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Kristan Sorenson Worthington, Jessica R. Thompson, Brian J. Green, Spencer J. Bunn, Emily E. Kaalberg, Rebecca M. Johnston, Luke A Wiley, Robert F Mullins, Edwin M Stone, C. Allan Guymon, Budd Tucker; Two-Photon Polymerization of High-Resolution 3D, Biodegradable Photoreceptor Cell Scaffolds. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3390.
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© ARVO (1962-2015); The Authors (2016-present)
Obstacles to the realization of polymer scaffold use for retinal cell replacement include 1) selection of appropriate chemistry and 2) microstructural control of cellular orientation and packing density. Poly(caprolactone) (PCL) is a good candidate material for retinal scaffolds, as it is biodegradable, biocompatible, and easily modified with reactive molecules. In this work, we optimized the conditions that contribute to photopolymerized PCL microstructure in order to create more effective retinal cell scaffolds.
We generated thin films of acrylated PCL via UV polymerization and determined the effect of the formulation on degradation time and biocompatibility using 1M NaOH and mouse induced pluripotent stem cells (iPSCs), respectively. We then used two-photon polymerization (TPP) with varying parameters to create biodegradable 3D-printed PCL structures with sub-micron resolution. Survival and identity of human iPSC derived retinal cells seeded on structurally optimized scaffolds was evaluated using immunocytochemistry.
Regardless of molecular weight or number of acrylate groups, PCL films supported the growth and mitosis of mouse iPSCs (Fig. 1A). Increasing PCL molecular weight decreased film degradation time, increased the laser power required to induce polymerization and decreased structural resolution. Two photon polymerization of triacrylated PCL (Fig. 1B-C) resulted in higher resolution and more easily distinguishable structures than diacrylated PCL. For triacrylated PCL, increasing either hatching or slicing distance decreased the structure’s deviance from the design (Fig 1C). Within two days of seeding, human iPSC derived retinal progenitor cells, which were isolated from developing 3D retinal cups, nested within and aligned along scaffold vertical pores. Cells obtained from younger iPSC derived retinal cups (i.e. ~30 days post-differentiation) yielded higher survival rates than cells obtained from older iPSC derived retinal cups (i.e. ~60 days post-differentiation).
The favorable biocompatibility and tunable degradation of PCL films and 3D-printed structures demonstrates that these structures are promising for transplantation purposes.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Figure 1. Crosslinked poly(caprolactone) diacrylate biocompatibility (A), two-photon printing threshold (B) two-photon polymerized scaffold (C).
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