L-Hydroxypyrene

An optical sensor for the measurement of carbon dioxide in modified atmosphere packaging (MAP) applications was developed89. It was based on the fluorescent pH indicator l-hydroxypyrene-3,6,8-trisulfonate (HPTS) immobilized in a hydrophobic organically modified (ormosil) matrix. The CO2 sensor was stable over a period of at least 7 months and its output was in excellent agreement with a standard reference method for carbon dioxide analysis. 

It was demonstrated that poly(styrene-b/oc -vinylpyrrolidone) beads (0 220 nm) are suitable for preparation of pH nanosensors [12]. Various fluorescein derivatives were embedded and did not leach out of the beads due to functionalization with highly lipophilic octadecyl anchor. The pK., of the indicators inside the nanobeads varied from 5.8 to 7.7 making them suitable for various biotechnological, biological and marine applications. The beads based on a lipophilic l-hydroxypyrene-3,6, 8-trisulfonate (pKa 6.9) were also manufactured. 

The first example employed an immobilization of GOx and a pH-sensitive dye (l-hydroxypyrene-3,6,8-trisulfonate, HPTS) on the tip of an optical fiber.44 As the local pH was reduced by gluconic acid production, measurable changes in fluorescence were observed. Using flow-through measurements with buffer solutions of various strengths, the optrode response time was determined to be 8-12 min, with a detection limit of 1.8-36 mg/dL glucose and response saturation at 36-54 mg/dL. 

Fig. 13.2 Structure of an optode for the detection of molecular oxygen and carbon dioxide. Fluorophore I (O2) tris(2,2 -bipyridyl)ruthenium(ll) dichloride fluorophore II (CO2) l-hydroxypyrene-3,6,8-trisulfonate. Adapted from Baldini et al. [4] with permission from Springer.

Enzymatically synthesized poly(l-hydroxypyrene). 1-Hydroxypyrene was enzymatically oxiized in a mixture of 50% ethanol and 50% buffer (O.OIM phosphate) at pH 6.0 at room temperature as shown in Scheme 3. 

Figure 5. Fluorescence spectra of polymer and monomer of l hydroxypyrene.

Electronic and photo active polymers such as polyaniline, polyazophenols and poly(l-hydroxypyrene) were synthesized by peroxidase-catalyzed polymerization. These enzymatically synthesized polymers showed interesting electronic and photonic properties. Optical devices such as SRG can be fabricated on the izymatically synthesize polymer thin film. The enzymatic... 

Funfak et al. [39] demonstrated recently that pH-sensitive microbeads based on 8-hydroxypyrene-l,3,6-trisulfonate covalently attached to amino-functionalized poly(hydroxyethylmethacrylate) (0 2.5 pm) can be successfully used to monitor... 

Fig. 1.5. Examples of hydrophobic, hydrophilic and amphiphilic probes. 1 pyrene. 2 8-hydroxypyrene-l,3,6-trisulfonic acid, trisodium salt (pyranine). 3 8-alkoxypyrene-l,3,6-trisulfonic acid, trisodium salt. 4 1-...

Pyranine, 8-hydroxypyrene-l,3,6-trisulfonic acid 8-Hydroxypyrene-1,3,6-trisulfonic acid (HPTS, also known as pyranine) can be used as a pH indicator. At low pH, HPTS fluorescence is greater with 405 nm excitation, whereas at neutral pH, fluorescence at 440 nm excitation is greater than at 405 nm excitation. Therefore, a strong fluorescence signal at 405 nm excitation indicates HPTS in acidic compartments (endosomes and lysosomes) a strong signal at 440 nm indicates HPTS in neutral compartments (cytosol) (126 128). 

Ertekin and coworkers developed an additional optical COj sensor based on the fluorescence signal intensity changes of the pH-sensitive fluorescent dye 8-hydroxypyrene-l,3,6-trisulfonic acid trisodium salt (HPTS) dissolved in ILs [18]. When HCO3 was added to HPTS solution, the fluorescence intensity of the peak centered around 520 nm decreased by 90% in [C4Qlm] [BF4] and by 75% in [C4Cilm]Br. The reported detection limit for CO2 (g) was 1.4% while the detection limit for dissolved COj was 10 M HCO3. The sensor exhibited excellent stability and repeatability over a time period >7 months. 

Ruthenium complexes with mixed bipyridyl ligands, immobilized inside a Nation film, may also be used as pH-sensitive sensor layers [90]. A completely different approach for a ratiometric imaging of pH sensor foils was developed for diagenetic studies of marine sediments, using the dual fluorescence excitation ratio of the pH-sensitive fluorophore 8-hydroxypyrene-l,3,6-trisulfonic acid (HPTS) [91]. Commonly used dual fluorophors with different absorption and emission maxima in the protonated and basic form for ratiometric measurements are the naphthofluorescein and seminaphthofluorescein derivates (SNARF and SNAFL) [92], It should be noted that ammonia or carbon dioxide can also be detected by some of these pH-sensitive materials [55,93]. 

Li, K., L. A. Woodward, A.E. Kara, et al. 2000. Immunochemical detection of polycyclic aromatic hydrocarbons and 1-hydroxypyrene in water and sediment samples. Anal. Chim. Acta 419 1-8. 

FIGURE 1. Pyrene derivatives used as photoadds 1-hydroxypyrene (IHP), 8-hydroxy-l,3,6-tris(A,A-dimethylsulfonamido)pyrene (HPTA) and 8-hydroxypyrene 1,3,6-trisuIfonate (HPTS)... 

Hydroxypropiophenones, synthesis of 645 Hydroxypyrenes—see also 8-Hydroxy-l, 3,6-tris(iV,iV-dimethylsulfonamido)pyrene chemical shifts for 338... 

Santella RM, Hemminki K, Tang D-L, etal. 1993. Polycyclic aromatic hydrocarbon-DNA adducts in white blood cells and urinary 1-hydroxypyrene in foundry workers. Cancer Epidemiology, Biomarkers Prevention 2 59-62. 

Proton transfer processes are specially important excited state properties, and several detailed time resolved studies have been reported. Time resolved fluorescence studies of excited l-naphthol-3,6-disulphonate shows there is geminate recombination by proton transfer. Another detailed study is the examination of proton transfer and solvent polarization dynamics in 3-hydroxyflavone . The dynamics of proton transfer using a geminate dissociation and recombination model has also been investigated with 8-hydroxypyrene-l,3,6-trisulphonate 5 and also with... 

Figure 6. Time-resolved fluorescence of the neutral form of 8-hydroxypyrene-l,3,6-tri-sulfonate in concentrated LiC104 solution. Measurements were carried out as in Figure 4. Line (a) 1M LiC104 (b) 2.5 M LiCl04.

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