22 nm Resolution Achieved by Femtosecond Laser Two-Photon Polymerization of a Hyaluronic Acid Vinyl Ester Hydrogel.

Three-dimensional (3D) bioinspired hydrogels have played an important role in tissue engineering, owing to their advantage of excellent biocompatibility. Here, the two-photon polymerization (TPP) of a 3D hydrogel with high precision has been investigated, using the precursor with hyaluronic acid vinyl ester (HAVE) as the biocompatibility hydrogel monomer, 3,3'-((((1,1')-(2-oxocyclopentane-1,3-diylidene) bis(methanylylidene)) bis(4,1-phenylene)) bis(methylazanediyl))dipropanoate as the water-soluble initiator, and dl-dithiothreitol (DTT) as the click-chemistry cross-linker. The TPP properties of the HAVE precursors have been comprehensively investigated by adjusting the solubility and the formulation of the photoresist. The feature line width of 22 nm has been obtained at a processing laser threshold of 3.67 mW, and the 3D hydrogel scaffold structures have been fabricated. Furthermore, the average value of Young's modulus is 94 kPa for the 3D hydrogel, and cell biocompatibility has been demonstrated. This study would provide high potential for achieving a 3D hydrogel scaffold with highly precise configuration in tissue engineering and biomedicine.