The Interaction of Polyvinylpyrrolidone with Aromatic Compounds in Aqueous Solution. Part I. Thermodynamics of the Binding Equilibria and Interaction Forces<sup>1</sup>

Molyneux, Philip; Frank, H. P.

doi:10.1021/ja01476a001

Cited by 188 publications

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“…Molyneux and Frank investigated the interaction between PNVP and a series of aromatic compounds in aqueous solution by an equilibrium dialysis method, and concluded that hydrophobic interactions and charge-transfer interactions are factors in the formation of the PNVP complex with aromatic compounds. 11 As mentioned above, PNVC has a molecular structure which is similar to that of PNVP, but the number of carbon atoms in the side chain of PNVC is larger than that of PNVP. The higher sensitivity of the PNVC-modified electrode is presumably due to the fact that the hydrophobic interaction between PNVC and catechol is stronger than that between PNVP and catechol.…”

Section: Resultsmentioning

confidence: 95%

Voltammetric Response of a γ-Irradiated Poly(N-vinylcaprolactam) Modified Graphite Electrode to Catechol and Ascorbic Acid

Takahashi

Imato

1999

ANAL. SCI.

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Highly discriminative properties between catecholamines and ascorbic acid are desirable for the development of a catecholamine sensor based on electrochemical detection, such as an amperometric or voltammetric type, because of a overlapping of the oxidation potential of catecholamines with that of ascorbic acid. The reason for this is that ascorbic acid is the most serious interferant in the electrochemical detection of catecholamines. In such cases, an electrochemical pretreatment or modification of the electrode has been shown to be effective to improve the selectivity of the sensor against ascorbic acid. A modification of the electrode with an anionic polymer film, such as Nafion 1,2 , Nafion/polyester ionomer 3 , styrene/maleic acid copolymer 4 , or negatively charged monolayers 5 , which exclude the penetration of ascorbic acid to the electrode surface, prevents interference from ascorbic acid.Heineman et al. reported on a model catechol sensor based on a poly(N-vinylpyrrolidone) (PNVP)-modified electrode 6-8 , which exhibits an enhanced response to catechol, along with selectivity against ascorbic acid. We have shown that the PNVP membrane had a concentration function with respect to catechol, and that the membrane plays a key role in the observed selectivity and enhanced the sensitivity of the sensor.9 Based on the above results, we fabricated a catechol sensor based on an ascorbate oxidase immobilized PNVPmodified electrode, in order to improve the selectivity against ascorbic acid, while maintaining an enhanced response to catechol.10 Poly(N-vinylcaprolactam) (PNVC) is the same type of N-vinylamide polymers as is PNVP, in which a five-membered ring of PNVP is replaced by a seven-membered ring, as shown in Fig. 1. If an electrode is modified with PNVC instead of PNVP, the resulting electrode would be expected to show a higher enhanced response to catechol, because the hydrophobic interaction of PNVC with catechol is generally thought to be stronger than that of PNVP, judging from the chemical structures of PNVP and PNVC. In this paper, we wish to report on the response behavior of a PNVC-modified electrode to catechol and ascorbic acid, compared with the PNVP-modified electrode. Experimental ChemicalsThe N-vinylcaprolactam (NVC) monomer was generously donated by BASF. The NVC monomer was distilled under reduced pressure to remove the inhibitor. Catechol and ascorbic acid of analytical grade were obtained from Kishida Kagaku Co., (Japan) and were used as received. A graphite electrode (4.6 mmφ×3.8 cm-long) was obtained from Poco Graphite, Inc. (USA). Preparation of PNVC-modified electrodePNVC was prepared by polymerizing the NVC monomer (10 g) in the presence of 2,2′-azobis(isobutyronitrile) (0.02 g) as an initiator in a 20-ml glass ampoule at 65°C for 72 h. The resulting polymer was dissolved in ethanol and the resulting ethanol solution was added dropwise to hexane. The precipitated polymer was purified by repeated reprecipitation.A graphite electrode was cleaned by sonicating in water and dried in the ...

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Section: Resultsmentioning

confidence: 95%

Voltammetric Response of a γ-Irradiated Poly(N-vinylcaprolactam) Modified Graphite Electrode to Catechol and Ascorbic Acid

Takahashi

Imato

1999

ANAL. SCI.

