Determination of the degree of acetylation of chitin materials by 13C CP/MAS NMR spectroscopy

Chitosan: Structural and Chemical Modification, Properties, and Application

Chitosan is a polymer of natural origins that possesses many favourable properties [...].

Cytotoxicity and Inflammatory Effects of Chitin Nanofibrils Isolated from Fungi

Fungal nanochitin can assist the transition from the linear fossil-based economy to a circular biobased economy given its environmental benefits over conventional crustacean-nanochitin. Its real-world implementation requires carefully assessing its toxicity so that unwanted human health and environmental issues are avoided. Accordingly, the cytotoxicity and inflammatory effects of chitin nanofibrils (ChNFs) from white mushroom is assessed. ChNFs are few nanometers in diameter, with a 75.8% N-acetylation degree, a crystallinity of 59.1%, and present a 44:56 chitin/glucan weight ratio. Studies are conducted for aqueous colloidal ChNF dispersions (0-5 mg·mL-1) and free-standing films having physically entangled ChNFs. Aqueous dispersions of chitin nanocrystals (ChNCs) isolated via hydrochloric acid hydrolysis of α-chitin powder are also evaluated for comparison. Cytotoxicity studies conducted in human fibroblasts (MRC-5 cells) and murine brain microglia (BV-2 cells) reveal a comparatively safer behavior over related biobased nanomaterials. However, a strong inflammatory response was observed when BV-2 cells were cultured in the presence of colloidal ChNFs. These novel cytotoxicity and inflammatory studies shed light on the potential of fungal ChNFs for biomedical applications.

From Chitosan to Chitin: Bio-Inspired Thin Films for Passive Daytime Radiative Cooling

Passive radiative daytime cooling is an emerging technology contributing to carbon-neutral heat management. Optically engineered materials with distinct absorption and emission properties in the solar and mid-infrared range are at the heart of this technology. Owing to their low emissive power of about 100 W m^-2 during daytime, substantial areas need to be covered with passive cooling materials or coatings to achieve a sizeable effect on global warming. Consequently, biocompatible materials are urgently needed to develop suitable coatings with no adverse environmental impact. It is shown how chitosan films with different thicknesses can be produced from slightly acidic aqueous solutions. The conversion to their insoluble form chitin in the solid state is demonstrated and the conversion is monitored with infrared (IR) and NMR spectroscopy. In combination with a reflective backing material, the films show below-ambient temperature cooling capabilities with a suitable emissivity in the mid-IR region and low solar absorption of 3.1-6.9%, depending on the film thickness. This work highlights the potential of chitosan and chitin as widely available biocompatible polymers for passive radiative cooling applications.

Determination of the degree of quaternization of N,N,N-trimethylchitosan by CP-MAS 13C NMR

Chitosan is used in several fields such as medicine, environment and advanced functional materials. The N-alkylation of chitosan into N,N,N-trimethylchitosan (TMC) allows to improve some properties. The current quantification methods of the degree of quaternization (DQ) like titration and ¹H NMR spectroscopy require the solubilization of TMC. In this study, a solid-state ¹³C NMR quantification method was developed for insoluble TMCs. For this purpose, four TMC derivatives acting as reference were synthesized and their degrees of quaternization, N,N-dimethylation (DD) and acetylation (DA) were determined in solution by ¹H NMR. CP-MAS ¹³C NMR spectra of those derivatives were deconvolved with Lorentz functions. Several ratios of the ¹³C NMR peak areas were correlated with the degrees of substitution obtained in ¹H NMR. The best quantification method of DQ involved the correlation of the carbon signal of methyl groups. The method was also applied for the determination of the DD and DA of TMCs.

Accurate Determination of the Degree of Deacetylation of Chitosan Using UPLC-MS/MS

The mole fraction of deacetylated monomeric units in chitosan (CS) molecules is referred to as CS's degree of deacetylation (DD). In this study, 35 characteristic ions of CS were detected using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS/MS). The relative response intensity of 35 characteristic ion pairs using a single charge in nine CS samples with varying DDs was analyzed using 30 analytical methods. There was a good linear relationship between the relative response intensity of the characteristic ion pairs determined using ultrahigh performance (UP) LC-MS/MS and the DD of CS. The UPLC-MS/MS method for determining the DD of CS was unaffected by the sample concentration. The detection instrument has a wide range of application parameters with different voltages, high temperatures, and gas flow conditions. This study established a detection method for the DD of CS with high sensitivity, fast analysis, accuracy, stability, and durability.

