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 polydopamine-polypyrrole 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. Turning conductive polymers into porous microcapsules makes it easier to deliver drugs and modify cell behavior using electrical stimulation. Electrical therapy can treat diseases such as Parkinson's by altering how cells grow and communicate with each other. Xiong Lu and co-workers from Southwest Jiaotong University in China now report a way to improve the precision of electrical treatments using porous electroresponsive microcapsules on three-dimensional printed porous titanium. The microcapsules consist of conductive polypyrrole molecules and cell-friendly mussel-inspired polydopamine units, and were prepared using polystyrene spheres template by electrochemical deposition. The microporous material capable of on-demand loading and release of drugs. High-throughput studies of bone marrow stromal cell cultures demonstrated that the new polymer can manipulate cell behavior by the synergistic effects of porous structure, cell-friendly units and electrical potentials during incubation. Electrical therapy has been recognized as an alternative medical treatment for tissue repair in recent years. The principle of electrical therapy is the modulation of cell behavior by applying electrical signals. However, to date, the effectiveness of electrical therapy is limited. Herein, we developed electroresponsive and conductive polydopamine-polypyrrole microcapsules on the surfaces of electrical therapy devices, which can locally and precisely release drugs and apply electrical stimulation to modulate cell behaviors.