Forced agglutination as a tool to improve the sensory response of a carboxylated poly(p-phenyleneethynylene)

A water-soluble biotinylated poly(p-phenyleneethynylene) (PPE, 3) was synthesized by postfunctionalization of an amine-PPE precursor 2a and investigated for sensory responses in aqueous buffer at physiological pH. Polymer 3 shows similar sensitivity (K-SV = 1.1 x 10(4) M-1) to Hg2+ ions when compared to PPE 1 (K-SV = 1.3 x 10(4) M-1); 3 was exposed to streptavidin-coated microspheres (SCM) to form a self-assembled complex, which exhibits an enhanced sensitivity toward Hg2+ ions. If 3 was exposed to either avidin, a streptavidin-rhodamine conjugate, or a streptavidin-Texas Red conjugate, fluorescence of 3 was quenched with K-SV values of 33 x 10(6), 28 x 10(6), and 9 x 10(6) M-1, respectively. When lightly cross-linked polymer arrays 3-avidin were exposed to Hg2+ ions, they were more sensitive than 3 alone. The complex was quenched by Hg2+ ions with a K-SV of 1.1 x 10(5) M-1. The negatively charged PPE 1 was incubated with the positively charged avidin to form an electrostatic 1-avidin complex. The 3-avidin complex was about 10 times as sensitive to Hg2+ ions as 1 and 25 times as sensitive to Hg2+ as 1-avidin.