Abstract
Chitin is a structural polysaccharide that is found in crustaceans, insects, fungi and some yeasts. Chitin deacetylation produces chitosan, a well-studied biopolymer with reported chemical and biological properties for diverse potential applications for drug delivery, metal ion absorption, scaffolds and tissue engineering. Most known properties of chitosan have been determined from samples obtained from a variety of sources and in different conditions, this is, from chitosans with a wide range of degrees of N-acetylation (DA) and molecular weight (MW). However, as for any copolymer, the physicochemical and mechanical characteristics of chitosan highly depend on their monomer composition (DA) and chain size (MW). This work presents a simple methodology to produce chitosans with specific and predictive DA and MW. Reaction with acetic anhydride proved to be an efficient method to control the acetylation of chitosan, DAs between 10.6% and 50.6% were reproducibly obtained. In addition to this, MWs of chitosan chains were reduced in a controlled manner in two ways, by ultrasound and by acidic hydrolysis at different temperatures, samples with MWs between 130 kDa and 1300 kDa were obtained. DAs were determined by 1H-NMR and MWs by gel permeation chromatography.
Highlights
Chitin is a structural biopolymer that is found in some marine invertebrates, insects, fungi and yeasts [1], it is a linear homopolymer composed of N-acetylated glucosamine repeat units and it is the second most abundant polysaccharide in nature [2]
Chitosan is generally soluble in dilute aqueous acidic solutions, which allows it to be purified by pH changes and to produce a myriad of forms such as gels, films, porous membranes, filaments, pellets and microparticles by evaporation or precipitation techniques [4]
Acetic anhydride can be used as an acetylation agent in a mild, simple and high-yield reaction that can be controlled by the molar ratio of the reagent to glucosamine repeat units in the substrate
Summary
Chitosan is generally soluble in dilute aqueous acidic solutions, which allows it to be purified by pH changes and to produce a myriad of forms such as gels, films, porous membranes, filaments, pellets and microparticles by evaporation or precipitation techniques [4]. In this regard, chitosan has been extensively studied for its potential in applications like drug delivery [5], water purification and heavy metal absorption [6], materials and coatings with antibacterial activity [7], hydrophilic and porous membranes [8], and scaffolds for tissue engineering [9]
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