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fluorescence at the body temperature B37 1C. The fluorescence
was triggered at elevated temperatures. Irreversibility of the
signal and the overall increase in fluorescence >10 times after a
complete heating–cooling cycle suggested its potential applic-
ability as nanothermometers. The nanothermometers reporting
function could be adjusted by changing the temperature sensi-
tive linker. This material could be potentially utilized with
thermal ablation therapies to report temperature and better
control the heating process. Future work will be focused on
demonstrating this feasibility in vivo under laser ablation and
radiofrequency heating and inclusion of NIR dyes for deeper
light penetration. In addition, the kinetics and computational
studies will be conducted to reveal the mechanism of the
release and optimize the structure of the nanothermometer.
We thank Prof. S. Emelianov and Dr. Y-S. Chen (UT Austin),
for help with gold nanorod synthesis. We gratefully acknowl-
Fig. 3 Change of the temperature under fast heating–cooling for
nanothermometers carrying conjugate 2 (red diamonds) and free conjugate 2
(
green circles). Normalized to the initial intensity =10 a.u.
an attachment of both cysteines on the gold surface introduces a edge financial support from the NCI/NIH R21CA149814, and
conformational strain. To release the strain, compound 3 was from the Washington University Molecular Imaging Center.
synthesized by adding a flexible spacer, a single glycine residue,
between the two cysteine residues. As expected, 3 demonstrated a
thermal activation at higher temperature near 70 1C (Fig. S4, ESI†),
Notes and references
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Under this rapid heating conditions, the nanoparticles become
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5
37 1C compared to the initial fluorescence and entirely irreversible.
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4
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1
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(
comparing future nanothermometers with improved design.
In summary, we present a new concept of clinically relevant
nanothermometers. Gold-nanoparticle based constructs with
temperature sensitive linkers and a fluorophore showed low
1
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82 Chem. Commun., 2013, 49, 680--682
This journal is c The Royal Society of Chemistry 2013