Novative Biomaterials Based on Chitosan and Poly(ε-Caprolactone): Elaboration of Porous Structures

The swelling capability of chitosan was explored in order to use water both, as volatile plasticizer and as pore-forming agent. Chitosan powder was swelled in acidic aqueous solution and melt blended with poly(ε-caprolactone) (PCL). After stabilization at 57% RH and 25 °C, samples suffered a water mass loss of around 30 wt% without dimensions variation. Despite the low miscibility of these biopolymers, quite homogeneous dispersion of chitosan within the polyester matrix was obtained. Some interactions between both biopolymers could be observed. To obtain chitosan phase with a thermoplastic-like behaviour, the plasticization effect was also studied by the addition of 25 wt% glycerol as non volatile plasticizer. The equilibrium moisture content of samples increased with the incorporation of glycerol due to its hydrophilic nature. Morphology, thermal and mechanical properties of the blends were determined after stabilization. The preparation of rich PCL blends allowed the formation of macroporous structures since samples were not contracted after water loss and stabilization. These biomaterials with such a porous structure could be used for biomedical applications.     

Evaluation of Extracted Chitosan from Portunus Pelagicus for the Preparation of Chitosan Alginate Blend Scaffolds

In recent years there is a growing need in generating a biocompatible and cost effective porous scaffold for tissue engineering purposes. Therefore, this study focused on conversion of the shell waste of locally available crab variety P.pelagicus (Blue swimming crab) into the chitosan scaffold. As the poor mechanical strength of chitosan limits its usage in tissue engineering, it was blended with alginate. The scaffolds were prepared by the freeze gelation method which requires less time and minimum energy, with fewer residual solvent and easier to scale up. To the best of our knowledge there are no reports on scaffold preparation from the extracted chitosan, blended with alginate by freeze gelation method. The biological properties of chitosan-alginate scaffolds (Cts–Alg) were evaluated and compared with those of chitosan scaffolds. The prepared scaffolds were characterized by SEM, swelling property, in vitro enzymatic degradation, and hemo, biocompatibility properties. Chitosan-alginate scaffolds had an average pore size of 40 μm and tensile strength of 0.564 ± 0.0.018 % MPa. Its swelling ratio was 27.5 ± 0.28 %, with mass loss percentage of 10 ± 0.33 % after 4 weeks of degradation. It has exhibited good hemocompatible properties too. Mouse fibroblast 3T3 cells were able to adhere and proliferate well in the blended scaffold. All these results indicated that chitosan-alginate scaffold is a suitable alternative substitute for tissue engineering.     

Recovery of gold by chicken egg shell membrane-conjugated chitosan beads

We have successfully prepared a bead-type adsorbent from two materials with different adsorption characteristics. Heavy metals were removed by greatly swollen egg shell membrane-conjugated chitosan beads. The egg shell membrane accumulated and removed precious metal ions from a dilute aqueous solution with a high affinity in a short contact time. Experiments suggested that chitosan beads could take up gold ions with great capacity and selectivity by conjugation with egg shell membrane. Under certain conditions, the selective removal of gold and copper in a mixture of gold and copper ions by egg shell membrane-conjugated chitosan beads was 100% and 2%, respectively. Egg shell membrane-conjugated chitosan beads can be seen as a promising material to recover gold in wastewater from various industries, such as electroplating.     

Enhanced Macroporous Cationic Chitosan Hydrogel by Freezing and Thawing Method with Superadsorption Capacity for Anionic Dyes

Journal of Polymers and the Environment - In this study, we have developed a simple technique to prepare cationic chitosan hydrogel with interconnected porous structure using freeze–thaw...     

Chitosan Functionalization with Amino Acids Yields to Higher Copper Ions Adsorption Capacity

Chitosan (Chi) beads were conjugated with three different amino acids [namely, glutamic acid (GLU), methionine (MET), and taurine (TAU)] aiming to increase the divalent copper ions uptake in aqueous media. Scanning Electron Microscopy evidenced the development of a large porous structure after amino acid functionalization, associated with the increase in a number of amino groups in the polymer backbone. X-Ray Photoelectron Spectroscopy and Fourier-Transform Infrared Spectra analyses were also employed to assess the conjugation of these three different amino acids in chitosan backbone. Adsorption experiments were conducted in a batch process, at 298 K, and kinetic data indicated a slightly better fitting for the pseudo-first-order model when compared to pseudo-second order. Intraparticle diffusion model suggested a three-step mechanism for Cu(II) adsorption kinetics, limited by the third step, the intraparticle diffusion. The isotherm data fitting to the traditional Langmuir and Freundlich models indicated a better fit for the former case. The amino acid conjugation resulted in the increase of the maximum adsorption capacity for Cu(II) from 1.30 mmol g^?1 prior to amino acid conjugation to values as high as 2.31 mmol g^?1, 2.40 mmol g^?1 and 2.68 mmol g^?1 for Chi–TAU, Chi–GLU, and Chi–MET, respectively. These results are attributed to the introduction of additional amino groups and new carboxylate and amino acid residues into the chitosan backbone, which might also be explored for amino acid demanding applications.     

