Chantal Khan-Malek from CNRS/FEMTO ST, France reviewed a publication from researchers of the University of California dealing with drug delivery. ‘Smart pill', which integrates microbattery, biosensor, control circuitry, valve and drug storage reservoir all in one miniature system, has started attracting more and more interest. Such responsive drug delivery system offers many advantages over traditional drug delivery methods, including a tightly controlled concentration of the drug in the patient's body as well as elimination of the need for regular testing of the drug or marker level by the patient or health care worker.

Most traditional actuator materials are not appropriate for biomedical applications. Actuator valve based on conducting polymers is an attractive candidate for the component of a drug delivery system. Polypyrrole (PPy) in particular presents a number of advantages that include easy synthesis and microfabrication, high tolerance to electrode materials and electrolytes, wide range of dopant species, good environmental stability, low voltage actuation and biocompatibility with physiological environment. In addition, extracellular fluids in human body, which possess high concentrations of Na2+ ions, create future possibilities for application of PPy polymer actuator in advanced implantable in vivo responsive drug delivery system.

The authors from the Mechanical and Aerospace Engineering Department of the University of California at Irvine report on the design, fabrication and prototype-testing of a novel drug delivery device based on electrochemically actuating an array of polymeric Au/PPy [dodecylbenzene sulfonate (DBS)] bilayer valves on a set of drug reservoirs.

This drug delivery device is suitable for drug formulations in states of solid, liquid or gel. Advantages of this device include low voltage actuation and low energy consumption, good reproducibility, tight drug dosage control, flexible activation and quick response time. In addition, these valves can be actuated underclosed-loop-control of sensors responding to a specific biological or environmental stimulus, leading to potential applications in advanced responsive drug delivery systems.
Although the authors don't demonstrate the whole system which would be a major achievement, it is an interesting concept. But the fact that it is electrically activated is a problem.

Source: Polymer actuator valves toward controlled drug delivery application; H. Xu, C. Wang, C. Wang, J. Zoval, M. Madou : Biosensors and Bioelectronics 21, 2094 (2006). EBio10-06-21