Implanted Miniature Light Devices for Phototherapeutics

Light-mediated healthcare has several very attractive features, including minimally invasive administration, reduced possibility of side effects, and potential for patient-specific treatment. However, the shallow penetration of light into skin and tissue is an inherent physical limitation that restricts the use of phototherapy to superficial sites of disease. To mitigate this major problem, researchers and clinicians are developing miniature light devices that can be implanted at strategic deep-tissue locations within a living subject. The work is leveraged by emerging new classes of light-absorbing drugs and light-activated drug delivery methods. This Perspective summarizes the major concepts and recent technical advances in this interdisciplinary subfield of advanced phototherapeutics. Fundamental factors are described, such as the wavelength dependence of light penetration and scattering through tissue, and the required power levels for the desired phototherapeutic effect. The implanted devices can be powered by an attached wire or otherwise powered wirelessly, and each approach has its own engineering challenges to produce desired performance features. A forward-looking conclusion section envisions future phototherapies that use implanted miniature light devices with the capacity to deliver phototherapy and monitor therapeutic response using sensors that provide immediate feedback and dose control.