR pattern of the synthesized composites indicating the functional Fe and Mn hydroxyl groups and the silicates in EMR were all successfully grafted onto the CS. This obtained composite showed a high Cr adsorption capacity with a maximum adsorption capacity of 133.64 mg·g−1, and the Cr(VI) removal rate could maintain a high level of 94.6 % after five adsorption–desorption cycles. Its adsorption isotherm matched with the Langmuir model, and the adsorption kinetics followed the pseudo-first-order model. According to the response surface CCD model, the optimal conditions for Cr(VI) removal were pH at 2, contact time at 53.0 min, and initial concentration at 100 mg·L-1. For the removal mechanism, Cr(VI) anions could be easily electrostatic adsorbed by –NH3+, or chelated with the Fe and Mn oxides. Meanwhile, partial Cr(VI) (∼35.7 %) was reduced into Cr(III) by the abundant hydroxyl group of chitosan on the surface of the as-obtained materials, and then the free Cr(III) could be easily chelated with three chitosan monomers. This work opens up a novel and green methodology to modify chitosan and reuse the solid waste EMR.

Chitosan Polysaccharides from a Polarizable Multiscale Approach.

We report simulations of chitosan polysaccharides in the aqueous phase, at infinite dilute conditions and zero ionic strength. Those simulations are performed by means of a polarizable multiscale modeling scheme that relies on a polarizable all atom force field to model solutes and on a polarizable solvent coarse grained approach. Force field parameters are assigned only from quantum chemistry ab initio data. We simulate chitosan monomer units, dimers and 50-long chains. Regarding the 50-long chains we simulate three sets of ten randomly built chain replica at three different pH conditions (corresponding to different chain protonation states, the chain degree of deacetylation is 85%). Our simulations show the persistence length of 50-long chitosan chains at strong acidic conditions (pH <5) to be 24 ± 2 nm (at weak/negligible ionic strength conditions), and to be 1 order of magnitude shorter at usual pH conditions. Our simulation data support the most recent simulation and experimental studies devoted to chitosan polysaccharides in the aqueous phase.

Understanding of the Effect of the Adsorption of Atom and Cluster Silver on Chitosan: An In Silico Analysis.

In this work, the structural, electronic, and optical stability properties of the chitosan monomer (M-Ch) and atomic silver complex are reported, as well as a unitary cell of a silver cluster in the gas phase and acetic acid. The generalized gradient approximation HSEh1PBE/def2-TZVPP50 results established the structures' anionic charge (Q = -1|e|) and the doublet state (M = 2). The high cohesive energy indicates structural stability, and the quantum-mechanical descriptors show a high polarity and low chemical reactivity. Also, the quantum-mechanical descriptors present a low work function that shows the structures are suitable for applications in light-emitting diodes. Finally, the electronic behavior observed by the |HOMO-LUMO| gap energy changes depending on the atomic silver incorporated into the complex.

Activity against SARS-CoV-2 of Various Anionic Disinfectants and Their Complexes with Hydrophobically Modified Chitosan

The aim of this work was to study virucidal activity against SARS-CoV-2 of several anionic disinfectants, which are antiseptics recommended by the U.S. Environmental Protection Agency (EPA), and to prepare their complexes with hydrophobically modified chitosan active against SARS-CoV-2. Experiments were per-formed using a clinical isolate of SARS-CoV-2 obtained from a patient in 2020. It was shown that sodium dodecyl benzene sulfonate (SDBS) is already active at rather small concentrations (above 2 mM), which completely deactivate the virus. In the same concentration range, sodium caprylate does not show activity; and sodium lactate is active against SARS-CoV-2 only at much higher concentrations (225 mM). The most effective disinfectant — sodium dodecylbenzene sulfonate — was used to prepare complexes with hydrophobically modified chitosan. It was found that such complexes exhibit antiviral activity at very low concentrations (1.9 mM chitosan monomer units and 0.25 mM SDBS), at which the polymer without surfac-tant is not active against SARS-CoV-2.

