Nanotechnology stocks have enjoyed a good run lately. But although mainstream stock indices have risen over the past two months, nanotech has stalled as investors have started to lose patience with some of the more fancied companies in the sector.

The Lux Research nanotechnology index, which tracks companies that make or use nanotech products and technologies, stagnated over that period — and a few of its component companies have taken a serious hit.

One of the worst performers was Nucryst Pharmaceuticals in Wakefield, Massachusetts, whose stock has halved from a peak of US$4 in late March. The company has established a successful business selling nanocrystalline silver used in wound dressings, but it is struggling to win approval for what investors had hoped would be a yet-more lucrative line in dermatology drugs.

Things have been just as bad at Symyx Technologies in Santa Clara, California. Stock in this nanotech materials company plunged from $18 to $11 on 26 April, after it announced a small quarterly loss. The company has made extensive changes to its management, but the stock hasn't recovered any of its losses.

Arrowhead Research, a diversified nanotech company based in Pasadena, California, has fared better: its price has moved steadily upwards from $4 at the end of March, when it took over Carbon Nanotechnologies, a nanotubes company in Houston, Texas, to more than $7 today.

But overall, the market has been sluggish. “It had been running level with the Nasdaq,” says Peter Hebert, chief executive of Lux Research, the New York consultancy that compiles the index. “But over the past couple of months, it has underperformed.”