Research

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13 pages, 1529 KiB

Open AccessArticle

Chitosan Composites Synthesized Using Acetic Acid and Tetraethylorthosilicate Respond Differently to Methylene Blue Adsorption

by Thomas Y. A. Essel, Albert Koomson, Marie-Pearl O. Seniagya, Grace P. Cobbold, Samuel K. Kwofie, Bernard O. Asimeng, Patrick K. Arthur, Gordon Awandare and Elvis K. Tiburu

Polymers 2018, 10(5), 466; https://doi.org/10.3390/polym10050466 - 24 Apr 2018

Cited by 26 | Viewed by 5495

Abstract

The sol-gel and cross-linking processes have been used by researchers to synthesize silica-based nanostructures and optimize their size and morphology by changing either the material or the synthesis conditions. However, the influence of the silica nanostructures on the overall physicochemical and mechanistic properties [...] Read more.

The sol-gel and cross-linking processes have been used by researchers to synthesize silica-based nanostructures and optimize their size and morphology by changing either the material or the synthesis conditions. However, the influence of the silica nanostructures on the overall physicochemical and mechanistic properties of organic biopolymers such as chitosan has received limited attention. The present study used a one-step synthetic method to obtain chitosan composites to monitor the uptake and release of a basic cationic dye (methylene blue) at two different pH values. Firstly, the composites were synthesized and characterized by Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) to ascertain their chemical identity. Adsorption studies were conducted suing methylene blue and these studies revealed that Acetic Acid-Chitosan (AA-CHI), Tetraethylorthosilicate-Chitosan (TEOS-CHI), Acetic Acid-Tetraethylorthosilicate-Chitosan (AA-TEOS-CHI), and Acetic Acid-Chitosan-Tetraethylorthosilicate (AA-CHI-TEOS) had comparatively lower percentage adsorbances in acidic media after 40 h, with AA-CHI adsorbing most of the methylene blue dye. In contrast, these materials recorded higher percentage adsorbances of methylene blue in the basic media. The release profiles of these composites were fitted with an exponential model. The R-squared values obtained indicated that the AA-CHI at pH ~ 2.6 and AA-TEOS-CHI at pH ~ 7.2 of methylene blue had steady and consistent release profiles. The release mechanisms were analyzed using Korsmeyer-Peppas and Hixson-Crowell models. It was deduced that the release profiles of the majority of the synthesized chitosan beads were influenced by the conformational or surface area changes of the methylene blue. This was justified by the higher correlation coefficient or Pearson’s R values (R ≥ 0.5) computed from the Hixson-Crowell model. The results from this study showed that two of the novel materials comprising acetic acid-chitosan and a combination of equimolar ratios of acetic acid-TEOS-chitosan could be useful pH-sensitive probes for various biomedical applications, whereas the other materials involving the two-step synthesis could be found useful in environmental remediation of toxic materials. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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17 pages, 3371 KiB

Open AccessArticle

Reversible pH-Sensitive Chitosan-Based Hydrogels. Influence of Dispersion Composition on Rheological Properties and Sustained Drug Delivery

by Nieves Iglesias, Elsa Galbis, Concepción Valencia, M.-Violante De-Paz and Juan A. Galbis

Polymers 2018, 10(4), 392; https://doi.org/10.3390/polym10040392 - 01 Apr 2018

Cited by 25 | Viewed by 6349

Abstract

The present work deals with the synthesis of micro-structured biomaterials based on chitosan (CTS) for their applications as biocompatible carriers of drugs and bioactive compounds. Twelve dispersions were prepared by means of functional cross-linking with tricarballylic acid (TCA); they were characterized by Fourier [...] Read more.

The present work deals with the synthesis of micro-structured biomaterials based on chitosan (CTS) for their applications as biocompatible carriers of drugs and bioactive compounds. Twelve dispersions were prepared by means of functional cross-linking with tricarballylic acid (TCA); they were characterized by Fourier transform infrared spectroscopy (FT-IR), modulated temperature differential scanning calorimetry (MTDSC) and scanning electron microscopy (SEM), and their rheological properties were studied. To the best of the authors’ knowledge, no study has been carried out on the influence of CTS concentration, degree of cross-linking and drug loading on chitosan hydrogels for drug delivery systems (DDS) and is investigated herein for the first time. The influence of dispersion composition (polymer concentration and degree of cross-linking) revealed to exert a marked impact on its rheological properties, going from liquid-like to viscoelastic gels. The release profiles of a model drug, diclofenac sodium (DCNa), as well as their relationships with polymer concentration, drug loading and degree of cross-linking were evaluated. Similar to the findings on rheological properties, a wide range of release profiles was encountered. These formulations were found to display a well-controlled drug release strongly dependent on the formulation composition. Cumulative drug release under physiological conditions for 96 h ranged from 8% to 67%. For comparative purpose, Voltaren emulgel^® from Novartis Pharmaceuticals was also investigated and the latter was the formulation with the highest cumulative drug release (85%). Some formulations showed similar spreadability values to the commercial hydrogel. The comparative study of three batches confirmed the reproducibility of the method, leading to systems particularly suitable for their use as drug carriers. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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9 pages, 1119 KiB

