Fast degrading polymer networks based on carboxymethyl chitosan

[EN] In this work macroporous membrane for mesenchymal stem cells, MSCs, transplant has been developed. The membranes support cell seeding and proliferation and completely degrade in less than one week in "in vitro" culture. The biodegradable material is a polymer network based on carboxymethyl chitosan( a water soluble modification of chitosan) crosslinked by poly(epsilon-caprolactone) PCL, fragments which are susceptible to hydrolytic degradation. Synthesis was performed in solution in a common solvent for the two components of the network. The gel fraction was assessed by extraction in selective solvents. Physical characterization of networks of varying composition included water sorption capacity and the crystallinity of poly(epsilon-caprolactone) in the network. In this way polymer networks are synthesized that lose between 66 +/- 5% and 89 +/- 1% of their mass when immersed in water for 28 days. The same weight loss is attained in enzymatic medium in only 4 days. Porcine bone marrow MSCs were seeded in macroporous membranes to show cell viability, and proliferation up to 7 days culture when the biomaterial is completely dissolved in the medium.Gamiz Gonzalez, MA.; Guldrís-Prada, P.; Antolinos Turpín, CM.; Ródenas Rochina, J.; Vidaurre, A.; Gómez Ribelles, JL. (2017). Fast degrading polymer networks based on carboxymethyl chitosan. Materials Today Communications. 10:54-66. doi:10.1016/j.mtcomm.2017.01.005S54661

Surfactant-polyelectrolyte complexes based on chitin derivatives

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Effect of polymer-precursor molecular mass on the formation and properties of covalently crosslinked chitosan cryogels

Features of cryotropic gelation in moderately frozen solutions of chitosan samples that have various molecular masses and that are covalently crosslinked with glutaraldehyde are studied. It is shown that the chain length of the macromolecular precursor, chitosan, affects the yield of the gel fraction; the swelling ability of the polymer phase of wide-pore cryogels; the dimensions of the gross capillary pores of cryogels; and, as a consequence, the hydrodynamic parameters of columns packed with a permeable continuous matrix based on the spongy gel material. The characteristics of the latter depend in a sophisticated manner on the molecular mass of the polymer used for formation of cryogels, a circumstance that is associated with competition of differently directed factors, specifically cryoconcentration effects, a strong increase in the viscosity of the reaction medium in the unfrozen liquid microphase, kinetic features of chain crosslinking at a high concentration of reagents, etc. Therefore, in each particular case, individual conditions for specific combination of the above-mentioned parameters of the process arise. As a result, a complex dependence corresponding is observed for the efficiency of cryostructuring of the chitosan-glutaraldehyde system and for the properties of the resulting cryogels

Synthesis and characteristics of cryogels of chitosan crosslinked by glutaric aldehyde

The mechanism of cryotropic gelation in moderately frozen solutions of chitosan crosslinked by glutaric aldehyde is studied. Chitosan cryogels with large pores are synthesized at a low content of crosslinking agent in the reaction mixture or under conditions that do not lead to gelation at temperatures above 0 degrees C. The dependences of the yield of gel fractions, the degree of swelling of the polymer phase of cryogels, and the hydrodynamic characteristics of cryogels on the temperature of synthesis are shown to be extremal. This result may be explained by the competition between the cryoconcentration of reagents in the nonfrozen liquid microphase, which assists the development of a crosslinked polymer network, and such factors as an increase in the viscosity of the reaction mixture and a reduced reagent mobility, which prevent gelation. The morphology of chitosan cryogels is studied, and the character of the macroporous structure of the samples prepared at different temperatures is shown to exert a stronger effect on the hydrodynamic characteristics of a cryogel than the degree of swelling of crosslinked polymers in the walls of its macropores

Biodegradable chitosan-poly(epsilon-caprolactone) dialdehyde copolymer networks for soft tissue engineering

[EN] Chitosan/PCL block-copolymer networks were synthesized using different amounts of aldehyde end capped polycaprolactone as crosslinking agent. The crosslinking reaction was performed by dissolving both components in the common solvent hexafluoroisopropanol (HFIP). The formation of the network was confirmed by solubility tests in good solvents of both components. The resulting composition was determined by thermogravimetric analysis. The hydrophilic/hydrophobic networks behave as hydrogels; water sorption at pH7 is around 70% that of pure chitosan for a network containing 36% PCL blocks. The PCL domains were not able to crystallize, except for the CHT-64 sample as shown by DSC and X-ray diffraction. Enzymatic degradation of these networks is quite fast, thus, the network with 36% PCL presented a remaining weight of 22 +/- 1% of their initial mass after 28 days of degradation in lipase. Nevertheless in purely hydrolytic degradation, the remaining weight was 86+3% for the same time and composition.The authors gratefully acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness through the MAT2013-46467-C4-1-R and MAT2016-76039-C4-1-R Project, including FEDER funds. CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Institute de Salud Carlos III with the assistance of the European Regional Development Fund. MAGG acknowledges a grant from the BES-2011-044740.Gámiz González, MA.; Vidaurre, A.; Gómez Ribelles, JL. (2017). Biodegradable chitosan-poly(epsilon-caprolactone) dialdehyde copolymer networks for soft tissue engineering. Polymer Degradation and Stability. 138:47-54. https://doi.org/10.1016/j.polymdegradstab.2017.02.005S475413