A facile approach for the determination of degree of deacetylation of chitosan using acid-base titration

Several spectroscopic techniques such as nuclear magnetic resonance (NMR), UV-visible, Fourier transform infrared (FT-IR), etc. have been already used for the determination of degree of deacetylation (DD) of chitosan. These techniques involve the interpretation of spectral data apart from sample preparation for obtaining DD of chitosan. In addition, inaccurate interpretation of data sometimes misleads researchers to get an exact value of DD of chitosan. Among them, NMR is an excellent technique for the estimation of DD of chitosan but expensive and not found easily in every research laboratory. On the other hand, titrimetric methods have been employed by many researchers for determining the DD of chitosan but these existing methods involve many complex calculations, which do not always give accurate results. Moreover, few of the acid-base titration methods are little complicated for execution. Therefore, in this present study, we adopted a very handy and simple acid-base titration method with a new approach and proposed a new equation facilitating the ease of calculation that is not reported elsewhere for the determination of DD value by observing the net volume of NaOH consumed for the complete neutralization of protonated amino groups (-NH₃⁺) of chitosan describing the novelty of the work. All the DD values (77.04 ± 1.36; 81.71 ± 1.73; 91.68 ± 1.42 for CS1, CS2, and CS3 respectively) obtained for various chitosan samples were in good agreement with the reported DD values (>75%, >80%, and >85% for CS1, CS2, and CS3 respectively) mentioned in the specifications of chitosan samples supplied by the manufacturer. Finally, the experimental DD values were further validated with the DD values (77.39%, 81.64%, and 90.5% for CS1, CS2, and CS3 respectively) obtained from the interpretation of ¹³C-NMR spectral data and all the experimental DD values were consistent with the DD values as calculated based on NMR spectra.

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The acid-base titration method with a new approach reported in this article for the determination of degree of deacetylation of chitosan provides an accuracy, reproducibility, and reliability.

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In addition, the reported method with a new approach is very convenient as compared to other existing methods to determine the degree of deacetylation of chitosan.

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The newly introduced equation to estimate degree of deacetylation of chitosan is very simple and convenient.

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The DD values of chitosan obtained by the acid-base titration method are perfectly validated based on ¹³C-NMR data.

Green Topochemical Esterification Effects on the Supramolecular Structure of Chitin Nanocrystals: Implications for Highly Stable Pickering Emulsions

In nature, chitin is organized in hierarchical structures composed of nanoscale building blocks that show outstanding mechanical and optical properties attractive for nanomaterial design. For applications that benefit from a maximized interface such as nanocomposites and Pickering emulsions, individualized chitin nanocrystals (ChNCs) are of interest. However, when extracted in water suspension, their individualization is affected by ChNC self-assembly, requiring a large amount of water (above 90%) for ChNC transport and stock, which limits their widespread use. To master their individualization upon drying and after regeneration, we herein report a waterborne topochemical one-pot acid hydrolysis/Fischer esterification to extract ChNCs from chitin and simultaneously decorate their surface with lactate or butyrate moieties. Controlled reaction conditions were designed to obtain nanocrystals of a comparable aspect ratio of about 30 and a degree of modification of about 30% of the ChNC surface, under the rationale to assess the only effect of the topochemistry on ChNC supramolecular organization. The rheological analysis coupled with polarized light imaging shows how the nematic structuring is hindered by both surface ester moieties. The increased viscosity and elasticity of the modified ChNC colloids indicate a gel-like phase, where typical ChNC clusters of liquid crystalline phases are disrupted. Pickering emulsions have been prepared from lyophilized nanocrystals as a proof of concept. Our results demonstrate that only the emulsions stabilized by the modified ChNCs have excellent stability over time, highlighting that their individualization can be regenerated from the dry state.

