Almost 30 biosensors have been developed for use with array SPRi or conventional SPR, including sensors for the determination of the known cancer biomarkers CA-125 [14], HE-4 [15] and CEA [16], as well as new promising cancer biomarkers such as circulating microRNA [17] or exosomes [18] in the case of breast cancer biomarkers. Here, WFDC2 is linked to cancer.