Novel non-cytotoxic alginate–lignin hybrid aerogels as scaffolds for tissue engineering
This paper presents a novel approach toward the production of hybrid alginate–lignin aerogels. The key idea of the approach is to employ pressurized carbon dioxide for gelation. Exposure of alginate and lignin aqueous alkali solution containing calcium carbonate to CO2 at 4.5 MPa resulted in a hydrogel formation. Various lignin and CaCO3 concentrations were studied. Stable hydrogels could be formed up to 2:1 (w/w) alginate-to-lignin ratio (1.5 wt% overall biopolymer concentration). Upon substitution of water with ethanol, gels were dried in supercritical CO2 to produce aerogels. Aerogels with bulk density in the range 0.03–0.07 g/cm3, surface area up to 564 m2/g and pore volume up to 7.2 cm3/g were obtained. To introduce macroporosity, the CO2 induced gelation was supplemented with rapid depressurization (foaming process). Macroporosity up to 31.3 ± 1.9% with interconnectivity up to 33.2 ± 8.3% could be achieved at depressurization rate of 3 MPa/min as assessed by micro-CT. Young's modulus of alginate–lignin aerogels was measured in both dry and wet states. Cell studies revealed that alginate–lignin aerogels are non-cytotoxic and feature good cell adhesion making them attractive candidates for a wide range of applications including tissue engineering and regenerative medicine.
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The research leading to these results has received funding from Fundação da Ciência e Tecnologia (FCT) through the project ENIGMA – PTDC/EQU-EPR/121491/2010, and from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. REGPOT-CT2012-316331-POLARIS and from Project “Novel smart and biomimetic materials for innovative regenerative medicine approaches (Ref.: RL1 – ABMR – NORTE-01-0124-FEDER-000016)” cofinanced by North Portugal Regional Operational Programme (ON.2-O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF) and FEDER. Authors are grateful for financial support from Fundação da Ciência e Tecnologia (FCT) through the grant BIM/PTDC/EQU-EPR/121491/2010/ENIGMA, bilateral cooperation project FCT-DAAD 57036335, and from DFG (projects SM 82/8-1 and SM 82/8-2). Pavel Gurikov acknowledges DAAD for supporting him through a postdoctoral fellowship.