Layer-by-Layer Deposition of Antibacterial Polyelectrolytes on Cotton Fibres

The introduction of molecules with biological properties on textile materials is essential for a number of biotechnological applications. With the purpose of testing new processes applied to textiles, in this study, we present the first results on the feasibility of using the Layer-by-Layer (LbL) deposition process in natural fibers such as cotton, with natural polyelectrolytes like chitosan (CH) and alginic acid sodium salt (ALG), the durability of CH/ALG multilayer on cotton were evaluated. The increase of negative charges to the substrate cotton was made with NaBr and TEMPO, to ensure the success of the process of LbL. Three characterization methods to assess electrostatic LbL deposition were performed: the contact angle between a liquid (water) and the sample surface, in order to characterize the wettability of the samples with the different layers of CH and ALG; dyeing of the CH/ALG assembled cotton fabric with cationic methylene blue that shows regular changes in terms of color depth (K/S value), which indicate that the surface were alternately deposited with CH and ALG layers and, finally, the analysis by infrared spectroscopy using Fourier Transform with Attenuated Total Reflection (ATR-FTIR), to assess the changes in the interaction between CH and ALG deposited on cotton samples.     

Sonophotocatalytic Degradation of Chitosan in the Presence of Fe(III)/H2O2 System

The degradation of chitosan by means of ultrasound irradiation and its combination with homogeneous photocatalysis (photo-Fenton) was investigated. Emphasis was given on the effect of additive on degradation rate constants. 24 kHz of ultrasound irradiation was provided by a sonicator, while an ultraviolet source of 16 W was used for UV irradiation. To increase the efficiency of degradation process, degradation system was combined with Fe(III) (2.5 × 10⁻⁴mol/L) and H₂O₂ (0.020–0.118 mol/L) in the presence of UV irradiation and the rate of degradation process change from 1.873 × 10⁻⁹−6.083 × 10⁻⁹ mol^1.7 L s⁻¹. Photo-Fenton process led to complete chitosan degradation in 60 min with the rate increasing with increasing catalyst loading. Sonophotocatalysis in the presence of Fe(III)/H₂O₂ was always faster than the respective individual processes. A synergistic effect between ultrasound and ultraviolet irradiation in the presence of Fenton reagent was calculated. The degraded chitosans were characterized by X-ray diffraction (XRD), gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) spectroscopy and average molecular weight of ultrasonicated chitosan was determined by measurements of intrinsic viscosity of samples. The results show that the total degree of deacetylation (DD) of chitosan change, partially after degradation and the decrease of molecular weight led to transformation of crystal structure. A negative order for the dependence of the reaction rate on total molar concentration of chitosan solution within the degradation process was suggested. Results of this study indicate that the presence of catalyst in the reaction medium can be utilized to reduce molecular weight of chitosan while maintaining the power of irradiated ultrasound and degree of deacetylation.     

Adsorption Kinetics of Dyes in Single and Binary Systems Using Cyanoguanidine-Crosslinked Chitosan of Different Deacetylation Degrees

The crosslinking of chitosan with cyanoguanidine shows some advantages, such as the improved the stability in acid solutions and the decrease of adsorbent cost. In this work, cyanoguanidine-crosslinked chitosan and pure chitosan were prepared to apply in the adsorption of Food Yellow 4 (FY4) and Food Blue 2 (FB2), in single and binary systems. Effects of pH and deacetylation degree (DD) of chitosan in adsorption were evaluated. The adsorbents were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The kinetic data were analyzed by pseudo-first order, pseudo-second order and Avrami models. The conditions of pH 3 and DD 95% were the more suitable to reach the highest adsorption capacities in all experimental assays. Under these conditions, the adsorption capacities for FY4 were approximately of 392 and 200 mg g^?1 and, for FB2 were approximately of 370 and 184 mg g^?1, respectively, in the single and binary systems. The Avrami model was suitable to represent the kinetic curves in all conditions, and the highest adsorption capacities were found for FY4 in binary aqueous system, being for the pure chitosan of 229 mg g^?1 and crosslinked chitosan of 218 mg g^?1. The Langmuir and extended Langmuir models presented a good fit to the equilibrium data in both systems. It was found that, the chitosan crosslinked with cyanoguanidine improved the chemical stability of chitosan as adsorbent.     

