Laser-Induced Forward Transfer (LIFT) based Bioprinting of the Collagen I with Retina Photoreceptor Cells

This study focuses on the 3D bioprinting of retina photoreceptor cells using a laser-induced forward transfer (LIFT) based bioprinting system. Bioprinting has a great potential to mimic and regenerate the human organoid system, and the LIFT technique has emerged as an efficient method for high-resolution micropatterning and microfabrication of biomaterials and cells due to its capability of creating precise, controlled microdroplets. In this study, the parameters for an effective femtosecond laser-based LIFT process for 3D bioprinting of collagen biomaterial were studied. Different concentrations of collagen I solutions were tested and 0.75 mg/ml to 1 mg/ml collagen I was identified as the right concentration that can be transferred through the LIFT system. Then, retinal cone cells were mixed with collagen I and Dulbecco's Modified Eagle's Medium (DMEM) and printed drop-by-drop lines. Some important laser parameters such as pulse energy and pulse pick divider were experimented with to form a successful, smooth, high-resolution deposition. The cell viability in the bioink and printed droplet was measured at different time horizons. A general full factorial design of the experiment was used to analyze and observe the relationship between the droplet quality and the LIFT process parameters. Using 15 μJ and 16μJ pulse energy, the cell-laden bioink was printed successfully. This research study will help to print other retinal neuron cells with collagen I in the LIFT system and show the way of constructing layer-by-layer different cell lines that will help to fabricate the retina ultimately.