Chitosan—A versatile semi-synthetic polymer in biomedical applications

Chitosan-based biomaterials for tissue engineering

This review describes the most common methods for recovery of chitin from marine organisms. In depth, both enzymatic and chemical treatments for the step of deproteinization are compared, as well as different conditions for demineralization. The conditions of chitosan preparation are also discussed, since they significantly impact the synthesis of chitosan with varying degree of acetylation (DA) and molecular weight (MW). In addition, the main characterization techniques applied for chitin and chitosan are recalled, pointing out the role of their solubility in relation with the chemical structure (mainly the acetyl group distribution along the backbone). Biological activities are also presented, such as: antibacterial, antifungal, antitumor and antioxidant. Interestingly, the relationship between chemical structure and biological activity is demonstrated for chitosan molecules with different DA and MW and homogeneous distribution of acetyl groups for the first time. In the end, several selected pharmaceutical and biomedical applications are presented, in which chitin and chitosan are recognized as new biomaterials taking advantage of their biocompatibility and biodegradability.

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Chitin and Chitosan Preparation from Marine Sources. Structure, Properties and Applications

The production of future transportation fuels and chemicals requires the deployment of new catalytic processes that transform biomass into valuable products under competitive conditions. Furfural has been identified as one of the most promising chemical platforms directly derived from biomass. With an annual production close to 300 kTon, furfural is currently a commodity chemical, and the technology for its production is largely established. The aim of this review is to discuss the most relevant chemical routes for converting furfural to chemicals, biofuels, and additives. This review focuses not only on industrially produced chemicals derived from furfural, but also on other not yet commercialised products that have a high potential for commercialisation as commodities. Other chemicals that are currently produced from oil but can also be derived from furfural are also reviewed. The chemical and engineering aspects such as the reaction conditions and mechanisms, as well as the main achievements and the challenges still to come in the pursuit of advancing the furfural-based industry, are highlighted.

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Furfural: a renewable and versatile platform molecule for the synthesis of chemicals and fuels

The total annual production of synthetic dye is more than 7 × 105 tons. Annually, through only textile waste effluents, around one thousand tons of non-biodegradable textile dyes are discharged into natural streams and water bodies. Therefore, with growing environmental concerns and environmental awareness there is a need for the removal of dyes from local and industrial water effluents with a cost effective technology. In general, these dyes have been found to be resistant to biological as well as physical treatment technologies. In this regard, heterogeneous advanced oxidation processes (AOPs), involving photo-catalyzed degradation of dyes using semiconductor nanoparticles is considered as an efficient cure for dye pollution. In the last two decades TiO2 has received considerable interest because of its high potential as a photocatalyst to degrade a wide range of organic material including dyes. This review starts with (i) a brief overview on dye pollution, dye classification and dye decolourization/degradation strategies; (ii) focuses on the mechanisms involved in comparatively well understood TiO2 photocatalysts and (iii) discusses recent advancements to enhance TiO2 photocatalytic efficiency by (a) doping with metals, non-metals, transition metals, noble metals and lanthanide ions, (b) structural modifications of TiO2 and (c) immobilization of TiO2 by using various supports to make it a flexible and cost-effective commercial dye treatment technology.

https://pubs.rsc.org/EN/content/articlepdf/2014/ra/c4ra06658h

Principles and mechanisms of photocatalytic dye degradation on TiO 2 based photocatalysts: a comparative overview

Chitin and its deacetylated derivative chitosan are natural polymers composed of randomly distributed � -(1-4)- linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). Chitin is insoluble in aqueous media while chitosan is soluble in acidic conditions due to the free protonable amino groups present in the D-glucosamine units. Due to their natural origin, both chitin and chitosan can not be defined as a unique chemical structure but as a fam- ily of polymers which present a high variability in their chemical and physical properties. This variability is related not only to the origin of the samples but also to their method of preparation. Chitin and chitosan are used in fields as different as food, biomedicine and agriculture, among others. The success of chitin and chitosan in each of these specific applica- tions is directly related to deep research into their physicochemical properties. In recent years, several reviews covering different aspects of the applications of chitin and chitosan have been published. However, these reviews have not taken into account the key role of the physicochemical properties of chitin and chitosan in their possible applications. The aim of this review is to highlight the relationship between the physicochemical properties of the polymers and their behaviour. A functional characterization of chitin and chitosan regarding some biological properties and some specific applications (drug delivery, tissue engineering, functional food, food preservative, biocatalyst immobilization, wastewater treatment, molecular imprinting and metal nanocomposites) is presented. The molecular mechanism of the biological properties such as biocompatibility, mucoadhesion, permeation enhancing effect, anticholesterolemic, and antimicrobial has been up- dated.

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Functional Characterization of Chitin and Chitosan

Chitosan nanoparticles and microspheres for the encapsulation of natural antioxidants extracted from Ilex paraguariensis

The effect of preparation processes on the physicochemical characteristics and antibacterial activity of chitooligosaccharides.

Among several commercial enzymes screened for chitosanolytic activity, Neutrase 0.8L (a protease from Bacillus amyloliquefaciens) was selected in order to obtain a product enriched in deacetylated chitooligosaccharides (COS). The hydrolysis of different chitosans with this enzyme was followed by size exclusion chromatography (SEC-ELSD), mass spectrometry (ESI-Q-TOF), and high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Neutrase 0.8L converted 10 g/L of various chitosans into mostly deacetylated oligosaccharides, yielding approximately 2.5 g/L of chitobiose, 4.5 g/L of chitotriose, and 3 g/L of chitotetraose. We found out that the neutral protease was not responsible for the chitosanolytic activity in the extract, while it could participate in the deacetylating process. The synthesized COS were tested in vitro for their neuroprotective (toward human SH-S5Y5 neurons) and anti-inflammatory (in RAW macrophages) activities, and compared with other functiona...

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Marian Mengíbar

Papers

Functional Characterization of Chitin and Chitosan

Chitosan nanoparticles and microspheres for the encapsulation of natural antioxidants extracted from Ilex paraguariensis

The effect of preparation processes on the physicochemical characteristics and antibacterial activity of chitooligosaccharides.

Enzymatic production of fully deacetylated chitooligosaccharides and their neuroprotective and anti-inflammatory properties

Influence of the physico-chemical characteristics of chito-oligosaccharides (COS) on antioxidant activity