Improvement of Physico-Mechanical Properties of Photo-Cured Chitosan Films with Ethylene Glycol Dimethacrylate and (2-Hydroxyethyl) Methacrylate

Chitosan, a natural polymer, was prepared by deacetylation of chitin which was obtained from dried prawn shell and was characterized. Thin chitosan film of chitosan was prepared by casting method from 0.2 % chitosan in 2 % acetic acid solution. Five formulations were developed with ethylene glycol dimethacrylate and (2-hydroxyethyl) methacrylate along with photo-initiator, Darocur-1664 (4 %). The chitosan film was soaked in the formulations at different soaking times and irradiated under UV-radiation at different intensities for the improvement of its physical and mechanical properties. The cured chitosan films were then subjected to various mechano-chemical tests like tensile strength, elongation at break, polymer loading, water absorption and gel content. The formulation containing 30 % ethylene glycol dimethacrylate and 66 % (2-hydroxyethyl) methacrylate showed the best performance at the 30th UV pass of UV-radiation for 3 min soaking time.     

Quaternized Chitosan for Ecological Treatment of Bauxite Mining Effluents

One of the major concerns of mining companies is the safety of their tailing dams. Among the cares required to operate such a dam, a proper treatment of the effluent composing its waste stands out, since that, waste must be treated before returned to the environment. In the process of bauxite beneficiation, the effluent level of turbidity is the discard parameter that deserves attention. In this work, quaternized chitosan (TMC_Cl^?) derivative with cationic charge was synthetized and investigated to be used as coagulant in bauxite treatment for tailing dam effluent. The chitosan (CHT) was quaternized by methylation reaction. The quaternized chitosan structure was characterized by the following techniques: FTIR Spectroscopy and ¹H nuclear magnetic resonance (NMR). Its thermal stability was analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis. After quaternized chitosan was obtained, analysis with aluminum sulfate, protonated and quaternized chitosan were executed in jar-test apparatus. The tests were conducted in order to find the optimum pH, velocity gradient, coagulant and alkalizer dosages, as well as coagulation, flocculation and decantation time. The studied coagulants showed good results and reduced the effluent turbidity to levels below determined by legislation. By comparing the coagulants, it was possible to state that quaternized chitosan presented higher reduction of effluent turbidity levels; the tests were performed in the same conditions.     

A New Approach for the Flocculation Mechanism of Chitosan

A peak III/I ratio (_peak) in pyrene-fluorescence spectrum was used to measure the polarity of microenvironment of chitosan adsorbing pyrene molecules. The authors detected the pyrene-fluorescence spectrum of chitosan with different degrees of deacetylation (DD) and determined the relationship between the flocculation of bentonite colloid and the _peak of chitosan with a different molecular weight (MW) and DD. It can be concluded that MW rather than DD plays a key role in the flocculation and that bond bridging rather than charge neutralization dominates the flocculation with chitosan from a microenvironmental structure of view.     

Chitin and Chitosan Extracted from Shrimp Waste Using Fish Proteases Aided Process: Efficiency of Chitosan in the Treatment of Unhairing Effluents

Extraction and depolymerisation of chitin and chitosan from shrimp waste material was carried out using fish proteases aided process. A high deproteinization level (80 %) was recorded with an Enzyme/Substrate ratio of 10 U/mg. The demineralization of shrimp waste was completely achieved within 6 h at room temperature in HCl 1.25 M, and the residual content of calcium in chitin was below 0.01 %. The degree of N-acetylation, calculated from the ¹³C CP/MAS-NMR spectrum, was 85 %. The chitin obtained was converted to chitosan by N-deacetylation. X-ray diffraction patterns also indicated two characteristics crystalline peaks approximately at 10° and 20° (2θ). Chitosan was then evaluated in the treatment of unhairing effluents from the tanning industry. A result showed that chitosan as a coagulant has good performance in alkaline pH and at concentration of 0.5 g/L. Within these conditions, chitosan could decrease turbidity value, total suspended solids (89 % at 1.5 g/L), biological oxygen demand (33.3 % at 1.5 g/L) and chemical oxygen demand (58.7 % at 1.5 g/L).     

