Tang, who headed the life-sciences group at the medical-instruments maker Olympus America Inc. and was CEO at the battery-maker Millennium Cell Inc. before heading the center, joined the OraSure board in 2011 and built "strong relationships" with managers and fellow directors, according to Charles Patrick, who heads OraSure's governance committee. Tang will give up the chairman's role when he becomes CEO.

Tang replaces OraSure CEO Douglas A. Michels, who joined OraSure in 2003. Chief financial officer Ronald H. Spair is also on his way out, the company said. "The retirements were completely personal decisions on their part," Tang told me.

"I was really pleased to be considered and ultimately hired as the next CEO," he added. "They now have a market capitalization of over $1 billion, and the fact they have $200 million on the balance sheet means they can look at sizable acquisitions."

OraSure shares were down modestly in trading after the CEO and CFO departures were disclosed Thursday morning. The stock closed Thursday at $19.25, up 1.1 percent and more than double the level of a year ago, but below its recent high of $22.50 in September. Sales totaled $165 million last year.

The center also credited Tang's administration with setting up Quorum, which organizes programs for technologists and investors, and backing the Port Business Incubator, which helped Avid Radiopharmaceuticals and other small companies stay in West Philly.

"We are far better off today than we were 10 years ago," Tang said, of Philadelphia's attractions as a tech business center. "We are still below scale, but we are fast approaching" parity with other tech centers. He said institutions were working more closely to attract investors and build support for technologists.

(This story has been corrected to show the University City Science Center was founded in 1963. Earlier versions gave a wrong year.)