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Proceedings Paper

Modified multi-walled carbon nanotubes potentially suitable for intracellular pH measurements
Author(s): Giacomo Ghini; Gian Luigi Puleo; Cosimo Trono; Ambra Giannetti; Lapo Luconi; Claudio Bianchini; Giuliano Giambastiani; Francesco Baldini
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Paper 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.

Paper Details

Date Published: 13 February 2010
PDF: 8 pages
Proc. SPIE 7574, Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications VII, 75740C (13 February 2010); doi: 10.1117/12.843556
Show Author Affiliations
Giacomo Ghini, Istituto di Fisica Applicata Nello Carrara, CNR (Italy)
Gian Luigi Puleo, Istituto di Chimica dei Composti Organo Metallici, CNR (Italy)
Cosimo Trono, Istituto di Fisica Applicata Nello Carrara, CNR (Italy)
Ambra Giannetti, Istituto di Fisica Applicata Nello Carrara, CNR (Italy)
Lapo Luconi, Istituto di Chimica dei Composti Organo Metallici, CNR (Italy)
Claudio Bianchini, Istituto di Chimica dei Composti Organo Metallici, CNR (Italy)
Giuliano Giambastiani, Istituto di Chimica dei Composti Organo Metallici, CNR (Italy)
Francesco Baldini, Istituto di Fisica Applicata Nello Carrara, CNR (Italy)


Published in SPIE Proceedings Vol. 7574:
Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications VII
Alexander N. Cartwright; Dan V. Nicolau, Editor(s)

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