Open AccessArticle

Recyclable Heterogeneous Chitosan Supported Copper Catalyst for Silyl Conjugate Addition to α,β-Unsaturated Acceptors in Water

by Lei Zhu, Bojie Li, Shan Wang, Wei Wang, Liansheng Wang, Liang Ding and Caiqin Qin

Polymers 2018, 10(4), 385; https://doi.org/10.3390/polym10040385 - 01 Apr 2018

Cited by 13 | Viewed by 3773

Abstract

The first example of an environmentally-benign chitosan supported copper catalyzed conjugate silylation of α,β-unsaturated acceptors was accomplished in water under mild conditions. This protocol provides an efficient pathway to achieve an important class of β-silyl carbonyl compounds and the desired products were obtained [...] Read more.

The first example of an environmentally-benign chitosan supported copper catalyzed conjugate silylation of α,β-unsaturated acceptors was accomplished in water under mild conditions. This protocol provides an efficient pathway to achieve an important class of β-silyl carbonyl compounds and the desired products were obtained in good to excellent yields. Gram-scale synthesis and easy transformation of obtained β-silyl products were also been demonstrated. Remarkably, this chitosan supported copper catalyst can be easily recycled and reused six times without any significant decrease of catalytic activity. The advantages of this newly developed method include operational simplicity, good functional group tolerance, scale-up ability, ready availability, and easy recyclability of catalyst. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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18 pages, 18321 KiB

Open AccessArticle

Sorption of Hg(II) and Pb(II) Ions on Chitosan-Iron(III) from Aqueous Solutions: Single and Binary Systems

by Byron Lapo, Hary Demey, Jessenia Zapata, Cristhian Romero and Ana María Sastre

Polymers 2018, 10(4), 367; https://doi.org/10.3390/polym10040367 - 25 Mar 2018

Cited by 34 | Viewed by 5428

Abstract

The present work describes the study of mercury Hg(II) and lead Pb(II) removal in single and binary component systems into easily prepared chitosan-iron(III) bio-composite beads. Scanning electron microscopy and energy-dispersive X-ray (SEM-EDX) analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and point [...] Read more.

The present work describes the study of mercury Hg(II) and lead Pb(II) removal in single and binary component systems into easily prepared chitosan-iron(III) bio-composite beads. Scanning electron microscopy and energy-dispersive X-ray (SEM-EDX) analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and point of zero charge (pH_pzc) analysis were carried out. The experimental set covered pH study, single and competitive equilibrium, kinetics, chloride and sulfate effects as well as sorption–desorption cycles. In single systems, the Langmuir nonlinear model fitted the experimental data better than the Freundlich and Sips equations. The sorbent material has more affinity to Hg(II) rather than Pb(II) ions, the maximum sorption capacities were 1.8 mmol·g⁻¹ and 0.56 mmol·g⁻¹ for Hg(II) and Pb(II), respectively. The binary systems data were adjusted with competitive Langmuir isotherm model. The presence of sulfate ions in the multicomponent system [Hg(II)-Pb(II)] had a lesser impact on the sorption efficiency than did chloride ions, however, the presence of chloride ions improves the selectivity towards Hg(II) ions. The bio-based material showed good recovery performance of metal ions along three sorption–desorption cycles. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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26 pages, 22538 KiB

Open AccessFeature PaperArticle

Bioactive Sr(II)/Chitosan/Poly(ε-caprolactone) Scaffolds for Craniofacial Tissue Regeneration. In Vitro and In Vivo Behavior

by Itzia Rodríguez-Méndez, Mar Fernández-Gutiérrez, Amairany Rodríguez-Navarrete, Raúl Rosales-Ibáñez, Lorena Benito-Garzón, Blanca Vázquez-Lasa and Julio San Román

Polymers 2018, 10(3), 279; https://doi.org/10.3390/polym10030279 - 07 Mar 2018

Cited by 11 | Viewed by 4823

Abstract

In craniofacial tissue regeneration, the current gold standard treatment is autologous bone grafting, however, it presents some disadvantages. Although new alternatives have emerged there is still an urgent demand of biodegradable scaffolds to act as extracellular matrix in the regeneration process. A potentially [...] Read more.

