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Scientists First Moscow state medical University named after I. M. Sechenov using 3D printing have created biocompatible structures based on chitin shells of crabs. The method allows to obtain structures of the desired shape for different biomedical tasks, including replacement of damaged soft tissues of the body. Article on the study published in Marine Drugs.
50 to 70% of the weight of all caught crabs in the world are the shells and other by-products. Typically, such waste is destroyed, requiring additional costs, and only a small portion is recycled. Meanwhile, marine crustaceans contain large amounts of chitin. This polysaccharide is often found in nature, made, for example, the exoskeletons of insects. If you remove from chitin by chemical acetyl groups part SN3SO, it is possible to obtain chitosan — a biopolymer with a unique set of biological and physico-chemical characteristics.
It is biocompatible, that is not cause by implanting in the body of inflammation or immune responses, antifungal, and antimicrobial properties and in the body eventually decomposes into non-toxic components. Therefore, chitosan and its derivatives are promising compounds for Biomedicine. On their basis it is possible to create new types of biocompatible structures for repairing damaged tissues or carriers for drug delivery.
the Classic method of obtaining chitosan from chitin requires the processing of raw materials, aggressive chemicals, such as concentrated alkaline solutions. Due to the small yield of chitosan and toxicity of the solvents required, such methods are not suitable for industrial use. The authors of the articles in Marine Drugs suggested more environmentally friendly method of modification of chitin — mechanochemical synthesis. The method is a triple impact on the solid mixture of reactants, pressure and shear stresses. It requires less alkali than in the classical chemical synthesis, as solvents, catalysts and initiators of chemical processes are not used. Obtained in this method, the chitosan can be used in medical purposes without further purification from toxic residues.
the same method the researchers used for the synthesis of chitosan-based several of its derivatives with different content (from 5 to 50%) of the allyl groups. With such a modification in the structure of chitosan is introduced allyl group which are derivatives of propylene, the organic substituents with a double bond between carbon atoms. Due to this, chitosan derivatives able to form under the action of UV and laser radiation and with the participation of the photoinitiator photossite film or three-dimensional structures of any complex geometry.
the film made of chitosan derivatives were obtained by photo-polymerization method: a polymer solutions in acetic acid was placed on a plastic substrate and irradiated with ultraviolet light to solidify. And for the formation of three-dimensional structures, the researchers have used laser stereolithography, one of the technologies of 3D printing. This is a simple and quick method of creating three-dimensional models that do not require expensive equipment. It lies in the layering formation in a given three-dimensional computer model of a frame scaffold. In the solution obtained chitosan derivative was introduced photoinitiator, and then ran the reaction of photopolymerization using a laser study. The resulting structures were initially frozen and then dried in a vacuum chamber — this method is called freeze-drying. The material structures became porous.
the Final part of the study was the implantation of the formed structures of white rats. Implants placed under the skin of rats in the interscapular region. The experiment in vivo, i.e. in live animals, continued for 90 days, and during this time, the implants showed no signs of toxicity, indicating the biocompatibility of the material of scaffolds. Scientists have found that biodegradation of implanted structures began only after 60 days of experiment. In the future, the researchers hope to learn how to manage this process and create implants with the desired speed barazarte.
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