Development of integrated protection for a miniaturized drug delivery system

Abstract

A bi-layer structure comprising a thin gold layer and a polypyrrole (PPy) film is developedas a valve. To create such structures, the thin metal layer is used as a working electrode,and the polypyrrole film is electrochemically deposited on the metal electrode. A layer ofCr deposited under a stationary part of the bi-layer flap adheres strongly to the gold layerand anchors the hinge of the flap, while the layer of polyimide deposited under amovable part of the flap adheres weakly to the gold layer of the flap. This bi-layerflap structure functions as an actuator valve for the opening and closing of anaperture. The actuation mechanism of the valve is based on a volume change inthe PPy layer as cations move in and out of the polymer film during reductionand oxidation reactions. A bias of 1.2 V is used to actuate the flap. A method isproposed to increase the drug release system’s functionality by placing the drugrelease flap within a protective enclosure that also serves as a drug reservoir. Thisintegrated protection ensures reliable operation of the drug release flap unencumberedby surrounding tissues when used in vivo. A prototype system using a PDMSdrug reservoir has been successfully tested in PBS buffer solution. The proposedintegrated protection system holds promise for implantable biomedical devices.