Modified multi-walled carbon nanotubes potentially suitable for intracellular pH measurements

Giacomo Ghini; Gian Luigi Puleo; Cosimo Trono; Ambra Giannetti; Lapo Luconi; Claudio Bianchini; Giuliano Giambastiani; Francesco Baldini

doi:10.1117/12.843556

12 February 2010 Modified multi-walled carbon nanotubes potentially suitable for intracellular pH measurements

Giacomo Ghini, Gian Luigi Puleo, Cosimo Trono, Ambra Giannetti, Lapo Luconi, Claudio Bianchini, Giuliano Giambastiani, Francesco Baldini

Author Affiliations +

Proceedings Volume 7574, Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications VII; 75740C (2010) https://doi.org/10.1117/12.843556
Event: SPIE BiOS, 2010, San Francisco, California, United States

Abstract

Carboxylic acid functionalized multi-walled carbon nanotubes (COOH-MWCNTs) have been studied as macromolecular carriers for pH indicators to be used inside cells. The activation of carboxylic groups with thionyl chloride (SOCl2) followed by the reaction with a family of fluorescein ethylen glycol derivatives led to dyes covalently anchored to the MWCNT surface. Such a functionalization was found to preserve wholly the fluorescence properties of the dye ultimately providing higher water solubility to the modified macromolecular systems. Moreover, the use of a polyether spacer between the dye and the MWCNT surface preserved from undesired florescence quenching effects. The pH dependence of the modified nanotubes was investigated interrogating a solution of MWCNTs, the pH of which was adjusted in the range 4-9 pH units by adding drops of hydrochloric acid and sodium hydroxide. Light from LED was suitably filtered at 480 nm with a high pass-band filter and coupled to an optical fiber which illuminates the solution containing the fluorescein-functionalised MWCNTs. An optical fiber, at 90° with respect to the LED illumination, is connected with a Hamamtsu spectrum analyzer for the recording of the fluorescence spectra. The modified MWCNTs exhibited linear pH dependence in the range between 6 and 8 pH units with a sensitivity less than 0.1 pH units.

Citation Download Citation

Giacomo Ghini, Gian Luigi Puleo, Cosimo Trono, Ambra Giannetti, Lapo Luconi, Claudio Bianchini, Giuliano Giambastiani, and Francesco Baldini "Modified multi-walled carbon nanotubes potentially suitable for intracellular pH measurements", Proc. SPIE 7574, Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications VII, 75740C (12 February 2010); https://doi.org/10.1117/12.843556

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