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 (KSV = 1.1 × 104 M-1) to Hg2+ ions when compared to PPE 1 (KSV = 1.3 × 104 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 KSV values of 33 × 106, 28 × 106, and 9 × 106 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 KSV of 1.1 × 105 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 ab...