Recently, the near-infrared-II (NIR-II, 1000–1350 nm) region has been extensively applied in deep-tissue photothermal therapy (PTT) on account of it having stronger tissue penetration and a higher maximum permissible exposure (MPE) than the near-infrared-I (NIR-I, 650–950 nm) region. In this study, we developed a rapid and convenient in situ polymerization strategy to fabricate polypyrrole nanosheets (PPy NSs) within a few minutes using manganese dioxide nanosheets (MnO₂ NSs) as both the oxidant and the self-sacrificed template. The fabricated PPy NSs exhibited excellent NIR-II absorption, which conferred its high photothermal conversion efficiency (66.01%) at 1064 nm and its photoacoustic (PA) imaging capability. Both in vivo and in vitro studies have shown that that PPy NSs possess good biological safety and excellent PTT efficacy and PA imaging performances. Thus, the as-synthesized PPy NSs could effectively achieve PA imaging-guided photothermal tumor ablation under 1064 nm excitation. Our work provides a novel and promising method for the rapid preparation of PPy NSs without the addition of exogenous oxidants and subsequent template removal, which could be regarded as potential photothermal agents (PTAs) to integrate the diagnosis and treatment of cancer.

Conductive polypyrrole (PPy) has excellent biocompatibility and structural stability. It is an ideal electroactive biomaterial that can apply exogenous electrical stimulation to promote osteoblast differentiation. However, PPy is a kind of bio-inert material, which does not have osteoinductive capacity. Therefore, we have introduced a kind of bioactive material, hydroxyapatite (HA), to construct PPy/HA composite to enhance bioactivity and osteoinduction. In addition, micron-topological morphology of scattered grid pattern has been designed and introduced to the PPy/HA coatings, which can further enhance the regulation ability of the coatings to the adhesion, proliferation and differentiation of MC3T3-E1 cells. In vitro simulated body fluids (SBFs) immersion test results have demonstrated that the fabricated micropatterned PPy/HA composite coatings perform bioactivity well and can promote the mineral deposition of HA on the surface. Moreover, it can also benefit the proliferation and osteognetic differentiation of MC3T3-E1 cells, when accompanied by external electrical stimulation (ES). In this study, we have successfully constructed electroactive and bioactive coatings, the method of which can potentially be applied to the surface functional modification of traditional bone repair metals.