Effects of Pulsed Red and Near-Infrared Light on Neuroblastoma Cells—Pilot Study on Frequency and Duty Cycle

Abstract

Transcranial photobiomodulation (tPBM) is an innovative intervention for a wide range of neurological and psychological conditions. tPBM therapy can enhance the metabolic capacity of neurons and bring about a variety of beneficial changes. This study mainly investigated the photobiological effects of pulsed red and near-infrared (NIR) light on neuron-like neuroblastoma SH-SY5Y cells by in vitro experiments. We covered the irradiation parameters, including wavelength (660, 850 nm), power density (5, 10, 20, 50, 100 mW/cm2), frequency (40, 100, 1000 Hz), and duty cycle (10%, 50%, 90%), finding that pulsed light generated a distinct effect compared with continuous-wave light on the cellular responses. Cell viability, mitochondrial membrane potential (MMP), adenosine triphosphate (ATP), and reactive oxygen species (ROS) showed significant increase after irradiation of the adequate fluence amount (4.8–9.6 J/cm2), and the enhancement was more notable under 40 Hz pulsed lighting. Under pulsed lighting with an average power density of 10 mW/cm2, cells that received irradiation of higher peak power density up to 100 mW/cm2 with a 10% duty cycle showed slightly higher metabolic responses. In addition, it was found that under same total fluence, short-term irradiation with high power density was more effective than long-term irradiation with low power density, which indicated the existence of a threshold to achieve effectiveness.

Keywords

• tPBM
• SH-SY5Y
• pulsed light
• ROS
• cell viability
• MMP