Arrowhead Research Corp. on Wednesday said that it had closed a direct offering of 6.6 million common shares and 3.3 million warrants, which raised $8.65 million.

After the Pasadena nanotechnology company announced the offering on June 17, its shares lost about a quarter of their value, and they haven’t recovered much since.

Arrowhead said the offering strengthens Arrowhead’s balance sheet, enables it to invest in its current businesses and take advantage of opportunities to acquire businesses. The company develops drugs and carbon nanotube technology for electronic applications.

The stock and warrants were sold in units at $1.312 each. Each unit consisted of one common share and a warrant to purchase one-half of one common share. Oppenheimer & Co. Inc. was the sole placement agent for the offering.

“Our lead subsidiaries, Calando (nanomedicine) and Unidym (nanotubes), are making significant progress and the current offering is important to continuing this momentum,” said Chief Executive Christopher Anzalone in a statement.

Shares were up 2 cents, or less than 2 percent, to $1.26 in midday trading on the Nasdaq.