T2 Biosystems has filed plans for a proposed IPO worth as much as $69 million, a big advance for the Massachusetts in vitro diagnostics company. Details aren't out yet. If the IPO goes through, T2 said it would trade on the Nasdaq under the symbol "TTOO." Goldman Sachs and Leerink Partners are listed as the underwriters in T2's July 2 S-1 SEC filing. Lexington-based T2, a 2012 Fierce 15 company, is hoping for big things for its T2Candida rapid diagnostic assay, which is designed to spot the deadly blood-borne fungal infection within two hours. The company is waiting for the FDA's decision on a de novo approval application for the Candida test and the technology that it submitted in late May. S-1 Filing