Recent advances of luminogens with aggregation-induced emission in multi-photon theranostics

Multi-photon theranostics, involving the absorption of two or three photons by luminogens, has come to occupy an important place in biomedical research, with its ability to allow real-time observation/treatment of dynamic structures in living cells and organisms. Luminogens with aggregation-induced emission characteristics are recognized as perfect candidates for multi-photon agents, owing to their flexibility of design, resistance to photobleaching, robust stability, and reduced cytotoxicity. Hence, in recent years, significant breakthroughs in design and application of such luminogens have been reported. In this review, we summarize the latest advances in molecular guidelines and photophysical process control for developing luminogens with large multi-photon action cross section. Special attention is paid to how the molecular structure and intermolecular interactions influence the intramolecular charge transfer, and how new strategies have been developed to advance the multi-photon imaging and therapeutic performance. With this review, we hope to encourage further exploitation of luminogens with aggregation-induced emission characteristics to advance multi-photon theranostics.