The Role of In Vitro cytotoxicity Testing
Patient positioning systems are designed to support precision in radiotherapy by enabling stable and reproducible treatment setups. As these devices come into direct contact with the patient’s skin and surrounding tissues, it’s essential to ensure they do not release substances that could harm living cells. Cytotoxicity testing evaluates whether materials used in these systems are safe at the cellular level, making it a vital part of biocompatibility assessment.
In radiotherapy, surface-contact materials used in immobilization and patient positioning systems must demonstrate non-cytotoxic behaviour to ensure their safe clinical use. To verify this, in vitro testing is conducted as per international standards.
Panacea Medical Technologies conducted an evaluation of its carbon fiber material, used in patient positioning boards that come in direct contact with patients, to confirm its non-sensitizing nature at a NABL-accredited test laboratory.
Testing facility: GLR Laboratories Private Limited
This summary outlines findings from a cytotoxicity evaluation using the elution method on a carbon fiber composite sheet planned for use in contact areas of radiotherapy systems.
Objective
To evaluate the in vitro cytotoxic potential of the test item extract on Balb/c 3T3 fibroblast cells using the Neutral Red Uptake (NRU) assay, as per ISO 10993-5:2009(E).
Method Summary
- Test System: Balb/c 3T3 mouse fibroblast cell line
- Extraction Medium: 1X DMEM + 10% serum
- Extraction Conditions:
- Surface area: 309 cm²
- Extraction ratio: 3 cm²/mL
- Duration: 24 h at 37 °C under aseptic conditions
- Controls:
- Positive: Sodium Lauryl Sulfate (0.2 mg/mL)
- Negative: High-Density Polyethylene (HDPE)
- Test Concentrations: 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%
- Evaluation Metrics:
- Qualitative: Cell morphology under microscopy
- Quantitative: Cell viability via NRU assay at 546 nm
Results
Qualitative Observations
- No cytopathic effects observed at any concentration.
- Cell morphology remained consistent with the negative control group across all test wells.
Quantitative Evaluation
- Cell viability ≥ 92.7% across all tested extract concentrations (30% to 100%)
- Cytotoxicity ≤ 7.2% at 100% concentration
- Assay validity criteria were met:
- Cell confluency > 70% prior to treatment
- Mean OD for negative control ≥ 0.3
- Positive control exhibited >30% cytotoxicity
- CV% < 15% for all replicates
Conclusion
Under the conditions tested and in compliance with ISO 10993-5:2009(E), the carbon fiber sheet extract demonstrated no cytotoxic effects on Balb/c 3T3 cells. The material is therefore classified as non-cytotoxic and suitable for use in medical devices involving limited (<24 h) patient skin contact.
Implication for Radiotherapy Practice
These findings confirm the cytocompatibility of the carbon fiber composite used in Panacea’s patient interface systems. The tested material supports:
- Safe skin contact during immobilization procedures
- Biological stability during treatment exposure
- Clinical suitability in scenarios requiring direct patient interface
“Cytotoxicity evaluation is a baseline requirement in material safety. Our positioning systems are validated through standardized in vitro assays to ensure they do not compromise cellular integrity during patient contact.”
