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Proceedings Paper

Targeted nanosensor aided three-dimensional pH mapping in tumor spheroids using two-photon microscopy
Author(s): Aniruddha Ray; Yong-Eun Koo Lee; Remy Elbez; Raoul Kopelman
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Paper Abstract

Tumors are generally characterized by a pH lower than the surrounding tissues. The mapping of tumor pH is of great importance as it plays a critical role in drug delivery and its effectiveness. Here we present a pH mapping technique in tumor spheroids, using targeted, ratiometric, fluorescent, pH nano-sensor that is based on two-photon excitation. Spheroids are micro-tumors that are widely used as an in-vitro three dimensional tumor model to study the different properties of the tumor for the purpose of drug delivery, therapy etc. The nanosensor consists of 8-Hydroxypyrene- 1,3,6-trisulfonic acid (HPTS), a pH sensitive dye, encapsulated in polyacrylamide hydrogel nanoparticle matrix and F3 peptide, conjugated to the nanoparticle's surface. The nanosensor has an average size of 68nm and contains approximately 0.5% dye by weight. The fluorescence intensity ratio, at the two-photon excitation wavelengths of 900nm and 750nm, increases linearly in the pH range from 6.0 to 8.0 and is used to determine the pH of the local environment. Our study reveals the pH distribution inside human cervix cancer spheroids (of different sizes) during the various stages of their formation. This information can be used to develop more efficient drug delivery mechanisms. The two-photon excitation used for this purpose is especially useful as it drastically minimizes both photobleaching and autofluorescence, thus leading to an increase in the signal-to-noise ratio. It also enables deep tissue imaging due to higher photon penetration depth.

Paper Details

Date Published: 9 February 2012
PDF: 7 pages
Proc. SPIE 8226, Multiphoton Microscopy in the Biomedical Sciences XII, 822613 (9 February 2012); doi: 10.1117/12.907518
Show Author Affiliations
Aniruddha Ray, Univ. of Michigan (United States)
Yong-Eun Koo Lee, Univ. of Michigan (United States)
Remy Elbez, Univ. of Michigan (United States)
Raoul Kopelman, Univ. of Michigan (United States)

Published in SPIE Proceedings Vol. 8226:
Multiphoton Microscopy in the Biomedical Sciences XII
Karsten König, Editor(s)

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