Carbohydrate-conjugated chlorins were synthesized for use as biosensors for the detection of the galectin-3 cancer marker. We used ELISA, SDS-gel electrophoresis, and Bradford assays to examine the binding of galectins to d-(+)-galactose- and b-lactose-conjugated chlorins. The binding affinities of these conjugated chlorins for galectin-3 were quantified using fluorescence spectroscopy. The fluorescence emission of the carbohydrate-conjugated chlorins decreased as the amount of galectin-3 in the binding reaction increased over a limited concentration range, indicating that carbohydrate-conjugated chlorins are potentially useful fluorescence biosensors for the galectin-3 cancer marker.