Table 1. Classification of Scaffolds with Their Most Important Characteristics.

Hydrogels
natural-based	synthetic	in nervous tissue
advantages:	advantages:	• retention of peptides and extracellular proteins stimulating axonal growth and myelination
• low inflammatory responses	• controllable chemical and physical properties	• neurotrophic growth factors and drug release
• biocompatibility and biodegradability	• well-defined mechanical and degradation properties	• conductive hydrogels can enhance the regeneration process through electrical stimulation
• low cost	• large scale productions
• easy extraction and synthesis	• low batch-to-batch variation
• low toxicity and nontoxic degradation	• stimuli responsiveness
• mechanical properties similar to those of living tissues
disadvantages:	disadvantages:
• difficult processability	• limited biocompatibility and biodegradability
• nonoptimal mechanical properties	• possible toxicity
• batch-to-batch variability
• possible too high degradation rate

Nanofibers
electrospinning	molecular self-assembling	in nervous tissue
advantages:	advantages:	• aligned fibers guiding axonal growth
• fabrication of biomimetic structures similar to the scale and morphology of ECM	• easy processability	• neurotrophic factors and drugs release
• cost-effective approach	• massive production is possible	• electrical stimulation is possible to enhance the regeneration process
• nanofiber properties can be tailored for the specific tissue application		• SAP degradation products can enhance repair and regeneration
• high surface area		• glial scar inhibiting SAP scaffolds
disadvantages:	disadvantages:
• low porosity	• lower ability to control the scale of the resulting fibers
• not applicable on all types of polymers	• time-consuming process
• poor loading efficiency and low porosity	• only lab scale production
• possible unstable structures	• not applicable on all types of polymers