Light-emitting diode therapy

Light-emitting diode therapy is a clinical approach that applies different wavelengths of light to cure diseases or conditions with skin-safe lights. Following NASA's innovation in the 1990s with Light Emitting Diodes that emit a specific narrow light spectrum, LED Therapy showed significant potential. The high precision of narrow-band LED therapy enabled its first use in clinical practices. The commonly used lights in LEDT are blue, red, green, yellow, and infrared.
LEDT's general mechanism is related to cellular receptor metabolism. Light functions as an external stimulus and influences cellular metabolism by initiating photo-biochemical reactions within cells. Light Emitting Diode Therapy encompasses two primary therapeutic approaches: photodynamic Therapy and photobiomodulation Therapy. Photodynamic therapy utilises light-sensitive compounds combined with LED light to generate reactive oxygen species, which selectively target and destroy abnormal cells. Oncology and certain skin conditions widely use this technique. Whereas photobiomodulation therapy utilizes low-level LED light to stimulate cellular repair, stimulate wound healing, and reduce inflammation, without the use of photosensitizing agents.
Different wavelengths and mechanisms are utilized for different therapeutic effects. The therapeutic advantages of LED therapy stem from its effectiveness in various treatments, including wound healing, acne treatment, sunburn protection, and the use of phototherapy for facial wrinkles and skin revitalization.
Compared to laser phototherapy, Light Emitting Diode Therapy is recognized for its enhanced safety profile, exhibiting fewer short-term and long-term side effects. This distinction stems from LEDT's use of non-coherent light at lower intensities, which minimizes the risks of tissue damage and discomfort often associated with the high-intensity, coherent light of lasers. Still, there are some side effects that can be commonly seen after exposure to light, that vary on the therapy patients take, PBMT or PDT.

History

The history of light therapy can be traced back to ancient Egypt and India, where therapy with natural sunlight was first used to treat leucoderma. In the 1850s, Florence Nightingale's advocacy of exposure to clean air and sunlight for health restoration also contributed to the initial development of light therapy for treatments. Later, Downes and Blunt's experiment in 1877 suggested sunlight's effect on fungal growth inhibition, which further evidenced the efficiency of light therapy .
The modern use of light therapy with artificial lights started in the late 19th century. The Danish Nobel Prize winner in medicine and physiology, Niels Finsen, pioneered the use of light as a therapy for skin tuberculosis. His creation of the light device "Finsen lamp" as a lupus vulgaris treatment marked the beginning of modern light therapy. The application of LED lights in cosmetology became more popular in the 1980s, particularly for acne recovery, due to its ability of collagen production. Since the early 2000s, the use of LED light therapy in the medical field has become more versatile, including treatment for skin conditions, chronic diseases, and the realignment of human circadian rhythm. It has now become a commonly used therapy in both the beauty and medical fields.

Mechanisms

LEDs are the most utilized optical semiconductor devices that transform electrical energy into light energy. LED therapy utilizes light-emitting diodes to deliver treatments based on mechanisms such as photodynamic Therapy and photobiomodulation. PDT targets and destroys diseased cells, while PBMT stimulates cellular repair and reduces inflammation. The effectiveness of LED therapy varies with the wavelength of light, allowing for diverse applications in healing, dermatology, and cancer treatment.

Photodynamic (PDT) mechanism

PDT can induce many cellular pathways, and its main purpose is to induce cell death, either by apoptosis or necrosis. The fundamental process of photodynamic reactions involves three elements: photosensitizers, light of a specific wavelength, and oxygen present in the cell. The interaction of these three components produced a desirable effect inside targeted tissues. Apart from light and oxygen, photosensitizers are compounds designed to absorb light at particular wavelengths during therapy, which enables them to initiate therapeutic processes.
Two pathway branches interact and contribute to different ratios during PDT therapy, affecting its efficiency. Both mechanisms have the same first stage. When cells absorb photosensitizers and are exposed to light that aligns with their absorption spectrum, these substances photo-excite from their stable ground state to an energised excited singlet state. Some energy is emitted as fluorescence, remaining energy directs the photosensitizer molecule into triplet state T¹.
Type I pathway of photodynamic reaction: T¹ state PS can then interact with nearby molecules. Energy transfers between the photosensitizer and other molecules in the form of hydrogen and electrons, resulting in the creation of free radicals and anion radicals. These radicals remain in ground state and react with oxygen, leading to the formation of reactive oxygen species and superoxide anion radicals, which further react with oxygen to generate ROS. The chain of reactions that generate reactive oxygen species results in oxidative stress, which ultimately causes cell damage.
Type II pathway of photodynamic reaction: After PS is excited into T¹ state, the energy is transferred directly between PS and O₂. This interaction transforms the oxygen molecules into a highly reactive form known as singlet oxygen. Singlet oxygen possesses potent oxidizing properties, making it extremely effective in reacting with and damaging cellular components. However, this reaction is selective; while most cellular components exist in a less reactive singlet state and remain unaffected, the singlet oxygen specifically targets and reacts with oxygen molecules in the cell cytoplasm.
PDT is used to treat cancer across diverse types and sites. A unique feature of PDT is that photosensitizers tend to accumulate more selectively in cancer cells than in normal cells. The high affinity of photosensitizers to low-density lipoprotein allows for selectivity. LDL acts as a carrier, allowing photosensitizers to travel into cancerous tissues. The interaction between photosensitizers and LDL makes it easier for therapeutic agents to reach the right places, which makes PDT more effective against cancer.

