Abstract
It is common knowledge that pure alginate hydrogel is more likely to have weak mechanical strength, a lack of cell recognition sites, extensive swelling and uncontrolled degradation, and thus be unable to satisfy the demands of the ideal scaffold. To address these problems, we attempted to fabricate alginate/bacterial cellulose nanocrystals-chitosan-gelatin (Alg/BCNs-CS-GT) composite scaffolds using the combined method involving the incorporation of BCNs in the alginate matrix, internal gelation through the hydroxyapatite-d-glucono-δ-lactone (HAP-GDL) complex, and layer-by-layer (LBL) electrostatic assembly of polyelectrolytes. Meanwhile, the effect of various contents of BCNs on the scaffold morphology, porosity, mechanical properties, and swelling and degradation behavior was investigated. The experimental results showed that the fabricated Alg/BCNs-CS-GT composite scaffolds exhibited regular 3D morphologies and well-developed pore structures. With the increase in BCNs content, the pore size of Alg/BCNs-CS-GT composite scaffolds was gradually reduced from 200 μm to 70 μm. Furthermore, BCNs were fully embedded in the alginate matrix through the intermolecular hydrogen bond with alginate. Moreover, the addition of BCNs could effectively control the swelling and biodegradation of the Alg/BCNs-CS-GT composite scaffolds. Furthermore, the in vitro cytotoxicity studies indicated that the porous fiber network of BCNs could fully mimic the extracellular matrix structure, which promoted the adhesion and spreading of MG63 cells and MC3T3-E1 cells on the Alg/BCNs-CS-GT composite scaffolds. In addition, these cells could grow in the 3D-porous structure of composite scaffolds, which exhibited good proliferative viability. Based on the effect of BCNs on the cytocompatibility of composite scaffolds, the optimum BCNs content for the Alg/BCNs-CS-GT composite scaffolds was 0.2% (w/v). On the basis of good merits, such as regular 3D morphology, well-developed pore structure, controlled swelling and biodegradation behavior, and good cytocompatibility, the Alg/BCNs-CS-GT composite scaffolds may exhibit great potential as the ideal scaffold in the bone tissue engineering field.
Highlights
Bone tissue engineering is one of the most promising approaches to achieve bone repair and regeneration, making use of a combination of cells, engineering and materials together with suitable biochemical and physicochemical factors [1,2]
Alg/bacterial cellulose nanocrystals (BCNs)-CS-GT composite scaffolds were successfully constructed by endogenous cross-linking of the HAP-GDL complex and the LBL assembly of polyelectrolytes, using BCNs as the reinforcing agent
The characterization of composite scaffolds indicated that the Alg/BCNs-CSGT composite scaffolds had a regular 3D morphology and a well-developed pore structure
Summary
Bone tissue engineering is one of the most promising approaches to achieve bone repair and regeneration, making use of a combination of cells, engineering and materials together with suitable biochemical and physicochemical factors [1,2]. Porous cellulose scaffolds and their hybrids with chitosan and alginate were fabricated for various applications in tissue engineering [21] Another versatile method to improve the mechanical properties of alginate hydrogel is internal gelation, which allows homogeneous alginate hydrogel to be obtained by the controlled release of Ca2+ from the insoluble calcium salts, such as hydroxyapatite (HAP), calcium carbonate (CaCO3) and calcium sulfate (CaSO4), in the presence of D-glucono-δ-lactone (GDL) [1,10,22]. The surface modification of the scaffold can be carried out by some anchoring processes such as cross-linking [26,27], benzyl-protected phosphonic anchors [28], thiol and phosphonate anchors [29], dopamine anchoring [30,31], photopolymerization [32] and layer-by-layer assembly [33] Among these methods, a simple and versatile technique of layer-by-layer (LBL) electrostatic assembly of polyelectrolytes can be applied to improve the mechanical and biological properties of alginate hydrogel. CCelellvl ivabiaibliitlyityof o(Af )(AM) GM63G6ce3llcseallnsda(nBd) M(BC) 3MT3C-3ET13c-eEl1ls cceullltsucreudltuornedtheoncotmhepocsoimtepsocasfitfeoldscsaffoforl2dsanfodr52daanysd, 5rAedlsgpa/ye0c.s4t,i%rveesBlpyCe:Nc(tasi-v)CeASly-lG:g(-TaC)aSAn-GdlgT(-f,C) (SAb-l)GgT/A0,l.(5gb%/)0.AB1%ClgN/B0sC-.C1N%Ss-G-BCCTS.N-*Gsr-TeC,pSr(-ecGs)eTAn, t(lscg)p/0A
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