An implantable biosensor system is disclosed for determining levels of cardiac markers in a patient to aid in the diagnosis, determination of the severity and management of cardiovascular diseases. The sensor includes nanowire sensor elements having a biological recognition element attached to a nanowire transducer that specifically binds to the cardiac marker being measured. Each of the sensor elements is associated with a protective member that prevents the sensor element from interacting with the surrounding environment. At a selected time, the protective member may be disabled, thereby allowing the sensor element to begin sensing signals within a living body.