Synthesis, characterization and fluorescence turn-on detection of BSA based on the cationic poly(diketopyrrolopyrrole-co-ethynylfluorene) through deaggregating process

A novel AIE-active diketopyrrolopyrrole (DPP) derivative containing anthranone and para-iodophenyl units (Monomer 1) are synthesized. Due to the presence of polymerisable group, Monomer 1 can be polymerized with 2,7-diethynyl-9,9-bis[6'-(N,N-diethylamino)-octyl]fluorene to yield corresponding neutral polymer N1, where AIE-acitve DPP and ACQ-active fluorene units are linked together with a flexible alkyl spacer in main chain. N1 is transformed to its polyelectrolyte P1 via ionization by CH3I. P1 emits purple fluorescence with two emission peaks at 440 and 625 nm in DMSO and is AIE-inactive due to its amphiphilic performance and the presence of ACQ-active fluorene unit. A fluorescence turn-on probe for bovine serum albumin (BSA) detection and quantification is developed by taking advantage of the deaggregating process of Pl. It is found that the fluorescence intensity of P1 in DMSO/PBS buffer (v/v= 1/1) at 450 and 645 nm is increased by 2.94 and 2.11-fold when the concentration of BSA increased from 0 to 70 mu M. In addition, P1 can be utilized as a fluorescent probe for cellular imaging of HeLa cells, where red fluorescence is observed in the cytoplasm. The CCK-8 assay shows that the cytotoxicity of P1 is low. (C) 2016 Elsevier B.V. All rights reserved.