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Highly water soluble polymer (DD) was prepared and evaluated for its fluorescence response towards various amino acids. The polymer consists of dansyl hydrazine unit conjugated into dextran template. The conjugation enhances higher water solubility of dansyl hydrazine moiety. Of screened amino acids, DD exhibited selective fluorescence quenching in the presence of aspartic acid (Asp) and glutamic acid (Glu). A plot of fluorescence intensity change of DD against the concentration of corresponding amino acids gave a good linear relationship in the range of 1 × 10(-4) M to 25 × 10(-3) M. This establishes DD as a potential polymeric sensor for selective sensing of Asp and Glu.

A new "turn-on" fluorescent chemosensor based on dansyl derivative was prepared for Cu ion sensing. Hydroxyl, imine and azomethine groups in Schiff base derived compound 1 were deliberately introduced for facilitating the binding of Cu ion. Of screen metal ions, compound 1 showed a high degree of selectivity toward Cu ion. Other interfering metal ions did not affect the fluorescence intensity of compound 1, except Hg and Fe ions exhibited a significant degree of fluorescence quenching. Upon binding of Cu ion, compound 1 displayed a chelation enhanced fluorescence (CHEF) resulting in increasing of the fluorescence intensity. The molecular optimized geometry indicated the binding ratio between compound 1 and Cu ion at 1:1 with the binding constant of 1.68 × 10 M. The optimized condition for sensing ability of compound 1 with a detection limit of 5 × 10 M was found at the physiological pH 7.2 with the excitation wavelength of 366 nm. Due to no cytotoxicity and good photophysical properties, compound 1 was extended its application for the detection of Cu ion in Vero cells. Compound 1 could be potentially used as an intracellular fluorescent chemosensor for tracking Cu ion. Graphical Abstract.

Mannose-rhodamine (Rh) conjugate (80% yield) was synthesized in a one-pot reaction and immobilized onto magnetic polymeric nanoparticles (MPNP; 43% magnetic content) of poly(styrene/divinyl benzene/acrylic acid). The resulting nanoparticles contained MPNP as a substrate, mannose as an E. coli receptor and Rh as a fluorescent signaling unit. TEM imaging clearly demonstrated that multiple mannose-Rh MPNPs could be captured by E. coli strain ORN178. The fluorescent signal from captured nanoparticles was emitted at 580 nm. These results indicate that mannose-Rh MPNP offers a simple and rapid strategy for bacterial detection.