PREPARATION AND THERMAL ANALYSIS OF DURIAN PEEL CELLULOSE GRAFTED WITH POLY (2-[ACRYLOYLOXYL]- ETHYL TRIMETHYL AMMONIUM CHLORIDE/CHITOSAN NANOCOMPOSITES AS ANTIMICROBIAL APPLICATION

In this work, facile preparation and low-cost utilizing durian peel organic waste as a cellulose (DPC) source and copolymerization grafted between 2-[acryloyloxyl]-ethyl trimethylammonium chloride (AETAC) and chitosan were developed. Accordingly, a grafting yield of 21.9 % was obtained. In addition, to further understand the characterization of grafted cellulose with AETAC and cellulose grafted with AETAC and chitosan through techniques, including FTIR, SEM, XRD, TGA, and contact angle confirmed the grafting of AETAC and chitosan monomers onto cellulose backbone (DPC-g-AETAC-co-chitosan). The morphology grafting process resulted in the DPC-g-AETAC-co–chitosan with wrinkle structure, coarse surface, and formation of pores, resulting in a crystallinity index slightly reduced from 36.58 to 19.3 %, however, DPC-g-AETAC-co-Chitosan increased in thermal stability. In addition, DPC-g-AETAC-co-chitosan demonstrated excellent antibacterial and antifungal ability against S. aureus, S. epidermis, and C. albicans

Effect of chitosan-protocatechuic acid conjugate on stability and encapsulation capacity of polysaccharide-based high internal phase emulsion

The aim of this work was to fabricate chitosan-protocatechuic acid (CSPA) conjugates by free radical grafting method and use them as novel emulsifiers to inhibit lipid oxidation and delay the photodegradation rate of curcumin in polysaccharide-based high internal phase emulsions (HIPEs). Results of UV–vis, FT-IR and 1H NMR spectra demonstrated that PA had been successfully bonded to chitosan (CS) through ester and amino linkages. CSPA conjugates (especially those with the ratio of CS to PA of 1:0.75) showed significantly increased water solubility and antioxidant activity than CS monomer. Furthermore, compared with sole OSA starch (OSAS), the electrostatic combination of CS and CSPA conjugate with OSAS could further reduce the interfacial tension, which was conducive to their adsorption at the oil-water interface. The introduction of CS and CSPA conjugate also increased the viscosity of aqueous phase and promoted the formation of gel-like percolating network structure, thereby effectively preventing droplets coalescence and endowing HIPEs with ideal viscoelasticity. More importantly, the contents of lipid hydroperoxide (24.09 μmol/g oil) and malondialdehyde (166.71 nmol/g oil) in HIPEs prepared by OSAS-CS-CSPA complexes were lower than those stabilized by OSAS, OSAS-CS and OSAS-CSPA complexes during accelerated storage. In addition, HIPEs prepared by OSAS-CS-CSPA complexes showed stronger protection capacity on curcumin against ultraviolet irradiation and natural light degradation. This study will provide useful information and technical reference for the fabrication of antioxidant polysaccharide-based HIPEs delivery vehicles.

De novo synthesis of a MIL-125(Ti) carrier for thermal- and pH-responsive drug release.

