Stability improvement of optochemical sol-gel film sensors by immobilisation of dye-labeled dextrans

Plaschke, M.; Czolk, R.; Reichert, Johannes; Ache, H. J.

doi:10.1016/0040-6090(95)08026-0

Cited by 29 publications

(17 citation statements)

References 7 publications

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“…The conjugates have been used for intracellular pH measurement or have been immobilized on silver island films for metal-enhanced fluorescence sensing. 416 Xanthene dyes also allow physical entrapment in hydrogels, 110 , 121 , 398 , 424 , 430 , 438 sol–gels, 399 , 402 , 403 , 407 , 414 , 422 , 431 poly(styrene- block -vinylpyrrolidone) nanobeads, 382 cross-linked poly(vinyl alcohol)-silica gel copolymers, 432 polyacrylamide, 88 and pHEMA. 56 , 419 To minimize leaching, the dyes can be alkyl substituted, 110 , 121 , 398 , 424 , 430 , 438 directly or via ester bonds, to enhance their hydrophobicity for incorporation into hydrophobic materials.…”

Section: Overview Of Commonly Used Luminescent Ph Probesmentioning

confidence: 99%

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

2020

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This is the first comprehensive review on methods and materials for use in optical sensing of pH values and on applications of such sensors. The Review starts with an introduction that contains subsections on the definition of the pH value, a brief look back on optical methods for sensing of pH, on the effects of ionic strength on pH values and p K a values, on the selectivity, sensitivity, precision, dynamic ranges, and temperature dependence of such sensors. Commonly used optical sensing schemes are covered in a next main chapter, with subsections on methods based on absorptiometry, reflectometry, luminescence, refractive index, surface plasmon resonance, photonic crystals, turbidity, mechanical displacement, interferometry, and solvatochromism. This is followed by sections on absorptiometric and luminescent molecular probes for use pH in sensors. Further large sections cover polymeric hosts and supports, and methods for immobilization of indicator dyes. Further and more specific sections summarize the state of the art in materials with dual functionality (indicator and host), nanomaterials, sensors based on upconversion and 2-photon absorption, multiparameter sensors, imaging, and sensors for extreme pH values. A chapter on the many sensing formats has subsections on planar, fiber optic, evanescent wave, refractive index, surface plasmon resonance and holography based sensor designs, and on distributed sensing. Another section summarizes selected applications in areas, such as medicine, biology, oceanography, bioprocess monitoring, corrosion studies, on the use of pH sensors as transducers in biosensors and chemical sensors, and their integration into flow-injection analyzers, microfluidic devices, and lab-on-a-chip systems. An extra section is devoted to current challenges, with subsections on challenges of general nature and those of specific nature. A concluding section gives an outlook on potential future trends and perspectives.

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Section: Overview Of Commonly Used Luminescent Ph Probesmentioning

confidence: 99%

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

2020

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“…2 One inherent problem associated with these studies is leaching, because the indicator dye is generally smaller in size than the average pore/channel size in the gel. Several methodologies have been used to help minimize leaching: (i) covalently immobilizing and modulating the physical size of the dye, [3][4][5][6] (ii) drying the doped sol-gel glass before it is used as a sensor, 7 and (iii) polymerization at high acidity and low water content. 8 More recently, sol-gel materials have been expanded into mesoporous materials.…”

Section: Introductionmentioning

confidence: 99%

Modification of mesostructure base on composition of silica materials and their applications to pH sensing

Kang

Shim

Kang

et al. 2006

Polymers for Advanced Techs

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This study induced a chemical combination of fluoresceinamine (FA) and (3-chloropropyl)triethoxysilane (CP-TEOS) in the presence of tetraethyl orthosilicate (TEOS) which is able to maintain the shape of the mesostructure without prior removal of the surfactant. The sol-gel derived silica films were controlled by the reaction time and molar ratios of TEOS and CP-TEOS, and characterized in terms of response to pH, pK a values, effects of oxidation number, leaching, and scanning electron microscopy (SEM) imaging. The conclusions include the effect on molar ratios and the choice of reaction time. The results of this study are summarized as follows: (1) increasing the molar ratio of TEOS, the mesostructure of these films exhibited not only perfect single-crystal morphology but also a hexagonal morphology; (2) the most suitable molar ration in this synthesis is the ratio of 1:1 (the molar ratio of TEOS and CP-TEOS); (3) the reaction time for this system should be controlled at least to over 6 hr in order to maintain high intensity absorbance against a minimum of indicator quantity. Leaching-out is more pronounced for films used directly after preparation and varies for different molar ratios. The long-term implication of leaching-out on sol-gel based pH sensors is discussed.

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“…20 ±23 An alternative strategy is to increase the size of the indicator by attaching it to a macromolecular carrier. 24 (T he term carrier is used here to refer to a water-soluble, chemically inert macrom olecule to which an indicator dye can be conjugated.) This approach is based on the observation that proteins do not leach signi® cantly from sol-gels; 3±6 this stability is presumably due to the size of the biomolecule relative to the average pore diameter in the gel.…”

Section: Introductionmentioning

confidence: 99%

“…Plaschke et al 24 showed that a 70 000 MW dextran carrier, labeled with¯uorescein and entrapped in a dried sol-gel ® lm, underwent much slower leaching into aqueous buffer than unconjugated¯uorescein. Many sensor applications do not require that an indicator-doped solgel be dried, which can shrink the pores and m ay alter the reactivity of the entrapped molecules to analytes.…”

Section: Introductionmentioning

confidence: 99%

Reduction of Indicator Leaching from Doped Sol-Gels by Attachment of Macromolecular Carriers

1999

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The extent of leaching of indicator dyes of varying molecular mass, following encapsulation into hydrated sol-gel monoliths prepared from tetramethylorthosilicate (TMOS), was investigated. Dye modification of a water-soluble phthalocyanine with poly(ethylene glycol) side chains (2000 MW) reduced leaching relative to the unmodified dye, but significant losses were still observed. Monoliths doped with fluorescein modified with dextrans of higher molecular weight were investigated in an attempt to determine the minimum size necessary for dye retention. In comparison to monoliths doped with unmodified fluorescein, attachment to a dextran carrier significantly decreased the extent of dye leaching. However, even a 70 000 MW carrier was not sufficient to prevent some loss of dye. In contrast, no leaching of myoglobin (18 000 MW) occurred, which shows that when the entrapped molecule has a organized tertiary structure, diffusion within the pores is eliminated. Malachite green and its dextran conjugate were used to examine the effect of electrostatic interactions on leaching. Minimal loss of both the dye and the conjugate was observed, which indicates that when a favorable interaction between the dye and sol-gel matrix exists, attachment to a macromolecular carrier may not be necessary to prevent leaching.

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Stability improvement of optochemical sol-gel film sensors by immobilisation of dye-labeled dextrans

Cited by 29 publications

References 7 publications

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

Modification of mesostructure base on composition of silica materials and their applications to pH sensing

Reduction of Indicator Leaching from Doped Sol-Gels by Attachment of Macromolecular Carriers

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