Functionality of Yeast β-Glucan Recovered from Kluyveromyces marxianus by Alkaline and Enzymatic Processes

β-Glucan (BG), one of the most abundant polysaccharides containing glucose monomers linked by β-glycosidic linkages, is prevalent in yeast biomass that needs to be recovered to obtain this valuable polymer. This study aimed to apply alkaline and enzymatic processes for the recovery of BG from the yeast strain Kluyveromyces marxianus TISTR 5925. For this purpose, the yeast was cultivated to produce the maximum yield of raw material (yeast cells). The effective recovery of BG was then established using either an alkaline or an enzymatic process. BG recovery of 35.45% was obtained by using 1 M NaOH at 90 °C for 1 h, and of 81.15% from 1% (w/v) hydrolytic protease enzyme at 55 °C for 5 h. However, BG recovered by the alkaline process was purer than that obtained by the enzymatic process. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy confirmed the purity, the functional groups, and the linkages of BG obtained from different recovery systems and different raw materials. The results of this study suggest that an alkaline process could be an effective approach for the solubilization and recovery of considerable purity of BG from the yeast cells. In addition, the obtained BG had comparable functional properties with commercially available BG. This study reveals the effectiveness of both chemical and biological recovery of BG obtained from yeast as a potential polymeric material.

IL versus DES: Impact on chitin pretreatment to afford high quality and highly functionalizable chitosan

Chitin is mainly extracted from crustaceans, but this resource is seasonally dependent and can represent a major drawback to satisfy the traceability criterion for high valuable applications. Insect resources are valuable alternatives due to their lower mineral content. However, the deacetylation of chitin into chitosan is still an expensive process. Therefore, we herein compare the impact of both DES/IL-pretreatments on the efficiency of the chemical deacetylation of chitin carried out over two insect sources (Bombyx eri, BE and Hermetia illucens, HI) and shrimp shells (S). The results showed that chitosans obtained from IL-pretreated chitins from BE larva, present lower acetylation degrees (13-17%) than DES-pretreated samples (18-27%). A selective N-acylation reaction with oleic acid has also been performed on the purest and most deacetylated chitosans leading to high substitution degrees (up to 27%). The overall approach validates the proper chitin source and processing methodology to achieve high quality and highly functionalizable chitosan.

Characterization of chitin-glucan complex from Tremella fuciformis fermentation residue and evaluation of its antibacterial performance

Submerged fermentation of fungi is an efficient way to obtain extracellular polysaccharides, however, in this process, excess discarded biomass is produced. In this study, Tremella fuciformis mycelia were reused as the raw material to isolate a novel fungal chitin-glucan complex (CGC-TFM) using alkaline extraction. Characteristic analysis revealed that the CGC-TFM consisted of glucosamine/acetylglucosamine and glucose (GlcN:Glc = 26:74 mol%), indicating a reference to the β polymorphism of chitin-glucan complex, with the molecular weight and crystallinity index of 256 ± 3.0 kDa and 54.25 ± 1.04%, respectively. Fourier transform infrared spectroscopy, X-ray diffraction, nuclear magnetic resonance, and scanning electron microscopy analyses confirmed that the chitin portion of the CGC-TFM exhibited a typical β configuration and N-acetylation degree of 70.52 ± 2.09%. Furthermore, the CGC-TFM exhibited good thermal stability and effective Escherichia coli inhibition ability, indicating that it could be applied as a potential food packaging material.

Determining the degree of acetylation of chitin/chitosan using a SSNMR 13C method on the basis of cross polarization reciprocity relation

The degree of acetylation (DA) is an essential parameter for chitin and its derivatives, which determines the chemical and physical properties of the polymers. As a consequene, fast and accurate technique to determine DA is widely required when developing the relating materials. Herein, an improved quantitative SSNMR method of rQCP_Z^RC, based on the cross polarization reciprocity relation, was discussed and employed for DA testing. Three chitin/chitosan samples were chosen to evaluate the performance of rQCP_Z^RC. In comparison with quantitative DP and optimized contact time CP methods, rQCP_Z^RC is revealed as an accurate and reliable DA testing method with relative percentage errors of less than 5%. Moreover, the experimental time of rQCP_Z^RC for each sample is 5.5 h, notably shorter than DP of 36-85 h. Thus, our work suggests rQCP_Z^RC as a tool for DA testing, which is capable to accomplish with high accuracy and efficiency.