Microporous round cake-like (diameter: 900±100nm) MIL-125(Ti) carrier with a central metal (Ti) exhibiting bio-affinity and possessing a great potential to be used as drug release platform, has been synthesized in the present study. The thermal and pH responsiveness of drug delivery systems (DDS) are the most important parameters for drug release and can be provided through polymer coating techniques. The Pluronic F127 (F127) and chitosan (CH) monomers were inserted into the crystal lattice of MIL-125(Ti) carrier during the de novo synthesis process, which were subsequently loaded with doxorubicin (DOX). The results reveal particle size changes (ranged between 30 and 50%) from the original size of the MIL-125(Ti) carrier in response to temperature and pH when the carrier reaches acid environment. The drug release profiles have been completed through self-design device, which provides for the real-time release in the DOX amounts via UV-Vis spectra. The kinetics analysis was used to evaluate the R2 values of first order, Higuchi, Korsmeyer-peppas, and Weibull fitting equations, where the Weibull fitting indicated the best R2. An increase by 59.3% of DOX released under the acid status (pH=5.4) was observed, indicating that the CH-MIL-125(Ti) carrier is temperature and pH responsive. Moreover, the lattice explosion resulting from the temperature increase in the range of 25-42°C caused an increase in F127-MIL-125(Ti) by 30.8-38.3%. The simulated SAXS/WAXS studies for the microstructures of MIL-125(Ti) based DDS at different temperatures after polymer coating (F127-MIL-125(Ti)) provide the possible mechanism of lattice explosion. As such, the responsive Ti-MOF has a highly potential for use in the applications of cancer treatment.

D-glucose and its analogue, d-glucosamine, as potential hydrogen storage materials: A quantum mechanical study

Cellulose and chitosan monomers have been studied as potential hydrogen storage materials with good gravimetric density and strong binding strength for the adsorption of hydrogen molecules. DFT calculations have been employed to examine the various available positions on the biomolecules for efficient hydrogen adsorption. FMO and NBO analysis revealed the strength of non-bonded interactions between adsorbent (cellulose, chitosan) and adsorbate (H2 molecules). MEP analysis helped understand the charge separation upon H2 adsorption at the available sites. The strong interaction is attributed to the presence of polar hydroxyl groups on the carbon backbone, which interacts with hydrogen through dipole-induced dipole interactions between the hydroxyl oxygen and H2 molecules. Topological analysis for real space functions like electron density, ELF, LOL, NCI, and electrostatic potential was used to establish the nature of interactions. These findings can significantly impact the design of new hydrogen storage materials based on naturally available biopolymers with high hydrogen storage capacity at ambient temperature.

Qualitative and quantitative discrimination of major elements in Chitosan (natural polymer) using laser induced breakdown spectroscopy

In this work, Laser-Induced Breakdown Spectroscopy (LIBS) is used for qualitative and quantitative analysis of Chitosan samples (natural polymer). For qualitative analysis, plasma parameters are determined, while for quantitative analysis, the initial concentration of chitosan samples is calculated. It developed a plasma plume using a second harmonic (532 nm) laser pulses, which makes the Q-Switched Nd: YAG laser compatible with delay generators and computing electronics. The component elements and their corresponding concentrations are calculated based on the strongest emission lines of the element using the line intensity ratio method and the calibration-free LIBS approach. The results obtained by both methods are compared for the effectiveness of the algorithm.In the chitosan monomer (C6H11NO4)n, four major elements (hydrogen, carbon, nitrogen and oxygen) were detected and their quantities were calculated. In addition to investigating the physical behavior of plasma in the interaction of laser beams with materials, the plasma parameters (electron number density and plasma temperature) are determined by stark-broadening profile fitting and Boltzmann plot method, respectively. The results obtained show that the LIBS can be exploited for quantitative and standard analysis of industrial grade materials for better results in applications.

Enantioselective chitosan-based racemic ketoprofen imprinted polymer: Chiral recognition and resolution study

This work presented a novel racemic imprinting process employing the chiral properties of chitosan monomer. The preparation of racemic ketoprofen (RS-KTP) imprinted polymer (RS-MIP) was conducted using glutaraldehyde as a crosslinker. The nature of elution solvent affected the % desorption ratio suggesting a heterogenous nature of the formed binding sites. Good imprinting was indicated by an imprinting factor of 3.50 for S-KTP. The enantioselectivity of the RS-MIP was indicated by enantioselectivity coefficient of 2.31 and % enantiomeric excess (%ee) of 28.55%. A SPE cartridge packed with RS-MIP enabled resolution of RS-KTP using gradient elution solvent system. Scatchard plot revealed two binding sites types of different affinity towards S-KTP and density observed for the RS-MIP. The binding capacity of RS-MIP showed observed dependence on the % ee of S-KTP indicating its enantioselectivity. The success of using racemic template for the preparation of enantioselective MIP brings a new possibility to achieve enantioseparation of racemic mixtures having very expensive or unavailable pure enantiomers.

