Chitosan based materials as chelating agents

Do sada, mali broj istraživanja posvećen je utjecaju dvovalentnih metalnih iona na strukturu i svojstva hidrogelova kitozana. S toga je cilj ovog rada pokazati kako se dodatkom dvovalentnih metalnih iona u dozvoljenim granicama toksičnosti može manipulirati strukturom, fizikalnim i biološkim svojstvima hidrogelova kitozana. Kitozan je netoksičan, biokompatibilan i biorazgradivi polimer koji se može koristiti kao nosač u području tkivnog inženjerstva. Ovisno o stupnju deacetilacije i molekulskoj masi polimera, dodatkom bakrovih i cinkovih iona (Cu2+ i Zn2+) dobivaju se hidrogelovi definirane strukture. Potencijalna metoda priprave hidrogelova kelata kitozan – metalni ion s točno određenom strukturom je proces keliranja. U eksperimentalnom dijelu rada, korištene su dvije vrste kitozana: srednje (C1) i visoke (C2) molekulske mase. Kao metalni prekursori korištene su soli acetata bakra i cinka, dok su koncentrirana otopina natrijevog hidroksida te zasićena atmosfera amonijaka služili kao neutralizirajući agensi. UV-Vis spektroskopska analiza otopina ukazala je na nastanak kelata kitozan – metalni ion. Pripremljeni hidrogelovi postupkom liofilizacije prevedeni su u nosače i kserogelove koji su okarakterizirani primjenom infracrvene spektroskopske analize s Fourierovim transformacijama (FTIR) i kvalitativnom rendgenskom difrakcijskom analizom (XRD). Morfologija i mikrostruktura uzoraka istražena je pomoću pretražnog elektronskog mikroskopa (SEM). Provedene analize ukazuju na interakcije Cu2+ i Zn2+ iona s amino i hidroksilnim skupinama polimera, kao i na nastanak anorganskih kristalnih faza kada je gelirajući agens otopina NaOH. Test citotoksičnosti pokazao je da su kelati kitozana s bakrovim(II) ionima koncentracije veće od 3 mmol dm^-3 citotoksični za Hek293 stanice, dok uzorci s cinkovim(II) ionima za sve istraživane koncentracije nisu pokazali citotoksična svojstva.Up till now, a small number of studies were focused on the influence of divalent metal ions on the structure and properties of chitosan hydrogels. The aim of this work was to manipulate the physical and biological properties of chitosan’s hydrogels by the addition of divalent metal ions at non-toxic concentrations. Chitosan is a non-toxic, biocompatible and biodegradable polymer which can be used as a scaffold in tissue engineering. Depending on the degree of deacetylation and molecular weight of polymer, hydrogels with specific structures can be produced by the addition of copper and zinc ions (Cu2+ and Zn2+). As a potential method, the chelation process can be used to prepare hydrogels of chelate chitosan – metal ion with defined structure. In the experimental part of this work, two types of chitosan were used: medium (C1) and high (C2) molecular weight. Copper and zinc acetate were used as metal precursors, while concentrated solution of sodium hydroxide and saturated ammonia atmosphere were used as the neutralisation agents. The UV-Vis spectrophotometric analysis of the chitosan–M2+ solutions indicated the formation of corresponding chelates. The prepared hydrogels were transformed into scaffolds and xerogels by the lyophilisation method and characterized by Fourier transform infrared spectroscopic analysis (FTIR) and qualitative X-ray diffraction analysis (XRD). The morphology and microstructure of the samples were investigated by scanning electron microscopy (SEM). The analyses indicated interactions of Cu2+ and Zn2+ ions with amino and hydroxyl groups of the polymer, as well as the formation of inorganic crystalline phases with the NaOH as gelling agent. The cytotoxicity test confirmed that chelates with the concentration of copper(II) ion higher than 3 mmol dm^-3 were cytotoxic for Hek293 cells, whereas chelates with zinc(II) ions of whole investigated concentration range did not show cytotoxic properties