Doxycycline-terminable intraocular drug delivery device

Abstract

Background: The options for ocular drug delivery to the posterior segment are limited. The challenge lies in the presence of various physical barriers. Currently, intravitreal injection is utilized for delivering therapeutics to the retina. However, repeated intravitreal injections pose multiple risks to the patients and increase the clinical burden of healthcare workers. Encapsulated cell therapy (ECT) is an attractive approach to provide long-term and sustained delivery of freshly synthesized therapeutics directly to target sites. We have previously developed an ECT intraocular device with a Tet-On inducible termination mechanism and sustained Glial-cell derived neurotrophic factor (GDNF) secretion, which showed clinical efficacy in promoting photoreceptors survival in a rat model with retinal degeneration. We also demonstrated successful in vivo termination of the device with 48 hours of oral doxycycline administration. Here, we further investigated the long-term in vivo biocompatibility, termination efficiency and post-termination status of the device after prolonged implantation over 28 days of study. Method: The intraocular drug delivery device was intravitreally implanted into healthy Royal College of Surgeons (RCS) rat at postnatal Day 28. 1mg/ml Doxycycline solution with 1% sucrose (+DOX) or normal drinking water (-DOX) was given orally from post-implantation Day 5 to Day 8 for 72 hours. Electroretinogram (ERG) was conducted to examine the retinal functions of rats that were sacrificed at post-implantation Day 8 and Day 28. Device was retrieved at both timepoints and examined with bright field microscope. MTS cell viability assay, Live/Dead assay and TUNEL assay were performed on the retrieved devices. Vitreous GDNF content were also quantified using GDNF ELISA. Retina were collected for Haematoxylin & Eosin (H&E) and immunohistochemical (IHC) staining for further histological assessment. Results: Under bright field examination, healthy cell colonies were observed in devices of the -DOX groups, while homogenous cell debris was observed in those from the +DOX groups. MTS cell viability assay, Live/Dead assay and TUNEL assays showed apoptotic dead cells in +DOX devices, whereas healthy and viable cell colonies were evident in -DOX ones. Accumulative vitreous GDNF levels were higher in -DOX groups than +DOX groups. H&E staining revealed no disruption of retinal cytoarchitecture in all groups. No increase in immune reactivity in D28 groups compared with normal control was detected using IHC staining. No functional retinal impairment was detected by scotopic flash ERG. Conclusion: We have established a Doxycycline-terminable intraocular drug delivery device with good biocompatibility and stability. Successful and complete termination of the device is achieved with 72 hours of Doxycycline administration through oral route. No adverse effect on the retinal anatomy or function of the retina has been observed.