Microwave Heating of Poly(N-isopropylacrylamide)-Conjugated Gold Nanoparticles for Temperature-Controlled Display of Concanavalin A.

We demonstrate microwave-induced heating of gold nanoparticles and nanorods. An appreciably higher and concentration-dependent microwave-induced heating rate was observed with aqueous dispersions of the nanomaterials as opposed to pure water and other controls. Grafted with the thermoresponsive polymer poly(N-isopropylacrylamide), these gold nanomaterials react to microwave-induced heating with a conformational change in the polymer shell, leading to particle aggregation. We subsequently covalently immobilize concanavalin A (Con A) on the thermoresponsive gold nanoparticles. Con A is a bioreceptor commonly used in bacterial sensors because of its affinity for carbohydrates on bacterial cell surfaces. The microwave-induced thermal transitions of the polymer reversibly switch on and off the display of Con A on the particle surface and hence the interactions of the nanomaterials with carbohydrate-functionalized surfaces. This effect was determined using linear sweep voltammetry on a methyl-α-d-mannopyranoside-functionalized electrode.