A low cytotoxic and ratiometric fluorescent nanosensor based on carbon-dots for intracellular pH sensing and mapping.
Intracellular pH plays a critical role in the function of cells, and its regulation is essential for most cellular processes. In this study, we demonstrate a fluorescence resonance energy transfer (FRET)-based ratiometric pH nanosensor with carbon-dot (CD) as the carrier. The sensor was prepared by covalently linking a pH-sensitive fluorescent dye (fluorescein isothiocyanate, FITC) onto carbon-dot. As the FRET donor, the carbon-dot exhibits bright fluorescence emission as well as λex-dependent photoluminescence emission, and a suitable excitation wavelength for the donor (CD) can be chosen to match the energy acceptor (fluorescein moiety). The fluorescein moieties on a CD undergo structural and spectral conversion as the pH changes, affording the nanoplatform a FRET-based pH sensor. The CD-based system exhibits a significant change in fluorescence intensity ratio between pH 4 and 8 with a pKa value of 5.69. It also displays excellent water dispersibility, good spectral reversibility, satisfactory cell permeability and low cytotoxicity. Following the living cell uptake, this nanoplatform with dual-chromatic emissions can facilitate real-time visualization of the pH evolution involved in the endocytic pathway of the nanosensor. This reversible and low cytotoxic fluorescent nanoplatform may be highly valuable in a variety of biological studies, such as endocytic trafficking, endosome/lysosome maturation, and pH regulation in subcellular organelles.
College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, People's Republic of China.
Fangkai
F
Du
Yunhao
Y
Ming
Fang
F
Zeng
Changmin
C
Yu
Shuizhu
S
Wu
D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D002021:Buffers; D002244:Carbon / Q000633:toxicity*; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000633:toxicity; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D053758:Nanoparticles / Q000633:toxicity* / Q000648:ultrastructure; D012996:Solutions / Q000737:chemistry; D014867:Water / Q000737:chemistry
D002021:Buffers; D005456:Fluorescent Dyes; D012996:Solutions; D014867:Water; D002244:Carbon; D016650:Fluorescein-5-isothiocyanate