Oxygen dependence devices

The problem of drifting cell potentials seems to arise from the fact that no defined reference potential exists at the interface between the internal metal wire and the polymeric membrane. Some workers postulate an oxygen-dependent half-cell potential at this interface with the required oxygen being able to permeate the PVC film (S2). Clearly, the question as to what is happening at the interfoce of the metal and the membrane needs to be resolved before CWEs of the above type gain widespread acceptance as useful analytical devices. 

In view of the chemical structure of MDMO-PPV, it is expected that this polymer is very sensitive to solar light. This is attested by several studies that clearly show that oxygen-dependent degradation of the polymer plays a significant role in the failure of devices based on MDMO-PPV [15-18]. Carbonyl defects were shown to have a major influence on devices like PLEDS and the increase of carbonyl defects was correlated to a dramatic reduction of the photoluminescence of the polymer [19,20], Understandings about the origin and the formation of these defects seem relevant in order to improve the stability of the devices based on this kind of polymer. 

The bioluminescence technique is applied for quantitative measurement of tumor burden, treatment response, immune cell trafficking, and detection of gene transfer [40]. The luminescence property depends on adenosine triphosphate and oxygen-dependent enzymatic conversion of exogenous luciferin to oxyluciferin by luciferase within living cells. An emission spectrum is produced with a peak of approximately 560 nm, which can be detected by a highly sensitive charge coupled device camera at 10-15 min after injection of luciferin and lasts for 60 min in mice [41]. 

Biomedical Applications Due to their excellent blood compatibility (low interaction with plasma proteins) and high oxygen and moisture permeabilities, siloxane containing copolymers and networks have been extensively evaluated and used in the construction of blood contacting devices and contact lenses 376). Depending on the actual use, the desired mechanical properties of these materials are usually achieved by careful design and selection of the organic component in the copolymers. 

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