Boronic acid based modular fluorescent sensors for glucose

Modular photoinduced electron transfer (PET) sensors bearing two phenylboronic acid groups, one or two fluorophores: pyrene(a), phenanthrene(b), anthracene(c), 1-naphthalene( d), 2-naphthalene(e) and alkylene linkers, from trimethylene(3) to octamethylene(8), have been evaluated. Systems with a single pyrene fluorophore 3(4a), 3(5a) and 3(6a) bind the strongest with D-glucose (3(6a) also binds well with D-melibiose). Whilst 3(7a) and 3(8a) bind the strongest with D-galactose. Changing the fluorophore, also, influences the binding, 3(6a), 3(6b) and 3(6c) are D-glucose selective, whilst 3(6d) and 3(6e) are D-galactose selective. Systems with two fluorophores 3(6a-a) and 3(6a-b) show an overall decrease in binding efficiency. Energy transfer in 3(6a-b) results in enhanced sensitivity and selectivity towards D-glucose.