Biomedical Engineering Reference
In-Depth Information
1.6
oPtical imaging witH nanoParticles (1980s-2000)
Optical imaging was one of the newest imaging modalities that marked its debut
for deep tissue imaging less than two decades ago. although observation of visu-
ally accessible body parts and some organs (such as the colon, throat) has been
accessed for centuries, the use of light to visualize internal organs did not begin
until the mid-1970s. Diaphanography [42] (a method for the evaluation of the
female breast) and eye angiography (see Section 1.6.1 “NIr cyanine dyes”) were
one of the first clinical applications of imaging with light in the 1970s. Typical
visible photons do not penetrate through biological tissues deeper than several
millimeters due to extensive scattering of photons by the tissue and significant
levels of endogenous chromophores such as melanin and hemoglobin that absorb
visible photons. In contrast, near-infrared (NIr) light (700-900 nm) can penetrate
the tissue much deeper: the scattering is lower and the endogenous absorption
in this spectral range is weak. With the development of NIr instrumentation such
as detectors, light sources, and especially NIr contrast agents in the middle of the
1990s, optical imaging quickly advanced from a preclinical stage to use in clinical
applications.
1.6.1
nir cyanine dyes
a large number of today's nanoparticle research involves decorating nanoparticles
with fluorescent NIr dyes from a class of cyanines. The history of cyanine dyes for
imaging applications started in the middle of the 1950s when an executive of eastman
Kodak company, who was pleased with the care he received from Dr. I. fox at the
Mayo clinic, offered to help him in his research. Dr. fox needed a biocompatible dye
that could be detected in blood. The executive sent an array of dyes from the eastman
Kodak laboratories for evaluation. Included among them was indocyanine green
(Icg) (fig. 1.9) developed as a sensitizer for photography by D. Heseltine and
l. Brooker [43]. The testing for measuring hepatic function began in 1957 [44], and
due to the low toxicity, the compound was rapidly approved by the fDa for this
application in the beginning of 1959. Several years later, this dye was clinically used
for measuring cardio function from Icg blood clearance curves.
The first attempt at using Icg for angiography was conducted by K. Kogure
and coworkers from the University of Miami in 1968 when they demonstrated
SO
3
H
SO
3
H
N
N
N
N
N
N
OOC
COOH
Cypate
ICG
Cy7
COOH
SO
3
-
SO
3
Na
figure 1.9
Structures of NIr dyes: indocyanine green, first approved near-infrared dye
developed by Kodak chemists Heseltine and Brooker in 1957 [44], cy7 developed by Waggoner
(1987) and later commercialized by amersham [47, 48], and cypate (2000) synthesized by
achilefu [49].
Search WWH ::
Custom Search