A drug refillable device for transscleral sustained drug delivery to the retina

Continuous drug administration with better adherence to treatment and less invasive procedures is important in treating retinal diseases such as age-related macular disease. In this study, we report a drug-refillable device consisting of a silicone reservoir and an injectable gelatin/chitosan gel (iGel). The silicone reservoir was fabricated with polydimethylsiloxane (PDMS) using a computer-aided design and manufacturing to have micropores at a releasing side for uniaxial release to the sclera. A stainless steel wire and sheet were combined in the side and bottom of the reservoir to ensure flexibility and to fit on the curvature of the eyeball and prevent irritation to the sclera through the bottom of the reservoir. The drug was injected and formulated in the reservoir by in situ crosslinking of gelatin/chitosan gel with the crosslinker; 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride. The in vitro release study using fluorescein molecules showed that the release rate from encapsulated iGel in the reservoir was slower than that from the original iGel. After reinjecting the iGel into the reservoir, the same release profile as the first injection was observed. The reservoir containing iGel was placed on the sclera of a rabbit and the distribution of 150 kDa fluorescein isothiocyanate-dextran (FD150) in the retina and choroid/retinal pigment epithelium (choroid/RPE) was studied. The cryosections showed that FD150 was observed in the choroid/RPE. Homogenates of the retina and choroid/RPE showed fluorescence during 12 weeks implantation, indicating the drug could be delivered to the retina by using the device. The drug filling was successful into the reservoir implanted on the sclera through the conjunctiva by using a needle. In conclusion, the refillable drug delivery device is a promising tool to administer drugs long-term by reinjection with less invasiveness to intraocular tissues.