In craniofacial tissue regeneration, the current gold standard treatment is autologous bone grafting, however, it presents some disadvantages. Although new alternatives have emerged there is still an urgent demand of biodegradable scaffolds to act as extracellular matrix in the regeneration process. A potentially useful element in bone regeneration is strontium. It is known to promote stimulation of osteoblasts while inhibiting osteoclasts resorption, leading to neoformed bone. The present paper reports the preparation and characterization of strontium (Sr) containing hybrid scaffolds formed by a matrix of ionically cross-linked chitosan and microparticles of poly(ε-caprolactone) (PCL). These scaffolds of relatively facile fabrication were seeded with osteoblast-like cells (MG-63) and human bone marrow mesenchymal stem cells (hBMSCs) for application in craniofacial tissue regeneration. Membrane scaffolds were prepared using chitosan:PCL ratios of 1:2 and 1:1 and 5 wt % Sr salts. Characterization was performed addressing physico-chemical properties, swelling behavior, in vitro biological performance and in vivo biocompatibility. Overall, the composition, microstructure and swelling degree (≈245%) of scaffolds combine with the adequate dimensional stability, lack of toxicity, osteogenic activity in MG-63 cells and hBMSCs, along with the in vivo biocompatibility in rats allow considering this system as a promising biomaterial for the treatment of craniofacial tissue regeneration. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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19 pages, 4233 KiB

Open AccessArticle

Biomaterials Based on Electrospun Chitosan. Relation between Processing Conditions and Mechanical Properties

by Christian Enrique Garcia Garcia, Félix Armando Soltero Martínez, Frédéric Bossard and Marguerite Rinaudo

Polymers 2018, 10(3), 257; https://doi.org/10.3390/polym10030257 - 01 Mar 2018

Cited by 28 | Viewed by 4520

Abstract

In this paper, it is shown that pure chitosan nanofibers and films were prepared with success in 0.5 M acetic acid as solvent using poly (ethylene oxide) (PEO) at different yields, allowing electrospinning of the blends. After processing, a neutralization step of chitosan [...] Read more.

In this paper, it is shown that pure chitosan nanofibers and films were prepared with success in 0.5 M acetic acid as solvent using poly (ethylene oxide) (PEO) at different yields, allowing electrospinning of the blends. After processing, a neutralization step of chitosan followed by water washing is performed, preserving the initial morphology of chitosan materials. The influence of the yield in PEO in the blend on the degree of swelling and hydrophilicity of films and nanofibers is demonstrated. Then, the mechanical behavior of blended nanofibers and films used as reference are determined for small stress applied in the linear domain by DMA and by uniaxial traction up to rupture. The dried and wet states are covered for the first time. It is shown that the mechanical properties are increased when electrospinning is performed in the presence of PEO up to a 70/30 chitosan/PEO weight ratio even after PEO extraction. This result can be explained by a better dispersion of the chitosan in the presence of PEO. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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18 pages, 3262 KiB

Open AccessFeature PaperArticle

Biosynthetic Pathway and Genes of Chitin/Chitosan-Like Bioflocculant in the Genus Citrobacter

by Masahiro Takeo, Kazuyuki Kimura, Shanmugam Mayilraj, Takuya Inoue, Shohei Tada, Kouki Miyamoto, Masami Kashiwa, Keishi Ikemoto, Priyanka Baranwal, Daiichiro Kato and Seiji Negoro

Polymers 2018, 10(3), 237; https://doi.org/10.3390/polym10030237 - 27 Feb 2018

Cited by 10 | Viewed by 5545

Abstract

Chitin/chitosan, one of the most abundant polysaccharides in nature, is industrially produced as a powder or flake form from the exoskeletons of crustaceans such as crabs and shrimps. Intriguingly, many bacterial strains in the genus Citrobacter secrete a soluble chitin/chitosan-like polysaccharide into the [...] Read more.

