Excerpt from BIOCHEMICAL MECHANISM OF LOW LEVEL LASER THERAPY FOR THE NON-INVASIVE REDUCTION OF SUBCUTANEOUS ADIPOSE

The question that immediately arises is, “How can light, when externally applied, be capable of inducing such a phenomenal effect at the cellular level?” Well, the answer is best explained using the basic principles of photochemistry. Photochemistry is a discipline of chemistry that studies the interaction between atoms, molecules, and light. According to quantum theory, light radiation energy is absorbed as discrete units called photons, and at the molecular level, it is this photon-induced chemistry that ultimately gives rise to the observable effect at the biological level. The first law of photochemistry states that the observable biological effects subsequent to LLLT can only transpire in the presence of a photoacceptor molecule, a molecule capable of absorbing the photonic energy being emitted. A molecule capable of photonic absorption usually contains a light-absorbing center, referred to as a chromophore. Light absorbing centers often house transition metals, elements that are readily identified by their incomplete subshell. Based on physicist Niel-Bohrs model, subshells of an atom identify the possible quantum states in which an individual electron can reside, depending on its energy level. Electrons are capable of undergoing quantum leaps, where an electron transitions between quantum states, shifting from one energy level to another following the absorption or emission of a photon. The shift from a lower energy state to a higher state is referred to as the excitation of an electron, the change from an occupied orbital to a given unoccupied orbital. Regarding transition elements, such as copper (Cu) or iron (Fe), these elements are more susceptible to an electron shift because of their unique electron configuration. The photoacceptor molecules responsible for the photobiological effects subsequent to laser irradiation contain transition metals. The photon absorption is followed by a rapid vibrational relaxation which causes the molecule to reach an equilibrium geometric configuration corresponding to its electronic excited state. This change may modulate the biological behavior of photoabsorbing molecules.