DFT Study of Chitosan Ascorbate Nanoparticles Structure

In recent years, use of chitosan (CS) nanoparticles as nanocarriers has received much attention due to their biodegradability, biocompatibility, and non-toxicity. CS nanoparticles containing drugs, flavors, enzymes, and antimicrobial agents can maintain their activity. Such nanoparticles can stimulate the stabilization of ascorbic acid (AA) and improve controlled release. This study investigates the interaction of CS monomer with AA and sodium tripolyphosphate (TPP) using density functional theory (DFT) during the formation of chitosan ascorbate (CA) nanostructure (CAN). Based on existing results, the formation of the CS monomer from the complexes occurs due to the donor-acceptor interaction, which is energetically favorable in all considered interactions according to the calculations. At close range, proton transfer has been identified with interaction energies, namely CS-AА (-6.82 kcal/mol), CS-TPP (–4.56 kcal/mol) in the aqueous phase, which indicates that in the process of CAN formation, in most cases, the formation of a donor-acceptor bond occurs between the amino groups of CS with the enol group of AA and the relative coordination of CS with TPP. The introduction of the aqueous phase led to a drop in the interaction energy. Based on our results for the linking types (interaction energies), we propose a simple mechanism for their impact on the CAN formation process.

Preparation of chitooligosaccharides by α‐amylase from chitosan with oxidative pretreatment

AbstractBACKGROUNDChitooligosaccharides possess good physiological activity and a wide range of uses. In view of the difficulty in controlling the degree of polymerization of chitooligosaccharides prepared by chemical methods and the low efficiency of enzymatic methods, the preparation process of chitooligosaccharides prepared by H2O2 oxidation pretreatment combined with α‐amylase catalysis was studied.RESULTSWater‐soluble chitosan was prepared by oxidation pretreatment of chitosan and then degradation by α‐amylase. The enzymatic hydrolysis conditions were determined as follows: pH, 6.0; temperature, 60 °C; liquid–solid ratio, 5:1. The degree of polymerization of chitooligosaccharides prepared was adjusted by the amount of enzyme and hydrolysis time. The average degree of polymerization of chitooligosaccharides obtained was 5.4 when the amount of enzyme was 20 U g−1 for a hydrolysis time of 1.5 h. The results of infrared spectroscopy showed that the oxidative pretreatment and α‐amylase degradation did not affect the molecular structure of the chitosan monomer. Using electrospray ionization mass spectrometry analysis, the degree of polymerization of the products was found to be mainly 2–8.CONCLUSIONSH2O2 oxidative pretreatment can significantly improve the degradation efficiency of α‐amylase, and the degree of polymerization of chitooligosaccharide products can be adjusted by regulating the hydrolysis conditions of the enzyme, which has ideal application prospects. © 2021 Society of Chemical Industry (SCI).

Nano iron oxides impregnated chitosan beads towards aqueous Cr(VI) elimination: Components optimization and performance evaluation

