Mid-infrared absorption by soft tissue sarcoma and cell ablation utilizing a mid-infrared interband cascade laser.

Significance: Mid-infrared (MIR) light refers to wavelengths ranging from 3 to 30  μm and is the most attractive spectral region for ablation of soft and hard tissues. This is because building blocks of biological tissue, such as water, proteins, and lipids, exhibit molecular vibrational modes in the MIR wavelengths that result in strong MIR light absorption. To date, researchers investigating MIR lasers for surgical applications have used bulky light sources, such as free electron lasers, nonlinear light generators, and carbon dioxide lasers. We demonstrate the use of a tiny (a few microns wide, a few millimeters long) MIR interband cascade laser (ICL) for surgical thermal ablation applications.

Aim: Our goal is to demonstrate the use of an ICL for surgical thermal ablation and demonstrate its efficacy in ablating normal fibroblasts and primary undifferentiated pleomorphic sarcoma tumor cells (C1619).

Approach: We conducted Fourier transform infrared spectroscopy analysis of healthy and cancerous tissue samples, which indicated that the absorption of tumor tissue is higher than healthy tissue around 3.3-μm wavelength. These results enabled us to select an ICL emission wavelength, λ, of 3.3  μm to probe normal fibroblast and primary undifferentiated pleomorphic sarcoma cell survival after ICL exposure.

Results: We show that the absorption of tumorous tissue is higher than that of healthy tissues around the 3-μm MIR wavelength. We demonstrate that the ICL is able to ablate cancer cells at very low-power levels that can be clinically implemented but that this effect does not appear to be specific to C1619 when compared to normal fibroblasts.

Conclusions: Our study demonstrates that ICLs may represent an exciting new avenue toward precise laser-based thermal ablation.