Diagnosis of early colorectal cancer using lectin-immobilized fluorescent nanospheres

Abstract

Peanut agglutinin(PNA)-immobilized polystyrene nanospheres with surface poly(N-vinylacetamide)(PNVA)chains encapsulating coumarin 6 were designed as a novel colonoscopic imaging agent. PNA was a targeting moiety that binds to β-D-galactosyl-(1-3)-N-acetyl-D-galactosamine, which is the terminal sugar of the Thomsen-Friedenreich antigen that is specifically expressed on the mucosal side of colorectal cancer cells. PNVA was immobilized with the aim of reducing nonspecific interactions between imaging agents and normal tissues. Coumarin 6 was encapsulated into nanosphere cores to provide endoscopically detectable fluorescence intensity. It is anticipated that the lectin-immobilized fluorescent nanospheres specifically accumulate on the surface of tumor tissues in the large intestine with resulting fluorescence. Real-time and accurate diagnosis of small-sized early colorectal cancer can be then achieved through observation of a clear fluorescence contrast between the normal and tumor tissues using the florescent endoscopy.