Bioprinting technologies in ophthalmology

Bioprinting allows additive fabrication of bioengineered constructs with defined two- or three-dimensional organization using live cells, biopolymers and other materials. This article reviews main bioprinting technologies and their capabilities in clinical and experimental ophthalmology. Analysis of literature sources helped reveal and describe the main types of bioprinting technologies: inkjet, laser-assisted, and extrusion. Extrusion bioprinting is the most widely used method, providing the ability to use various types of bioinks and a wide range of cell concentrations. The following materials can be used as the base for bioinks: alginate, collagen, gelatin, hyaluronic acid, chitosan, fibrin, as well as their different combinations. These materials can be modified for best bioprinting properties by adding various functional groups. The major directions of application of bioprinting technologies in ophthalmology are tissue engineering for regenerative medicine and fabrication of model systems for fundamental and preclinical studies. Experiments in creating a bioprinted cornea are being conducted in the field of regenerative medicine. Furthermore, there are studies on fabricating retinal tissue equivalents, although tissue engineering of this structure is a task of great complexity. Model systems, which can be fabricated by bioprinting, are represented by tissue equivalents of ocular structures and the appendages of the eye, as well as by microphysiological organ-on-a-chip systems. Another promising application of bioprinting is fabrication of biocompatible implantable electrode arrays for visual neuroprostheses.