Novel non-cytotoxic alginate–lignin hybrid aerogels as scaffolds for tissue engineering

Abstract

a b s t r a c tThis 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 CO 2 at 4.5 MPa resulted in a hydrogel formation. Various lignin and CaCO 3 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 CO 2 to produce aerogels. Aerogels with bulk density in the range 0.03-0.07 g/cm 3 , surface area up to 564 m 2 /g and pore volume up to 7.2 cm 3 /g were obtained. To introduce macroporosity, the CO 2 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.

Preparation of Biopolymer Aerogels Using Green Solvents

“…Fast depressurization can lead to increased macroporosity of the gels. This phenomena can be applied for tissue engineering applications where macroporosity of the material with interconnectivity is an important feature for the growth and proliferation of cells 13,14 . In addition, the crosslinking degree in Protocol Section 1 plays an important role in the syneresis and swelling property of the amidated pectin hydrogels.…”

Strengthening effect of nanofibrillated cellulose is dependent on enzymatically oxidized polysaccharide gel matrices

“…The high surface area of aerogels is needed for some applications, particularly for active compound/ drug release (García-González, Alnaief, & Smirnova, 2011;Tsutsumi et al, 20014). However, biopolymer-based aerogels with lower surface area and larger pore size may be utilized in tissue engineering, for example (Podlipec et al, 2014;Quraishi et al, 2015). Freeze-dried aerogels having supermacroporous structures with pores of 40 to 200 μm were successfully utilized as tissue scaffold (Bhat, Tripathi & Kumar, 2011;Swieszkowski, Bersee & Kurzydlowski, 2006).…”

“…Freeze-dried aerogels having supermacroporous structures with pores of 40 to 200 μm were successfully utilized as tissue scaffold (Bhat, Tripathi & Kumar, 2011;Swieszkowski, Bersee & Kurzydlowski, 2006). Supercritical drying using CO 2 is successfully applied commercially to produce aerogels; however, it offers little control over the meso-and macropors distribution (Quraishi et al, 2015).…”

Hybrid alginate based aerogels by carbon dioxide induced gelation: Novel technique for multiple applications

“…This synergy of properties has prompted to view biopolymer aerogels as promising candidates for a wide gamut of applications. Up-to-date reports on biopolymer aerogels describe their use for thermal insulation [3][4][5][6][7][8], tissue engineering and regenerative medicine [9], drug delivery systems [10,11], functional foods [12], as catalysts and sensors [13,14], adsorbents [15][16][17]and as starting materials for carbon aerogels [18] and porous mixed-oxides [13,19].…”

“…On the other hand, gelation can also be performed under CO 2 pressure (3 -15 MPa) using its weak acidity in water medium. CO 2 induced gelation has been studied for some biopolymer systems such as silk protein [24,25], alginate [8]and alginate-lignin [9].It is thereby advantageous to reduce the number of steps in aerogel production as far as possible by combining gelation, solvent exchange and sc-drying into an integrated approach using CO 2 . This one-pot technique has recently been exemplified in theproduction of calcium alginate aerogels [8].…”