Photo-sensitive hydrogels for three-dimensional laser microfabrication in the presence of whole organisms

Abstract

Hydrogels are polymeric materials with water contents similar to that of soft tissues. Due to their biomimetic properties, they have been extensively used in various biomedical applications including cell encapsulation for tissue engineering. The utilization of photopolymers provides a possibility for the temporal and spatial controlling of hydrogel cross-links. We produced three-dimensional (3-D) hydrogel scaffolds by means of the two-photon polymerization (2PP) technique. Using a highly efficient water-soluble initiator, photopolymers with up to 80 wt.% water were processed with high precision and reproducibility at a writing speed of 10 mm/s. The biocompatibility of the applied materials was verified using Caenorhabditis elegans as living test organisms. Furthermore, these living organisms were successfully embedded within a 200×200×35 μm³ hydrogel scaffold. As most biologic tissues exhibit a window of transparency at the wavelength of the applied femtosecond laser, it is suggested that 2PP is promising for an in situ approach. Our results demonstrate the feasibility of and potential for bio-fabricating 3-D tissue constructs in the micrometre-range via near-infrared lasers in direct contact with a living organism.

Two-photon polymerization of hydrogels – versatile solutions to fabricate well-defined 3D structures

“…50 mm s À1 ) at low laser power (as low as 20 mW). This writing speed was particularly important with respect to the previously reported 10 mm s À1 for PEGDA structures, 101 and the results were not only due to the improved fabrication setup, but also due to the novel 2PP thiol-ene chemistry. The osteosarcoma cells seeded inside the GH-VE/BSA hydrogels with various macromer ratios showed a preference for the structure with higher gelatin (GH-VE) content.…”

“…81,97,[107][108][109] Despite the fact that most of the methods used to date were different from 2PP, the applications perfectly match the objectives of hydrogels combined with the 2PP technique.…”

“…64,95 However, this photoinitiator suffered from low 2PA cross-section therefore required high laser intensity and long exposure times. Several groups 85,[96][97][98] proved that an efficient way to produce water soluble photoinitiators is to create conjugated molecules. Quaternary ammonium cations or carboxylic sodium salts combined with an effective six-member ring in a series of benzilidene ketone-based water soluble photoinitiators increased the 2PA cross-sections up to 200 GM (see Table 1).…”

“…97 In a similar manner, GelMOD was processed in formulations with up to 80% water in the presence of living cells. 86 In this case, the benzylidenecycloketones (G2CK and P2CK) were used as photoinitiators ( Table 1) that allowed the fabrication of well-dened microstructures.…”

Printing Polymer Nanocomposites and Composites in Three Dimensions

“…Electromagnetic shielding and absorption, biomedical applications [21][22][23]75] Selective laser sintering (SLS)…”