Nanocages
Encyclopedia
Inorganic Nanocages are hollow porous gold
nanoparticles ranging in size from 10 to over 150 nm. They are created by reacting silver
nanoparticles with chloroauric acid
(H
Au
Cl
4) in boiling water. While gold nanoparticles absorb light in the visible spectrum
of light (at about 550 nm), gold nanocages absorb light in the near-infrared, where biological tissue
s absorb the least light. Because they are also biocompatible, gold nanocages are promising as a contrast agent for optical coherence tomography
, which uses light scattering in a way analogous to ultrasound
to produce in-vivo images of tissue with resolution approaching a few micrometres. A contrast agent is required if this technique will be able to image cancers at an early, more treatable stage. Gold nanocages also absorb light and heat up, killing surrounding cancer cells
. The Xia group at Washington University, the original inventors of the nanocages, has functionalized nanocages with cancer-specific antibodies so they specifically attach to cancer cells.
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
nanoparticles ranging in size from 10 to over 150 nm. They are created by reacting silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
nanoparticles with chloroauric acid
Chloroauric acid
Chloroauric acid is a inorganic compound with the formula HAuCl4. This pale yellow compound is a common precursor to gold in a variety of purposes. The term chloroauric acid is also sometimes used to describe other gold chlorides....
(H
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
Au
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
Cl
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
4) in boiling water. While gold nanoparticles absorb light in the visible spectrum
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of...
of light (at about 550 nm), gold nanocages absorb light in the near-infrared, where biological tissue
Biological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
s absorb the least light. Because they are also biocompatible, gold nanocages are promising as a contrast agent for optical coherence tomography
Optical coherence tomography
Optical coherence tomography is an optical signal acquisition and processing method. It captures micrometer-resolution, three-dimensional images from within optical scattering media . Optical coherence tomography is an interferometric technique, typically employing near-infrared light...
, which uses light scattering in a way analogous to ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
to produce in-vivo images of tissue with resolution approaching a few micrometres. A contrast agent is required if this technique will be able to image cancers at an early, more treatable stage. Gold nanocages also absorb light and heat up, killing surrounding cancer cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
. The Xia group at Washington University, the original inventors of the nanocages, has functionalized nanocages with cancer-specific antibodies so they specifically attach to cancer cells.