Mini Drug Pump for Ophthalmic Use

Abstract

Purpose: To evaluate the feasibility of developing a novel mini drug pump for ophthalmic use.

Methods: Using principles of microelectromechanical systems engineering, a mini drug pump was fabricated. The pumping mechanism is based on electrolysis and the pump includes a drug refill port as well as a check valve to control drug delivery. Drug pumps were tested first on the bench-top and then after implantation in rabbits. For the latter, we implanted 4 elliptical (9.9 × 7.7 × 1.8 mm) non-electrically active pumps into 4 rabbits. The procedure is similar to implantation of a glaucoma aqueous drainage device. To determine the ability to refill and also the patency of the cannula, at intervals of 4–6 weeks after implantation, we accessed the drug reservoir with a transconjunctival needle and delivered approximately as low as 1 µL of trypan blue solution (0.06%) into the anterior chamber. Animals were followed by slit lamp examination, photography, and fluorescein angiography.

Results: Bench-top testing showed 2.0 µL/min delivery when using 0.4 mW of power for electrolysis. One-way valves showed reliable opening pressures of 470 mmHg. All implanted devices refilled at 4–6 weeks intervals for 4–6 months. No infection was seen. No devices extruded. No filtering bleb formed over the implant.

Conclusions: A prototype ocular mini drug pump was built, implanted, and refilled. Such a platform needs more testing to determine the long term biocompatibility of an electrically-controlled implanted pump. Testing with various pharmacological agents is needed to determine its ultimate potential for ophthalmic use.

KEYWORDS::

• Drug delivery
• Ocular
• Pump
• Rabbit eye
• Refilling

ACKNOWLEDGMENTS

This work was supported by grants R21EY018490 and Core Grant EY03040 from the National Institutes of Health and grant EEC 0310723 from the National Science Foundation.

Declaration of interest: Dr. Humayun and Dr. Varma are consultants and have equity in Replenish Inc. All authors except Dr. Varma stand to get royalties through University of Southern California patents licensed to Replenish Inc.