Journal
ACS NANO
Volume 6, Issue 4, Pages 2917-2924Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn2038077
Keywords
quantum dot; GFP-Iike fluorescent protein; FRET; pH sensing; intracellular sensing
Categories
Funding
- National Institutes of Health [HHSN268201000043C]
- NIH Nanomedicine Development Center [PN2EY018244]
- National Science Foundation [CBET- 0939511]
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Intracellular pH (pHs) 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, 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 Forster 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.
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