Preparation and characterization of squid pen chitooligosaccharide–epigallocatechin gallate conjugates and their antioxidant and antimicrobial activities

Chitooligosaccharide (COS) and epigallocatechin-3-gallate (EGCG) at various concentrations were used for the preparation of COS–EGCG conjugates. The highest total phenolic content (TPC), representing the amount of EGCG conjugated, was obtained for 1 wt% COS together with EGCG at 0.5 wt% (C1-E0.5-conjugate) or 1.0 wt% (C1-E1.0-conjugate) (66.83 and 69.22 mg EGCG per g sample, respectively) (p < 0.05). The 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities (DRSA and ARSA, respectively) and ferric reducing antioxidant power (FRAP) of all the samples showed similar trends with TPC. The C1-E0.5-conjugate had higher DRSA, ARSA, FRAP and oxygen radical absorbance capacity (ORAC) values than COS (p < 0.05). Similarly, the antimicrobial activity of COS increased when conjugated with EGCG (p < 0.05). FTIR, ¹H-NMR and ¹³C-NMR analyses confirmed the successful grafting of EGCG with COS. Therefore, 1 wt% COS and 0.5 wt% EGCG were used for the production of a conjugate with augmented antioxidant activity, which could be used to retard lipid oxidation of fatty foods.

Chitooligosaccharide from squid pen showed increases in both antioxidant and antimicrobial activities via conjugation with epigallocatechin-gallate (EGCG).

Effects of Carrageenan and Chitosan as Coating Materials on the Thermal Degradation of Microencapsulated Phycocyanin from Spirulina sp

Phycocyanin is a natural substance that can be used as an antioxidant and food colorant. The quality of phycocyanin deteriorates when it is exposed to heat, and such deterioration is evidenced by decreases in its antioxidant activity and color. Encapsulation, which introduces a coating material over a substance of interest, has been applied to prevent changes in substance quality. The objective of the present research is to evaluate the kinetics of thermal degradation of phycocyanin coated with carrageenan or chitosan. Encapsulated phycocyanin samples were exposed to temperatures of 40, 50, or 60 °C for 90 min, and kinetics of the resulting degradation was evaluated to determine changes in sample quality. The results showed that the thermal degradation of encapsulated phycocyanin at 40–60 °C follows first-order reaction kinetics with reaction rate constants (k) of 4.67–9.17 × 10–5 s-1 and 3.83–7.67 × 10–5 s-1 for carrageenan and chitosan, respectively, and that the k of encapsulated phycocyanin is slower than that obtained from samples without the coating materials (control). Encapsulation efficiencies (EE) of 68.66 % and 76.45 %, as well as loading capacities of 45.28 % and 49.16 %, were, respectively, obtained for carrageenan and chitosan.

Integration of electron microscopy and solid-state NMR analysis for new views and compositional parameters of Aspergillus fumigatus biofilms

The general ability and tendency of bacteria and fungi to assemble into bacterial communities, termed biofilms, poses unique challenges to the treatment of human infections. Fungal biofilms, in particular, are associated with enhanced virulence in vivo and decreased sensitivity to antifungals. Much attention has been given to the complex cell wall structures in fungal organisms, yet beyond the cell surface, Aspergillus fumigatus and other fungi assemble a self-secreted extracellular matrix that is the hallmark of the biofilm lifestyle, protecting and changing the environment of resident members. Elucidation of the chemical and molecular detail of the extracellular matrix is crucial to understanding how its structure contributes to persistence and antifungal resistance in the host. We present a summary of integrated analyses of A. fumigatus biofilm architecture, including hyphae and the extracellular matrix, by scanning electron microscopy and A. fumigatus matrix composition by new top-down solid-state NMR approaches coupled with biochemical analysis. This combined methodology will be invaluable in formulating quantitative and chemical comparisons of A. fumigatus isolates that differ in virulence and are more or less resistant to antifungals. Ultimately, knowledge of the chemical and molecular requirements for matrix formation and function will drive the identification and development of new strategies to interfere with biofilm formation and virulence.