Chitin/chitosan, one of the most abundant polysaccharides in nature, is industrially produced as a powder or flake form from the exoskeletons of crustaceans such as crabs and shrimps. Intriguingly, many bacterial strains in the genus Citrobacter secrete a soluble chitin/chitosan-like polysaccharide into the culture medium during growth in acetate. Because this polysaccharide shows strong flocculation activity for suspended solids in water, it can be used as a bioflocculant (BF). The BF synthetic pathway of C. freundii IFO 13545 is expected from known bacterial metabolic pathways to be as follows: acetate is metabolized in the TCA cycle and the glyoxylate shunt via acetyl-CoA. Next, fructose 6-phosphate is generated from the intermediates of the TCA cycle through gluconeogenesis and enters into the hexosamine synthetic pathway to form UDP-N-acetylglucosamine, which is used as a direct precursor to extend the BF polysaccharide chain. We conducted the draft genome sequencing of IFO 13545 and identified all of the candidate genes corresponding to the enzymes in this pathway in the 5420-kb genome sequence. Disruption of the genes encoding acetyl-CoA synthetase and isocitrate lyase by homologous recombination resulted in little or no growth on acetate, indicating that the cell growth depends on acetate assimilation via the glyoxylate shunt. Disruption of the gene encoding glucosamine 6-phosphate synthase, a key enzyme for the hexosamine synthetic pathway, caused a significant decrease in flocculation activity, demonstrating that this pathway is primarily used for the BF biosynthesis. A gene cluster necessary for the polymerization and secretion of BF, named bfpABCD, was also identified for the first time. In addition, quantitative RT-PCR analysis of several key genes in the expected pathway was conducted to know their expression in acetate assimilation and BF biosynthesis. Based on the data obtained in this study, an overview of the BF synthetic pathway is discussed. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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8 pages, 3864 KiB

Open AccessCommunication

Nanosphere Lithography of Chitin and Chitosan with Colloidal and Self-Masking Patterning

by Rakkiyappan Chandran, Kyle Nowlin and Dennis R. LaJeunesse

Polymers 2018, 10(2), 218; https://doi.org/10.3390/polym10020218 - 23 Feb 2018

Cited by 9 | Viewed by 9790

Abstract

Complex surface topographies control, define, and determine the properties of insect cuticles. In some cases, these nanostructured materials are a direct extension of chitin-based cuticles. The cellular mechanisms that generate these elaborate chitin-based structures are unknown, and involve complicated cellular and biochemical “bottom-up” [...] Read more.

Complex surface topographies control, define, and determine the properties of insect cuticles. In some cases, these nanostructured materials are a direct extension of chitin-based cuticles. The cellular mechanisms that generate these elaborate chitin-based structures are unknown, and involve complicated cellular and biochemical “bottom-up” processes. We demonstrated that a synthetic “top-down” fabrication technique—nanosphere lithography—generates surfaces of chitin or chitosan that mimic the arrangement of nanostructures found on the surface of certain insect wings and eyes. Chitin and chitosan are flexible and biocompatible abundant natural polymers, and are a sustainable resource. The fabrication of nanostructured chitin and chitosan materials enables the development of new biopolymer materials. Finally, we demonstrated that another property of chitin and chitosan—the ability to self-assemble nanosilver particles—enables a novel and powerful new tool for the nanosphere lithographic method: the ability to generate a self-masking thin film. The scalability of the nanosphere lithographic technique is a major limitation; however, the silver nanoparticle self-masking enables a one-step thin-film cast or masking process, which can be used to generate nanostructured surfaces over a wide range of surfaces and areas. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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21 pages, 3040 KiB

Open AccessArticle

Neodymium Recovery by Chitosan/Iron(III) Hydroxide [ChiFer(III)] Sorbent Material: Batch and Column Systems

by Hary Demey, Byron Lapo, Montserrat Ruiz, Agustin Fortuny, Muriel Marchand and Ana M. Sastre

Polymers 2018, 10(2), 204; https://doi.org/10.3390/polym10020204 - 19 Feb 2018

Cited by 32 | Viewed by 5784

Abstract

A low cost composite material was synthesized for neodymium recovery from dilute aqueous solutions. The in-situ production of the composite containing chitosan and iron(III) hydroxide (ChiFer(III)) was improved and the results were compared with raw chitosan particles. The sorbent was characterized using Fourier [...] Read more.

A low cost composite material was synthesized for neodymium recovery from dilute aqueous solutions. The in-situ production of the composite containing chitosan and iron(III) hydroxide (ChiFer(III)) was improved and the results were compared with raw chitosan particles. The sorbent was characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive X-ray analyses (SEM-EDX). The equilibrium studies were performed using firstly a batch system, and secondly a continuous system. The sorption isotherms were fitted with the Langmuir, Freundlich, and Sips models; experimental data was better described with the Langmuir equation and the maximum sorption capacity was 13.8 mg g-1 at pH 4. The introduction of iron into the biopolymer matrix increases by four times the sorption uptake of the chitosan; the individual sorption capacity of iron (into the composite) was calculated as 30.9 mg Nd/g Fe. The experimental results of the columns were fitted adequately using the Thomas model. As an approach to Nd-Fe-B permanent magnets effluents, a synthetic dilute effluent was simulated at pH 4, in order to evaluate the selectivity of the sorbent material; the overshooting of boron in the column system confirmed the higher selectivity toward neodymium ions. The elution step was carried out using MilliQ-water with the pH set to 3.5 (dilute HCl solution). Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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14 pages, 4105 KiB

