Polydopamine capsule has aroused wide attention since its emergence, because of its biocompatibility and the great potential as drug delivery carrier. However, preparing the nanometer PDA capsule (PDAC) is still remained a challenge, especially with the size below 300 nm. Moreover, there is little research about its photoacoustic imaging (PAI) and photothermal therapy (PTT) effect. In this paper, we reported an improved DMDES emulsion template method to obtain 200 nm PDAC, and act as highly efficient theranostic agent for photoacoustic imaging (PAI) and chemo-photothermal synergistic therapy. Due to its hollow structure and the higher photothermal conversion efficiency (η), the PDAC showed excellent PAI ability as its PA intensity was far outweigh the PBS and over two folders than the same size polydopamine particles (PDAP) at the same concentration in vitro. The animal experiment also verified this conclusion. Then the anticancer drug-doxorubicin (DOX) was loaded on PDAC via electrostatic interaction and π–π stacking. Moreover, the drug release was pH responsive and NIR laser responsive to minimize the side effect, and this system was proved to efficiently ablate the tumor in vitro and in vivo experiments. This research highlights the great potential of PDA capsule as a new theranostic agent.

Homogenous poly(pyrrole-3-carboxylic acid) nanoparticles with high near-infrared absorption and abundant functional groups were fabricated using a facile reverse microemulsion method.

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