Conjugated Polyelectrolyte-Ag+ Fluorescent Switch for Biothiol Sensing

A new "off-on" switch for sensitive and selective fluorescence detection of biothiols[glutathione(GSH), cysteine(Cys) and homocysteine(Hcy)] was developed based on an anionic conjugated polyelectrolyte(CPE), pyridyl-functionalized poly(phenylene ethynylene)(P1). The fluorescence of P1 can be significantly quenched by Ag⁺ due to complexation-mediated interpolymer aggregation. Furthermore, biothiols can efficiently recover the fluorescence intensity of P1 as a result of the stronger binding between thiol group and Ag⁺, which dissociates P1 from the P1/Ag⁺ complex and disrupts interpolymer aggregation. Under optimum conditions, a good linear relationship in a range of 100―4200 nmol/L is obtained for GSH with a detection limit of 80 nmol/L(S/N=3). As a result of specific interaction between the thiol group and Ag⁺, the proposed method shows a high selectivity for biothiols. In addition, the CPE-based fluorescence "off-on" switch has been used to quantitatively detect total biothiols in cell lysates.