This disclosure relates to a method of measuring a glucose concentration metric or a glucose metric in a patient by contacting an implantable glucose-sensing device with a test sample, which may be in the patient, under conditions that permit a sugar-binding molecule and a functionalized polymer or nano-particle ligand present throughout the matrix of a hydrogel to interact in a glucose-dependent manner to produce an optical signal resulting from quenching of a first fluorophore linked to the ligand or sugar-binding molecule and having a fluorescent emission spectrum quenched upon binding or release of glucose. Next the first fluorophore may be excited with light of a certain wavelength. Then at least one wavelength of light in the glucose-dependent optical signal from the fluorophore may be detected with a detector to produce a detected light signal, which may be processed to produce a glucose metric, such as a glucose concentration metric.