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Hydrogen peroxide (H2O2) is widely involved in various physiological or pathological processes such as cell differentiation, proliferation, tumorigenesis, and immune responses. The accurate detection of H2O2 is highly required in many situations ranging from chemical sensing to biomedical diagnosis. However, it is exceedingly challenging to develop a single sensor that can respond to H2O2 in different conditions. Herein, a three-in-one stimulus-responsive nanoplatform (Au@MnO2@Raman reporter) was designed for colorimetry/SERS/MR tri-channel H2O2 detection which satisfied different applications. The MnO2 shell acted as a distance mediator between the gold nanoparticle (Au NP) core and the Raman reporter layer. In the presence of H2O2, the MnO2 shell is degraded, thus releasing the Mn2+ and Au NP core, which act as magnetic resonance (MR) and colorimetry signals, respectively. Simultaneously, the Raman reporters adsorb on the exposed Au NPs, resulting in the surface-enhanced Raman scattering (SERS) effect. The Au NP-based colorimetric assay was employed as H2O2 sensors for glucose detection while the turn-on signals of SERS and MR were used for H2O2 sensing and imaging in live cells and tumors, showing great versatility and flexibility of the multichannel probes in diverse situations.

Photothermal therapy with minimal invasiveness and high selectivity has been regarded as a powerful technique for tumor therapy to overcome the risks of toxic side effects and limited therapeutic efficacy of clinic cancer treatments. Among various photothermal therapeutic agents, polypyrrole (PPy) nanoparticles show a promising prospect in tumor ablation in vivo due to their admirable biocompatibility and outstanding photothermal performance. Besides, polypyrrole nanoparticles are extensively applied in biosensors, electrochemical sensors, tissue engineering, flexible microelectronics, and so on. However, the available synthesis methods of PPy nanoparticles are all time-consuming and seriously hindered their highly efficient production for diverse applications. Here we present a microwave-assisted strategy for the fabrication of PPy nanoparticles in 2 min, and the required synthesis time is shortened by 120-720 times compared to that in traditional ways. The prepared PPy nanoparticles possess uniform size, favorable aqueous solubility, and enhanced photothermal performance derived from the stronger near-infrared absorbance. Low cytotoxicity and in vivo toxicity of the nanoparticles were confirmed via comprehensive assessments. The PPy nanoparticle-based photothermal therapy in vitro led to a remarkable death of tumor cells, and in vivo tumor ablation using the nanoparticles was achieved under mild laser irradiation with a FDA-approved safe power. The proposed microwave-assisted synthesis strategy opens up a facile and ultrafast way for the construction of organic nanoparticles and facilitates a wide range of applications of them in biomedicine and other fields.

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