X-ray induced bio-acoustic emissions from cultured cells

Purpose We characterise for the first time the emission of bio-acoustic waves from cultured cells irradiated at doses of X-ray photon radiation relevant to medical and accidental exposure. Methods and materials Human cancer cell lines (MCF-7, HL-60) and control cell-free media were exposed to 1 Gy X-ray photons while recording the sound generated before, during and after irradiation. Cellular cytotoxicity following photon irradiation was determined by extracellular LDH levels, and irradiated cell conditioned media were tested for their ability to elicit a bystander effect in reporter cells. Results We report the first recorded acoustic signals captured from a collective pressure wave response to ionising irradiation. The signature of the collective acoustic peaks was temporally wider and with higher acoustic power for irradiated HL-60 than for irradiated MCF-7. Conclusions We show that at doses of X-ray irradiation capable of producing the release of bystander effect-inducing activity, both cell types emit a characteristic acoustic signal for the duration of the radiation pulse. The rapid signal decay is consistent with a passive rather than an active acoustic signal generation. This preliminary study suggests that further work on the potential role of radiation induced acoustic emission (RIAE) in the cellular bystander effect is merited. ### Competing Interest Statement The authors have declared no competing interest.