Updated: Dec 23, 2020
Today we're talking about wavelength, the color of the light that you use for therapy. Does it matter? Why does it matter? What happens in the tissues with different wavelengths? I'm going to be referring back to a review that was published in May of '17, in the AIMS Biophysics journal, and this is by the esteemed Dr. Michael Hamblin. And the review's title is "Mechanisms and Applications of the Anti-inflammatory Effects of Photobiomodulation."
Now, I'm just taking a very small snippet out of this study to bring out information about wavelengths, because it gives us a really good review on what we know to date about wavelengths and how they behave in the tissues, but there is so much more to this review. So if you'd like to get a hold of it, it's about 20 or so pages, it's really technical, but it's some very, very good information. If you want to get ahold of it, email me firstname.lastname@example.org, and we'll get a link over to you so you can read it for yourself.
Photobiomodulation and Wavelength
When we say wavelength, we're talking specifically about wave like behavior. So photons have a wave behavior, photons of light travel in a wave form. The distance between the peaks of the wave is how we label what type of wave this is; so very, very short wave, we're talking less than 400 nanometers from peak to peak, those are going to be your invisible types of radiation, like ultraviolet and x-rays and gamma rays. Very, very short, oftentimes damaging to the tissues, but, over 400 is where we get into the visible spectrum; purple, blue, green, yellow, orange, and then red all the way up to about 700 nanometers, that's our visible spectrum that we as humans get to enjoy being able to see every day. From 700 up to about 2000 nanometers is what we'd term near infrared. Now this is invisible, but doesn't have the damaging characteristics that UV and x-rays do. And this goes all the way up to the far infrared that CO2 surgical lasers will put out at 10,600 nanometers. Once you get far enough in the wavelengths and you get into radar, FM channels, TV, short wave, and AM radio waves,
When we are talking about photobiomodulation, those wavelengths are specifically between six and 700 nanometers as well as from 770 to about 1064. Those are our most common and seemingly most efficient parameters for wavelengths, when we're going to be using it for photo biomodulation or laser therapy or light therapy.
The penetration of the light into the tissues is governed by the absorption and the scattering and the reflection at the surface, as well as by the molecules and the structures that are present in the tissues. Dr. Hamblin says that both absorption and scattering of light become significantly less as the wavelength gets longer, but once you get long enough, water becomes a very key absorber and then penetration depth gets shorter again. So the maximum penetration depth you can get with near infrared light is at 810 nanometers. That's going to be your deepest penetrating wavelength.
And penetration is one thing, but absorption is important too. It needs to be absorbed properly by the target tissues. Now, maximum absorption in water, which is the most common part of our tissues, happens at its maximum amount at about 980 nanometers or higher. And for that reason, those higher wavelengths generally have worse penetration profiles into tissues than the little bit shorter wavelengths around that 810nm mark.
Next, if we can get the light into the tissues, if we're using the right wavelength to get the penetration and the absorption we want, what are we actually talking about happening in the tissues? What does this particular color of light that you're using do? What's happening chemically in those tissues? Well, we have to look at what's called chromophores, which are biological molecules that undergo a conformational change when they absorb a photon of light at a certain wavelength. One is cytochrome C oxidase. And if you've looked at laser therapy, if you looked at light therapies and photobiomodulation in general, you've probably heard about cytochrome C oxidase. What is it specifically? Well, it's unit IV in the mitochondrial electron transport chain. It produces a proton gradient that ATP synthase enzyme needs in order to synthesize ATP. And because of the way that it is built, it absorbs light in the near infrared spectrum very well up to about 950 nanometers.
So what happens when cytochrome C oxidase absorbs one of those key wavelengths? What goes on there? Well, we can only know what we observe. We know we see an increase of enzyme activity, increased oxygen consumption, and increased ATP production. And the best theory we have is that this is based on photo dissociation of inhibitory nitric oxide. Nitric oxide will block oxygen. So a very low energy photon absorbed into cytochrome C oxidase actually kicks out nitric oxide and allows more cellular respiration and energy production to take place.
The next chromophore that Dr. Hamblin brings up is water. Now specifically, we're talking about structured water layers or interfacial water and water clusters. These are all tiny amounts of water between the cells and around proteins and within the cells, even specifically around the mitochondria. When these small amounts of water absorb light, then we see a very small increase in vibrational energy and charge separation when it absorbs this near infrared light and that's right around 980nm and up to about 1200 and sometimes even higher than 1200nm. This can affect the conformation of cellular proteins. It can reduce the viscosity of the interfacial water within the mitochondria and allow for faster ADP synthase action.
Photobiomodulation Clinical Training
I'd like you to contact me about if you have further questions on how to translate this information into patient results. If you want your patients to get better utilizing laser therapy, you need to know something about how these mechanisms work, but more than that you need to know how to actually put them into practice where your patients can see meaningful results. That's where the protocols, the time, the power, the wavelength, all of those factors that matter need to be worked in correctly so that you can get reproducible, predictable results for your patients.