Intraocular Delivery of CNTF Using Modified NT-501 Devices Manufactured With Different Medias and Membranes of Different Porosities

Abstract

Purpose: : To investigate the effects of different media formulations and implants manufactured with membranes of different porosities on the intraocular delivery of CNTF in rabbits.

Methods: : Modified NT-501 implants assembled with membranes with different porosities were manufactured using established procedures and held at 37°C in closed packages containing 37 mls of different medias. Prior to implant, the devices were pulsed for CNTF release in 1 ml of the respective hold media for 24 hours. Cell containing implants were subsequently analyzed for metabolic activity and then subjected to either total DNA or histological analysis. The duration of the implantation period ranged from 1 to 3 months. Explanted devices were pulsed for CNTF release and subjected to histological analysis. During explant procedures, vitreal samples were collected and analyzed for CNTF levels. The CNTF released from devices was quantified using a commercial ELISA kit (R&D Systems). Cell metabolism was determined using the CCK-8 assay (Dojindo). Total DNA was determined using the Hoefer DyNA Quant 200 fluorometer. Histological examination of the devices was performed using standard hematoxylin and eosin staining techniques.

Results: : In vitro stability: The NT-501 devices using the different membrane configurations released variable levels of CNTF during the testing period and CCK-8 results showed that all devices maintained viable cells. Total DNA analysis showed devices contained cells at levels which were maintained during the testing period and histological analysis of device sections showed a high density of healthy cells distributed evenly throughout the device.In vivo performance: All devices appeared to be well tolerated during the implantation period. Explanted devices contained healthy cells and released consistent levels of CNTF upon explant at 1 and 3 months.

Conclusions: : The data suggested that the Encapsulated Cell Technology platform was able to achieve sustained, long term intraocular delivery of CNTF for periods up to 3 months in rabbits using modified capsules and media formulations. Both the change in hold media and the different membranes were well tolerated. By varying the media formulations and membrane characteristics, this technology could potentially be customized to deliver other factors at specific dosages for a broad range of indications where long-term treatment is required.

Keywords: retina