What is Photobiomodulation (PBM) Technology?

Understanding Photobiomodulation (PBM)

Photobiomodulation (PBM) refers to the metabolic and cellular responses of living cells to photons, or light energy. This process occurs across the visible spectrum, near-infrared (NIR), and ultraviolet (UV) bands of electromagnetic radiation (EMR).

The term “photobiomodulation” is derived from three components: “photo” (light), “bio” (living cells), and “modulation” (alteration or influence). It describes the biochemical reactions that occur within living cells in response to light exposure.

PBM is a natural phenomenon that occurs in all biological organisms. It is triggered when cells are exposed to sunlight or specific wavelengths of artificial light. This process is present in plants, animals, and bacteria, stimulating growth, supporting cellular respiration and reproduction, promoting DNA repair, and maintaining molecular functions in cells, tissues, and organs. In complex organisms such as primates and humans, PBM plays a crucial role in nervous system development, blood circulation, immune response activation, and stem cell differentiation.

 

How Does Photobiomodulation Occur?

PBM naturally takes place under both sunlight and artificial light exposure. The effects of light on living cells can be beneficial or harmful, depending on the energy absorbed, which is determined by specific light parameters:

• Wavelength (measured in microns or nanometers)

• Power density (also known as irradiance, measured in watts or watts per square centimeter)

• Total energy (dose) (measured in electron volts, joules, or joules per square centimeter)

The biological response varies depending on the organism, tissue, and cell type. Broad-spectrum light sources, such as sunlight, contain both beneficial and harmful wavelengths. Their net impact depends on the light’s color temperature (spectral composition) and the total energy dose for each wavelength.

Short-wavelength ultraviolet (UVC) radiation, with high energy content (E > 4 eV), can be extremely damaging to biological organisms. Fortunately, natural UVC and other shortwave EMR (such as X-rays and gamma rays) emitted by the sun are blocked by Earth’s magnetic field, ionosphere, and atmospheric layers—including stratospheric ozone (O3) and water vapor. Without this protective barrier, continuous DNA damage would threaten life’s sustainability.

Due to the risks of skin damage, burns, and cancer, medical professionals avoid using artificial UV light sources (λ < 400 nm) in treatments, except for severe skin conditions that do not respond to other therapies.

Conversely, the medical applications of PBM therapy (described below) are subject to strict regulatory oversight, typically classified as Class II medical devices or higher (Class III/IV lasers). PBM treatments are conducted within well-established safe wavelength ranges, primarily in the near-infrared and visible light spectrum between 400 nm and 700 nm.

 

How Does Photobiomodulation Work?

PBM works by transferring light energy into molecules within cells and organelles, triggering chemical, electrochemical, and thermal responses. These reactions induce changes in cellular metabolism and gene expression.

At the atomic and molecular level, PBM occurs through energy transfer processes. Photons—small energy carriers known as quanta—deliver precise energy levels to molecules within living cells and their organelles. The number of photons absorbed by specific cells (and the energy received) depends on their type, structure, and the wavelength of incoming light.

Some light is reflected or scattered, never entering the cell. A portion of the energy is absorbed, while the remaining unabsorbed energy passes through to the next cellular layer.

According to the laws of thermodynamics, some absorbed light inevitably generates heat, creating a photothermal response. Additional absorbed photons stimulate PBM through the photoelectric effect, photochemical reactions, or a combination of both. As illustrated below, absorbed photons may break or form molecular bonds, leading to changes in Gibbs free energy within the molecule.

Photobiomodulation is a promising technology with diverse applications in medicine, wellness, and biotechnology. It continues to be extensively researched for its potential in accelerating healing, reducing inflammation, enhancing cellular function, and improving overall health outcomes.