Table 1 Summary of synthetic polymeric materials commonly used in constructing bioscaffolds.

PCL

Well-controllable properties and high biological safety²⁴⁴; high crystallinity, suitable mechanical strength, bioabsorbable and biocompatible nature²⁴⁵.

Slow degradation rate in vivo²⁴⁶; hydrophobicity-mediated poor cell attachment^247,248.

PCL scaffolds loaded with activated Schwann cells and iPSCs-NSCs increased tissue remodeling and promoted motor function recovery in transected spinal cord model rats²⁴⁹.

Using PCL as a drug delivery system to deliver uric acid, Singh and coworkers successfully protected spinal cord tissue from excitotoxic injury in an in vitro injury model²⁵⁰.

PEG

Stability, nontoxicity, biocompatibility²⁵¹.

Relatively low drug loading capacity²⁵¹; poor efficacy when applied alone²⁵².

Polyethylene glycol microgel scaffolds can be used to deliver human bone marrow MSCs (hMSCs) and promote their secretory potential to repair nerve damage²⁵³.

Before cell transplantation, utilizing macroporous PEG tubes to serve as a soft substrate can create a more permissive injection site, thus improving the survival of mouse embryonic day 14 spinal progenitors²⁵⁴.

PLA

Suitable processability, mechanical strength, biocompatibility and biodegradability^255,256.

Hydrophobicity, low impact toughness and slow degradation rate²⁵⁷.

Polypyrrole/PLA nanofibrous scaffolds loaded with bone marrow MSCs can inhibit glial scarring, promote axonal regeneration, bridge lesion gaps, and restore nerve electrical conduction⁸³.

In an SCI animal model, codelivery of DHA and BDNF from a PLA/DHA/BDNF electrospun aligned core–shell fibrous membranes could provide neuroprotection and promote neuroplasticity changes in recovered neuronal tissue²⁵⁸.

PLGA

Adjustable physicochemical properties²⁵⁹; favorable thermal stability, biocompatibility, biodegradability, sustained-release properties, and film-forming ability²⁴⁵.

Weak electrical conductivity²⁶⁰; high hydrophobicity²⁶¹.

Local delivery of IGF-1 and BDNF immobilized to PLGA/GO hybrid nanofibers could reduce cavity formation, increase the number of neurons at the injury site, and significantly improve functional locomotor recovery after SCI in rats²⁶².

In SCI model mice, copolymer PLGA-PEI-mPEG loaded ACPP and etanercept suppressed the inflammation and promoted neuronal survival and locomotor recovery²⁶³.

PVA

Hydrophilicity, swellability, nontoxicity, biodegradability, and ease of conversion to hydrogel²⁴⁵; sufficient mechanical strength for tissue engineering⁷⁴.

Relatively low biocompatibility and slow degradability⁷⁴.

As an implantable drug delivery system, genistein based on chitosan/PVA nanofibers decreased the levels of nitric oxide (NO), malondialdehyde and tumor necrosis factor-α (TNF-α), while causing an increase in the activity of super oxide dismutase and the level of interleukin-10 (IL-10) in the injured spinal cord tissue of rats, thereby ameliorating the marked oxidative damage and inflammation induced by SCI²⁶⁴.

pHEMA

Low interfacial tension in the liquid state and similar mechanical properties to the spinal cord in the hydrogel state^265,266.

Nonbiodegradability; insufficient functional recovery after SCI after hydrogel implantation⁷⁴.

Following the implantation of iPSC-NPs into laminin-coated pHEMA-MOETACL hydrogels, the material was found to integrate into the chronic injured spinal cord, reducing cavitation and supporting iPSC-NPs survival; however, the recovery of motor function was not statistically significant²⁶⁷.

pHPMA

Similar physical and chemical properties to pHEMA; positive effect on functional recovery after SCI after hydrogel implantation²⁶⁸.

Similar properties to pHEMA such as nonbiodegradability.

There is little research on pHPMA in the past five years; examples of research in the earlier years are as follows:

Implantation of pHPMA hydrogel into hemisected T10 rat spinal cord resulted in improvements in locomotor and neurophysiology²⁶⁸.

A form of pHPMA hydrogel with RGD modification enhanced axonal growth across the reconstructed lesion, displaying the potential to repair tissue defects in the CNS²⁶⁹.