Room: Exhibit Hall
Purpose: The production of reactive oxygen species (ROS) is one of the mechanisms through which ionizing radiation leads to cell death, engendering radiotherapy itself. ROS production is involved in radioprotection, radioresistance and radiosensitization. Since conventional chemotherapeutics are already in clinical use as radiosensitizers and many other radiosensitizers are under development, including nanoparticles, there is increasing need for robust assessment of ROS production in candidate radiosensitizers. Here, we used the modulation of fluorescence intensity in quantum dots (QD) by cells to quantify ROS production following radiotherapeutic X-Ray doses.
Methods: We irradiated erythroid (K562), myeloid (HL60), cortico-neuronal (HCN2) and glioblastoma (T98G) cells with low dose (2 Gy) and high dose (20 Gy) X-Rays by means of a radiotherapy-grade cell irradiator (CellRad, Faxitron). We also treated the myeloid and erythroid cells with common chemotherapeutics (Daunorubicin and Doxorubicin) in view of our goal of characterizing radiosensitizers. We assessed the fluorescence of UV excited hydrophilic CdSe/ZnS core-shell QDs dispersed in suspensions of irradiated cells. We also used a custom-designed microfluidic device to assess changes in the cytoskeletal properties of cells following irradiation.
Results: We found statistically significant (p < 0.0001) quenching of the emission spectra of the colloidal dispersions due to the ROS produced by the myeloid and erythroid cells following both chemotherapy and radiotherapy (20 Gy). Interestingly, for glioblastoma cells, the result was biphasic with both quenching and enhancement (p < 0.01) of QD fluorescence intensity. We describe this intensity modulation as cyto-molecular tuning of QDs. The microfluidic assessment revealed that radiotherapeutic doses induced significant cell stiffening before cell death.
Conclusion: The modulation (quenching or enhancement) of QD fluorescence intensity due to ROS production by irradiated cells which we have found, presents itself as a novel means of evaluating radiosensitizers in order to improve radio-therapeutic outcomes.