ChemicalScienceView Article OnlineView Journal|View Issue View Article OnlineEdge ArticleChemical Science CrossMark97.9% of the attached cells. In solution, over 95.8% ofE.coli K12 cells were still viable after one hour. One advantage ofCP surfaces is that the surface potential can be activelycontrolled. By applying a lower potential (0 V), the oxidizedcationic PSBDEOT surface can switch to a reduced zwitterionicsurface. Due to the repulsive force generated by strong hydra-tion of the zwitterionic side chains and the disappearance of theattractive force between the negatively charged bacteria andpositively charged PSBDEOT surfaces, the killed bacterial cellscan be released. To confirm the hypothesis, a bacterial cellreleasing experiment was conducted using PSBEDOT and goldsurfacestthatccarried killed bacterialcells fromnthe Fig. 4 Representative fluorescence microscopy images of the bacterial adhesion, antimicrobial and release studies on PSBEDOT and controlsurfaces. Attached E. coli K12 from a suspension with 10°cells per mL on gold (A) and oxidized PSBEDOT (D); the viability of the attached E. coliK12 on gold (B) and oxidized PSBEDOT (E) after subjection to 0.6 V for 1 hour; and the remaining E. coli K12 on gold (C) and oxidized PSBEDOT (F)after subjection to 0 V for 1 hour. In the viability study, bacterial cells were stained using a LIVE/DEAD BacLight Bacterial Viability assay kit. Cellswith a damaged cytoplasm membrane are in yellow and red, and cells with an intact cytoplasm membrane are in green. Fig. 5 Quantitative bacterial adhesion, antimicrobial and releasestudies on PSBEDOT and control surfaces. (A) Attachment of E. coli K12from a suspension with 10° cells per mL on oxidized (Ox) PSBEDOT,reduced (Red) PSBEDOT and controlsurfaces; (B) bactericidal activityresults of PSBEDOT and the control surface against E. coli K12 aftersubjection to 0.6 V for 1 hour; and (C) detachment of E. coli K12 fromoxidized PSBEDOT and gold after subjection to 0 V for 1 hour. antimicrobial study. As shown in Fig. 5C, 96.7% of E. coli K12cells on the PSBDEOT surface were released within 1 hour underthe static conditions after the potential was decreased to 0 Vfrom 0.6 V, while only 30% of the cells on the gold surface werereleased. The final cell density on PSBEDOT was less than 3% ofthat on the gold substrate. It should be noted that the release ofkilled bacterial cells is critical for implanted materials, since the attached dead cells may cause chronic inflammation and leadto the failure of implanted materials/devices. Previously severalswitchable antifouling/antimicrobial materials have been re-ported.18,20,32 These zwitterionic polymers can undergo ringformation to become cationic under low pH conditions (pH<5)and can switch back to their zwitterionic state under neutral orbasic conditions. In this work, the electrochemical approachallows for more rapid and active control of the state of thezwitterionic materials. Through this study, we have demon-strated that PSBEDOT surfaces could effectively resist cellattachment in their reduced state, kill the small amount ofattached cells in their oxidized state and release the dead cellsafter switching back to the reduced state. Numerous applications, ranging from the field of solid statetechnology33,34 to biomedical engineering,33,35,36 need to usehigh performance CPs as the key components that determinethe function and properties of the devices, so the developmentof novel multifunctional CPs is of great importance. One of themost attractive features of CPs over traditional biomaterials isthat they could allow electrical stimulation of the attachedtissues and cells. It is expected that the novel PSBEDOT couldbe used to manipulate cell attachment through electrochemicalcontrol and also could serve as a protective coating to reduceprotein adsorption and cell attachment thus prolonging thelifetime of implanted devices. Although there is much work tobe done to fully understand and realize the potential of zwit-terionic conjugated polymers, we believe this work will funda-mentally advance the development of bioelectronics. Conclusions In this work we designed and synthesized a novel antifoulingand electroactive PSBEDOT material. Zwitterionic PSBEDOTcan be facilely polymerized in aqueous solution through anelectrochemical method. The PSBEDOT polymer films exhibitexcellent electrochemical properties, low interfacial impedance,stability and switchable antifouling/antimicrobial properties.The interfacial impedance of PSBEDOT was less than 10% ofthat of bare gold at low frequency. It also showed superiorantifouling properties against whole blood, mammalian cellsand bacteria. The PSBEDOT surface can also be switchedbetween cationic antimicrobial and zwitterionic antifoulingstates by applying different potentials. It can kill over 89% ofattached cells in one hour at 0.6 Vand release over 96.7% of thedead cells in one hour at 0 V under static conditions. It showsgreat promise for applications in bioelectronics. This newmaterial may significantly increase the performance and servicelife, minimize the foreign body reaction, improve the biocom-patibility and reduce the infection of bio-electronic devices. Acknowledgements This work is supported by the US National Science Foundation(ECCS-1200032 and DMR-1454837). 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