Open AccessArticle

Rheo-Kinetic Study of Sol-Gel Phase Transition of Chitosan Colloidal Systems

by Piotr Owczarz, Patryk Ziółkowski, Zofia Modrzejewska, Sławomir Kuberski and Marek Dziubiński

Polymers 2018, 10(1), 47; https://doi.org/10.3390/polym10010047 - 05 Jan 2018

Cited by 20 | Viewed by 5210

Abstract

Chitosan colloidal systems, created by dispersing in aqueous solutions of hydrochloric acid, with and without the addition of disodium β-glycerophosphate (β-NaGP), were prepared for the investigation of forming mechanisms of chitosan hydrogels. Three types of chitosan were used in varying molecular weights. The [...] Read more.

Chitosan colloidal systems, created by dispersing in aqueous solutions of hydrochloric acid, with and without the addition of disodium β-glycerophosphate (β-NaGP), were prepared for the investigation of forming mechanisms of chitosan hydrogels. Three types of chitosan were used in varying molecular weights. The impacts of the charge and shape of the macromolecules on the phase transition process were assessed. The chitosan system without the addition of β-NaGP was characterized by stiff and entangled molecules, in contrast to the chitosan system with the addition of β-NaGP, wherein the molecules adopt a more flexible and disentangled form. Differences in molecules shapes were confirmed using the Zeta potential and thixotropy experiments. The chitosan system without β-NaGP revealed a rapid nature of phase transition—consistent with diffusion-limited aggregation (DLA). The chitosan system with β-NaGP revealed a two-step nature of phase transition, wherein the first step was consistent with reaction-limited aggregation (RLA), while the second step complied with diffusion-limited aggregation (DLA). Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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3624 KiB

Open AccessArticle

Chitosan–Zinc(II) Complexes as a Bio-Sorbent for the Adsorptive Abatement of Phosphate: Mechanism of Complexation and Assessment of Adsorption Performance

by Maryam Roza Yazdani, Elina Virolainen, Kevin Conley and Riku Vahala

Polymers 2018, 10(1), 25; https://doi.org/10.3390/polym10010025 - 25 Dec 2017

Cited by 47 | Viewed by 7664

Abstract

This study examines zinc(II)–chitosan complexes as a bio-sorbent for phosphate removal from aqueous solutions. The bio-sorbent is prepared and is characterized via Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and Point of Zero Charge (pH_PZC)–drift method. The adsorption capacity [...] Read more.

This study examines zinc(II)–chitosan complexes as a bio-sorbent for phosphate removal from aqueous solutions. The bio-sorbent is prepared and is characterized via Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and Point of Zero Charge (pH_PZC)–drift method. The adsorption capacity of zinc(II)–chitosan bio-sorbent is compared with those of chitosan and ZnO–chitosan and nano-ZnO–chitosan composites. The effect of operational parameters including pH, temperature, and competing ions are explored via adsorption batch mode. A rapid phosphate uptake is observed within the first three hours of contact time. Phosphate removal by zinc(II)–chitosan is favored when the surface charge of bio-sorbent is positive/or neutral e.g., within the pH range inferior or around its pH_PZC, 7. Phosphate abatement is enhanced with decreasing temperature. The study of background ions indicates a minor effect of chloride, whereas nitrate and sulfate show competing effect with phosphate for the adsorptive sites. The adsorption kinetics is best described with the pseudo-second-order model. Sips (R² > 0.96) and Freundlich (R² ≥ 0.95) models suit the adsorption isotherm. The phosphate reaction with zinc(II)–chitosan is exothermic, favorable and spontaneous. The complexation of zinc(II) and chitosan along with the corresponding mechanisms of phosphate removal are presented. This study indicates the introduction of zinc(II) ions into chitosan improves its performance towards phosphate uptake from 1.45 to 6.55 mg/g and provides fundamental information for developing bio-based materials for water remediation. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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5695 KiB

Open AccessArticle

Aerogels from Chitosan Solutions in Ionic Liquids

by Gonzalo Santos-López, Waldo Argüelles-Monal, Elizabeth Carvajal-Millan, Yolanda L. López-Franco, Maricarmen T. Recillas-Mota and Jaime Lizardi-Mendoza

Polymers 2017, 9(12), 722; https://doi.org/10.3390/polym9120722 - 16 Dec 2017

Cited by 27 | Viewed by 5897

Abstract

Chitosan aerogels conjugates the characteristics of nanostructured porous materials, i.e., extended specific surface area and nano scale porosity, with the remarkable functional properties of chitosan. Aerogels were obtained from solutions of chitosan in ionic liquids (ILs), 1-butyl-3-methylimidazolium acetate (BMIMAc), and 1-ethyl-3-methyl-imidazolium acetate (EMIMAc), [...] Read more.

