Monitoring of thermal dose during ablation therapy using quantum dot-mediated fluorescence thermometry

Purpose: 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). Materials and 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-3cells 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-3cells) 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-3cell line, the activation energy and frequency factor of the Arrhenius model were 86.78kcal/mol and 6.35×10⁵⁵ Hz, respectively. During LGNS ablation of PC-3cells, 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-3cell death by LGNS ablation. This approach holds promises for a better monitoring of thermal ablation procedures in clinical practice.