Colorimetric sensing method for polyamines utilising an inclusion complex of stimuli-responsive amylose

Incorporation of carboxyl groups into amylose led to a unique stimuli-responsive supramolecular system that shows distinct colour change in response to biologically important polyamines. When spermine was added to an aqueous solution containing iodine and amylose modified with carboxyl groups, the solution clearly changed from colourless to bluish purple. This colour change was attributed to the encapsulation of iodine into the helical cavity of amylose, which was triggered by the electrostatic association between the amylose and spermine.