α‐Cyanostilbene represents one of the easily functionalized aggregation‐induced emission (AIE) scaffolds. It has been widely adopted for the construction of fluorescent materials for broad applications. Here, we further expanded the utilization of α‐cyanostilbene derivatives for the detection of hypoxia or proteostasis imbalance in live cells. Four different amine containing donors were introduced to construct α‐cyanostilbene derivatives (R‐ASC) with donor‐acceptor scaffolds. Equipped with the cysteine (Cys) reactive group, maleimide (MI), R‐ASC‐MI shows fluorescence turn‐on property upon binding with unfolded proteins in vitro and in live cells under proteostatic stress. By virtue of R‐ASC‐MI, the level of unfolded protein loads in cells can be quantified by flow cytometry, or visualized under microscope. Furthermore, we also characterized the performance of R‐ASC‐NO2, synthetic precursors of R‐ASC‐MI, in cellular hypoxia. R‐ASC‐NO2 revealed upregulated activities of nitroreductase, as well as increased hydrophobicity in live cells, under either chemical (NaN3) induced or atmospheric (1 % O2) hypoxia. Together, the advantages of easy modification and high signal‐to‐noise ratio of new α‐cyanostilbene derivatives reported in this work highlight the great potential of α‐cyanostilbene in constructing functional biosensors and many other domains. [ABSTRACT FROM AUTHOR]

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