San Diego

A Chinese-born scientist has been held in a Californian jail for nearly three weeks, after being arrested for allegedly stealing materials and methods used to grow corneal cells which, police files claim, he intended to export to China.

Veterinary researcher Bin Han was jailed on 17 May after police searched his home and found records of stem-cell experiments and serum samples allegedly misappropriated from the University of California, Davis, where he is employed. They also found a ticket for a round-trip to China for the following week.

The jailing of Han — who was born in China but has been a US citizen since 1999 — is the latest example of the increasingly hard line US authorities are taking with researchers who stand accused of exporting biological samples or information without permission. Last May, for example, two Japanese researchers were charged with industrial espionage for their alleged involvement in such exports (see Nature 411, 225–226; 200110.1038/35077271).

At a state court hearing on 4 June in a suburb of Sacramento, California, a judge allowed Han to be released after authorities had taken possession of his passports. Han now faces a preliminary hearing on 16 July on at least one felony charge of embezzlement.

Since 1990, Han has worked in various laboratories at the University of California, Davis, after coming to the United States in 1989. During one period, according to university records, he also said he was running an investment firm on behalf of Chinese financiers.

Two years ago, Han became a postdoctoral fellow in the laboratory of ophthalmologist Ivan Schwab and dermatologist Rivkah Isseroff — who are investigating how to make stem cells grow into corneal epithelial cells to replace damaged eye tissue. The technique might also have wide application for making other epithelial cells, researchers say.

Early last month, court records show, officials at the University of California, Davis, became suspicious of Han after learning that he was setting up a stem-cell research laboratory in China, where he frequently travelled. Police raided Han's home after vials of human sera used in Schwab and Isseroff's research went missing.

If convicted, Han could face a prison term. Neither he nor his attorney could be reached for comment.