Blindness and visual impairment are largely caused by irreversible loss of light sensitive photoreceptors and retinal pigment epithelium cells in the retina. Some pro-survival therapeutic proteins, such as ciliary neurotrophic factor (CNTF), can improve retinal cell survival in the damaged retina, but require controlled delivery systems due to their short half-lives and rapid clearance. To achieve local controlled release, we designed an affinity-based system that sustains the release of bioactive proteins from an injectable, thermogel.<br/>In this strategy, we designed a hyaluronan-methylcellulose (HAMC) polymer blend, with shear-thinning and inverse thermogelling properties, that allows injection through fine gauge needles, forms a gel at body temperature, and is stable for at least 10 days in vitro. Furthermore, HAMC is cytocompatible with photoreceptors in vitro, confirming its appropriateness for intravitreal injections.<br/>To control protein release, we exploit the interaction of a well-known intracellular protein, Src homology 3 (SH3), with its binding peptides. Specifically, by (i) expressing fusion proteins of SH3 with the protein of interest and (ii) chemically modifying the HAMC hydrogel with the corresponding binding peptides, the release can be computationally predicted and designed. In this study, an SH3-CNTF fusion protein was successfully expressed and CNTF bioactivity was confirmed in vitro with a cell-based assay, showing a similar response to commercially available CNTF. The controlled release of SH3-CNTF from peptide-modified HAMC was confirmed over 10 days in vitro. A bioactivity assay on the released samples showed sustained activity over a week, validating SH3-CNTF as a candidate for local affinity release to the retina. Intravitreal injections of the bioengineered hydrogel were investigated to evaluate the in vivo protein activity and the anticipated protective effects of its sustained release on the retina. This system lays the foundation for future in vivo studies where combining cell and biomolecule delivery will enhance cell survival after transplantation.

Bioengineered injectable thermogel for intravitreal protein controlled release to the retina

255th National Meeting (2018)

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