Abstract
Different hydrogels were prepared starting from natural or semi-synthetic polysaccharides (carboxymethylcellulose, hyaluronic acid and chitosan) which were cross-linked by the addition of a cross-linking agent chosen according to the chemical groups present along the polymer chains. The cross-linking reaction allows for the formation of a three-dimensional network made of covalent bonds between the polymer chains, which is stable under physiological conditions. The presence of a substantial amount of water within the polysaccharide matrices makes such systems unique among hydrophilic gels. Water itself is responsible for some of their peculiar characteristics, one of which is their injectability which makes these hydrogels suitable for using as matrices for mini-invasive surgery and localized therapy.
Highlights
The use of natural polymers, or biopolymers, as materials is not new
The synthesis of CMC- and Hyal-based hydrogels exploits the formation of an amide bond between the carboxylate groups of the polymer chains and the primary amine groups of
1,3 diaminopropane (DAP), which is added to the polymer aqueous solution as the cross-linking agent of the polymer chain. 1-ethyl-3-[3-(dimethyl-amino)propyl] carbodiimide hydrochloride (EDC) works as the activating agent of the carboxylic groups, and N-hydroxysuccinimide (NHS) as the proton exchanger [26]
Summary
The use of natural polymers, or biopolymers, as materials is not new. For instance, in nature, cellulose has always been used to provide structure for plants, chitin as the exoskeleton of crawfish and shrimps, collagen for mechanical support in connective tissues, and silk in spider’s webs. CMC and CHT hydrogels, once pre-synthesized can be extensively purified in order to remove all impurities and fully characterized They can be squeezed through a syringe needle, offering the advantage of opening up new perspectives in minimally-invasive surgery by using a pre-formed safe material with well known chemical and mechanical properties [7]. The second type is bound water, which is directly bound to the polymer chain through hydrophilic groups or via hydrogen bonds It is an integral part of the hydrogel structure and cannot separated from the hydrogel. This paper deals with the physico-chemical characterization of the polysaccharide based hydrogels, focused to understand the role of water molecules in affecting the structure and the properties of the material in terms of swelling degree, rheological properties and infrared analysis either in the native state or after a mechanical stress
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