Indirect 3D bioprinting and characterization of alginate scaffolds for potential nerve tissue engineering applications

Abstract

<p>Low-concentration hydrogels have favorable properties for many cell functions in tissue engineering but are considerably limited from a scaffold fabrication point of view due to poor three-dimensional (3D) printability. Here, we developed an indirect-bioprinting process for alginate scaffolds and characterized the potential of these scaffolds for nerve tissue engineering applications. The indirect-bioprinting process involves (1) printing a sacrificial framework from gelatin, (2) impregnating the framework with low-concentration alginate, and (3) removing the gelatin framework by an incubation process, thus forming low-concentration alginate scaffolds. The scaffolds were characterized by compression testing, swelling, degradation, and morphological and biological assessment of incorporated or seeded Schwann cells. For comparison, varying concentrations of alginate scaffolds (from 0.5 to 3%) were fabricated and sterilized using either ultraviolet light or ethanol. Results indicated that scaffolds can be fabricated using the indirect-bioprinting process, wherein the scaffold properties are affected by the concentration of alginate and sterilization technique used. These factors provide effective means of regulating the properties of scaffolds fabricated using the indirect-bioprinting process. Cell-incorporated scaffolds demonstrated better cell viability than bulk gels. In addition, scaffolds showed better cell functionality when fabricated with a lower concentration of alginate compared to a higher concentration. The indirect-bioprinting process that we implemented could be extended to other types of low-concentration hydrogels to address the tradeoffs between printability and properties for favorable cell functions.</p>

Fundamentals and Current Strategies for Peripheral Nerve Repair and Regeneration

“…Marked neurite outgrowth was evident over 150 μm, indicating that pores and channels created within the alginate were providing a favourable environment for neurite development. Other studies have focused on using alginate as NGCs luminal fillers, with promising results[159][160][161].…”

Multicomponent polysaccharide alginate-based bioinks

“…75,76 The group of Chen tried to overcome these problems by printing low concentration alginate bioinks incorporating Schwann cells on pre-formed sacrificial gelatin scaffolds. 77 The bioinks were prepared using 0.5, 1.5 and 3.0% wt alginate concentrations and displayed differences in their swelling and degradation profiles. The scaffolds were fabricated by an indirect bioprinting process, which involved different steps (Fig.…”

“…38 We have described various examples of bioink formulations for neural scaffolds in which alginate was the only component. 35,[73][74][75][76][77][78] Such scaffolds were fabricated using alginate concentrations between 0.5-3.0% wt/vol, with the best results in terms of cell growth at low alginate concentrations. 75,76 The use of gelatin sacrificial templates allowed materials with higher mechanical stability and better shape fidelity.…”

“…75,76 The use of gelatin sacrificial templates allowed materials with higher mechanical stability and better shape fidelity. 77,78 The combination of alginate with other polysaccharides is a way of avoiding the use of sacrificial templates. Examples of multicomponent bioinks were obtained by combining alginate with agarose (1.5% wt/vol) 87,88 or hyaluronic acid (0.25% wt/vol), 76,149,150 which provided the necessary mechanical support to the 3D printed structures (Fig.…”

3D Printing and Bioprinting Nerve Conduits for Neural Tissue Engineering

“…Compared with implanted collagen sponge and fibrin glue, nerve regeneration in alginate hydrogel is much better. Saman et al [ 73 ] used indirect 3D printing to prepare a sodium alginate hydrogel scaffold that embeds Schwann cells at the expense of gelatin frames. The results of the study showed that Schwann cells in this scaffold were more viable than those in bulk gel.…”