Preactivated thiolated glycogen as mucoadhesive polymer for drug delivery

The purpose of this study was to synthesize and characterize a novel thiolated glycogen, so-named S-preactivated thiolated glycogen, as a mucosal drug delivery systems and the assessment of its mucoadhesive properties. In this regard, glycogen-cysteine and glycogen-cysteine-2-mercaptonicotinic acid conjugates were synthesized. Glycogen was activated by an oxidative ring opening with sodium periodate resulting in reactive aldehyde groups to which cysteine was bound via reductive amination. The obtained thiolated polymer displayed 2203.09±200μmol thiol groups per gram polymer. In a second step, the thiol moieties of thiolated glycogen were protected by disulfide bond formation with the thiolated aromatic residue 2-mercaptonicotinic acid (2MNA). In vitro screening of mucoadhesive properties was performed on porcine intestinal mucosa using different methods. In particular, in terms of rheology investigations of mucus/polymer mixtures, the S-preactivated thiolated glycogen showed a 4.7-fold increase in dynamic viscosity over a time period of 5h, in comparison to mucus/Simulated Intestinal Fluid control. The S-preactivated polymer remained attached on freshly excised porcine mucosa for 45h. Analogous results were obtained with tensile studies demonstrating a 2.7-fold increase in maximum detachment force and 3.1- fold increase in total work of adhesion for the S-preactivated polymer compared to unmodified glycogen. Moreover, water-uptake studies showed an over 4h continuing weight gain for the S-preactivated polymer, whereas disintegration took place for the unmodified polymer within the first hour. Furthermore, even in the highest tested concentration of 2mg/ml the new conjugates did not show any cytotoxicity on Caco-2 cell monolayer using an MTT assay. According to these results, S-preactivated glycogen represents a promising type of mucoadhesive polymers useful for the development of various mucosal drug delivery systems.

Characterization of bioactive chitosan and sulfated chitosan from Doryteuthis singhalensis (Ortmann, 1891)

Chitosan was extracted from the pen of squid Doryteuthis singhalensis and characterized using FT-IR, NMR, CHN, SEM and DSC analysis. Purified chitosan was sulfated with chlorosulfonic acid in N,N-dimethylformamide and the added sulfate group was confirmed with FT-IR analysis. The molecular weight and degree of deacetylation (DDA) of chitosan was found 226.6kDa and 83.76% respectively. Chitosan exhibited potent antioxidant activity evidenced by reducing power, chelating ability on ferrous ions and scavenging activity on DPPH, superoxide and hydroxyl radicals. The anticoagulant assay using activated partial thromboplastin time (APTT) and prothrombin time (PT) showed chitosan as a strong anticoagulant. The results of this study showed possibility of using D. singhalensis pen as a non-conventional source of natural antioxidants and anticoagulant which can be incorporated in functional food formulations.

"The Good, the Bad and the Ugly" of Chitosans

The objective of this paper is to emphasize the fact that while consistent interest has been paid to the industrial use of chitosan, minor attention has been devoted to spread the knowledge of a good characterization of its physico-chemical properties. Therefore, the paper attempts to critically comment on the conflicting experimental results, highlighting the facts, the myths and the controversies. The goal is to indicate how to take advantage of chitosan versatility, to learn how to manage its variability and show how to properly tackle some unexpected undesirable features. In the sections of the paper various issues that relate chitosan properties to some basic features and to advanced solutions and applications are presented. The introduction outlines some historical pioneering works, where the chemistry of chitosan was originally explored. Thereafter, particular reference is made to analytical purity, characterization and chain modifications. The macromolecular characterization is mostly related to molecular weight and to degree of acetylation, but also refers to the conformational and rheological properties and solution stability. Then, the antimicrobial activity of chitosan in relation with its solubility is reviewed. A section is dedicated to the formulation of chitosan biomaterials, from gel to nanobeads, exploring their innovative application as active carrier nanoparticles. Finally, the toxicity issue of chitosan as a polymer and as a constructed nanomaterial is briefly commented in the conclusions.

Antioxidant and antimicrobial proprieties of chitin and chitosan extracted from Parapenaeus Longirostris shrimp shell waste

INTRODUCTION

Chitosan, the linear polymer, is produced by alkali deacetylation of chitin (CHI). Recently chitin and chitosan were attracted marked interest due to their biocompatibility, biodegradability and non-toxicity.

MATERIALS AND METHODS

In this study, chitin was extracted from shrimp shell (Parapenaeus longirostris) and chitosan was deacetylated by classical and ultrasound-assisted method. The identification of functional groups and the determination of degree of deacetylation of chitin (CHI), classical deacetylated chitosan (CDC) and ultrasound-assisted deacetylated chitosan (UDC) were carried through Fourier Transform-Infrared Spectroscopy. Their antimicrobial and antioxidant activity were also investigated.