Photo-biomodulation therapy (PBMT) mechanism

Photobiomodulation therapy uses low-power densities and is characterized by its non-heat producing effects, a feature previously associated only with laser light. Nowadays, low-level LED lights offer a cost-effective alternative, expanding the accessibility and application of this therapeutic approach.
PBMT raising ROS levels, 2) creating adenosine triphosphate helping to turn on transcription factor. That can trigger biochemical change within the cells, involve photon emitting light absorbed by the photoreceptor and cascade reaction. When exposed to LED light, the cytochrome c oxidase inside the electron transport chain of mitochondria is targeted. Its two heme and two copper subunits are oxidized or reduced, enabling it to absorb light at various wavelengths. CCO is the main target of near-infrared and red wavelengths.
Cytochrome c oxidase is a key protein in the Electron Transport Chain, responsible for transferring electrons to the final oxygen acceptor. This action helps build a substantial proton gradient across the inter-membrane space of mitochondria; a process critical for the synthesis of ATP. The increased production of ATP because of this activity. CCO is also a photoreceptor, the photon absorption of CCO can lead to enhanced enzyme activity, increased oxygen consumption and usage of ATP production and the release of NO.
The NO can then contribute to two suggested pathways. Under typical conditions, nitric oxide interacts non-covalently with the heme and copper subunits of CCO, competing with oxygen molecules and inhibiting cellular respiration, leading to reduced production of adenosine triphosphate. Low energy light can revise the mitochondrial inhibition of cellular respiration by photodissociating of NO from CCO, and thereby increasing ATP synthesis.
The second pathway proposes that released nitric oxide will boost Cytochrome c Oxidase activity, as an enzyme nitrite reductase. This mechanism includes the transfer of electrons to oxygen molecules, resulting in the production of water and reactive oxygen species. The ROS then activates enzymes necessary for producing vital cellular components like nucleic acids and proteins. LED therapy may also increase ROS, which may activate transcription factors that manage genes important for cell growth, cytokine production, and making growth factors for cell repair and proliferation.

Wavelength

LEDs produce wavelengths that span from UV-A to near-infrared . The wavelength of the LED light can target different tissues. Long wavelength lights such as NIR/dark red can have better tissue penetration and can easily absorb cytochrome c oxidase targets by PBMT. Therefore, the long wavelength light is used for dermatology and cosmetics applications. While short wavelength light, green or blue light can be absorbed and target hemoglobin in the blood.

Current application of LED light therapy

Red light therapy, utilising red LED lights, originated from techniques intended to enhance plant growth in space and aid in astronauts' wound healing. Primarily used in dermatology, it enhances skin conditions by stimulating mitochondria, thereby increasing collagen production and blood circulation while reducing inflammation. Additionally, it plays a crucial role in photodynamic therapy, where it combines with photosensitive drugs to target and destroy cancerous cells through a light-induced chemical reaction.
Blue light therapy is also a common LED light therapy to treat acne, skin cancer, and depression. While blue light therapy has similar mechanisms for skin enhancement as red light therapy, its usage for photodynamic therapies in treating cancer are slightly different. Blue light therapy stimulates immune system defences, destroys blood vessels that help cancer cells grow, and causes cell death by reacting with oxygen. It also prevents skin cancer and metastasis by removing precancerous and cancerous skin lesions.
Application of red and blue LED light for photodynamic treatments are generally safe and can be used to treat different cancers. However, they may differ in the efficiency and response. For instance, In the treatment of Gorlin syndrome, a genetic disorder predisposed to cancer, studies have shown that blue light therapy achieves a higher tumor clearance rate and induces less pain than red light therapy.
As a result of the increasing popularity of LED light therapies for skin improvements, a wide range of skincare devices utilizing this technology are readily available on the market. LED red light products are most common for domestic LED light therapy, including LED light masks, panels, handheld devices, and belts. Typically, individuals buy these items to address issues like wrinkles and acne, reduce puffiness, and promote hair growth.