# Research Progress on Conducting Polymer-Based Biomedical Applications
## 5 Summary  
In summary, we first reviewed the motivation and function of the CPs in biomedical applications including biosensors, tissue engineering, artificial muscles, and drug delivery. The CPs have been widely developed and studied in biomedical engineering over the past few decades; they can provide unique optical and electrical properties along with the advantages of ease of controlling their morphology, high chemical and environmental stability, and biocompatibility. The most commonly used CPs are PPy, PANI, PT, and PEDOT, which are simply synthesized via chemical or electrochemical  
Figure 11: A schematic of the release of dexamethasone from the PLGA nanofiber and the PEDOT-coated PLGA nanofiber (**a**). A mechanism of drug release resulting from contraction of the PEDOT nanotube by a positive applied voltage (**b**). Cumulative mass of dexamethasone released over time from the PLGA nanofibers (black), the PEDOT/PLGA nanofibers with no electrical stimulation (red), and the PEDOT/PLGA nanofibers when 1 V was applied at five specific points (**c**). Scanning electron micrographs of the PEDOT nanotubes after removal of PLGA (**d–f**). Adapted with permission from [145]. Copyright 2006 John Wiley and Sons.  
redox polymerizations. In biosensors, the CPs act as a transducer that turns chemical reactions into electrical signals. As a scaffold in tissue engineering, they serve to promote the proliferation and differentiation of cells. Furthermore, these polymers are utilized not only as actuators for artificial muscles, because of their volume change properties upon redox reactions, but also as a drug carrier in the process of drug delivery, because of their ability to release drugs upon electrical stimulation.  
However, the use of the CPs in biomedical engineering has been limited by a lack of biodegradability, low hydrophilicity, low charge-carrier mobility, and a small loading capacity of biomolecules. Nevertheless, ongoing studies have been investigating a wide range of possibilities for resolving these issues. As a response to low biodegradability, it has been strongly suggested that the CPs should be blended with biodegradable polymers because the blend scaffolds are expected to degrade faster than pure CP ones. To enhance the hydrophilicity of the CPs, surface modification and functionalization have been attempted using the chemicals and small molecules that possess hydrophilic properties. Hybridization with other conducting materials, such as carbon nanotubes and nanofibers, have proven to be an effective strategy that supplements the low charge-carrier mobility of the CPs. Finally, it has been reported that the limit in drug-loading capacity can be overcome by forming nanostructures with higher porosity and surface area.  
In spite of significant advances in biomedical engineering by the use of the CPs as a biomaterial, there are still many challenges to be surmounted, including poor biodegradability, low hydrophilicity, low charge-carrier mobility, and small loading capacity of biomolecules. However, we believe that the CPs will become more promising materials for biomedical research in the near future, as a variety of ways to overcome the weaknesses of the CPs are continuously being explored.  
Writing--Original Draft Preparation, Y.P., J.J., and M.C. Writing--Review & Editing Y.P., J.J., and M.C.  
This work was supported by the National Research Foundation of Korea (NRF) with a grant funded by the Korean government (Ministry of Science, ICT & Future Planning, MSIP) (NRF-2017R1C1B5017856 and NRF-2017R1C1B1004605).  
The authors declare no conflict of interest.