Table 4.

Effects of blue light on mammalian cells

In vitro studies
Light source	Radiant exposure	Cell type	Treatment outcome	Ref.
Narrow-band blue light 420 nm.	54 mJ/cm2 and 134 mJ/cm2.	Keratinocyte cell lines: HaCaT and hTERT.	Blue light has anti-inflammatory effects on keratinocytes by decreasing the cytokine-induced production of IL-1α and ICAM-1.	(Shnitkind et al., 2006)
LED 412, 419, 426, and 453 nm.	66–100 J/cm2 for 412, 419, and 426 nm; 4500 J/cm2 for 435 nm. The exposures were measured at the LED apertures.	Human keratinocytes, skin-derived endothelial cells.	Irradiations with 412, 419, 426 nm at 66–100 J/cm2 and 453 nm at 4500 J/cm2 is cytotoxic for skin cells.	(Liebmann et al., 2010)
Dental light sources: quartz–tungsten–halogen (QTH), plasma-arc (PAC), and laser. The majority of the light flux fell between 400–500 nm.	1.3 to 60 J/cm2.	3T3 mouse fibroblasts.	Exposures ranging from 5 J/cm2 laser) to 15 J/cm2 (PAC, QTH) irreversibly suppressed SDH activity nearly 100% up to 72 h post-exposure. For the PAC and QTH sources, exposures as low as 3.5 J/cm2 also irreversibly suppressed SDH activity.	(Wataha et al., 2004b)
Visible light 390–550 nm.	Up to 6 h irradiation at 2.8 mW/cm2 (or up to 60.5 J/cm2).	Human primary retinal epithelial cells.	A small loss of mitochondrial respiratory activity was observed at 6 h. Light exposure significantly damaged mitochondrial DNA at 3 h.	(Godley et al., 2005)
Xenon arc lamp filtered to 400–410, 445–455, 450–490, or 485–495 nm.	20–40 min illumination at 6.3 mW/cm2 (or 7.6 –15.2 J/cm2).	Mouse fibroblasts (3T3), African green monkey kidney epithelial cells, and human foreskin keratinocytes.	Blue light stimulated H2O2 production in cultured mammalian cells.	(Hockberger et al., 1999)
In vivo study
Light source	Radiant exposure	Subject	Treatment outcome	Ref.
Visible light 380–480 nm with a peak emission at 420 nm.	Each day, 20 J/cm2 was given to a cumulative dose of 100 J/cm2.	Eight healthy volunteers with skin type I–III and an average age of 20.9 years (19–24 years).	No inflammatory cells and sunburn cells were visible after irradiation. A significant increase in the peri-nuclear vacuolization of keratinocytes was demonstrated. No significant change in p53 expression was seen. Signs of elastosis and changes in MMP-1 expression were absent. Minimal clinical hyperpigmentation of the irradiated skin was confirmed with a significant increase in Melan-A-positive cells.	(Kleinpenning et al., 2010)