The design of bright NIR-II luminescent nanomaterials that enable efficient labelling of proteins without disturbing their physiological properties in vivo is challenging. We developed an efficient strategy to synthesizebright NIR-II gold nanoclusters (AuN Cs) protected by biocompatible cyclodextrin (CD). Leveraging the ultrasmall sizeo fA uN Cs (< 2nm) and strong macrocycle-based host-guest chemistry, the as-synthesized CD-AuN Cs can readily label proteins/ antibodies.M oreover,t he labelled proteins/antibodies enable highly efficient in vivo trackingd uring blood circulation, without disturbing their biodistribution and tumor targeting ability,thus leading to asensitive tumor-targeted imaging. CD-Au NCs are stable in the harsh biological environment and show good biocompatibility and high renal clearance efficiency.T herefore,t he NIR-II biolabels developed in this study provideapromising platform to monitor the physiological behavior of biomolecules in living organisms.

Aggregation-induced emission (AIE) has attracted much attention in the past 2 decades. To develop novel AIE-active materials, ACQ-to-AIE transformation via regioisomerization is one of the most straightforward method. However, most of the reported ACQ-to-AIE transformations are achieved by migrating bulky units. In this work, a facile conversion was realized by migrating a small pyrrolidinyl group from para- to ortho-position on the rofecoxib scaffold. As a result, a pair of new isomers named MOX2 and MOX4 exhibited AIE behavior and ACQ activity, respectively. Moreover, MOX2 also showed solvatochromic, mechanochromic, and acidochromic properties with reversible multi-stimulus behavior. Single crystal X-ray analysis of MOX2 revealed that the molecular conformation and its packing mode were responsible for the AIE emission behavior. Further investigation indicated that MOX2 showed high lipid droplets staining selectivity. Taken together, the current work not only provides a new design philosophy for achieving ACQ-to-AIE conversion by migrating a small pyrrolidinyl group but also presents a promising candidate MOX2 for potential applications such as in security ink, optical recording and biological applications.

Cyclooxygenase-2 (COX-2) fluorescent probes are promising tools for early cancer diagnosis. Traditionally, COX-2 probes were designed by connecting two parts, a fluorophore and a COX-2 binding unit, via a flexible linker. Herein, a new class of COX-2-specific fluorescent probes have been developed by one-step modification from rofecoxib by an integrative approach to combining the fluorophore and binding units into one. Among them, several new rofecoxib analogues not only retained their COX-2 binding ability but also exhibited attractive fluorescent properties, such as tunable Blue-Red emission, solvatochromism, AIE behavior and mechanochromism. Notably, the emission of 2a16 can be switched between greenish-yellow in the crystalline state to red-orange in the amorphous state by grinding and fuming treatments. Furthermore, the highly fluorescent compound 2a16 (Фf = 0.94 in powder) displayed much stronger fluorescent imaging of COX-2 in HeLa cancer cells overexpressing COX-2 than RAW264.7 normal cells with minimal expressing of COX-2. Most importantly, 2a16 can light up human cancer tissues from adjacent normal tissues with much brighter fluorescence by targeting COX-2 enzyme. These results illustrate the potential of 2a16 as a new red fluorescent probe for human cancer imaging in clinical applications.