A Novel Approach to Design Chitosan-Polyester Materials for Biomedical Applications

Abstract

A novel approach to design chitosan-polyester materials is reported. The method is based on mechanical activation and effective intermixing of the substrates under high pressure and shear deformation in the course of solid-state reactive blending. The marked departure of this approach from previous practice resides on exploitation of a variety of chemical transformations of the solid polymers that become feasible under conditions of plastic flow. Low temperatures (aboveTgbut below the melting points of the crystalline polymers) are maintained throughout the process, minimizing mechanical and oxidative degradation of the polymers. Morphology as well as structural, mechanical, and relaxation properties of those prepared blends of chitosan with semicrystalline poly(L,L-lactide) and amorphous poly(D,L-lactide-co-glycolide) has been studied. Grafting of polyester moieties onto chitosan chains was found to occur under employed pressures and shear stresses. The prepared polymer blends have demonstrated an amphiphilic behavior with a propensity to disperse in organic solvents that widens possibilities to transform them into promising materials for various biomedical applications.

Polylactide-based microspheres prepared using solid-state copolymerized chitosan and d , l -lactide

“…Thus, the grafting mainly proceeded via chitosan amino group acetylation.As shown in theTable 2, the degree of N-substitution (grafting sites) calculated using CNH content of the fractions after long-term dialysis varied in a range of 0.19-0.41, while the polymerization degree of the branched oligolactide chains reached up to 10. The achieved substitution degree as well as the proposed reaction channel were in a good correlation with our previous results on chitosan acetylation by hydroxycarboxylic acid through SSRB technique[20]. When the molar ratio of lactide to chitosan increased from 0.5 to 1, the number of grafting sites significantly increases, while degree of polymerization of the side chains was affected slightly.…”

“…Mechanochemical reactions under the action of shearing forces and local pressures have been described earlier [16][17][18]. This approach to polymer modification has been successfully applied for the preparation of a number of chitosan-based copolymers and derivatives with high yield of the desired products [19][20][21].…”

Chitosan‐g‐Polyester Microspheres: Effect of Length and Composition of Grafted Chains

“…Indeed polyester grafting could proceed through N ‐acylation of chitosan amino groups with the polyester terminal carboxyl groups or through aminolysis or alcoholysis of the ester bonds mediated with the chitosan functional groups. Statistical nature of these reactions could give rise to a broad range of macromolecular structures in our copolymers, although the higher reactivity of amino groups due to their relatively higher nucleophilicity should be certainly dominated . Unfortunately, classical analytical methodologies could not give us accessibility to the detailed macromolecular features of the copolymers.…”

“…A chitosan type II ( M w = 350 kDa; acetylation degree of 0.14) was purchased from Sonat (Russia). Graft copolymers, made from chitosan and oligo/polyesters, were prepared by solid‐state synthesis in ISPM RAS (Russia) . This synthetic route relies on the generation of reactive sites in polymer chains and chemical reaction that is induced by the direct absorption of mechanical energy .…”

“…The other set of copolymers, namely labeled CP‐40/60, CP‐60/40, were prepared by solid‐state reactive co‐extrusion of PLLA and chitosan type I. The copolymers were analyzed using fractional analysis, UV, DSC, FTIR, and 1 H‐NMR‐spectroscopy according to methods published earlier . The copolymers were used for microparticle fabrication without any additional purification.…”