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Updated: Jan 8, 2026
Synthesis and Calibration of Phosphorescent Nanoprobes for Oxygen Imaging in Biological Systems
Published on: March 3, 2010
Optimization of bulkiness/dynamicity and pH utilizing
Yuji Mikata1, Saori Yasuda2, Poonyawee Suwankeeree3
1Laboratory for Molecular & Functional Design, Department of Engineering, Nara Women's University, Nara 630-8506, Japan; Cooperative Major in Human Centered Engineering, Nara Women's University, Nara 630-8506, Japan; KYOUSEI Science Center, Nara Women's University, Nara 630-8506, Japan.
Abstract:
Two methyl substituents of TriMeOBQDMEN (L0, N,N'-bis(5,6,7-trimethoxy-2-quinolylmethyl)-N,N'-dimethylethylenediamine) have been changed to 3-pentyl, cyclopentyl, and cyclohexyl groups to achieve better Cd2+ selectivity on fluorescence enhancement upon metal ion binding. Bulky alkyl substituents result in weak metal binding affinity of the ligand, which decreases the fluorescence intensity in the presence of excess amount of metal salt, even for Cd(ClO4)2 in DMF-H2O (1:1). During the titration, the protons generated in the presence of excess metal perchlorate inhibit the complexation by protonation of the ligand. Addition of chloride ion minimizes the fluorescence drop in the presence of excess cadmium salt via formation of dinuclear bis(μ-chloro) cadmium complex. Intrinsic fluorescent Cd/Zn selectivity of the ligand can be assessed in DMF-HEPES buffer (1:1, 50 mM HEPES, 0.1 M KCl, pH = 7.5). The use of DMF-borate buffer (1:1, 50 mM M boric acid, 50 mM KCl, pH = 10) effectively discriminates Cd2+ from Zn2+ (IZn/ICd = 0.7 % in the presence of 3 equiv. of metal ions) by utilizing the TriMeOBQDPEN (L2, N,N'-bis(5,6,7-trimethoxy-2-quinolylmethyl)-N,N'-di(3-pentyl)-ethylenediamine) with moderate metal binding affinity. Lowering pH also increases the Cd2+ selectivity (IZn/ICd = 9 % in the presence of 5 equiv. of metal ions) of TriMeOBQDCPEN (L3, N,N'-bis(5,6,7-trimethoxy-2-quinolylmethyl)-N,N'-di(cyclopentyl)ethylenediamine) in DMF-glutarate buffer (1:1, 10 mM 3,3-dimethylglutaric acid, 0.1 M NaCl, pH = 6).