Clean Preparation Process of Chitosan Oligomers in Gly Series Ionic Liquids Homogeneous System

Chitosan oligomers because of its water solubility has some special physiological functions, such as binding lipid, affecting the mitogenic response, restraining the growth of tumors, and was widely used in cosmetics and health. H₂O₂/Gly (Glycine) series ionic liquids system, a new solvable-catalytic system, was an efficient clean process for preparation of chitosan oligomers. The effects of the anions of Gly series ionic liquids on the solubility and degradation for chitosan were investigated, and the results showed that [Gly]Cl aqueous solution was of good solubility and assistant degradation for chitosan. In additional, the mechanism for oxidative degradation of chitosan in ionic liquids (ILs) was studied. The effect on the property of chitosan oligomers catalyzed by H₂O₂, in two different kinds of solvents (HAc and [Gly]Cl) were compared. It was found that the performance of moisture absorption and retention of chitosan oligomers using ionic liquid aqueous solution as solvent was better than that using HAc aqueous solution as solvent, and even superior to that of hyaluronic acid. Furthermore, [Gly]Cl could be easily separated from the product and reused with only slight loss. It could provide an efficient and environmental friendly method for the preparation of chitosan oligomers in H₂O₂/ILs system.     

Fabrication and Characterization of Biodegradable Composite Films Made of Using Poly(caprolactone) Reinforced with Chitosan

Chitosan was dissolved in 2?% aqueous acetic acid solution and the films were prepared by solution casting. Values of tensile strength (TS), tensile modulus (TM), elongation at break (Eb?%) and water vapor permeability (WVP) of the chitosan films were found to be 30?MPa, 450?MPa, 8?% and 4.7?g?mm/m²?day?kPa, respectively. Poly(caprolactone) (PCL) films were prepared from its granules by compression molding and the values of TS, TM, Eb and WVP were 14?MPa, 220?MPa, 70?% and 1.54?g?mm/m²?day?kPa, respectively. PCL was reinforced with chitosan films, and composite films were prepared by compression molding. Amount of chitosan in the composite films varied from 10 to 50?% (w/w). It was found that with the incorporation of chitosan films in PCL, both the values of TS and TM of composite films increased significantly. The highest mechanical properties were found at 50?% (w/w) of chitosan content. The Oxygen transmission rate (OTR) of composite film was found to decrease significantly than PCL films. Thermal properties of the composite were also improved as compared to PCL. The water uptake test of the composite also showed promising results with a good stability of composite films. The interface of the composite was investigated by scanning electron microscopy and showed good interfacial adhesion between PCL and chitosan films.     

Chitosan/Hydrophilic Plasticizer-Based Films: Preparation,Physicochemical and Antimicrobial Properties

The addition of plasticizers to biopolymer films is a good method for improving their physicochemical properties. The aim of this study was to evaluate the effect of chitosan (CHI) blended with two hydrophilic plasticizers glycerol (GLY) and sorbitol (SOR), at two concentrations (20 and 40 wt%) on their mechanical, thermal, barrier, structural, morphological and antimicrobial properties. The chitosan was prepared through the alkaline deacetylation of chitin obtained from fermented lactic from shrimp heads. The obtained chitosan had a degree of deacetylation (DA) of 84 ± 2.7 and a molecular weight of 136 kDa, which indicated that a good film had formed. The films composed of CHI and GLY (20 wt%) exhibited the best mechanical properties compared to the neat chitosan film. The percentage of elongation at break increase to over 700 % in the films that contained 40 % GLY, and these films also exhibited the highest values for the water vapor transmission rate (WVTR) of 79.6 ± 1.9 g m² h^?1 and a yellow color (b _o  = 17.9 ± 2.0) compared to the neat chitosan films (b _o  = 8.8 ± 0.8). For the structural properties, the Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analyses revealed an interaction in the acetamide group and changes in the crystallinity of plasticized films. The scanning electron micrographs revealed that all formulations of the chitosan films were smooth, and that they did not contain aggregations, pores or microphase separation. The thermal analysis using differential scanning calorimetry (DSC) revealed a glass transition temperature (Tg) of 130 °C for neat chitosan film, but the addition of SOR or GLY elicited a decrease in the temperature of the peak (120 °C). In addition, the antimicrobial activity of the chitosan films was evaluated against Listeria monocytogenes, and reached a reduction of 2 log after 24 h. The plasticizer concentration of 20 % GLY is sufficient for obtaining flexible chitosan films with good mechanical properties, and it could serve as an alternative as a packaging material to reduce environmental problems associated with synthetic packaging films.     

