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David B Cordes

Publications and source records attributed to David B Cordes.

9 recordsLinked to original sources
PubMed2006

Helices versus zigzag chains: one-dimensional coordination polymers of Ag(I) and Bis(4-pyridyl)amine.

Five one-dimensional coordination polymers were prepared by the reaction of a bent bridging ligand, bis(4-pyridyl)amine (bpa), with an extensive series of AgX salts (X = CF3SO3, PF6, ClO4, NO3). The 1D polymer networks formed with AgCF3SO3 (1), AgPF6 (2.MeCN), and AgClO4 (3.2MeCN) all incorporated MeCN and were found to adopt a zigzag arrangement. The networks formed with AgClO4 (4) and AgNO3 (5) did not contain any solvent and adopted a single-stranded helical arrangement. Two-dimensional H-bonding networks were formed for 1 and 3.2MeCN, with network topologies 4.8(2) and (4, 4), respectively, whereas three-dimensional H-bonded networks of helices were formed for 4, showing an (8, 3)-a network topology, and 5, showing the topology of the alpha-polonium net. The three-dimensional networks both exhibited 4-fold interpenetration. The NO3- anion in 5 appeared to be acting as a template for the 3D structure.

Journal Article↗
PubMed2006

Continuous glucose sensing with fluorescent thin-film hydrogels. 2. Fiber optic sensor fabrication and in vitro testing.

BACKGROUND: There continues to be a need for better sensors for continuous glucose monitoring. We are working on a two-component sensing system based on a viologen boronic acid and a fluorescent dye, which are immobilized in a hydrogel. This system has the potential for further development into a real-time glucose-monitoring device. The current study reports the fabrication of sensors using preformed hydrogels and the first in vitro monitoring of glucose concentrations in a prototype sensor configuration. METHODS: Glucose sensing hydrogels containing a fluorescent dye and viologen boronic acid quencher were preformed in a mold. These preformed hydrogels were then attached to the distal end of a plastic fiber optic cable using different adhesives to prepare the in vitro sensors. These sensors were connected to a flow cell and monitored using a fluorescence spectrometer. The fluorescence emitted by the hydrogel changes depending on the glucose concentration. Hydrogel components were modified in order to optimize the performance of the sensors. RESULTS: A soft tissue adhesive used by veterinarians was found to be an effective adhesive for bonding the hydrogel to the fiber tip. This adhesive did not affect the glucose sensing ability of the hydrogels after fabrication. Several sensors were fabricated with varying composition of sensing elements, and all of them showed stable and reversible glucose response. The glucose signal was found to be stable over months on repeated testing. Glucose sensing studies using the sensors with hydrogels containing different compositions of sensing elements showed that the ratio of dye to quencher is an important parameter in determining the magnitude and linearity of glucose response in the biological range. The response time of the sensor was shown to be dependent on the hydrophilicity of the hydrogels. Modifying the hydrogels with ionic comonomers shortened the response time. CONCLUSIONS: The combination of the anionic dye 2 and viologen-based boronic acid 1 immobilized in a 2-hydroxyethyl methacrylate hydrogel functions well in a fiber optic configuration. This preliminary study suggests that the two-component sensing system has several advantages in terms of stability and ease of fabrication. Improvement of the configuration of the sensor and further development of the sensor towards application for in vitro study are underway.

Drug Monitoring↗
PubMed2005

The interaction of boronic acid-substituted viologens with pyranine: the effects of quencher charge on fluorescence quenching and glucose response.

The fluorescence sensing of several monosaccharides using boronic acid-substituted viologen quenchers in combination with the fluorescent dye pyranine (HPTS) is reported. In this two-component sensing system, fluorescence quenching by the viologen is modulated by monosaccharides to provide a fluorescence signal. A series of viologen quenchers with different charges were prepared and tested for their ability both to quench the fluorescence of HPTS and to sense changes in glucose concentration in aqueous solution at pH 7.4. Both quenching efficiency and sugar sensing were found to be strongly dependent upon viologen charge. The molar ratio between HPTS and each of the viologen quenchers was varied in order to obtain an optimal ratio that provided a fairly linear fluorescence signal across a physiological glucose concentration range. Both the quenching and sugar sensing results are explained by electrostatic interaction between dye and quencher.

Arylsulfonates↗
PubMed2005

Flexible ligands and structural diversity: isomerism in Cd(NO3)2 coordination polymers.

The ligands 1,4-bis(2-pyridylmethylsulfanylmethyl)benzene (L1) and 2,5-bis(2-pyridylmethylsulfanylmethyl)pyrazine (L2) were treated with Cd(NO3)2.4H2O in metal-to-ligand ratios of 1:1 and 2:1, respectively; L2 was also treated with CdCl2.2.5H2O in a 2:1 ratio. All products were found to be coordination polymers. The crystal structures of {[Cd(L1)(NO3)2].CH2Cl2}infinity (1a), {[Cd(L1)(NO3)2].4/3CH3CN}infinity (1b), {[Cd2(L2)(NO3)4].2CH3CN}infinity (2.2CH3CN), and {[Cd2(L2)Cl4].2CH2Cl2}infinity (3.2CH2Cl2) were determined. Compounds 1a and 1b were found to be conformational supramolecular isomers. The structure of 1b displayed topological isomerism with two isomeric polymer chains, 1b(1) and 1b(2), in the one crystal forming a single supramolecular array. The structure of 2.2CH(3)CN showed Cd2(L2) units linked together by nitrates bridging between the Cd(II) centers in a mode previously not seen in Cd(II) compounds. The overall structure of 3.2CH2Cl2 was found to be similar to that of 2.2CH3CN despite the presence of different anions and solvent molecules. Powder X-ray diffraction was used to investigate the nature of bulk preparations of compounds 1-3.

Journal Article↗
PubMed2005

Optical glucose detection across the visible spectrum using anionic fluorescent dyes and a viologen quencher in a two-component saccharide sensing system.

A very general system is described in which anionic fluorescent dyes possessing a wide range of absorbance and emission wavelengths are used in combination with a boronic acid-modified viologen quencher to sense glucose at pH 7.4 in buffered aqueous solution. The present study demonstrates this capability with the use of eleven anionic fluorescent dyes of various structural types. Signal modulation occurs as the monosaccharide binds to the viologen quencher and alters its efficiency in quenching the fluorescence of the anionic dyes. The degree of quenching and the magnitude of the glucose signal were found to correlate roughly with the number of anionic groups on the dye. Optimal quencher : dye ratios were determined for each dye to provide a fairly linear signal in response to changes in glucose concentration across the physiological range.

Anions↗
PubMed2004

Evaluation of pyranine derivatives in boronic acid based saccharide sensing: significance of charge interaction between dye and quencher in solution and hydrogel.

In an ongoing program to synthesize a glucose sensing polymer that could be used for real time glucose monitoring in vivo, we have been exploring the use of boronic acid functional viologens as glucose responsive quenchers for fluorescent dyes. The present study focuses on the effect of ionic interactions between pyranine or its various sulfonamide derivatives and the viologen quenchers. Dyes bearing anionic groups were quenched more efficiently when compared to dyes with nonionic substituents. The anionic dyes in conjunction with the cationic quenchers exhibited a broader range of glucose response both in solution and when immobilized in a hydrogel. The interaction of glucose with the sensing components was similar whether they are soluble or immobilized.

Algorithms↗