Monitoring of thermal dose during ablation therapy using quantum dot-mediated fluorescence thermometry.
OBJECTIVE
The objective of this study was to demonstrate the feasibility of quantum dot (QD)-mediated fluorescence thermometry to monitor thermal dose in an in-vitro thermal ablation zone generated by laser-heated gold nanoshells (LGNS).


METHODS
Hyperthermic cell death of human prostate cancer cell line (PC-3) was determined after various heating settings and correlated to the thermal conditions using an Arrhenius model prior to LGNS ablation. PC-3 cells with gold nanoshells (GNS) and QDs were exposed to a near-infrared laser and QD excitation light. When the cells were heated by GNS, local temperature was measured using the temperature-dependent fluorescence intensity of QDs. Using the predetermined Arrhenius model, the thermal dose (i.e., cell death of PC-3 cells) by LGNS was estimated with local temperatures measured with QD-mediated thermometry. The estimated thermal dose was confirmed with calcein-acetoxy-methylester viability assay.


RESULTS
For PC-3 cell line, the activation energy and frequency factor of the Arrhenius model were 86.78 kcal/mol and 6.35 × 10(55) Hz, respectively. During LGNS ablation of PC-3 cells, QD-mediated temperature measurement showed that the temperature of the laser spot increased rapidly to ∼58 °C ± 4 °C. The estimated thermal dose showed that cell death reached to ∼90% in 120 seconds. The death cell zone observed after staining corresponded to a peak area of the temperature profile generated after analysis of the QD fluorescence intensity.


CONCLUSIONS
This study shows that the QD fluorescence thermometry can accurately monitor the PC-3 cell death by LGNS ablation. This approach holds promises for a better monitoring of thermal ablation procedures in clinical practice.
Bensalah
Karim
K
Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9110, USA.
Tuncel
Altug
A
Hanson
Willard
W
Stern
Joshua
J
Han
Bumsoo
B
Cadeddu
Jeffrey
J
D016923:Cell Death / Q000528:radiation effects; D045744:Cell Line, Tumor; D005453:Fluorescence; D006046:Gold / Q000737:chemistry; D006358:Hot Temperature; D006801:Humans; D006979:Hyperthermia, Induced / Q000379:methods*; D053685:Laser Therapy / Q000379:methods*; D008954:Models, Biological; D008991:Monitoring, Physiologic / Q000379:methods*; D057145:Nanoshells / Q000737:chemistry; D045663:Quantum Dots; D013696:Temperature
D006046:Gold