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A visible light and pH responsive anticancer drug delivery system based on polymer-coated mesoporous silica nanoparticles (MSNs) has been developed. Perylene-functionalized poly(dimethylaminoethyl methacrylates) sensitive to visible light and pH are electrostatically attached on the surface of MSNs to seal the nanopores. Stimulation of visible light and acid can unseal the nanopores to induce controlled drug release from the MSNs. More interestingly, the release can be enhanced under the combined stimulation of the dual-stimuli. The synergistic effect of visible light and acid stimulation on the efficient release of anticancer drugs from the nanohybrids endows the system with great potential for cancer therapy.

Photoacoustic imaging (PAI) is an emerging whole‐body imaging modality offering high spatial resolution, deep penetration and high contrast in vivo. Signals for PAI are generated from contrast agents, where the laser‐generated optical energy is transferred to acoustic emissions and detected by an ultrasound transducer. A great deal of research over the past ten years has shown that near‐infrared absorption nanomaterials such as organic dye‐based nanoparticals, polymer‐based nanoparticles, carbon‐based nanomaterials and metallic nanomaterials are promising photoacoustic (PA) contrast agents, which can increase the imaging resolution, contrast and depth of detection. Hence, it is an attractive research field to develop new PA contrast agents. Herein, we reviewed this rapidly growing field and described the applications of nanomaterial‐based PA contrast agents for biomedical imaging. Particular focus was given to organic near‐infrared absorbing dyes including cyanine, porphyrin and boron‐dipyrromethene derivatives.

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