Figure 9.

The design of long-acting implantable systems. (A) Polymer-based implants. (B) Osmotic pumps are composed of a drug reservoir, an osmotic engine and a movable piston. A semipermeable membrane is used to separate the osmotic from the outside, and micro-holes are designed to connect the drug reservoir and the outside. The increased hydrostatic pressure in the osmotic engine is the motive force of pumps for drug release. (C) Positive displacement is the motive force of peristaltic pump for transporting the fluid inside the tube. (D) Implantable infusion pumps are divided into three parts including a propellant, a collapsible bellow and drug reservoir. The propellant changes bigger in the volume under body temperature leading to compression of collapsible bellow, following the drug release. (E) The mechanism of implantable chip is that the single reservoir can be opened by applying an electrical potential to the gold membrane resulting in the complete dissolution of the membrane, which subsequently results in the release of the drug. (F) A drug reservoir can be conveniently covered by the nanochannel delivery system (nDS) membrane to achieve zero-order kinetic drug release from the reservoir. Reproduced with the permission from Ref. 153. Copyright © 2019 Springer Nature.