Ratiometric Luminescence Sensing of Bio-Macromolecules via Highly Sensitive Templated Pyrene-Based nanoGUMBOS

Abstract

A series of pyrene-based ionic liquids comprised of a group of uniform materials based on organic salt (GUMBOS) were synthesized by incorporating pyrene butyrate with quaternary alkyl phosphonium and ammonium-based ionic liquid via ion exchange reaction incorporating a variation in alkyl chain length. Water-suspended crystalline pyrene-assimilated nanoparticles (nanoGUMBOS) were subsequently fabricated from the prepared GUMBOS via the reprecipitation method. Different photophysical and microscopic measurements were performed to confirm the crystalline molecular level stacking of pyrene fluorophores inside the nanoparticles. The pyrene moieties within the nanoGUMBOS showed a pronounced tendency for self-association upon excitation, resulting in a novel excited state aggregation-induced emission (ESAIE). Due to the bathochromically shifted strong aggregation-induced emission, this nanoGUMBOS is further employed in the sensitive and selective ratiometric detection of biomacromolecules in aqueous and serum media. As the excessive use of some biomacromolecules (heparin (HP) and protamine (PS)) can lead to undesired side effects in living systems, hence such detection can be very crucial. In most cases, interaction with biomacromolecules like heparin facilitates the formation of excimer species in pyrene systems, but to our utter surprise we observed the opposite phenomenon of excimer disintegration here. This presents a convenient method for detecting heparin in aqueous and serum media. Furthermore, using the nanoGUMBOS-heparin complex, we can also detect protamine sulfate. A detailed study of the detection mechanism is presented in this report.