Conducting polymers (CPs) are conjugated polymers with interesting chemical and physical properties. CP-based drug delivery systems (DDSs) have been developed rapidly in the past few decades. The advantages of CPs as potential candidates for application in DDSs are derived from their inherent electroactivity, ease of preparation and applicability to a wide spectrum of dopants, including anionic, cationic and neutral biomolecules. More importantly, due to the switching property of the redox states external electrical stimulations can be used to alter the electronegativity, conductivity, doping level and volume of CPs. Moreover, the structure and surface morphology of CPs can be tailored by incorporating different dopants or carbon nanotubes (CNTs) as well as by different preparation methods. Capitalizing the unique properties, CP-based DDSs can provide high drug load, trigger release of the incorporated drugs, control drug release and modify the release rate of the drugs. In this review, we briefly introduce the properties and preparation methods of CPs, and summarize the research progress of drug loading and release of CP-based DDSs. Finally, potential problems, challenges and future development in this area are proposed and discussed.

Contents
1 Introduction
2 The properties and preparation of conducting polymers
3 Drug incorporation and release of conducting polymer-based drug delivery system
3.1 Drug incorporation
3.2 Drug release
4 The modification of conducting polymer-based drug delivery system
4.1 Nano modification
4.2 Conducting hydrogel
4.3 Biotin-doped modification
4.4 Bilayer system
4.5 Self-powered system
4.6 Fluorescence imaging system
5 Challenges and future directions