Multifunctional materials for implantable and wearable photonic healthcare devices

Abstract

Numerous light-based diagnostic and therapeutic devices are routinely used in the clinic. These devices have a familiar look as items plugged in the wall or placed at patients' bedsides, but recently, many new ideas have been proposed for the realization of implantable or wearable functional devices. Many advances are being fuelled by the development of multifunctional materials for photonic healthcare devices. However, the finite depth of light penetration in the body is still a serious constraint for their clinical applications. In this Review, we discuss the basic concepts and some examples of state-of-the-art implantable and wearable photonic healthcare devices for diagnostic and therapeutic applications. First, we describe emerging multifunctional materials critical to the advent of next-generation implantable and wearable photonic healthcare devices and discuss the path for their clinical translation. Then, we examine implantable photonic healthcare devices in terms of their properties and diagnostic and therapeutic functions. We next describe exemplary cases of noninvasive, wearable photonic healthcare devices across different anatomical applications. Finally, we discuss the future research directions for the field, in particular regarding mobile healthcare and personalized medicine.

Fig. 1 |. Fundamental mechanisms underlying representative photonic healthcare applications.

a | Schematic illustration of wavelength-dependent light-penetration depth and of photonic diagnosis via pulse oximetry, in which light absorption is detected in peripheral blood using a light-emitting diode (LED) and a photodetector (PD). b | Schematic illustrations of: photothermal therapy, in which light-triggered thermal ablation is used on diseased tissues; photodynamic therapy, which uses reactive oxygen species (ROS) generated by a photosensitizer; and photobiomodulation, which uses photonic stimulation of mitochondrial chromophores to produce nitric oxide (NO) and ROS. ATP, adenosine triphosphate.

Fig. 2 |. Multifunctional material platforms for implantable and wearable photonic healthcare devices.

Materials platforms include: a | light-responsive materials, b | light-delivering materials, c | stretchable electronic materials, d | self-healing materials and biodegradable materials and e | biologically triggered photonic materials. BRET, bioluminescence resonance energy transfer; CNT, carbon nanotube; NIR, near infrared; PEG, polyethylene glycol; PLA, poLy(l-Lactic acid). Part a is adapted from REFs^,, Springer Nature Limited, and with permission from REF., Wiley-VCH. Part b is reproduced from Valentyn Volkov/Alamy Stock Photo and adapted from REFs^,, Springer Nature Limited, and with permission from REF., Wiley-VCH. In panel c, the image of conjugated polymers is adapted with permission from REF., AAAS. Part d (left) is adapted with permission from REF., Wiley-VCH. Part d (right) is adapted with permission from REF., National Academy of Sciences. Part e is adapted with permission from REF., Elsevier and REF., Frontiers.

Fig. 3 |. Implantable photonic healthcare devices.

The essential components include micro light-emitting diodes μLEDs) and their stretchable arrays (part a), flexible and stretchable antennas for wireless power and communication (part b) and stretchable interconnections between the components (part c). Photonic healthcare devices can be used for different applications, including health monitoring and photodynamic and optogenetic therapies (part d). IOP, intraocular pressure. Part a is adapted from REF., Springer Nature Limited, and with permission from REF., Elsevier. Part b is adapted from REF., Springer Nature Limited, and with permission from REF., Elsevier. Part c is adapted from REF., Springer Nature Limited and with permission from REF., AAAS.

Fig. 4 |. Wearable photonic healthcare devices.

Applications of wearable photonic devices for photonic health monitoring using smart contact lenses and skin pulse oximetry devices (part a) and health intervention for mental and skin disorders (part b). DDS, drug-delivery system (can also be used for theranostic applications); LED, light-emitting diode. The skin device in part a is adapted with permission from REF., AAAS. Part b is reprinted from Hugh Threlfall/Alamy Stock Photo and Guy Corbishley/Alamy Stock Photo.

Fig. 5 |. Schematic illustration of mobile health and personalized telemedicine.

Implantable and wearable healthcare devices, combined with the Internet of things, big data and artificial intelligence, will, in the future, enable mobile and personalized telemedicine.