Nano iron oxide based sorbents are very promising candidates for Cr(VI) removal from water. However, powdery nano iron oxides are difficult to separate from water, limiting their application in water treatment process. Herein, granular adsorbents (nano iron oxides impregnated chitosan beads, NIOC) were developed via green synthesis route using Fe(III) salts and chitosan for Cr(VI) removal. The NIOC with millimeter size displayed bi-function (sorption combined with group reduction) towards Cr(VI). Key synthesis parameter i.e. the molar ratio of Fe(III)/chitosan monomer (denoted as R) was optimized and the sorption performance of adsorbents with different R values (R = 0–4.8) was evaluated. Results indicate that all the sorbents displayed excellent mechanical strength (>10.428 N). NIOC-2 (R = 1.6) was found to show the maximum adsorption capacity towards Cr(VI) (92.04 mg/g) and total Cr (86.16 mg/g) at pH 5, 20 °C. Characterization analyses indicate that the main crystalline phases in NIOC-2 were iron oxide nanoparticles (β-FeOOH and α-Fe2O3). Coexistent PO43− and SO42− had a significant competitive effect on Cr(VI) adsorption. Cr(VI)-loaded NIOC-2 could be effectively regenerated with NaOH solution and used repeatedly. FTIR and XPS analyses show that Cr(VI) removal mechanisms included electrostatic attraction, ligand exchange, reduction of Cr(VI) into Cr(III) and re-sorption of Cr(III) via amino complexation. Long-term column experiment shows that the number of treated bed volume in flow-through system was large (~ 4800) and long run time could be maintained (~ 75 d) before breakthrough. The synthesis procedure of granular NIOC-2 is simple, green and cheap, thereby it is a potential sorbent to be utilized in fixed-bed system for Cr(VI) removal from drinking water.

Predicting the molecular mechanism of glucosamine in accelerating bone defect repair by stimulating osteogenic proteins.

Bone defect is serious condition that is usually caused by traffic accident. Chitosan is a polymer developed as a scaffold to treat bone defect. However, the mechanism by which chitosan can accelerate bone growth in defect area is still unclear. This study aims to identify proteins which are crucial to the osteogenic properties of chitosan monomer using an in silico study. Molecular docking was carried out on chitosan monomer, which are d-glucosamine and glucosamine 6-phosphate units against bone morphogenetic protein 2 (BMP-2), fibronectin, fibroblast growth factor (Fgf), and phosphate transporter (PiT) using AutoDock Vina. Ligand preparation was carried out using Chem3D version 15.0.0.106, while protein preparation was performed using AutoDockTools version 1.5.6. The results showed that glucosamine 6-phosphate had the best binding affinity with fibronectin and PiT, which was-5.7kcalmol-1 on both proteins, while d-glucosamine had the best binding affinity with PiT (-5.2kcalmol-1). This study suggests that the osteogenic properties of chitosan may be due to the presence of bonds between glucosamine units and fibronectin and/or PiT. However, in vitro studies need to be done to prove this.

3D Yolk–Shell Structured Si/void/rGO Free-Standing Electrode for Lithium-Ion Battery

In this study, we have successfully prepared a free-standing Si/void/rGO yolk–shell structured electrode via the electrostatic self-assembly using protonated chitosan. When graphene oxide (GO) is dispersed in water, its carboxyl and hydroxyl groups on the surface are ionized, resulting in the high electronegativity of GO. Meanwhile, chitosan monomer contains -NH2 and -OH groups, forming highly electropositive protonated chitosan in acidic medium. During the electrostatic interaction between GO and chitosan, which results in a rapid coagulation phenomenon, Si/SiO2 nanoparticles dispersed in GO can be uniformly encapsulated between GO sheets. The free-standing Si/void/rGO film can be obtained by freeze-drying, high-pressure compression, thermal reduction and HF etching technology. Our investigation shows that after 200 charge/discharge cycles at the current density of 200 mA·g−1, the specific discharge capacity of the free-standing electrode remains at 1129.2 mAh·g−1. When the current density is increased to 4000 mA·g−1, the electrode still has a specific capacity of 469.2 mAh·g−1, showing good rate performance. This free-standing electrode with a yolk–shell structure shows potential applications in the field of flexible lithium-ion batteries.

