Cytotoxic Effect of White LED Light on Human Oral Keratinocytes

Objectives: The widespread use of light emitting diodes (LED) as a light source for medical applications and in everyday use of equipment such as home appliances and electronics has caused concerns about the safety of this technology, since these devices will illuminate their houses and the most public and private places, such as dental clinics. Thus, due to the fact that humans are increasingly exposed to LEDs, the scientific community has not been worried about the possible biological effects on tissues caused by this exposure, the objective of this study was to evaluate the cytotoxic effects of white LED light at different intensities on human oral keratinocytes (NOK-si).

Methods: The cells were cultivated in Dulbecco’s Eagle (DMEM) culture medium in a 96 wells plates and were underwent to the illumination with white LED at 300, 400 and 500 lux. Then, the cell viability was achieved 12, 24 and 48 hours after the illumination using the Alamar Blue assay was. After the treatments, two intensities and two periods of time, were chosen to perform the analysis of cell membrane integrity, intimately linked to necrosis cell death, using the Homogeneous Membrane Integrity Assay (CytoTox-ONE assay).

Results: Data were submitted to Two-Way ANOVA and Tukey post hoc (p < 0.05) for multiple comparisons. Surprisingly, the results showed 98% of cell death after illumination with 500 lux, when compared to the control group. The CytoTox-ONE assay revealed that this phototherapy damaged the membrane integrity of the oral keratinocytes (98%), suggesting necrosis.
Conclusions:
In summary, the white LED was toxic for NOK-si cells and its potential biological effect on human body, should be better investigated.