Near-infrared emissive AIE nanoparticles for biomedical applications: From the perspective of different nanocarriers

Fluorescent imaging based on near-infrared (NIR) fluorophores has revolutionized the techniques employed for detecting biological events in depth owing to their advantages referring to diminished photon scattering, high signal-to-noise ratio and better light transparence through tissue. As for conventional luminogens, the nanofabrication of those innately hydrophobic π-conjugated architectures into water-dispersible nanoparticles (NPs) may result in attenuated fluorescent intensity deriving from the detrimental distribution of π-π interactions in the confined space. Oppositely, chromophores possessing aggregation-induced emission (AIE) characteristics emit boosted brightness at aggregate level according to the mechanism of restriction of intramolecular motion (RIM). In this review, we summarize the recent progresses of NIR emissive AIE NPs for multifarious biomedical applications from the viewpoint of different fabricated manners, mainly covering self-assembly and matrices assisted approaches. Furthermore, the current challenges and future research directions of NIR AIE NPs are briefly discussed.