Chitosan aerogels conjugates the characteristics of nanostructured porous materials, i.e., extended specific surface area and nano scale porosity, with the remarkable functional properties of chitosan. Aerogels were obtained from solutions of chitosan in ionic liquids (ILs), 1-butyl-3-methylimidazolium acetate (BMIMAc), and 1-ethyl-3-methyl-imidazolium acetate (EMIMAc), in order to observe the effect of the solvent in the structural characteristics of this type of materials. The process of elaboration of aerogels comprised the formation of physical gels through anti-solvent vapor diffusion, liquid phase exchange, and supercritical CO₂ drying. The aerogels maintained the chemical identity of chitosan according to Fourier transform infrared spectrophotometer (FT-IR) spectroscopy, indicating the presence of their characteristic functional groups. The internal structure of the obtained aerogels appears as porous aggregated networks in microscopy images. The obtained materials have specific surface areas over 350 m²/g and can be considered mesoporous. According to swelling experiments, the chitosan aerogels could absorb between three and six times their weight of water. However, the swelling and diffusion coefficient decreased at higher temperatures. The structural characteristics of chitosan aerogels that are obtained from ionic liquids are distinctive and could be related to solvation dynamic at the initial state. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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Review

Jump to: Research

51 pages, 21605 KiB

Open AccessReview

Chitosan in Non-Viral Gene Delivery: Role of Structure, Characterization Methods, and Insights in Cancer and Rare Diseases Therapies

by Beatriz Santos-Carballal, Elena Fernández Fernández and Francisco M. Goycoolea

Polymers 2018, 10(4), 444; https://doi.org/10.3390/polym10040444 - 15 Apr 2018

Cited by 85 | Viewed by 11028

Abstract

Non-viral gene delivery vectors have lagged far behind viral ones in the current pipeline of clinical trials of gene therapy nanomedicines. Even when non-viral nanovectors pose less safety risks than do viruses, their efficacy is much lower. Since the early studies to deliver [...] Read more.

Non-viral gene delivery vectors have lagged far behind viral ones in the current pipeline of clinical trials of gene therapy nanomedicines. Even when non-viral nanovectors pose less safety risks than do viruses, their efficacy is much lower. Since the early studies to deliver pDNA, chitosan has been regarded as a highly attractive biopolymer to deliver nucleic acids intracellularly and induce a transgenic response resulting in either upregulation of protein expression (for pDNA, mRNA) or its downregulation (for siRNA or microRNA). This is explained as the consequence of a multi-step process involving condensation of nucleic acids, protection against degradation, stabilization in physiological conditions, cellular internalization, release from the endolysosome (“proton sponge” effect), unpacking and enabling the trafficking of pDNA to the nucleus or the siRNA to the RNA interference silencing complex (RISC). Given the multiple steps and complexity involved in the gene transfection process, there is a dearth of understanding of the role of chitosan’s structural features (M_w and degree of acetylation, DA%) on each step that dictates the net transfection efficiency and its kinetics. The use of fully characterized chitosan samples along with the utilization of complementary biophysical and biological techniques is key to bridging this gap of knowledge and identifying the optimal chitosans for delivering a specific gene. Other aspects such as cell type and administration route are also at play. At the same time, the role of chitosan structural features on the morphology, size and surface composition of synthetic virus-like particles has barely been addressed. The ongoing revolution brought about by the recent discovery of CRISPR-Cas9 technology will undoubtedly be a game changer in this field in the short term. In the field of rare diseases, gene therapy is perhaps where the greatest potential lies and we anticipate that chitosans will be key players in the translation of research to the clinic. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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14 pages, 300 KiB

Open AccessReview

Application of Chitin/Chitosan and Their Derivatives in the Papermaking Industry

by Zhaoping Song, Guodong Li, Feixiang Guan and Wenxia Liu

Polymers 2018, 10(4), 389; https://doi.org/10.3390/polym10040389 - 01 Apr 2018

Cited by 80 | Viewed by 10855

Abstract

Chitin/chitosan and their derivatives have become of great interest as functional materials in many fields within the papermaking industry. They have been employed in papermaking wet-end, paper surface coating, papermaking wastewater treatment, and other sections of the papermaking industry due to their structure [...] Read more.

