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 importantrole in tissue engineering, owing to their advantage of excellentbiocompatibility. Here, the two-photon polymerization (TPP) of a 3Dhydrogel with high precision has been investigated, using the precursorwith hyaluronic acid vinyl ester (HAVE) as the biocompatibility hydrogelmonomer, 3,3 '-((((1E,1 ' E)-(2-oxocyclopentane-1,3-diylidene) bis-(methanylylidene)) bis-(4,1-phenylene))bis-(methylazanediyl))-dipropanoate as the water-soluble initiator,and d l-dithiothreitol (DTT) as the click-chemistrycross-linker. The TPP properties of the HAVE precursors have beencomprehensively investigated by adjusting the solubility and the formulationof the photoresist. The feature line width of 22 nm has been obtainedat a processing laser threshold of 3.67 mW, and the 3D hydrogel scaffoldstructures have been fabricated. Furthermore, the average value ofYoung's modulus is 94 kPa for the 3D hydrogel, and cell biocompatibilityhas been demonstrated. This study would provide high potential forachieving a 3D hydrogel scaffold with highly precise configurationin tissue engineering and biomedicine.