Chemistry Reference
In-Depth Information
FIGURE 14.21
Maps of the phosphorescence intensity (a), goodness of fit shown by R-factor
(b), phosphorescence lifetime (c), and oxygen pressure (d). The maps correspond to a region
whose physical dimensions are 0.92mm
1.2mm [121]. Reproduced with permission from
the Optical Society of America. (See the color version of this figure in Color Plates section.)
Oxygen dependent quenching of phosphorescence has been applied from its early
days to image oxygen in the eye [118]. Some more recent examples include
application of dendritic polyglutamic probes, such as Oxyphor R2 [119]. An
important advance in the technology was made by Shonat et al. [120], who
implemented frequency-domain approach to image phosphorescence in wide field
in the retinal tissue. This approach was later refined in our laboratory to image oxygen
with microscopic resolution in the mouse eye using gen 2 polyglutamic Pd tetra-
benzoporphyrin dendrimer (Oxyphor G2, Figure 14.7) [121].
The probe was excited at its Soret band (450 nm) in order to induce phosphores-
cence only in the superficial layers for higher resolution. The phosphorescence
intensity and lifetime images from the retinal vascular bed (Figure 14.21) show that
the vessel structure can be easily identified and that the arteriols and venules can be
distinguished solely based on their pO
2
levels (Figure 14.21d). The imaging reso-
lution in this case was
m.
One of the goals of this study was to test the method's ability to detect eye injury
due to the pathology involving microvessel failure, where blockage of a capillary
would result only in local hypoxic regions no more than 10-100
5-10
m
m
m in diameter.
Localized injuries, about 75
mindiameter,werecreatedbywayoflaserphoto-
coagulation, assisted by indocyanine green dye (ICG). The injury was restricted
to the microvessels within the focal area. The resulting pO
2
maps are shown in
Figure 14.22.
m
