Electroresponsive and cell-affinitive polydopamine/polypyrrole composite microcapsules with a dual-function of on-demand drug delivery and cell stimulation for electrical therapy

Electrical therapy has attracted significant attention because it can modulate cell behaviors and accelerate tissue repair. However, the effectiveness of electrical therapy is limited. This work develops electroresponsive and conductive polydopaminepolypyrrole microcapsules (PDA-PPy-MCs) on titanium surfaces using electrochemical deposition. During the electrochemical process, PDA and dexamethasone (DEX) as the anion are doped into a PPy backbone to neutralize its positive charge. PDA-PPy-MCs possess the cell affinity of PDA, the microstructure of MCs and the electroresponsive capability of PPy. The incorporation of PDA promotes the conductivity and adhesive strength of PPy. PDA-PPy-MCs can respond to electrical signals to release DEX on demand because of the redox behavior of PPy. The microstructure and PDA improve the drug-loading capability of PDA-PPy-MCs. A high-throughput bone marrow stromal cell (BMSC) culture system is designed to study the synergistic effects of composition, microstructure and electrical stimulation on cell behavior. The results indicate that PDA and the microporous structure not only enhance the biocompatibility of PDA-PPy-MC but also strengthen the effect of electrical stimulation. In vivo implantation shows that PDA-PPy-MCs have good biocompatibility. The high cell affinity, microstructure, conductivity and ability to control drug delivery using electrical signals make PDA-PPy-MCs a promising candidate for an on-demand drug delivery and electrical therapy system. NPG Asia Materials (2017) 9, e358; doi:10.1038/am.2017.16; published online 10 March 2017