Cryosurgery has attracted much attention for the treatment of tumors owing to its clear advantages. However, determining the volume of frozen tissues in real‐time remains a challenge, which greatly lowers the therapeutic efficacy of cryosurgery and hinders its broad application for the treatment of cancers. Herein, we report a freezing‐induced turn‐on strategy for the selective real‐time imaging of frozen cancer cells. As a type of aggregation‐induced emission (AIE) fluorogen, TABD‐Py molecules interact specifically with ice crystals and form aggregates at the ice/water interface. Consequently, bright fluorescent emission appears upon freezing. TABD‐Py molecules are enriched mostly in the cancer cells and exhibit high biocompatibility as well as low cytotoxicity; therefore, a freezing‐induced turn‐on imaging modality for cryosurgery is developed, which will certainly maximize the therapeutic efficacy of cryosurgery in treating tumors.

Insufficient intratumoral penetration and limited stroma distribution of the imaging probes or theranostics can lead to a poor-quality diagnosis or therapeutic resistance. Multicellular tumor spheroids can recapitulate the physiological environment of tumor tissues with the extracellular matrix and is thus a better in vitro tumor model to evaluate the imaging performance and barrier penetration capability of advanced cancer imaging probes. In this Article, we designed and synthesized a series of quinoline-based fluorophores with strong emissions in both solution and solid states. The quinoline core can be constructed via a one-pot iron-catalysis reaction. Optical properties and single crystal structures of these quinoline derivatives were tuned by varying the substitutes at the 6-position of the quinoline core. The twisted intramolecular charge transfer effect can enhance the fluorescent efficiency, resulting in the high quantum yield of TPQ-TPA in both solution (70%) and solid (48%) states (TPQ, triphenylquinoline; TPA, triphenylamine). In addition, TPQ-TPA exhibited a good biocompatibility and can deeply penetrate into 3D tumor spheroids within 12 h. The results indicated that quinoline can be a new fluorescent scaffold, and the employment of quinoline-based probes will provide a new platform for biological applications.

A novel "turn-on" fluorescent bioprobe, 1,2,3,4,5-penta(4-carboxyphenyl)pyrrole sodium salt (PPPNa), with aggregation-enhanced emission characteristics was synthesized for the in situ quantitative detection of Al in serum. It exhibited a high selectivity to Al in both simulated serum and fetal calf serum with no interferences from other metal ions or serum components observed and no isolation required. A weak interaction between PPPNa and serum albumin was found, which caused no interference, but enhanced fluorescence response of PPPNa to Al and improved detection sensitivity. The limit of detection was determined to be 1.50 μmol/L Al in phosphate-buffered saline solution containing 33 μg/mL bovine serum albumin (BSA) and decreased to 0.98 μmol/L as BSA concentration increased to 100 μg/mL. The fluorescence "turn-on" mechanism of the PPPNa probe to detect Al was proposed. A bidentate complex is formed between the carboxy group of PPPNa and Al, causing the photoluminescence (PL) emission enhancement by aggregation. BSA chains further strengthen the stacking compactness of the aggregates of PPPNa and Al and consequently enhance the PL emission of PPPNa by further promoting the restriction of intramolecular rotation of the phenyl ring. Its application to the in situ Al was successfully demonstrated with HeLa cells and NIH 3T3 cells. The low cytotoxicity and highly selective response of PPPNa to Al endow its great potentials to in vivo detecting and imaging of Al as well as an absorbent of Al.

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