Towards the Development of an Integrated Cell-Microdosimetry System Based on Raman Spectroscopy
Abstract
Purpose
To develop a Raman spectroscopy (RS)-based experimental microdosimetry system capable of read-out of a model system of cells cultured on a radiochromic film (RCF) dosimeter substrate that can measure energy deposited by ionizing radiation within individual cells.
Methods
A model system of MC38 murine colon carcinoma cells cultured on RCF (EBT3) was investigated for its feasibility for experimental microdosimetry. The integrated (cells+RCF) system was irradiated with 6 MV X-rays (Elekta Synergy linear accelerator) to doses between 0 Gy (control) and 5 Gy. A custom-built confocal Raman microscope with a 785 nm laser excitation (75 mW average power, 1-µm lateral and 6-µm axial resolution) was used to acquire Raman spectra from different depths of the cells+RCF system. The selected depths are used to probe the cells and RCF to analyze cell signals registered to dose measured from the RCF response in the same Raman acquisition session. To separate the spectral contributions of cells from RCF, test Raman measurements were performed individually for each component: irradiated MC38 cells cultured on quartz substrates, and irradiated RCF samples.
Results
Several peaks in the Raman spectrum of the active layer of the RCFs (e.g. 1445 cm-1) are sensitive to doses as low as 0.01 Gy. The Raman spectra of irradiated MC38 cells on quartz exhibit dose-dependent changes with DNA/RNA Raman bands (782 cm-1) decreasing by ~30% in intensity while protein bands (1001 cm-1) increase by ~20% with dose. While the Raman spectrum of the integrated cells+RCF system reveals a unique peak at 1665 cm-1 associated with cellular components, significant overlap exists between cell and RCF features necessitating additional analysis to decouple individual spectral signals.
Conclusion
The model cells+RCF system is a potential platform capable of simultaneously reading-out the Raman response from individual cells undergoing radiation induced biochemical changes and from the RCF dosimeter substrate.