Needling cells: stem cells could take their cues from silicon nanowires.The ability to make new heart muscle from a patient's own stem cells stem cells, unspecialized human or animal cells that can produce mature specialized body cells and at the same time replicate themselves. Embryonic stem cells are derived from a blastocyst (the blastula typical of placental mammals; see embryo), which is very young is a dream for many cardiologists. By growing stem cells on a bed of silicon needles, researchers may have found a way to give the cells a push in the right direction.
Peidong Yang of the University of California, Berkeley The University of California, Berkeley is a public research university located in Berkeley, California, United States. Commonly referred to as UC Berkeley, Berkeley and Cal and Bruce Conklin of the Gladstone Institute of Cardiovascular Disease Cardiovascular disease
Disease that affects the heart and blood vessels.
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cardiovascular disease in San Francisco San Francisco (săn frănsĭs`kō), city (1990 pop. 723,959), coextensive with San Francisco co., W Calif., on the tip of a peninsula between the Pacific Ocean and San Francisco Bay, which are connected by the strait known as the Golden have succeeded in growing mouse and human stem cells that are pierced by silicon nanowires--conducting structures that could give the cells an electrical nudge to spur their development.
Researchers suspect that stem cells require a series of biochemical, mechanical, or electrical signals to form different types of tissue (SN: 3/6/04, p. 155). It's unclear, however, what mix of cues is necessary to produce any given outcome.
Since heart-muscle cells are electrically active, Yang and Conklin wanted to develop a technique that might enable them to electrically stimulate individual stem cells to become cardiac cells.
Yang's group used chemical-vapor deposition to create an array of vertically aligned silicon nanowires, tipped with gold, on a sticon surface. Each wire measured, on average, 90 nanometers wide and 6 microns high.
Next, the team deposited embryonic stem cells from mice onto the bed of nanowires. The wires penetrated the cells without any prompting by the researchers. "Embryonic stem cells are very sensitive to their environment," says Conklin. "The main purpose of the experiment was to see if the cells would remain alive."
Indeed they did. When the researchers placed mouse embryonic cells that had already begun to differentiate into heart muscle cells onto the bed of needles, the Needles, the, England: see Wight, Isle of. cells continued to develop normally. In fact, they grew on the surface and continued to beat for up to a month, Yang and Conklin report in the June 13 Journal of the American Chemical Society
The technology "has exciting potential," says Timothy McKnight, a bioengineer at Oak Ridge Oak Ridge, city (1990 pop. 27,310), Anderson and Roane counties, E Tenn., on Black Oak Ridge and the Clinch River; founded by the U.S. government 1942, inc. as an independent city 1959. (Tenn.) National Laboratory. Researchers could insert biomolecules--genes and proteins--inside the cells by tethering the molecules to the wires, he adds.
As a proof of concept, Yang and Conklin showed that they could introduce bits of DNA DNA: see nucleic acid.
or deoxyribonucleic acid
One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. into human embryonic kidney cells. Unfortunately, most of the DNA molecules stayed on the wires. Changing the method of binding DNA to the wires could fix that, the researchers say.
"Nanowire arrays are not ... representative of anything that really happens in nature,' says Conklin. "But they might allow us to push the cells in new directions."
The next step will he to use the conducting nanowires to monitor the electrical activity of stem cells and to attempt to control their differentiation into cardiac cells. There are half a dozen different types of heart-muscle cells, each with its own spontaneous beating rate, says Oscar Abilez of Stanford University School of Medicine Stanford University School of Medicine is affiliated with Stanford University and is located at Stanford University Medical Center in Stanford, California, adjacent to Palo Alto and Menlo Park. . He is also growing stem cells on nanowire arrays but has not yet published his findings. Turning stem cells into various types of heart muscle might require using different electrical signals, he suggests.