Biocompatibility and stability of doxycycline-terminable intraocular drug delivery cell-encapsulating device

Abstract

Purpose : There is currently limited option to deliver drug to the posterior eye. Cell-encapsulating hydrogel device provides a way of localized, sustained and freshly made therapeutics to the diseased site directly. We have previously developed an intravitreally injectable cell-encapsulating device made of collagen-alginate hydrogel and genetically modified cells with Tet-On termination system and sustained Glial-cell derived neurotrophic factor (GDNF) secretion, which showed photoreceptor rescue in rat with inherited retinal degeneration. We previously tested for successful device termination after doxycycline(Dox) administration for 72 hours in vivo. Here, we also tested the long-term biocompatibility and mechanical stability of the device after prolonged implantation for 28 days. Methods : Cell-encapsulating hydrogel device was implanted into healthy Royal College of Surgeons (RCS) rat intravitreally at postnatal Day 28. 1mg/ml Dox with 1% sucrose solution was given for 72 hours starting 5 days post-implantation with water as control. Rats were sacrificed at Day 8 and Day 28 post-implantation. The device was retrieved and examined with phase contrast microscopy. Dox-induced cell death in retrieved device was assayed by MTS cell viability assay, Live/Dead assay and TUNEL assay. Retina was collected for Haematoxylin & Eosin (H&E) staining for the assessment of retinal cytoarchitecture. Results : Under phase contrast microscopy, healthy cell colonies were observed in non-Dox treated cell-encapsulating hydrogel devices at both Day 8 and Day 28 post implantation. Cell debris was observed in Dox treated groups regardless of the time of retrieval. MTS assay, Live/Dead assay and TUNEL assay demonstrated DNA fragments by apoptosis and no viable cells in Dox-treated group, while absence of apoptosis and viable cell colonies were evident in non-Dox treated group. Both time points showed similar results. H&E staining showed similar architectural histology of retina regardless of dox treatment and device implantation duration. Conclusions : We have established a Dox-terminable intraocular drug delivery encapsulated-cell device with good biocompatibility and stability.