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

Abstract

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.

Deep-Brain Three-Photon Imaging Enabled by Aggregation-Induced Emission Luminogens with Near-Infrared-III Excitation

“…The wavelength of each photon absorbed in the 3P process is nearly three times longer than that in one-photon excitation. In this case, it is possible to use the long-wavelength light in NIR-III for excitation, while bypassing the difficulties in the material design of luminogens with long-wavelength absorption. , Furthermore, because the light absorption increases cubically with the excitation intensity, the fluorescence excitation is largely confined to the vicinity of the focal point . This feature not only offers an intrinsic capability in optical 3D sectioning but also reduces the chance of photobleaching, thus enabling long-time observations of in vivo dynamic processes. − Hence, 3P imaging is potentially an excellent tool for studying cerebral microvessels.…”

Overcome the “Buckets Effect”: Integration of AIEgens into Proteins for Fluorescence‐Enhanced Two‐Photon Imaging

“…[1] Compared with conventional one-photon fluorescence imaging, 2PFI has three major advantages, including large imaging depth, high spatial resolution, and long observation time. [2] The merits of 2PFI are attributed to the highly restricted scattered photons in their origin by virtue of the localized generation of nonlinear signals. [3] So far, great strides have been made toward understanding the metabolism, [4] structure, [5,6] and activity [7] in biology science, especially brain science.…”

Multifunctional Self-Assembled Nanoplatform with AIEgen and Rapamycin-Mediated Tumor Microenvironment Remodeling via mTOR Axis to Enhance Photodynamic Therapy

“…13,14 Since Academician Tang Benzhong introduced the new physical phenomenon of AIE in 2001, the development of AIEgens as a new generation of PS has received extensive attention. 10,15,16 AIEgens not only endow PS with strong fluorescence characteristics, making it easier to track but also increase the production rate of ROS of PS and play a more potent anticancer effect. 17−20 Additionally, it is well-known that PS triggers two main PDT mechanisms to produce various ROS: the type I mechanism that produces free radicals via electron transfer and the type II mechanism that produces singlet oxygen via energy transfer.…”

“…Since Academician Tang Benzhong introduced the new physical phenomenon of AIE in 2001, the development of AIEgens as a new generation of PS has received extensive attention. ,, AIEgens not only endow PS with strong fluorescence characteristics, making it easier to track but also increase the production rate of ROS of PS and play a more potent anticancer effect. − Additionally, it is well-known that PS triggers two main PDT mechanisms to produce various ROS: the type I mechanism that produces free radicals via electron transfer and the type II mechanism that produces singlet oxygen via energy transfer . Currently, most of the developed PS are type II, which essentially rely on O 2 to produce ROS, so the ubiquitous hypoxic microenvironment of solid tumors limits the application. , Compared with type II PS, type I PS has less dependence on O 2 and more potent cytotoxicity of free radical ROS. , Therefore, exploring type I AIEgens with high-performance ROS production is necessary to enhance the PDT efficacy.…”