Oxygen optodes

Borisov SM, Klimant I (2007) Ultrabright oxygen optodes based on cyclometalated Iridium (III) coumarin complexes. Anal Chem 79 7501-7509... 

WenzhbferF., Holby O., and Kohls O. (2001) Deep penetrating oxygen profiles measured in situ by oxygen optodes. Deep-Sea Res. 48, 1741-1755. 

In vivo test of an oxygen optode in an ewe The breath gas composition was varied as shown on top, and the change in PO2 was followed with the inserted fiber sensor. The data points are values obtained ex vivo with a blood gas analyzer. From [56]. 

Response of glucose sensor with an oxygen optode as the transducer to various concentrations of glucose passing by. From [69]. 

Terasaka, K., Hullmann, D., and Schumpe, A. (1998), Mass transfer in bubble columns studied with an oxygen optode, Chemical Engineering Science, 53(17) 3181-3184. 

Weigl BH, Holobar A, Trettnak W, Klimant I, Kraus H, O Leary P, Wolfbeis OS (1994) Optical triple sensor for measuring pH oxygen and carbon dioxide. J Biotechnol 32 127-138 Borisov SM, Klimant I (2007) Ultrabright oxygen optodes based on cyclometalated iridium (111) coumarin complexes. Anal Chem 79 7501-7509... 

Later on, such S-layer-based sensing layers were also used in the development of optical biosensors (optodes), where the electrochemical transduction principle was replaced by an optical one [97] (Fig. 10c). In this approach an oxygen-sensitive fluorescent dye (ruthenium(II) complex) was immobilized on the S-layer in close proximity to the glucose oxidase-sensing layer [97]. The fluorescence of the Ru(II) complex is dynamically quenched by molecular oxygen. Thus, a decrease in the local oxygen pressure as a result of... 

Holst G., Glud R. N., Kuehl M., Klimant I., A micro-optode array for fine-scale measurement of oxygen distribution, Sensor Actuat B-Chem 1997 B38 122, and refs, cited. 

Lubbers D.W., Opitz N., The pC02-/p02 optode, a new probe for measurement of partial pressure of carbon dioxide or partial pressure of oxygen in fluids and gases, Z. Naturforsch. 1975 30C 532. 

Other optodes have been developed and tested in-vivo, all of them using a fluorophore, the fluorescence of which is quenched by oxygen. In the intravascular sensor developed by CDI, previously described, a specially synthesised fluorophore, a modified decacyclene ( Lexc=385 nm, em=515 nm), is combined with a second reference-fluorophore that is insensitive to oxygen, and is incorporated into a hydrophobic silicon membrane that is permeable to oxygen. 

Frederiksen, M. S., and Glud, R. N. (2006). Oxygen dynamics in the rhizosphere of Zostera marina A two-dimensional planar optode smdy. Limnol. Oceanogr. 51(2), 1072—1083. 

Lubbers DW, Koster T, Holst GA. 02 flux optode a new sensing principle to determine the oxygen flux and other gas diffusions. Adv Exp Med Biol 1996 388 59-68. 

Glud, R. N., Wenzhofer, F., Tengberg, a., Middelboe, M., Oguri, K. Kitazato, H. 2005. Distribution of oxygen in surface sediments from central Sagami Bay, Japan In situ measurements by microelectrodes and planar optodes. Deep-Sea Research I, 52, 1974-1987. 

So-called planar optodes were developed in recent years, which, for example, allow us to draw two-dimensional maps showing the oxygen distribution in a sediment. The fluorescence induced by oxygen can be measured and made visible on a particularly processed stretch of foil (e.g. Gludet al. 2001). 

Since microelectrode measurements are limited to a few centimeters of sediment depth, oxygen penetration depths have been difficult to obtain in strongly oligotrophic areas until the late 1990s. The invention of optode techniques, however, allows measurements up to several decimeters into the sediment (Fig. 6.22). The example is from a station located in the oligotrophic western equatorial Atlantic. 

Fig. 6.22 Oxygen concentration profile measured with an in situ optode technique (after Wenzhofer et. al. 2001b).

Three methods have been described for three halogens, two based on fluorescence and one on absorption. In the first [87], the fluorescence of rubrene in polystyrene is quenched by traces of iodine. This method is nonselective and the optode is also sensitive to oxygen. In another sensor, naphthoflavone in solution in a material of the silicone or PVC type serves as a sensitive layer for free halides [88]. The absorption technique uses a fiber with a liquid CS2 core [89] to detect 10 ng of iodide using a S m long capillary cell with sample circulation. The Hber itself constitutes the active optode (total reflection in the liquid core). A comparison of optodes based on dynamic quenching of absorbed Rhodamine 6G by iodide was reported [90]. Three solid supports for immobilization were used PTFE tape, XAD resin beads and crushed XAD-4 resin. The limits of detection are 0.18-0.30 and 1.1 mM respectively. Some anions (eg. Cl , Br , CN ) interfere at the 1-M level. 

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