Preparation and Thermo-Mechanical Characterization of Chitosan Loaded Methylcellulose-Based Biodegradable Films: Effects of Gamma Radiation

Chitosan (0.1–1%, w/w), dissolved in 2% acetic acid solution, was added into 1% methylcellulose (MC)-based formulation containing 0.5% vegetable oil, 0.25% glycerol and 0.025% Tween^?80. Films were prepared by casting. Puncture strength (PS), puncture deformation (PD), viscoelasticity coefficient and water vapour permeability (WVP) of the films were measured. The PS value of 312 N/mm was observed for MC-based films containing 0.25% chitosan. Values of PD, viscoelasticity coefficient and WVP of these films were 5.0 mm, 44.1%, and 6.0 g mm/m² day kPa, respectively. The MC-based films containing 0.25% chitosan were also exposed to gamma radiation (0.5–50 kGy). The PS of the treated films decreased significantly from 312 at 0 kGy to 201 N/mm when treated at a dose of 50 kGy. However, WVP values were not affected by increasing irradiation the dose used. The Fourier Transform Infrared spectroscopy supported the molecular interactions due to addition of chitosan in MC-based films. Thermo gravimetric analysis and differential scanning calorimetric experiments showed that thermal properties of the films were significantly improved by chitosan loading. Surface topography of the films was studied by scanning electron microscopy and found rougher due to chitosan addition.     

Renewable Resources and Enzymatic Processes to Create Functional Polymers: Adapting Materials and Reactions from Food Processing

We are exploiting materials and concepts from food science to create functionalized, environmentally friendly derivatives of the biopolymer chitosan, a byproduct of seafood processing. Functional groups are grafted onto chitosan using tyrosinase, the enzyme responsible for food browning. The functionalizing groups studied include low-molecular-weight phenols derived from natural sources and high-molecular-weight proteins. The approach of using low-molecular-weight phenols to functionalize chitosan is illustrated with arbutin, a natural phenol found in pears. Results demonstrate that tyrosinase initiates reactions that lead to the conversion of arbutin–chitosan solutions into gels. These gels can be rapidly broken by treatment with the chitosan-hydrolyzing enzyme chitosanase, demonstrating that the chitosan derivatives remain biodegradable. We briefly review other studies in which low-molecular-weight natural phenols are enzymatically grafted onto chitosan to confer functional properties. The creation of co-polymers is illustrated by results in which tyrosinase is used to couple gelatin onto chitosan. Gelatin is a proteinaceous byproduct of meat production. The tyrosinase-generated gelatin–chitosan conjugates have been observed to offer interesting rheological and thermal properties. These results demonstrate the potential for using renewable resources and enzymatic processing to create environmentally friendly polymers with useful functional properties.     

Mechanical and Barrier Properties of Biodegradable Films Made from Chitosan and Poly (Lactic Acid) Blends

Biodegradable film blends of chitosan with poly(lactic acid) (PLA) were prepared by solution mixing and film casting. The main goal of these blends is to improve the water vapor barrier of chitosan by blending it with a hydrophobic biodegradable polymer from renewable resources. Mechanical properties of obtained films were assessed by tensile test. Thermal properties, water barrier properties, and water sensitivity were studied by differential scanning calorimeter analysis, water vapor permeability measurements, and surface-angle contact tests, respectively. The incorporation of PLA to chitosan improved the water barrier properties and decreased the water sensitivity of chitosan film. However, the tensile strength and elastic modulus of chitosan decreased with the addition of PLA. Mechanical and thermal properties revealed that chitosan and PLA blends are incompatible, consistent with the results of Fourier transform infrared (FTIR) analysis that showed the absence of specific interaction between chitosan and PLA.     

Influence of the Concentrations of Chitosan and Glycerol on Edible Film Properties Showed by Response Surface Methodology

The individual and interactive effects of glycerol and chitosan concentrations on edible film properties were investigated using response surface methodology. The results of ANOVA indicated that all the independent variables exhibited significant effect on the film properties. Chitosan concentration had a positive effect on CO₂ permeability and negative effect on O₂ while the glycerol concentration had a positive effect on permeability to both gases. Regarding water vapor permeability, the chitosan concentration had a negative effect, whereas the glycerol had no influence. Moreover, both chitosan and glycerol concentration influenced the elongation at break point (%A), and only glycerol concentration had a significant effect on tensile strength. Optimization by desirability approach was carried out on the independent variables to get the optimum levels within the experimental conditions. It was found that 1.5 % of chitosan and 25 % of glycerol (wt/wt of chitosan) retarded respiration and showed a strong permeability to water vapor.