Grand Challenges and Opportunities in Biophotonics

Biophotonics is the scientific field at the interface of life and light sciences. It encompasses the use of light as the energy source that enables fundamental studies and application developments in biological, pharmaceutical, environmental and agricultural sciences, and medicine. While the term is contemporary, some of the earliest recorded history of the field probably dates back to the 17th century with the first microbial observations by Antony van Leeuwenhoek using single lenses (Ford, 1985). In 1903, The Noble Prize in Physiology or Medicine was awarded to Niels Ryber Finsen “in recognition of his contribution to the treatment of diseases, especially lupus vulgaris, with concentrated light radiation, whereby he has opened a new avenue for medical science”. Fast forward to 21st century where The Noble Prize in Chemistry was awarded “for the discovery and development of the green fluorescent protein” in 2008, and “for the development of super-resolved fluorescence microscopy” in 2014. The Noble Prize in Physics in 2018 was partly awarded to Arthur Ashkin “for the optical tweezers and their application to biological systems”. At the most fundamental level, the nature of the interaction of light with biological and organic matters provides the basis for both basic and translational work in biophotonics. These interactions involve the absorption and scattering of photons, and have led to the development of diverse technologies including various types of optical spectroscopy methods such as UV-VIS-IR spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), and Raman scattering; microscopy methods including confocal and multiphoton, fluorescence lifetime imaging (FLIM), and nanoscale optical microscopy (Hermann and Gordon, 2018); and clinical diagnostic and imaging technologies such as pulse oximetry, optical coherence tomography (OCT) (Huang et al., 1991), and fluorescence-guided surgery (Landau et al., 2016). On the therapeutic side, Leon Goldman pioneered the use of lasers in dermatology (Goldman et al., 1963). Soon after, clinical applications of lasers were extended to ophthalmology for treatment of diabetic retinopathy (L’Esperance, 1969) and photodynamic therapy, and more recently to photoimmunotherapy (Kobayashi and Choyke, 2019; Xu et al., 2020). Optical neuromodulation including optogenetics and non-genetic photostimulation methods for optical manipulation of cellular and sub-cellular activities have recently emerged (Boyden et al., 2005; Jiang et al., 2019). Despite these remarkable achievements and tremendous contributions to life sciences and medicine, there are significant challenges and yet exciting opportunities in biophotonics. Inherently, depth of optical penetration in biological materials remains limited to a few cm. Furthermore, increased optical penetration depth is accompanied by decreased spatial resolution. Methodologies that can enable increased penetration depth and spatial resolution would have great impact in photo-therapeutics and optical imaging applications. In vivo measurements of optical Edited and reviewed by: Marco Peccianti, University of Sussex, United Kingdom