Study On Photobiological Safety Of White LED For Indoor Lighting Based On Cellular Level Characterization

LED technology is undergoing the period of fast development with its application expanding from outdoor to indoor illumination.LED is expected to be the predominant light source of ordinary indoor illumination,so the photobiological safety has become a forefront issue in light environment of building.However the current photobiology safety evaluation on LED lighting products is short of a comprehensive research and related test methods based on the characterization of human cells in terms of photo biological safety of indoor white LED.The test method for the photobiological safety of indoor white LED is conducted in the first stage of the research:in combination with the previous achievement of the research,taking florescent powder stimulated white LED as the test light,HaCat(immortalized keratinocyte cells),HS68(normal male balanus cells),SRA01/04(human lens epithelial cells)and D407(human retinal pigment epithelial cells)as test cells,the determination test on cells vitality–evaluation indicator of photobiological safety is carried out under different irradiation time,intensity and color temperature by using MTT colorimetric method.The mechanism of indoor white LED caused cell injury is conducted in the second stage of the research:in combination with the achievement of the first stage,taking florescent powder stimulated white LED with 4000K color temperature as the test light,HaCat(immortalized keratinocyte cells),HS68(normal male balanus cells),SRA01/04(human lens epithelial cells)and D407(human retinal pigment epithelial cells)as test cells,and taking human skin cells-1 hour and human eye cells-2 hours as the test irradiation time,60W/m~2 as the irradiation intensity,determinations on degree of cell membrane lipid peroxidation,degree of injured cell membrane,cells'ROS level,level of cell apoptosis,expression level of proteins and signal path related to cell apoptosis adjustment are completed respectively.The following research achievements are obtained through scientifically screening and analysis on the original test data of the two stages:The first stage:a comprehensive,fast,accurate test method for photo biological safety of indoor white LED has been established.The second stage:the mechanism of indoor white LED caused cell injury has been obtained:test illumination causes ROS increasing and lipid peroxidation,reduced cell vitality,and cell membrane injury so that cells is induced to apoptosis;ROS may use up-regulated Bax expression(apoptosis promoting protein)and down-regulated Bcl-2expression(apoptosis inhibitory protein)to induce the cell apoptosis;ROS may induce cell apoptosis through three signal paths such as ERK,JNK and p38.The main signal path for HaCat(immortalized keratinocyte cells)and HS68(normal male balanus cells)is p38;the main signal path for SRA01/04(human lens epithelial cells)and D407(human retinal pigment epithelial cells)is JNK.