A colorimetric sensing system based on gold nanoparticles functionalized with a water-soluble anion-recognition motif, an o-(carboxamido)trifluoroacetophenone analogue, has been developed. The nanoparticle system selectively senses specific isomers of dicarboxylates that are geometrically favorable for the binding-induced aggregation process; thus, it discriminates a trans-dicarboxylate fumarate from its cis-isomer maleate, and benzene-1,4-dicarboxylate from its isomeric benzene-1,2-and benzene-1,3-dicarboxylates in water, exhibiting a color change from red to blue.

A microarray-chip assay system for the fluorescence detection of phosphate-containing analytes in aqueous media has been constructed from stimuli-responsive polymerized poly(diacetylene)-liposomes for the first time. Proper combination of the liposome components (Zn(II)-dipicolylamine for phosphate binding and an amine-terminated component for anchoring the liposome onto an aldehyde-derivatized glass plate), has led to a microarray chip that selectively detects pyrophosphate, an important biomarker, over competing anions, such as phosphate and adenosine triphosphate, with nanomolar sensitivity. The chip-based assay shows advantages, such as high specificity and sensitivity, over solution-based assays that use the same liposomes, and over known homogeneous molecular sensing systems.

A trifurcate receptor containing Zn(II)-dipicolylamine ligands is developed for the fluorescent sensing of IP 3, myo-inositol 1,4,5-tris(phosphate), through an indicator displacement approach. The chemosensing ensemble containing the Zn(II) complex and eosin Y as indicator shows the maximum fluorescence restoration for IP 3 among various other anions including phosphate derivatives in water buffered at pH = 7.

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A trifurcated receptor system containing three Cu(II)-dipicolylamine ligands has been studied for the molecular sensing of phytate, myo-inositol hexakis(phosphate) sodium salt, through an indicator displacement approach. From the Cu(II) complex, a molecular sensing ensemble system was best constructed with eosin Y as indicator. The addition of phytate to the chemical ensemble system in an aqueous medium of physiological pH resulted in the restoration of fluorescence of eosin Y as it is displaced from the metal complex by the anion added. The ensemble system shows the maximum fluorescence change in the case of phytate, about 70% change in the cases of myo-inositol 1,4,5-tris(phosphate) and pyrophosphate ions, and negligible changes in the cases of monovalent anions (HPO 4 22 , CH 3 CO 2 2 , CO 3 22 , Cl 2 , Br 2 , ClO 4 2 , N 3 2 , NO 3 2 ) and inositol. A binding study by isothermal titration calorimetry suggests that the Cu(II) complex tends to recognize phytate preferably in a 2:1 binding mode with K 1 of 7.7 3 10 8 M 21 , accompanied with a large favorable entropy change (TDS 5 19.4 kcal mol 21 ) and an unfavorable enthalpy change (DH 5 7.1 kcal mol 21 ) at 303 K. The present chemical ensemble system thus can be used for fluorescence sensing of phytate in the mM range.