Surface-enhanced Raman scattering (SERS) technique has shown extraordinary features for biomedical applications. The implementation of SERS nanotags has opened a new era for bioimaging and detections. As a powerful tool, SERS nanotags provide favorable properties such as fingerprint spectrum, narrow peak linewidth, good photostability, and high spatial resolution accompanied by various rational designs of nanoparticles. They have proven as useful imaging agents for in vivo, ex vivo, and in vitro detection of cancerous cells and tissues. This tutorial provides the basic principles of SERS and SERS nanotags, including recent progress of SERS-based bioimaging applications, as well as the outlooks into the future developments toward practical clinical SERS.

Oxygen consumption but hypoxic tumor environment has been considered as the major obstacle in photodynamic therapy. Although oxygen-supplied strategies have been reported extensively, they still suffer from the complicated system and unsatisfied PDT efficiency. Herein, one-component layered nickel silicate nanoplatforms (LNS NPs) are successfully synthesized using natural vermiculite as the silica source, which can simultaneously supply oxygen (O2) and generate superoxide radicals (O2 –•) under near-infrared irradiation. The appropriate electron band structure endows LNS NPs with attractive optical properties, where the bandgap edges determine the performance of redox activity and spectral response characteristic. Evidenced by both in vitro and in vivo investigations, LNS NPs can generate sufficient superoxide radicals under 660 nm laser irradiation to induce tumor cell apoptosis even in a severe hypoxic environment, which benefits from self-supplied oxygen. Besides, the photoacoustic oxy-hem imaging and histologic assay further demonstrated that the generated oxygen can relieve the inherent intratumoral hypoxia. Therefore, LNS NPs not only serve as superoxide radical generator but also produce oxygen to modulate hypoxia, suggesting that it can be used for superoxide radical-mediated photodynamic therapy with enhanced antitumor effect.

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