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Beating Cancers to Death with Nanorods of
Gold
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by John Emsley
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Chemistry Top Ten
Papers
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Rank
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Papers
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Citations This Period
(Sep-Oct 07)
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Rank Last Period (Jul-Aug
07)
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1
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X. Huang, et al., "Cancer cell imaging and
photothermal therapy in the near-infrared region by using
gold nanorods," J. Am. Chem. Soc.,
128(6): 2115-20, 15 February 2006. [Georgia Inst. Tech.,
Atlanta; U. Calif., San Francisco] *014AX
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29
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†
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2
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E.V. Shevchenko, et al., "Structural
diversity in binary nanoparticle superlattices,"
Nature, 439(7072): 55-9, 5 January 2006. [IBM,
Yorktown Heights, NY; Columbia U., New York, NY; U.
Michigan, Ann Arbor] *999HA
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24
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†
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3
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M.J. Earle, et al., "The distillation and
volatility of ionic liquids," Nature,
439(7078): 831-4, 16 February 2006. [Queen’s U.
Belfast, U.K.; U. Nova de Lisboa, Portugal; NIST, Boulder,
CO] *012JA
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22
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†
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4
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J.L. Rowsell, O.M. Yaghi, "Effects of
functionalization, catenation, and variation of the metal
oxide and organic linking units on the low-pressure
hydrogen adsorption properties of metal-organic
frameworks," J. Am. Chem. Soc., 128(4):
1304-15, 1 February 2006. [U. Michigan, Ann Arbor] *007BA
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20
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†
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5
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D. Enders, et al., "Control of four
stereocentres in a triple cascade organocatalytic
reaction," Nature, 441(7095): 861-3, 15
June 2006. [Aachen U., Germany] *052SL
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18
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8
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6
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J.K. Holt, et al., "Fast mass transport
through sub-2-nanometer carbon nanotubes,"
Science, 312(5776): 1034-7, 19 May 2006. [Lawrence
Livermore Natl. Lab., Livermore, CA; U. Calif., Berkeley]
*043UX
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18
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†
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7
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D.I. Enache, et al., "Solvent-free
oxidation of primary alcohols to aldehydes using
Au-Pd/TiO2 catalysts,"
Science, 311(5759): 362-5, 20 January 2006.
[Cardiff U., U.K.; Lehigh U., Bethlehem, PA] *007AE
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18
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3
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8
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G.K. Mor, et al., "Use of highly-ordered
TiO2 nanotube arrays in dye-sensitized solar
cells," Nano Lett., 6(2): 215-8, February
2006. [Pennsylvania State U., University Park] *015DS
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17
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†
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9
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S.Z. Luo, et al., "Functionalized chiral
ionic liquids as highly efficient asymmetric
organocatalysts for Michael addition to
nitroolefins," Angew. Chem.-Int. Ed.,
45(19): 3093-7, 5 May 2006. [Chinese Acad. Sci., Beijing;
Nankai U., Tianjin, China] *042MY
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15
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†
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10
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A. Corma, P. Serna, "Chemoselective hydrogenation
of nitro compounds with supported gold catalysts,"
Science, 313(5785): 332-4, 21 July 2006. [U.
Polytec. Valencia, Spain] *065IV
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15
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SOURCE: Thomson Scientific's
Hot Papers Database. Read the
Legend.
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Nano-sized particles of gold feature in the papers which top and tail the
current Hot Ten, offering hope in the treatment of cancer (#1) and a new,
environmentally preferred method of industrial synthesis (#10).
Paper #1 comes from a group lead by Mostafa El-Sayed at the Laser Dynamics
Laboratory of the Georgia Institute of Technology, in collaboration with
his son Ivan El-Sayed, of the Comprehensive Cancer Center of the University
of California at San Francisco. It reports the first combined application
of the optical and photothermal properties of gold nanorods, whose method
of preparation and mode of operation the El-Sayeds have been researching
for several years, and which now demonstrate that they can be used in the
diagnosis and treatment of cancer.
The gold nanorods are attractive compared to other contrast agents because
of the ease of synthesis, their optical tunability, and their absorption in
the near infrared (NIR) which allows for in vivo and clinical
applications. The nanorods can be incorporated into monoclonal antibodies
which bind selectively to the surface of malignant cells. The El-Sayeds
have developed simple and unique techniques in cancer imaging and
photothermal therapy based on them.
When exposed to light, electrons in the conduction band of a gold nanorod
oscillate in a way that resonates with electromagnetic radiation of a
frequency that depends on the size and shape of the nanorods. Due to their
strong scattering, they are ideal for probing and imaging sites within the
body and in particular cancerous growths. Not only are the nanorods ideal
for imaging, they are also the right shape for absorbing near-infrared
low-energy radiation from a continuous-wave laser and converting this to
heat. It is this which offers remarkable benefits.
This localized heating of a gold nanorod is so powerful it can cause it to
melt, and even to result in the rapid sublimation of its atoms which may be
propelled at jet-speed velocities. These projectiles, and the heating of
the associated cancer cell, can lead to its destruction.
Gold nanorods are grown from a dilute solution of auric acid
(HAuCl4) to which has been added cetyltrimethylammonium bromide,
benzyldimethylhexadecylammonium chloride, a silver salt, and ascorbic acid.
The solution is seeded by adding gold nanoparticles smaller than 5 nm. The
overall dimension of the nanorods is the key to their success, and this is
measured in terms of the aspect ratio, which is the length divided by the
width.
This ratio can be varied by changing the concentration of silver ions in
the growth medium. It is critical to the way the nanorods absorb and
scatter the near-infrared radiation (NIR) to which the tissues are most
transparent, and this will be the key to their successful use in medicine.
By changing the shape of the nanorods it became possible to change their
absorption and scattering wavelengths from the visible to the NIR region.
Recently the El-Sayeds have extended the work in paper #1. In Nano
Letters, (see X.H. Huang, et al., 7[6]: 1591-7; 2007), they
report that human oral cancer cells are found to assemble and align gold
nanorods conjugated to anti-epidermal growth factor receptor (anti-EGFR)
antibodies. Molecules on the cancer near the nanorods are found to give a
strong, sharp, polarized Raman spectrum which is greatly enhanced and so
can be used as diagnostic signatures for these cancer cells. Currently they
are doing animal-model experiments using nanorods, and these show great
promise.
Gold nanoparticles also appear in the current Hot Ten at #10, which comes
from Avelino Corma and Pedro Serna of the Instituto de Tecnologia Quimica
at Valencia, Spain. This paper reports their use as catalysts when
supported on substrates of titanium oxide or iron(III) oxide, and
especially for the reaction of nitroarenes with hydrogen gas.
For example, 3-nitrosytrene undergoes 99% conversion and 96% selectivity to
3-vinylaniline in six hours at 120° C. What is more, there is no
formation of the by-product hydroxylamine styrene, and it is the
non-formation of this which Corma says gives their discovery commercial
significance. The reaction reported in #10 offers an environmentally
preferred way to the industrially important chemical cyclohexanone whose
production at present involves this undesirable by-product.
Dr. John Emsley is based at the Department of Chemistry, Cambridge
University, U.K.
What's Hot In... : What's Hot In Chemistry Menu : Beating Cancers to Death with Nanorods of Gold - Chemistry - Mar/Apr 2008
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