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Is there a biostimulating effect of blue light?

By Jan Tunér

In recent years, lasers and LEDs in the blue part of the spectrum have been introduced on the market. It is known that blue light has a bactericidal effect (1) but is there also a biostimulatory effect? If so, it would offer two advantages in one light source. For superficial structures laser and LEDs are fairly equal in efficacy. The literature is so far scant and inconclusive, but let’s see what there is. First, some negative reports:

Yoo (2) found that 405 nm laser light reduced tibial trabecular bone in mice. Teuschl (3) writes: Illumination substantially affected cell viability and cell growth. Blue light strongly decreased proliferation and augmented apoptosis in all 3 cell types and increased necrosis rates in C2C12 and NIH/3T3 cells. In contrast, red light did not alter apoptosis in either cell type but promoted proliferation in all 3 cell types with significant effects in C2C12 and NIH/3T3 cells and shortened time to closure in all 3 cell types. Hochman et al. compared 470 and 660 nm LED, 660 and 810 nm laser in the skin of healthy rats, looking at changes in Calcitonin gene-related peptide (CGRP) and substance P (SP). 810 nm laser had the best effect. Notably, 40 J was applied to a single point in a very small animal.

Now, some positive results:

Dungel (4) compared 470 and 629 nm LEDs, 50 mW/cm². The aim of this study was to evaluate and compare the therapeutic value of blue or red light emitting diodes (LEDs) on wound healing in an ischemia disturbed rodent flap model. LED therapy with both wavelengths significantly increased angiogenesis in the sub-epidermal layer and intramuscularly which was associated with significantly improved tissue perfusion 7 days after the ischemic insult. Accordingly, tissue necrosis was significantly reduced and shrinkage significantly less pronounced in the LED-treated groups of both wavelengths.

Ban Frangez (5) studied the effect of LED irradiation on sperm motility in infertile men with impaired sperm motility. Four different irradiation protocols were selected: (1) 850 nm, (2) 625, 660 and 850 nm, (3) 470 nm and (4) 625, 660 and 470 nm. LED improved the sperm motility regardless of the wavelength.

Adamskaya (6) performed circular excisions on either the left or right side were illuminated post-OP and on five consecutive days for 10 min by LED at 470 nm or 630 nm. Illumination substantially influenced wound healing. Blue light significantly decreased wound size on day 7, which correlated with enhanced epithelialisation. Light also affected mRNA expression. Both wavelengths decreased keratin-1 mRNA on day 7 post-OP, while keratin-10 mRNA level was elevated in both light treated group compared to control. Keratin-17 mRNA was also elevated in the red light group, but was unchanged in the blue light group.

Olivieri [7] studied the efficacy of PBM on hair regrowth in dogs with non-inflammatory alopecia Each dog was treated twice weekly for a maximum of 2 months with a therapeutic laser producing the following three different wavelengths emerging simultaneously from 21 foci: 13 × 16 mW, 470 nm; 4 × 50 mW, 685 nm; and 4 × 200 mW, 830 nm. At the end of the study, coat regrowth was greatly improved in six of seven animals and improved in one of seven. A weakness in this study is that several wavelengths were used at the same time and the possible effect of a specific wavelength cannot be evaluated. The same problem appears in the following study:

Figurová (8) used minipigs in a wound healing study, using a combination of 685 and 470 nm. Most PBM wound healing studies have been performed on various types of rat models, with their inherent limitations. Minipigs are evolutionary and physiologically closer to humans than rats. This is an obvious advantage of the study. The results demonstrate that the current dose of combined red and blue PBM improves the healing of sutured skin incisions in minipigs. The authors discuss the possible antimicrobial effect of 470 nm light. However, there is no group with initial infection, so this aspect cannot be evaluated. Further, as with the Olivieri study, the possible combination effect cannot be evaluated unless there are separate groups for the two light sources and the combination.

From the about examples, it is obvious that 470 nm can have a biostimulatory effect in addition to its known bactericidal effect. But the results are unambiguous and it is likely that there are dosage windows for the 470 nm effects.

References:

  1. Enwemeka C S, Williams D, Enwemeka S K, Hollosi S, Yens D. Blue 470-nm light kills methicillin-resistant Staphylococcus aureus (MRSA) in vitro. Photomed Laser Surg. 2009; 27 (2): 221-226.
  2. Yoo YM et al. Decreased Bone Volume and Bone Mineral Density in the Tibial Trabecular Bone Is Associated with Per2 Gene by 405 nm Laser Stimulation. Int J Mol Sci. 2015; 16 (11): 27401-27410.
  3. Teuschl A et al. Phototherapy with LED light modulates healing processes in an in vitro scratch-wound model using 3 different cell types. Dermatol Surg. 2015; 41 (2): 261-268.
  4. Dungel P, Hartinger J, Chaudary S, Slezak P, Hofmann A, Hausner T, Strassl M, Wintner E, Redl H, Mittermayr R. Low level light therapy by LED of different wavelength induces angiogenesis and improves ischemic wound healing. Lasers Surg Med. 2014; 46 (10): 773-780.
  5. Ban Frangez H et al. Photobiomodulation with light-emitting diodes improves sperm motility in men with asthenozoospermia. Lasers Med Sci. 2015; 30 (1): 235-240.
  6. Adamskaya N et al. Light therapy by blue LED improves wound healing in an excision model in rats. Injury. 2011;42(9):917-921.
  7. Olivieri L et al. Efficacy of low-level laser therapy on hair regrowth in dogs with noninflammatory alopecia: a pilot study. Vet Dermatol. 2015; 26 (1): 35-9, e11.
  8. Figurová M et al. Histological Assessment of a Combined Low-Level Laser/Light-Emitting DiodeTherapy (685 nm/470 nm) for Sutured Skin Incisions in a Porcine Model: A Short Report. Photomed Laser Surg. 2016 ; 34 (2): 53-55.