Chitin/chitosan and their derivatives have become of great interest as functional materials in many fields within the papermaking industry. They have been employed in papermaking wet-end, paper surface coating, papermaking wastewater treatment, and other sections of the papermaking industry due to their structure and chemical properties. The purpose of this paper is to briefly discuss the application of chitin/chitosan and their derivatives in the papermaking industry. The development of their application in the papermaking area will be reviewed and summarized. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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29 pages, 5407 KiB

Open AccessFeature PaperReview

Chitin Deacetylases: Structures, Specificities, and Biotech Applications

by Laia Grifoll-Romero, Sergi Pascual, Hugo Aragunde, Xevi Biarnés and Antoni Planas

Polymers 2018, 10(4), 352; https://doi.org/10.3390/polym10040352 - 22 Mar 2018

Cited by 95 | Viewed by 9662

Abstract

Depolymerization and de-N-acetylation of chitin by chitinases and deacetylases generates a series of derivatives including chitosans and chitooligosaccharides (COS), which are involved in molecular recognition events such as modulation of cell signaling and morphogenesis, immune responses, and host-pathogen interactions. Chitosans and [...] Read more.

Depolymerization and de-N-acetylation of chitin by chitinases and deacetylases generates a series of derivatives including chitosans and chitooligosaccharides (COS), which are involved in molecular recognition events such as modulation of cell signaling and morphogenesis, immune responses, and host-pathogen interactions. Chitosans and COS are also attractive scaffolds for the development of bionanomaterials for drug/gene delivery and tissue engineering applications. Most of the biological activities associated with COS seem to be largely dependent not only on the degree of polymerization but also on the acetylation pattern, which defines the charge density and distribution of GlcNAc and GlcNH₂ moieties in chitosans and COS. Chitin de-N-acetylases (CDAs) catalyze the hydrolysis of the acetamido group in GlcNAc residues of chitin, chitosan, and COS. The deacetylation patterns are diverse, some CDAs being specific for single positions, others showing multiple attack, processivity or random actions. This review summarizes the current knowledge on substrate specificity of bacterial and fungal CDAs, focusing on the structural and molecular aspects of their modes of action. Understanding the structural determinants of specificity will not only contribute to unravelling structure-function relationships, but also to use and engineer CDAs as biocatalysts for the production of tailor-made chitosans and COS for a growing number of applications. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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33 pages, 4306 KiB

Open AccessReview

Chitosan Derivatives: Introducing New Functionalities with a Controlled Molecular Architecture for Innovative Materials

by Waldo M. Argüelles-Monal, Jaime Lizardi-Mendoza, Daniel Fernández-Quiroz, Maricarmen T. Recillas-Mota and Marcelino Montiel-Herrera

Polymers 2018, 10(3), 342; https://doi.org/10.3390/polym10030342 - 20 Mar 2018

Cited by 116 | Viewed by 12513

Abstract

The functionalization of polymeric substances is of great interest for the development of innovative materials for advanced applications. For many decades, the functionalization of chitosan has been a convenient way to improve its properties with the aim of preparing new materials with specialized [...] Read more.

The functionalization of polymeric substances is of great interest for the development of innovative materials for advanced applications. For many decades, the functionalization of chitosan has been a convenient way to improve its properties with the aim of preparing new materials with specialized characteristics. In the present review, we summarize the latest methods for the modification and derivatization of chitin and chitosan under experimental conditions, which allow a control over the macromolecular architecture. This is because an understanding of the interdependence between chemical structure and properties is an important condition for proposing innovative materials. New advances in methods and strategies of functionalization such as the click chemistry approach, grafting onto copolymerization, coupling with cyclodextrins, and reactions in ionic liquids are discussed. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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10 pages, 3388 KiB

Open AccessReview

The Use of Polymer Chitosan in Intravesical Treatment of Urinary Bladder Cancer and Infections

by Andreja Erman and Peter Veranič

Polymers 2018, 10(3), 265; https://doi.org/10.3390/polym10030265 - 05 Mar 2018

Cited by 9 | Viewed by 5706

Abstract

The most frequent diseases of the urinary bladder are bacterial infections and bladder cancers. For both diseases, very high recurrence rates are characteristic: 50–80% for bladder cancer and more than 50% for bladder infections, causing loss of millions of dollars per year for [...] Read more.

