Amphiphilic Au Nanoclusters Modulated by Magnetic Gemini Surfactants as a Cysteine Chemosensor and an MRI Contrast Agent

Abstract

Cationic magnetic Gemini surfactants (mag-G-surfs ), [C14H29(CH3)(2)N(CH2)(2)N(CH3)(2)C14H292+center dot 2[XCl3Br](-) (14-2-14.2X, X = Ce, Gd, or Ho), efficiently induce the aggregation of glutathione-protected Au nanoclusters (NCs) (GSH-Au NCs). These magnetic luminescent aggregates not only possess aggregation-induced emission (AIE) behavior but also display aggregation-induced magnetic enhancement. In particular, 14-2-14.2Ce and 14-2-14.2Gd have a better effect on boosting the luminescence intensity, quantum yield (QY), and luminescence lifetime (tau). The luminescent aggregates of GSH-Au NCs triggered by 14-2-14.2Gd or 14-2-14.2Ho exhibit more favorable paramagnetic behavior. Other Au NCs containing a Au(I)-thiolate complex shell also exhibit the obvious AIE phenomenon after introducing 14-2-14.2Gd, demonstrating the luminescence enhancement effect of mag-G-surfs. The luminescent aggregate 14-2-14.2Ce@GSH-Au NCs can serve as a "light up" fluorometric probe to detect cysteine selectively with the detection limit (DL) of 36 mu M, and the magnetic luminescent aggregate 14-2-14.2Gd@GSH-Au NCs has the potential to be a novel contrast agent in T-1-weighted magnetic resonance (MR) imaging due to its satisfactory contrasting ability.