In situ probing of intracellular pH by fluorescence from inorganic nanoparticles

Intracellular pH (pH(i)) plays a critical role in the physiological processes of cells. Nanoscale sensors based on pH-sensitive fluorescent proteins attached on nanoparticles (NPs) have been designed but inorganic NP-dependent fluorescent nanosensors have not yet been explored. Herein we describe a pH sensitive inorganic semiconductor fluorescent probe based on ultrathin 3C-SiC NPs which can effectively monitor pH in the range of 5.6-7.4 by taking advantage of the linear dependence between the fluorescent intensity ratio of the surface OH- and H+ bonding states to band-to-band recombination and pH. Detection of pH; is demonstrated in living HeLa cells. In particular, pH(i) measurements during apoptosis confirm the validity and sensitivity of this technique in monitoring real-time changes in the intracellular environment. Toxicity assessment and confocal laser scanning microscopy indicate that the 3C SiC NPs have low cytotoxicity and are compatible with living cells. (C) 2013 Elsevier Ltd. All rights reserved.