Phan C-M, Wulff D, Garg P, Jones L.. Developing a novel in vitro eye model using 3D bioprinting for drug delivery studies The Association for Research in Vision and Ophthalmology, Denver, CO, USA, 2022 [ Show Abstract ]

Purpose: To develop an in vitro eye model using a novel 3D bioprinting method for testing the release of ophthalmic formulations to the posterior ocular region.

Methods: The eye model was designed using CAD software and includes both an anterior aqueous chamber and a posterior vitreous chamber. The vitreous chamber is surrounded by a blood chamber to mimic vessels that can be used to transport a blood-like substance. Three inlet ports control the flow of fluid into the chambers and the blood channels, and the three outlet ports allow fluids to exit these compartments. The eye model was 3D printed on a commercial mSLA printer (Photon Mono X, AnyCubic), which was retrofitted with a humidity and temperature control module to create a printing environment at 37°C and >80% humidity. The bioink formulation consisted of 10% gelatin methacrylate (GelMa). After printing, the models were incubated at 37°C to remove any uncured GelMa within any hollow compartments. For this study, phosphate-buffered saline was used as an aqueous and vitreous humour mimic. To evaluate the diffusion of a small hydrophilic molecule on the eye model, a contact lens (Air Optix) was soaked with a water-soluble red food dye for 1 hour and then placed on the eye model. The amount of dye in the anterior chamber, posterior chamber, and blood channels was measured using UV spectrophotometry after 24 hours.

Results: The entire model can be printed without any support structures within approximately 3 hours. The 3D printed eye model can also be autoclaved for testing that requires sterility. Because there were no diffusion barriers present in the current model, the red dye was detected in all three chambers after 24 hours. The highest concentration of dye was found in the anterior chamber, followed by the blood chamber and then the posterior chamber.

Conclusions: The prototype developed in this study can be used as a starting point to develop enhanced 3D printed eye models to test drug release kinetics of various devices and formulations. Future work will focus on adding the appropriate diffusion barriers to better simulate drug diffusion through ocular tissues.

Layman Abstract: The aim of the study was to create an advanced eye model using commercial 3D printing methods. Current 3D bioprinters are extremely expensive and regular commercial 3D printers do not have the capabilities to print biological materials. We are developing a method to 3D print sophisticated eye models using inexpensive 3D printers. The models from this research can further be refined for studying drug absorption in the eye. This research will also enable researchers to create their own biological models using 3D printing methods.

Wulff D, Phan C-M, Jones L. 3D printing using a novel bioink with a commercial mSLA printer to fabricate a model contact lens The Association for Research in Vision and Ophthalmology, Denver, CO, USA, 2022 [ Show Abstract ]

Purpose: To develop a cost-effective and scalable 3D printing method and novel bioinks to fabricate contact lenses.

Methods: The bioink formulations consisted of GelMA (gelatin methacrylate), LAP (Lithium phenyl-2,4,6-trimethylbenzoylphosphinate), and a yellow food-grade dye. The dye minimizes unwanted light leakage during the photopolymerization process. A commercial mSLA (masked stereolithography) printer, the Photon Mono X (AnyCubic, Shenzhen), was retrofitted with a custom temperature and humidity control kit. The printing process was performed at 40 oC and 90% humidity to ensure that the GelMA remained at a liquid state and to prevent the bioink from drying out, respectively. A set of matrix cubes of varying sizes with holes was used as a standard control. Images of the cubes were taken with a camera, top-down and side-review, analyzed with the ImageJ software and compared with the original CAD designs to derive an overall print quality score. Two print variables, exposure time (5 s to 40 s) and yellow dye concentration (1 – 7%), were analyzed in this study.

Results: The best resolution with the highest print scores were obtained at either 5% yellow dye concentration and 30 seconds exposure time, or 3% yellow dye concentration and 20 seconds exposure time. There was an overall optimal range for both print times (20 - 30 s) and yellow dye concentration (3 - 5%). Values above or below this critical value resulted in lower print quality scores of the standard cubes. A prototype contact lens with a 200 µm thickness was able to be 3D printed using the developed print methods and parameters, with a total print time of approximately 20 minutes. Approximately 28 contact lenses can be printed at the same time using the 3D printer. However, the surface and edges of the 3D printed contact lens were still visually very rough.

Conclusions: The current study demonstrated that a low-cost commercial 3D mSLA printer can be used to fabricate model contact lenses using a hydrogel material. Still, further work is necessary to improve the print quality for fabricating ultra-thin devices such as contact lenses. Future work will use this 3D printing method to fabricate contact lenses for drug delivery.