Electrosteric stabilization of oil/water emulsions by adsorption of chitosan oligosaccharides—An electrokinetic study

The present study was focused on investigation of electrokinetic behaviour of lecithin-stabilized oil/water emulsions in the presence of chitosan oligosaccharides (COS). The oligosaccharides give unique opportunity for precisely characterization of the properties of chitosan as a function of the degree of acetylation (DA) and degree of polymerization (DP) of the polymer. For the study were chosen well characterized ultra pure COS molecules with completely acetylated monomers and mixture of COS molecules with acetylated and deacetylated monomers. The obtained results confirmed experimentally for the first time, the suggestion for the predominant contribution of hydrophobic (at high DA) and electrostatic (at low DA) interactions between chitosan monomers and the lecithin-covered droplet surface.

Multiscale Modeling Reveals Physical Interactions that Influence the Mechanical Behaviour of Polysaccharide-Surfactant Hydrogels

Chitosan is a gel-forming polysaccharide biopolymer. The amine groups on chitosan monomers ionize with a pKa ∼6.5 which facilitates pH-responsive transition from an insoluble physically crosslinked hydrogel at basic pH, to a soluble polycationic state at acidic pH. However, addition of anionic surfactants such as sodium dodecyl sulfate (SDS) to cationic chitosan allows the formation of electrostatically linked hydrogels. In contrast to the elastic nature of chitosan gels at basic pH, these acid-stable SDS:chitosan gels have been shown to display viscoelasticity and self-healing properties. This tunable nature of chitosan makes it an attractive biomaterial for bioelectronics fabrication, and other biomedical applications. Here, we use a multiscale molecular modeling approach to identify the molecular interactions responsible for the orthogonal dependence of mechanical properties on pH and SDS concentration. We use coarse-grained molecular dynamics to self-assemble large, space-spanning SDS:chitosan networks. We then back-map these networks to atomistic resolution to further investigate the finer differences between their interaction profiles. Our findings show that water mediated contacts are the predominant crosslinking interaction at basic pH, but not at acidic pH. Instead, SDS-chitosan salt bridges and hydrogen bonds are the dominating crosslinks at acidic pH. Furthermore, direct chitosan-chitosan hydrogen-bonds appear to have a much smaller role in hydrogel structure than previously thought. These findings offer valuable insights into the fine molecular interactions that stabilize these polysaccharide-surfactant hydrogels. Taken together with the known mechanical behaviours of these hydrogels, our results offer directions for the rational design of chitosan materials from the bottom up.

Chitosan-GPTMS-Silica Hybrid Mesoporous Aerogels for Bone Tissue Engineering.

This study introduces a new synthesis route for obtaining homogeneous chitosan (CS)-silica hybrid aerogels with CS contents up to 10 wt%, using 3-glycidoxypropyl trimethoxysilane (GPTMS) as coupling agent, for tissue engineering applications. Aerogels were obtained using the sol-gel process followed by CO2 supercritical drying, resulting in samples with bulk densities ranging from 0.17 g/cm3 to 0.38 g/cm3. The textural analysis by N2-physisorption revealed an interconnected mesopore network with decreasing specific surface areas (1230–700 m2/g) and pore sizes (11.1–8.7 nm) by increasing GPTMS content (2–4 molar ratio GPTMS:CS monomer). In addition, samples exhibited extremely fast swelling by spontaneous capillary imbibition in PBS solution, presenting swelling capacities from 1.75 to 3.75. The formation of a covalent crosslinked hybrid structure was suggested by FTIR and confirmed by an increase of four hundred fold or more in the compressive strength up to 96 MPa. Instead, samples synthesized without GPTMS fractured at only 0.10–0.26 MPa, revealing a week structure consisted in interpenetrated polymer networks. The aerogels presented bioactivity in simulated body fluid (SBF), as confirmed by the in vitro formation of hydroxyapatite (HAp) layer with crystal size of approximately 2 µm size in diameter. In vitro studies revealed also non cytotoxic effect on HOB® osteoblasts and also a mechanosensitive response. Additionally, control cells grown on glass developed scarce or no stress fibers, while cells grown on hybrid samples showed a significant (p < 0.05) increase in well-developed stress fibers and mature focal adhesion complexes.