Plasmonic nanomaterials: A versatile phototheranostic platform of cancers

Phototheranostic platform emerges as a highly powerful tool against cancers due to unique features such as minimal invasiveness, high spatiotemporal resolution, and function integration. Plasmonic nanomaterials are able to achieve a myriad of diagnostic and therapeutic functionalities owing to their superior photophysical properties stemming from local surface plasmon resonance (LSPR), and enable them to act as a versatile phototheranostic platform. Therefore, a bridge is needed to link the underlying LSPR process and the plasmonic theranostic functionalities. To fill the gap, this review ventures to summarize the plasmonic nanomaterials-based phototheranostic modalities in mechanistic physics. Three major physical processes and the corresponding theranostic functionalities are outlined: (1) the excitation of LSPR arises significant field enhancement near the plasmonic nanomaterials, which can be harvested to magnify the output signal for fluorescence imaging, Raman scattering, and boost reactive oxygen species (ROS) production. (2) LSPR subsequently generates abundant hot carriers that are capable of catalyzing intracellular reactions and producing ROS, thereby fulfilling therapeutic purposes. (3) the LSPR finally decays either through heat or fluorescence, which indicates the plasmonic nanomaterials can either act as a heat source to trigger drug release, damage cellular component and delineate cancers, or enable visualizing tumor sites explicitly by fluorescence. This review hopes to give assistance on integration of these diagnostic and therapeutic functions by providing a big picture of the plasmonic nanomaterials-based nanomedicine. Finally, several limitations of current research in this regard are pointed out.