Serologicals Corp. announced Friday that it would not open its $28 million bio-manufacturing plant in the East Hills Business Park, and instead would prepare the property for sale.

The plant, once hailed as the cornerstone for the city’s life-sciences development efforts, has been idle for nearly a year, after the company laid off 19 of the plant’s 26 employees. The plant was to produce Ex-Cyte, a cell-culture medium used by pharmaceutical companies and others for research and development.

The Atlanta-based company said that it would sell the Lawrence plant and another in Toronto, and their operations would be transferred to an existing plant in Kankakee, Ill.

The Lawrence plant never did reach full production Although it did run test batches of Ex-Cyte that met internal standards, Serologicals officials maintained that some of the company’s biggest customers had yet to run their own tests.

Just last month, a company official said that four out of five “big-pharma” companies had completed their tests, and that the fifth would be done by the end of March – the deadline company officials had maintained for starting full production at the plant.