Quantum Dot-Fluorescent Protein FRET Probes for Sensing Intracellular pH

• Type of Material: Article
• Authors: Allison M. Dennis, Georgia Institute of Technology; Won Jong Rhee, University of Incheon; David Sotto, Georgia Institute of Technology; Steven N. Dublin, Georgia Institute of Technology; Gang Bao, Emory University
• Language: English
• Date: 2012-04-01
• Publisher: AMER CHEMICAL SOC
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2012 American Chemical Society.
• Final Published Version (URL): http://dx.doi.org/10.1021/nn2038077
• Title of Journal or Parent Work: ACS NANO
• Volume: 6
• Issue: 4
• Start Page: 2917
• End Page: 2924
• Grant/Funding Information: This work was supported by the National Institutes of Health as an NHLBI Program of Excellence in Nanotechnology Award (HHSN268201000043C to GB), as an NIH Nanomedicine Development Center Award (PN2EY018244 to GB), and by the National Science Foundation as a Science and Technology Center Grant (CBET- 0939511).
• Keywords: CELLS; RESONANCE ENERGY-TRANSFER; Science & Technology - Other Topics; Chemistry; BIOSENSORS; Materials Science, Multidisciplinary; pH sensing; Chemistry, Physical; SENSOR; Nanoscience & Nanotechnology; Chemistry, Multidisciplinary; intracellular sensing; NANOPARTICLES; Science & Technology; DELIVERY; ORANGE; FRET; quantum dot; GFP-Iike fluorescent protein; DESIGN; ASSEMBLIES; Materials Science; Technology; Physical Sciences; LIGAND
• Research Categories: Chemistry, Physical; Biology, Cell

Abstract

Intracellular pH (pH i) plays a critical role in the physiological and pathophysiological processes of cells, and fluorescence imaging using pH-sensitive indicators provides a powerful tool to assess the pH i of intact cells and subcellular compartments. Here we describe a nanoparticle-based ratiometric pH sensor, comprising a bright and photostable semiconductor quantum dot (QD) and pH-sensitive fluorescent proteins (FPs), exhibiting dramatically improved sensitivity and photostability compared to BCECF, the most widely used fluorescent dye for pH imaging. We found that Förster resonance energy transfer between the QD and multiple FPs modulates the FP/QD emission ratio, exhibiting a >12-fold change between pH 6 and 8. The modularity of the probe enables customization to specific biological applications through genetic engineering of the FPs, as illustrated by the altered pH range of the probe through mutagenesis of the fluorescent protein. The QD-FP probes facilitate visualization of the acidification of endosomes in living cells following polyarginine-mediated uptake. These probes have the potential to enjoy a wide range of intracellular pH imaging applications that may not be feasible with fluorescent proteins or organic fluorophores alone.