Near-Infrared Lifetime Nanothermometry Detects Microwave-Induced Brain Heating

Abstract

In modern environments, the brain is continuously exposed to numerous external stimuli, including the microwave radiation used in telecommunication technologies. It has been suggested that the absorption of this radiation by brain tissue can induce local heating. Because brain temperature influences neural activity, metabolism, and overall brain function, microwave-induced heating raises concerns over the safety of such technologies. Proper evaluation of the risks associated with microwave-based technologies thus requires accurate quantification of heating in deep organs without disrupting their physiology. This study, demonstrates that microwave-induced brain heating can be remotely monitored in vivo via luminescence thermometry using near-infrared luminescent silver sulfide (Ag2S) nanoparticles. Their temperature-dependent luminescence lifetime is a reliable thermometric parameter for the measurement of absolute brain temperature. The in vivo results offer direct, real-time evidence of brain heating (up to 4 °C) under telecom exposure conditions (3 GHz). Moreover, they establish lifetime thermometry as a reliable, minimally invasive approach for investigating thermoregulation in deep tissues even under external electromagnetic stimulation.