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Although the peripheral nervous system has an intrinsic ability for repair and regeneration after injury, bridging long peripheral nerve defects remains a challenge. Functional nerve regeneration depends on interactions among axons, Schwann cells, fibroblasts and immune cells. Macrophages, as immune cells recruited early in this process, show polarization toward phenotypes that are detrimental or beneficial to tissue remodeling depending on the microenvironment of the scaffolds. In this study, we investigated the effects of macrophage phenotypes modulated by collagen VI on axonal regeneration and functional recovery by bridging a 15-mm-long sciatic nerve defect in rats. Our results showed that local delivery of collagen VI within a polycaprolactone (PCL) electrospun conduit increased the recruitment of macrophages and their polarization toward the pro-healing (M2) phenotype. In addition, the axonal regeneration and neurologic functional recovery in the PCL/collagen VI conduit group are equivalent to that of an autograft. In conclusion, the present study confirmed that PCL/collagen VI conduits with sustained release of collagen VI in the local microenvironment may, through triggering macrophage M2 polarization to enhance the nerve regeneration, suggest that our combined biomaterial-immunomodulatory system may be an attractive candidate for peripheral nerve regeneration.

We report a new supramolecular method for the synthesis of well-defined pristine C 60/polymer colloid nanocomposites in water. The colloids include polymer micelles and emulsion particles. To a polymer colloid solution in water or alcohol, we introduced C 60 solution in a solvent that is miscible with water or alcohol. After the two solutions mixed, polymer colloids and C 60 spontaneously assembled into stable colloidal nanocomposites. After a dialysis process, a nanocomposite dispersion in pure water was obtained. As characterized by DLS and (Cryo-)TEM, the nanocomposites have a core-shell structure with C 60 aggregated on the surface of emulsion particles or micellar cores. The resulting nanocomposites have many potential applications such as biomedicals and photovoltaics.

Uniform and porous chitosan-based microparticles with injectable and shape-memory properties are particularly attractive due to their promising application potential for tissue engineering and regenerative medicine. However, simple and efficient methods for producing this kind of microparticle are still desirable. In this study, we report that uniform, injectable, and shape-memory chitosan microsponges were efficiently prepared by combining microfluidic emulsion with further freezing and in situ thawing processes without using any potentially cytotoxic chemical cross-linker. The produced chitosan microsponges have controllable size and could be easily injected with syringe needles. Structural observations confirmed that the chitosan microsponge had an interconnected porous structure with pore size of several micrometers and could withstand a large compressive strain of ∼93% and then recover ∼96% of its initial diameter without structural damage. The chitosan microsponges showed a high porosity (∼84%) and swelling ratio (∼3800%) as well as good antibacterial activity. Additionally, an in vitro cell coculturing investigation revealed that they also had good biocompatibility and exhibited great superiority to support cell adhesion and proliferation in three dimensions. The kind of chitosan microsponge presented here has great potential to serve as cell carriers for biomedical applications, especially as injectable scaffolds for regeneration and reconstruction of tissue defects.

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