Fluorescent block amphiphilic copolymers are one of the most important bioimaging materials which are highly desirable for early stage cancer diagnosis and treatment. However, sometimes the application of the fluorescent block copolymers is severely limited because of the aggregation-caused quenching (ACQ) effect. In this study, new aggregation induced emission polymer dots (AIE Pdots) were prepared through a self-assembly process by using an AIE-conjugated block copolymer containing an AIE fluorophore, 9,10-bis(4-hydroxystyryl)anthracene, hydrophobic poly(ε-caprolactone) segments, hydrophilic poly(ethylene glycol) segments and folate groups. The AIE Pdots are monodispersed in H₂O with an average diameter of 15 nm, and possess strong emission and high solid state fluorescence quantum efficiency (Φ = 27.0%). Furthermore, the AIE Pdots show good stability and little toxicity to living cells and thus can be utilized for targeted HeLa cell imaging. Biological imaging investigation indicated that the folic acid functionalized AIE Pdots can be applied for targeted HeLa intracellular imaging.

Near-infrared emissive organic dots with a high fluorescence quantum efficiency (AEE dots) are prepared by using an amphiphilic polymer poly(styrene-co-maleic anhydride) (PSMA) as the co-encapsulation matrix and a novel small molecule fluorogen (DPPBPA) with high near-infrared emission as the core. The PSMA dots show small particle size of about 20 nm, a large Stokes shift of 304 nm and really high fluorescence quantum efficiency of 20%. The streptavidin-dots are obtained by conjugating streptavidin to carboxyl groups on the surface of PSMA dots. These streptavidin-dots can effectively and specifically label the target cell without any nonspecific binding, such as MCF-7 cells. Together with the negligible cytotoxicity, the near-infrared emissive AEE dots are promising red fluorescent probes for future bioimaging applications.

Herein, a novel on-off-on fluorescent chemosensor for copper (II) ion (Cu²⁺), iron (III) ion (Fe³⁺) and cysteine is developed simply by the nano-precipitation method. The prepared organic dots with AIEgens (AIE dots) are advantageous over other metal ions in detecting Cu²⁺, Fe³⁺ with high selectivity and sensitivity by forming agglomerations (on-off). The agglomerations formed by AIE dots and Cu²⁺ redistributed and the fluorescence was obviously recovered in the presence of cysteine (off-on). This sensor has a wide linear range for Cu²⁺, Fe³⁺ and cysteine. The fluorescent detection limits of AIE dots are calculated to be 107 nM for Cu²⁺, 120 nM for Fe³⁺ and 78 nM for cysteine, respectively. These results indicate that the AIE dots can be used as a potential probe for Cu²⁺, Fe³⁺ and cysteine detection.