Hydrogel systems and their role in neural tissue engineering

Abstract

Neural tissue engineering (NTE) is a rapidly progressing field that promises to address several serious neurological conditions that are currently difficult to treat. Selecting the right scaffolding material to promote neural and non-neural cell differentiation as well as axonal growth is essential for the overall design strategy for NTE. Among the varieties of scaffolds, hydrogels have proved to be excellent candidates for culturing and differentiating cells of neural origin. Considering the intrinsic resistance of the nervous system against regeneration, hydrogels have been abundantly used in applications that involve the release of neurotrophic factors, antagonists of neural growth inhibitors and other neural growth-promoting agents. Recent developments in the field include the utilization of encapsulating hydrogels in neural cell therapy for providing localized trophic support and shielding neural cells from immune activity. In this review, we categorize and discuss the various hydrogel-based strategies that have been examined for neural-specific applications and also highlight their strengths and weaknesses. We also discuss future prospects and challenges ahead for the utilization of hydrogels in NTE.

Keywords: axonal growth; chemical cues; hydrogel; neural tissue engineering; physical guidance.

Figure 1.

Schematic overview depicting the different characteristics of hydrogel systems that can be used for neuronal growth and differentiation. (Online version in colour.)

Figure 2.

Edge and contrast-enhanced image of a calcein-stained PC-12 cell encapsulated in a collagen type I–alginate hydrogel matrix, showing an extended neurite manoeuvring through the hydrogel matrix (depicted by arrows). (Online version in colour.)

Figure 3.

(a,b) Representative scanning electron microscopy images of the 3D-PEGDA-hydrogel scaffold cultured with neuro2A cells. (c) Representative Z-stacked two-photon confocal image depicting the presence of neuro-2A cellular network (DAPI, blue; phalloidin, red; β-tubulin, green). (All images were kindly provided by Dr Angelo Accardo, TU Delft (Delft University of Technology), Department of Precision and Microsystems Engineering (PME), The Netherlands.) (Online version in colour.)