Why is indocyanine green a stain is of great significance in medicine?

We have many practical stains in the current biomedical experiments, such as previously introduced malachite green, Sudan red B, hematoxylin, etc. Still, if it is in the medical aspect, there is a stain more practical than these three. This stain is indocyanine green. For these stains, what are indocyanine green characteristics in the end?

What is indocyanine green?

Indocyanine green is a tri-carbocyanine type dye with infrared absorption properties. It is an important fluorescent dye that can bind plasma proteins and lipoproteins. With excitation poles of 750 ~ 800 nm and emission poles greater than or equal to 800 nm, it can penetrate deeper into living tissue than the Cy series (anthocyanine type) dyes (630-670 nm, 650-700 nm).

History of indocyanine green

Indocyanine green was developed as a medical material during World War II. After receiving FDA approval in 1959, indocyanine green also was used primarily for liver function diagnosis and cardiology. In 1964, S. Schilling used indocyanine green to determine renal blood flow. Since 1969, indocyanine green has also been used in the study and diagnosis of subretinal lesions (choroid) of the eye. Since 1980, many technical difficulties have been overcome with the development of new cameras and better film materials or new photometric devices. At the same time, using indocyanine green in medicine (especially in fluorescence angiography in ophthalmology) has become standard.

In cancer diagnosis and treatment, indocyanine green is used as a visualization dye and a thermotherapeutic agent. There is almost no absorption in the visible range, caused by low autofluorescence, tissue absorption, and scattering at near-infrared wavelengths (700-900 nm). This indocyanine green azide can be used for the selective labeling of alkyne-labeled biomolecules (e.g. proteins, lipids, nucleic acids, and sugars) by the well-known click chemistry.

Mechanism of action of indocyanine green

Indocyanine green is used in medicine to determine cardiac blood excretion, liver, and gastric blood flow, and for ophthalmic angiography because it has a spectral absorption peak at around 800 nm. These infrared frequencies penetrate the retinal layers, allowing indocyanine green angiography to image deeper circulatory patterns than fluorescein angiography. Indocyanine green binds tightly to plasma proteins and is confined to the vascular system. Indocyanine green has a half-life of 150 – 180 seconds and is completely excreted from the circulation by the liver into bile.

I have used Indocyanine Green from BenchChem in my medical experiments. I could observe that the experimental rabbits were targeted for atherosclerosis 20 minutes after the injection of Indocyanine Green and provided sufficient signal enhancement for the detection of lipid-rich, inflammatory, coronary atheromatous plaques in atherosclerosis in rabbits.

Because of the unique infrared absorption properties of indocyanine green, this stain is often used in medicine to detect cardiac output, liver function, and liver blood flow. It is also used to help certain parts of the eye become more visible during medical procedures, such as angiography. Preparations containing indocyanine green are now widely used for clinical and surgical applications, including retinal angiography, intraocular surgery, cardiac output, and liver condition monitoring.

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