Biophotonics is a multidisciplinary field that involves the development and application of light-based technologies to study, monitor, and treat biological systems. The ability to directly image cells and molecules has led to many fundamental discoveries in the past century. More recently, the terahertz (THz) region of the electromagnetic spectrum has attracted growing interest as a promising frontier for advancing biological research.
The THz frequency range is associated with several fundamental biological processes. Although THz radiation is strongly absorbed by water, traditionally viewed as a limitation, this property can enable sensitive characterization of hydration states and water content. Compared to visible light, THz waves can also penetrate certain biological tissues more effectively. However, despite steady advancements, the adoption of THz biophotonics still lags behind visible light-based techniques in directly observing cellular and molecular dynamics. This is largely due to several challenges, including relatively low spatial resolution (a consequence of the longer THz wavelengths), high sensitivity to water that complicates measurements, slower imaging speeds, and bulky instrumentation. Fortunately, recent developments suggest strong future potential.
To highlight these advancements, Associate Professor Kazunori Serita from the Graduate School of Information, Production, and Systems, Waseda University, Japan, together with Special-Appointment Professor Masayoshi Tonouchi from the Research Institute for Interdisciplinary Science, Okayama University, Japan, presented a comprehensive review summarizing current efforts to address limitations and improve the adoption of THz biophotonics. The study was published in the Journal of Physics Photonics on May 28, 2026.
"THz biophotonics is a fascinating research area for next-generation biomedical technologies. Currently, THz biomedical applications are restricted to a few niche domains with many technical limitations. Recent developments in emerging THz technologies have greatly increased the potential for overcoming these technical limitations," says Serita.
In their review, the researchers first outline how THz radiation interacts with biological processes, highlighting key advantages such as sensitivity to molecular fingerprint spectra and the ability to enable non-invasive, non-destructive, and label-free measurements. They also discuss the strong dielectric dispersion and absorption of water. Next, they trace the historical development of key THz technologies, including THz time-domain spectroscopy, the evolution of THz imaging techniques, and the emergence of THz metamaterial biosensors that can be used to probe complex and small biological samples.
A major focus was on fields that show strong potential for early application. For example, THz imaging is gaining attention in skin cancer diagnosis due to its sensitivity to tissue composition and is progressing toward clinical trials. Wound assessment is another field where THz imaging is being increasingly applied. Margin assessment in breast cancer is also a key area where THz technology has high potential for practical clinical application, offering a pathway to simplify current procedures. The review also highlights applications in drug discovery and pharmaceutical analysis.
Beyond these areas, the review identifies emerging directions such as single-cell THz imaging, molecular-scale THz studies, diagnostics for internal organs (including the gastrointestinal and respiratory systems), and THz-based blood analysis. In addition, it highlights future technologies that can enable THz observation of cells and molecules under physiological conditions, including the recently developed "point-terahertz source" technology by Serita and colleagues.
"THz measurement technologies can benefit not only medicine, but also a wide range of industries, including drug discovery, food inspection, environmental monitoring, semiconductor evaluation, and biotechnology," says Serita.
Finally, the researchers presented the main areas for future research, including identifying the precise origins of THz contrast in biological samples and improving the understanding of water dynamics to improve reliability.
"Our study provides a roadmap of emerging approaches that could help transform the field of THz biophotonics from proof-of-concept studies to practical biomedical applications," concludes Serita.
