**4. Conclusion**

The functional repair of peripheral and central nervous system injuries is a major challenge. Based on the advances of development of novel biomaterials, biochemistry and fabrication techniques, bioengineered scaffold enhanced with bioactive motifs and engrafted cells can provide a regeneration-facilitating environment for injured nervous tissues, and effectively promote the host's capacity of neural regeneration and plasticity. Numerous *in vitro* models have demonstrated that 3-D bioscaffold, in particular the nanofibre scaffold, can greatly support the attachment, proliferation, migration and neural differentiation of various neural cells. Moreover, significant neuroprotection and axonal regeneration have been achieved in *in vivo* neural injury models after treatment with these novel scaffolds. More importantly, the recovery of injured sensory and locomotor function has been shown to occur in a number of peripheral and central injury models using different animal species. However, critical issues such as functional integration of host-implant, organized regeneration pattern with updated bioengineering scaffolds and further restoration of useful neurology function, remain to be addressed in future researches.

Immunohistochemistry with Neurofilament(NF) staining showed a number of NF-positive axons (Green)penetrated into the lesion sites with SAPNS+CT04 treatment(A). Counterstained DAPI area (blue) indicated the gross structure of the injured spinal cord. (B) is the high power magnification corresponding to the boxed area of (A) demonstrated the NF-positive axons in the center of lesion area. Quantification analysis of the NF-positive axons in the center of the lesion area indicated that axonal regeneration was significantly improved by the SAPNS+CT04 implants compared to the only SAPNS group (Student t test, \*p<0.05).

**Figure 1.** Axonal regeneration in the SAPNS-treated groups.

muscle action potential and distal motor latency, the nanofibre-group showed greater improvement than the microfiber group (Jiang et al., 2012). These positive observations provide useful insights for the applications of electrospun nanofibrous nerve conduits with

SAPNS has a well-defined sequence of L-amino acids that self-assemble under physiologi‐ cal conditions to form a fibrous scaffold within the nanoscale (∼10 nm in diameter). In the recent decades, SAPNS has been shown to facilitate the survival and growth of various neural cells within a 3D matrice, and effectively improved the axonal regeneration and tissue repair in context of CNS injuries. It also has significant potential for PNI repair. For example, a novel SAPNS-based nerve conduit was generated by RAD-I SAPNS ensheath‐ ed with a segment of aortic wall. With a sciatic nerve transection model of rat, the SAPNSnerve conduit was used to bridge a 10mm nerve gap. Neural histomorphology, retrogradelabeling and locomotor functional assessments demonstrated significant therapeutic effects of SAPNS-based nanofiber conduit implant on axonal regeneration, remyelination and target reinnervation (Fig.2,). Additionally, SAPNS acts as a designer peptide backbone and provides the opportunity to integrate various growth factor, or functional motifs for cell adhesion, differentiation and homing, and to define and direct biological commitment of seeding cells; furthermore, functional SAPNS will provide better support for viability, migration and differentiation of engrafted stem cells in vivo and lead to better perform‐

The functional repair of peripheral and central nervous system injuries is a major challenge. Based on the advances of development of novel biomaterials, biochemistry and fabrication techniques, bioengineered scaffold enhanced with bioactive motifs and engrafted cells can provide a regeneration-facilitating environment for injured nervous tissues, and effectively promote the host's capacity of neural regeneration and plasticity. Numerous *in vitro* models have demonstrated that 3-D bioscaffold, in particular the nanofibre scaffold, can greatly support the attachment, proliferation, migration and neural differentiation of various neural cells. Moreover, significant neuroprotection and axonal regeneration have been achieved in *in vivo* neural injury models after treatment with these novel scaffolds. More importantly, the recovery of injured sensory and locomotor function has been shown to occur in a number of peripheral and central injury models using different animal species. However, critical issues such as functional integration of host-implant, organized regeneration pattern with updated bioengineering scaffolds and further restoration of useful neurology function, remain to be

Immunohistochemistry with Neurofilament(NF) staining showed a number of NF-positive axons (Green)penetrated into the lesion sites with SAPNS+CT04 treatment(A). Counterstained

designed nanostructure in the development of peripheral nerve guide conduits.

**3.2. Reconstruction of injured PNS with SAPNS**

ance of neural repair in vivo.

addressed in future researches.

**4. Conclusion**

192 Advances in Nanofibers

With NF/MBP-double immunofluoresent labeling, in sharp contrast to that of Empty Nerve Conduit (ENC) group (A-C), significant remyelination of regenerated axons was detected throughout the entire Nanofiber Nerve Conduit (NNC) 16 weeks after treatment (D-F). Representative transverse sections of proximal, middle and distal parts of Nerve Conduit (NC) were demonstrated at panel (A, D), (B, E), and (C, F) in ENC and NNC group, respectively. (G) is the higher magnification of boxed area of (E) with arrows indicating the representative remyelinated fibers. Furthermore, with electron microscopy, typical remyelinated fibers (arrowheads) could be found in both NC groups, while the diameter of the fiber and the thickness of the myelin are greater in NNC (H) compared with ENC (I). (J,K) showed the quantification analysis of the myelinated fiber caliber and the G-ratio ( an index of myelin thickness) separately. Both comparisons using student's t test indicated significantly statistical differences (\*p<0.05;\*\*p<0.01).

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**Figure 2.** Remyelination of regenerated axons in the peripheral nerve conduits