RESULTS

The degree of deacetylation of CHI, CDC and UDC is 33.64%, 73.68% and 83.55%, respectively. Results showed that CHI, CDC and UDC exhibited a good antimicrobial activity against (S. aureus, E. coli, P. aeruginosa, K. pneumonia) and (C. albicans and C. parapsilosis). The scavenging ability of CHI, CDC and UDC on 1,1-diphenyl-2-picrylhydrazyl radicals is ranging from 4.71% to 21.25%, 11.45% to 32.78% and 18.27% to 44.17%, respectively, at the concentrations of 0.25 to 1mg/mL. The inhibition of lipid peroxidation with thiobarbituric acid-reacting substances is ranging from 11.7% to 51.63%, 17.24% to 63.52% and 29.31% to 77.39%, respectively, at varying concentrations of 0.25 to 1mg/mL.

CONCLUSION

The effectiveness of CHI, CDC and UDC is correlated with their degree of deacetylation. The results indicate the possibility of exploiting chitin and chitosan as antimicrobial agent.

Solid-State 13 C CP MAS NMR Spectroscopy as a Tool for Detection of (1 3, 1 6)- -D-Glucan in Products Prepared from Pleurotus ostreatus

The 13C CP/MAS NMR solid-state NMR technique was used to detect the presence of β-D-glucan and trace compounds in samples prepared from dried, naturally grown oyster mushroom (Pleurotus ostreatus) and commercially available products of dried, specially cultivated oyster mushroom and β-D-glucan isolated from this mushroom. The NMR spectra of all samples displayed signals typical for (1→3, 1→6)-β-D-glucan; however, signals which could be assigned to other trace compounds—(1→3)-α-glucan, chitin, and proteins—were also observed in the spectra. The amount of trace compounds was negligible in the commercially available products.

Green synthesis approach: extraction of chitosan from fungus mycelia

Chitosan, copolymer of glucosamine and N-acetyl glucosamine is mainly derived from chitin, which is present in cell walls of crustaceans and some other microorganisms, such as fungi. Chitosan is emerging as an important biopolymer having a broad range of applications in different fields. On a commercial scale, chitosan is mainly obtained from crustacean shells rather than from the fungal sources. The methods used for extraction of chitosan are laden with many disadvantages. Alternative options of producing chitosan from fungal biomass exist, in fact with superior physico-chemical properties. Researchers around the globe are attempting to commercialize chitosan production and extraction from fungal sources. Chitosan extracted from fungal sources has the potential to completely replace crustacean-derived chitosan. In this context, the present review discusses the potential of fungal biomass resulting from various biotechnological industries or grown on negative/low cost agricultural and industrial wastes and their by-products as an inexpensive source of chitosan. Biologically derived fungal chitosan offers promising advantages over the chitosan obtained from crustacean shells with respect to different physico-chemical attributes. The different aspects of fungal chitosan extraction methods and various parameters having an effect on the yield of chitosan are discussed in detail. This review also deals with essential attributes of chitosan for high value-added applications in different fields.

Bioactive glass/polymer composite scaffolds mimicking bone tissue

The aim of this work was the preparation and characterization of scaffolds with mechanical and functional properties able to regenerate bone. Porous scaffolds made of chitosan/gelatin (POL) blends containing different amounts of a bioactive glass (CEL2), as inorganic material stimulating biomineralization, were fabricated by freeze-drying. Foams with different compositions (CEL2/POL 0/100; 40/60; 70/30 wt %/wt) were prepared. Samples were crosslinked using genipin (GP) to improve mechanical strength and thermal stability. The scaffolds were characterized in terms of their stability in water, chemical structure, morphology, bioactivity, and mechanical behavior. Moreover, MG63 osteoblast-like cells and periosteal-derived stem cells were used to assess their biocompatibility. CEL2/POL samples showed interconnected pores having an average diameter ranging from 179 ± 5 μm for CEL2/POL 0/100 to 136 ± 5 μm for CEL2/POL 70/30. GP-crosslinking and the increase of CEL2 amount stabilized the composites to water solution (shown by swelling tests). In addition, the SBF soaking experiment showed a good bioactivity of the scaffold with 30 and 70 wt % CEL2. The compressive modulus increased by increasing CEL2 amount up to 2.1 ± 0.1 MPa for CEL2/POL 70/30. Dynamical mechanical analysis has evidenced that composite scaffolds at low frequencies showed an increase of storage and loss modulus with increasing frequency; furthermore, a drop of E' and E″ at 1 Hz was observed, and for higher frequencies both moduli increased again. Cells displayed a good ability to interact with the different tested scaffolds which did not modify cell metabolic activity at the analyzed points. MTT test proved only a slight difference between the two cytotypes analyzed.

