Photothermal responsive cell-laden PNIPAM self-rolling hydrogel containing dopamine enhanced MWCNTs for peripheral nerve regeneration

In vitro construction of cell-laden nerve grafts has huge promising for promoting nerve regeneration after peripheral nerve injury (PNI). Herein, a photothermal responsive cell-laden self-rolling poly-N-isopropylacrylamide (PNIPAM) hydrogel containing dopamine hydrochloride (DOPA) modified multi-walled carbon nanotubes (MWCNTs) is fabricated by surface modification technology and in-situ free radical polymerization. The MWCNTs modified with 2 mg/mL dopamine (2 DM) has the most obvious photothermal responsiveness with good dispersibility and stability. The PNIPAM photothermal responsive hydrogel containing 2 DM displays a porous structure, good hydrophilicity, and reversible photothermal responsiveness. MTT detection shows that the hydrogel is non-toxic while near infrared radiation does not affect Schwann cell's viability. Compared with the Schwann cells grown on the 2D plane, the Schwann cells in the 3D hydrogel possess better growth behavior, release more nerve growth factors, and significantly upregulate the gene expression related to myelin sheath and cytoskeleton. Thus, the prepared hydrogel here possesses a promoting effect on nerve cells growth, and is expected to further improve the capability of nerve grafts on repairing PNI. The study is expected to provide experimental and theoretical basis for the design and preparation of cell-laden tissue-engineered nerve grafts with excellent performance.