Li et al. developed an immunosensor based on cadmium selenide (CdSe)-QD-melamine networks for the detection of the carcinoembryonic antigen (CEA) cancer biomarker, see Figure 3I. The CdSe-QDs and the amino groups of each melamine molecule form a strong network to link later a secondary antibody anti-CEA (Ab2) through the EDC/NHS coupling chemistry (CdSe-Ab2). Here, CEACAM5 is linked to cancer.