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“…The strong adsorption of DIC on HEMA monomers may be attributed, not only to hydrogen bonding between the three H bond acceptors in DIC and the hydroxyl groups in HEMA, but also to interactions between PVP chains and the aromatic rings in the DIC molecules. In fact, Molyneux and Frank (Molyneux and Frank, 1961) reported significant interactions of PVP and aromatic compounds in aqueous solution through hydrophobic bonding and interactions between PVP and the aromatic π electrons of the solutes.…”

Section: Discussionmentioning

confidence: 99%

Controlled drug release from hydrogels for contact lenses: Drug partitioning and diffusion

Pimenta

Ascenso

Fernandes

et al. 2016

International Journal of Pharmaceutics

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Optimization of drug delivery from drug loaded contact lenses assumes understanding the drug transport mechanisms through hydrogels which relies on the knowledge of drug partition and diffusion coefficients. We chose, as model systems, two materials used in contact lens, a poly-hydroxyethylmethacrylate (pHEMA) based hydrogel and a silicone based hydrogel, and three drugs with different sizes and charges: chlorhexidine, levofloxacin and diclofenac. Equilibrium partition coefficients were determined at different ionic strength and pH, using water (pH 5.6) and PBS (pH 7.4). The measured partition coefficients were related with the polymer volume fraction in the hydrogel, through the introduction of an enhancement factor following the approach developed by the group of C. J. Radke (Kotsmar et al., 2012;Liu et al., 2013). This factor may be decomposed in the product of three other factors , and which account for, respectively, hard-sphere size exclusion, electrostatic interactions, and specific solute adsorption. While and are close to 1, >>1 in all cases suggesting strong specific interactions between the drugs and the hydrogels. Adsorption was maximal for chlorhexidine on the silicone based hydrogel, in water, due to strong hydrogen bonding.The effective diffusion coefficients, , were determined from the drug release profiles.Estimations of diffusion coefficients of the non-adsorbed solutes = × allowed comparison with theories for solute diffusion in the absence of specific interaction with the polymeric membrane.

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“…However, it is unlikely that there are any previously hidden binding sites ready to be exposed as the extent of binding increases, because the PVP molecule already has a very open, random-coil type of conformation in aqueous solution (1). Indeed, if anything the binding of such phenolic cosolutes leads to a shrinkage in the encompassed volume of the polymer coil (3), but the fact that the present effects are not observed with simple phenolic cosolutes (2) indicates that such a contraction does not lead to the build-up of additional binding sites.…”

Section: Co-operative Effects As the Explanation For The Observed Shamentioning

confidence: 97%

The interaction of polyvinylpyrrolidone with aromatic compounds in aqueous solution Part IV. Evaluation of the co-operativity parameter, and the methylene-group contribution to the binding strength, for the alkyl parahydroxybenzoates

Molyneux

Cornarakis-Lentzos

1979

Colloid Polymer Sci

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The Interaction of Polyvinylpyrrolidone with Aromatic Compounds in Aqueous Solution. Part I. Thermodynamics of the Binding Equilibria and Interaction Forces¹

Cited by 188 publications

References 0 publications

Voltammetric Response of a γ-Irradiated Poly(N-vinylcaprolactam) Modified Graphite Electrode to Catechol and Ascorbic Acid

Voltammetric Response of a γ-Irradiated Poly(N-vinylcaprolactam) Modified Graphite Electrode to Catechol and Ascorbic Acid

Controlled drug release from hydrogels for contact lenses: Drug partitioning and diffusion

The interaction of polyvinylpyrrolidone with aromatic compounds in aqueous solution Part IV. Evaluation of the co-operativity parameter, and the methylene-group contribution to the binding strength, for the alkyl parahydroxybenzoates

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The Interaction of Polyvinylpyrrolidone with Aromatic Compounds in Aqueous Solution. Part I. Thermodynamics of the Binding Equilibria and Interaction Forces1

Cited by 188 publications

References 0 publications

Voltammetric Response of a γ-Irradiated Poly(N-vinylcaprolactam) Modified Graphite Electrode to Catechol and Ascorbic Acid

Voltammetric Response of a γ-Irradiated Poly(N-vinylcaprolactam) Modified Graphite Electrode to Catechol and Ascorbic Acid

Controlled drug release from hydrogels for contact lenses: Drug partitioning and diffusion

The interaction of polyvinylpyrrolidone with aromatic compounds in aqueous solution Part IV. Evaluation of the co-operativity parameter, and the methylene-group contribution to the binding strength, for the alkyl parahydroxybenzoates

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The Interaction of Polyvinylpyrrolidone with Aromatic Compounds in Aqueous Solution. Part I. Thermodynamics of the Binding Equilibria and Interaction Forces¹