Fabrication and characterization of 8‐nm‐sized conjugated polymer nanoparticles (CPNs) and two‐photon (2P) imaging of CPN labeled endothelial cells in a collagen‐gel‐based microfluidic device is described. CPNs exhibit super brightness and photostability comparable to quantum dots. The hydrophilicity and non‐toxicity of CPNs enable long‐term monitoring of cells in a tissue model, supporting CPNs' potential in biological and biomedical applications.

[structure: see text] A model system has been developed to study the synergy between aromatic stacking and hydrogen bonding in the binding of a flavin derivative. The results show that the identity of both the hydrogen bonding and pi-stacking units strongly determine the overall receptor affinity for flavin in both the oxidized and radical anion forms.

We report the synthesis of two water-soluble BODIPY dyes with far-red absorption and near-infrared fluorescence following cell membrane insertion. Introduction of dicationic or dianionic groups imparts water solubility and prevents translocation of the dye through the plasma membrane for highly effective labeling. The dicationic form is particularly well localized to the plasma membrane and resists quenching even after >8 min of continuous light exposure. The dyes are almost completely nonemissive in water and other highly polar solvents, but display high-fluorescence yields in chloroform and upon insertion into the extracellular leaflet.

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