3D printed microtissue cassettes enabling high throughput proton radiobiological assays

Area of Science:

• Radiobiology
• Medical Physics
• Biotechnology

Background:

• Relative Biological Effectiveness (RBE) is crucial for translating photon therapy experience to proton beam therapy.
• Uncertainties in proton RBE within the spread-out Bragg peak (SOBP) can lead to suboptimal treatment and increased toxicity.
• Accurate RBE determination is essential for precise proton therapy planning.

Purpose of the Study:

• To develop and validate a reliable analytical method for determining proton RBE in vitro.
• To assess proton RBE along the SOBP and distal fall-off regions.
• To enable high-throughput assessment of radiobiological effects using a 3D microtissue cassette.

Main Methods:

• Development of a 3D microtissue cassette for high-throughput biological assays.
• In vitro irradiation of microtissues using a single proton beam.
• Assessment of cell survival using clonogenic assays.
• Quantification of DNA double-strand breaks using the γ-H2AX assay.

Main Results:

• Proton RBE values determined by clonogenic assay were 1.3, 1.5, and 1.6 at 90%, 50%, and 10% cell survival, respectively.
• RBE values from the γ-H2AX assay were consistent with clonogenic assay results (1.58 at 10% cell survival).
• The 3D cassette demonstrated high spatial resolution, detecting subtle changes in DNA damage response.

Conclusions:

• The 3D printed cassette reliably addresses critical radiobiological questions regarding proton RBE.
• This high-throughput methodology reduces time and resource burdens for clinical facilities.
• The approach is adaptable for investigating other charged particle radiation therapy modalities.