The selective response to glucose is possible by using a poly(phenylboronic acid) microgel under a rational design. Such a microgel is made of graphene covalently immobilized in a microgel of poly(4-vinylphenylboronic acid) cross-linked with N,N?-methylenebis(acrylamide). Unlike the microgels reported in previous arts that would undergo volume phase transition in response to both glucose and other monosaccharides, the proposed microgels shrink upon adding glucose, whereas keep unchanged in the size upon adding other monosaccharides (with fructose, galactose, and mannose as models). Although the polysaccharides/glycoproteins (with dextran and Ribonuclease B as models) that contain many glycosyl residues can slightly absorb on the microgel surface and lead to a small impact on glucose-response, it can be addressed by further coating the microgel as a core with a thin nonglucose-responsive poly(N-isopropylacrylamide) gel shell. This selectively glucose-responsive volume phase transition behavior enables turn-on photoluminescence detection of glucose in blood serum (a model for complex biosystems).