Inverness Medical Innovations Inc. is launching an unsolicited $79.9 million bid to acquire a 40 percent stake in a South Korean diagnostics provider.

The proposed tender offer calls for Waltham, Mass.-based Inverness to pay $24.70 each for roughly 3.2 million shares in Standard Diagnostics Inc., which produces chemical markers and other diagnostic tools used to identify tumors, hepatitis and other infectious diseases as well as fertility and drug testing kits.

Coinciding with the bid, Inverness said it plans to soon sell up to $150 million in new debt securities. Proceeds from the sale of 7-year notes will be used to complete the acquisition of Concateno plc, a drug testing products maker based in Wales. The cash-and-stock transaction, first announced in June, is expected to close next Tuesday.

Inverness officials said they hope to wrap up the tender bid by Aug. 24.

According to its website, Standard Diagnostics opened its doors in 1999, quickly attracting investment backing from two American venture capital funds. The company went public on the Korea Exchange in early 2003.

In more recent years, Standard Diagnostics patented a rapid test for Alzheimer’s disease and received CE Mark certification to market a blood-glucose monitoring system and an HIV test kit in the European Union.

The $24.70-a-share offer would be about a 13.5 percent premium to the stock’s last closing price before the deal was announced. There was no immediate comment from officials at Standard Diagnostics about the bid.