The most frequent diseases of the urinary bladder are bacterial infections and bladder cancers. For both diseases, very high recurrence rates are characteristic: 50–80% for bladder cancer and more than 50% for bladder infections, causing loss of millions of dollars per year for medical treatment and sick leave. Despite years of searching for better treatment, the prevalence of bladder infections and bladder cancer remains unchanged and is even increasing in recent years. Very encouraging results in treatment of both diseases recently culminated from studies combining biopolymer chitosan with immunotherapy, and chitosan with antibiotics for treatment of bladder cancer and cystitis, respectably. In both pathways of research, the discoveries involving chitosan reached a successful long-lasting cure. The property of chitosan that boosted the effectivity of illness-specific drugs is its ability to enhance the accessibility of these drugs to the very sources of both pathologies that individual treatments without chitosan failed to achieve. Chitosan can thus be recognised as a very promising co-player in treatment of bladder cancer and bacterial cystitis. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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32 pages, 3043 KiB

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Chitosan Based Self-Assembled Nanoparticles in Drug Delivery

by Javier Pérez Quiñones, Hazel Peniche and Carlos Peniche

Polymers 2018, 10(3), 235; https://doi.org/10.3390/polym10030235 - 26 Feb 2018

Cited by 221 | Viewed by 20350

Abstract

Chitosan is a cationic polysaccharide that is usually obtained by alkaline deacetylation of chitin poly(N-acetylglucosamine). It is biocompatible, biodegradable, mucoadhesive, and non-toxic. These excellent biological properties make chitosan a good candidate for a platform in developing drug delivery systems having improved [...] Read more.

Chitosan is a cationic polysaccharide that is usually obtained by alkaline deacetylation of chitin poly(N-acetylglucosamine). It is biocompatible, biodegradable, mucoadhesive, and non-toxic. These excellent biological properties make chitosan a good candidate for a platform in developing drug delivery systems having improved biodistribution, increased specificity and sensitivity, and reduced pharmacological toxicity. In particular, chitosan nanoparticles are found to be appropriate for non-invasive routes of drug administration: oral, nasal, pulmonary and ocular routes. These applications are facilitated by the absorption-enhancing effect of chitosan. Many procedures for obtaining chitosan nanoparticles have been proposed. Particularly, the introduction of hydrophobic moieties into chitosan molecules by grafting to generate a hydrophobic-hydrophilic balance promoting self-assembly is a current and appealing approach. The grafting agent can be a hydrophobic moiety forming micelles that can entrap lipophilic drugs or it can be the drug itself. Another suitable way to generate self-assembled chitosan nanoparticles is through the formation of polyelectrolyte complexes with polyanions. This paper reviews the main approaches for preparing chitosan nanoparticles by self-assembly through both procedures, and illustrates the state of the art of their application in drug delivery. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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25 pages, 995 KiB

Open AccessReview

Cosmetics and Cosmeceutical Applications of Chitin, Chitosan and Their Derivatives

by Inmaculada Aranaz, Niuris Acosta, Concepción Civera, Begoña Elorza, Javier Mingo, Carolina Castro, María De los Llanos Gandía and Angeles Heras Caballero

Polymers 2018, 10(2), 213; https://doi.org/10.3390/polym10020213 - 22 Feb 2018

Cited by 260 | Viewed by 18827

Abstract

Marine resources are well recognized for their biologically active substances with great potential applications in the cosmeceutical industry. Among the different compounds with a marine origin, chitin and its deacetylated derivative—chitosan—are of great interest to the cosmeceutical industry due to their unique biological [...] Read more.

Marine resources are well recognized for their biologically active substances with great potential applications in the cosmeceutical industry. Among the different compounds with a marine origin, chitin and its deacetylated derivative—chitosan—are of great interest to the cosmeceutical industry due to their unique biological and technological properties. In this review, we explore the different functional roles of chitosan as a skin care and hair care ingredient, as an oral hygiene agent and as a carrier for active compounds, among others. The importance of the physico-chemical properties of the polymer in its use in cosmetics are particularly highlighted. Moreover, we analyse the market perspectives of this polymer and the presence in the market of chitosan-based products. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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10 pages, 230 KiB

Open AccessReview

Recent Advances of Chitosan Applications in Plants

by Massimo Malerba and Raffaella Cerana

Polymers 2018, 10(2), 118; https://doi.org/10.3390/polym10020118 - 26 Jan 2018

Cited by 156 | Viewed by 9976

Abstract

In recent years, the search for biological methods to avoid the application of chemical products in agriculture has led to investigating the use of biopolymers-based materials. Among the tested biomaterials, the best results were obtained from those based on the biopolymer chitosan (CHT). [...] Read more.

In recent years, the search for biological methods to avoid the application of chemical products in agriculture has led to investigating the use of biopolymers-based materials. Among the tested biomaterials, the best results were obtained from those based on the biopolymer chitosan (CHT). CHT, available in large quantities from the deacetylation of chitin, has multiple advantages: it is safe, inexpensive and can be easily associated with other compounds to achieve better performance. In this review, we have summarized the latest researches of the application of CHT on plant productivity, plant protection against the attack of pathogens and extension of the commercial life of detached fruits. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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