Scaffolds for tissue engineering and 3D cell culture

In tissue engineering applications or even in 3D cell cultures, the biological cross talk between cells and the scaffold is controlled by the material properties and scaffold characteristics. In order to induce cell adhesion, proliferation, and activation, materials used for the fabrication of scaffolds must possess requirements such as intrinsic biocompatibility and proper chemistry to induce molecular biorecognition from cells. Materials, scaffold mechanical properties and degradation kinetics should be adapted to the specific tissue engineering application to guarantee the required mechanical functions and to accomplish the rate of the new-tissue formation. For scaffolds, pore distribution, exposed surface area, and porosity play a major role, whose amount and distribution influence the penetration and the rate of penetration of cells within the scaffold volume, the architecture of the produced extracellular matrix, and for tissue engineering applications, the final effectiveness of the regenerative process. Depending on the fabrication process, scaffolds with different architecture can be obtained, with random or tailored pore distribution. In the recent years, rapid prototyping computer-controlled techniques have been applied to the fabrication of scaffolds with ordered geometry. This chapter reviews the principal polymeric materials that are used for the fabrication of scaffolds and the scaffold fabrication processes, with examples of properties and selected applications.

Esferas de quitosana/Fe na degradação do corante Azul QR-19 por processos foto-Fenton utilizando luz artificial ou solar

A contaminação dos recursos hídricos é um dos maiores problemas ambientais da atualidade. Dentre as várias fontes poluidoras, destacam-se as indústrias têxteis, por serem fontes geradoras de grandes volumes de efluentes, muitas vezes tratados de maneira ineficiente. A principal causa do grande impacto ambiental decorrente deste descarte é a presença dos corantes, tais como os compostos do tipo azo, que podem gerar subprodutos de caráter carcinogênico e/ou mutagênico, ou como os de base antraquinona, que são muito resistentes à degradação natural e portanto persistem no efluente por um longo tempo. O objetivo do presente trabalho consiste na utilização de processos foto-Fenton assistidos por luz artificial e solar, utilizando ferro imobilizado em esferas de quitosana reticulada com glutaraldeído, para promover a degradação do corante reativo Azul QR-19, de base antraquinona, em solução aquosa. As esferas obtidas apresentaram tamanho regular com diâmetro de 4,0 mm. Os resultados demonstraram 90% de descoloração do sistema em 180minutos e redução de 60% do teor de carbono orgânico total (COT), para o sistema foto-Fenton utilizando luz artificial. Para o sistema fotoassistido com luz solar, a descoloração foi integralmente obtida em 120 minutos com 70% de redução do teor de COT. Foi observado que o ferro permaneceu na matriz após o tratamento, possibilitando sua reutilização.

Application of spectroscopic methods for structural analysis of chitin and chitosan

Chitin, the second most important natural polymer in the world, and its N-deacetylated derivative chitosan, have been identified as versatile biopolymers for a broad range of applications in medicine, agriculture and the food industry. Two of the main reasons for this are firstly the unique chemical, physicochemical and biological properties of chitin and chitosan, and secondly the unlimited supply of raw materials for their production. These polymers exhibit widely differing physicochemical properties depending on the chitin source and the conditions of chitosan production. The presence of reactive functional groups as well as the polysaccharide nature of these biopolymers enables them to undergo diverse chemical modifications. A complete chemical and physicochemical characterization of chitin, chitosan and their derivatives is not possible without using spectroscopic techniques. This review focuses on the application of spectroscopic methods for the structural analysis of these compounds.

Elucidação parcial da estrutura de aminoglucanooligossacarídeos (AGO's) produzidos enzimaticamente

O presente trabalho visou a aplicação da enzima quitinolítica purificada da linhagem Cellulosimicrobium cellulans 191 e da preparação comercial de papaína na hidrólise da quitina coloidal. A quitina coloidal foi caracterizada quanto ao grau de desacetilação e apresentou GD de 14% por espectroscopia na região do infravermelho. A quitinase purificada hidrolisou a quitina coloidal liberando di-N-acetilquitobiose, enquanto que a preparação comercial de papaína atuando sobre o mesmo substrato formou di-N-acetilquitobiose e tri-N-acetilquitotriose. A estrutura química dos aminoglucanooligossacarídeos foi elucidada por espectrometria de massa.