Advances in direct optical detection

Today’s societal grand challenges drive the need for new sensing principles, new sensors, and entirely new analytical solutions as never before. Global challenges, such as climate change, infectious diseases and their migration, air and ocean pollution, food and water safety, and security, will require our attention for decades to come. The Food and Agriculture Organization of the United Nations (FAO) raises the question of how to feed 10 billion people in 2050 which not only calls for a needed dramatic increase in available safe food and its hopefully sustainable agricultural production strategies, but also relates to our ability to monitor conditions required to achieve this challenge. The Covid-19 pandemic of 2020 caused by Coronavirus SARS-CoV-2 reminded all of us of the urgent need for rapid point-of-care diagnostics, the need that exists also for many other health conditions. New sensors for the monitoring of patients at their bedsides or at home are envisioned to be important technologies that will support personalized medicine, lead to reductions of the health care costs, and enable health care in resource-limited settings. The increasingly global dimension in the food supply chain raises the need for sensing technologies to ensure food quality and safety and to combat food fraud. Although analytical chemistry has solutions for many of these challenges today, they often require costly and bulky laboratory equipment not suited for rapid analysis in the field.

Using light for sensing is a century-old principle, which, combined with advances in physics, engineering, materials research, and (bio) chemistry, offers a myriad of strategies to address current and future analytical challenges. The main drivers of current sensor research include the needs for the detection of analytes at very low levels in complex real-world samples, robustness for applications in the field, and the ability to parallelize assays for multiparameter and multianalyte measurements. As this topical collection demonstrates, current optical sensors use a multitude of optical methods (spectroscopies, scattering, interferometry, surface plasmon resonance, luminescence) and platforms (optical waveguides and fibers, resonators, etc.) which employ electromagnetic radiation across a broad range of wavelengths (from UV and Vis, through IR to THz). Their combination with selective coatings and microfluidic devices is vital for the development of analytical systems and has been gaining much interest. The five critical reviews collected in this special issue highlight centrally important lines of research in direct optical sensing, also including emerging areas, such as droplet-based approaches, micro-optofluidics, and enhanced sensing through advanced nanostructures. The research papers discuss new developments in sensing methods and applications that range from biochemical and cell-based studies to medical diagnostics and environmental monitoring. Emphasis of this topical collection is on label-free approaches for direct optical detection. They are well suited not only for on-site detection due to shorter assay times and simple assay protocols, but also for the real-time measurement of biomolecular interactions. As the bio (medical) community is increasingly interested in antibody identification, target screening, protein-protein interactions, and immunological screening, such label-free direct optical sensing approaches can in fact provide a platform for the necessary high-throughput screening.

We would like to thank all of the authors for their interesting, high-quality, and timely contributions. We are also grateful to all of the reviewers whose constructive criticisms and thoughtful suggestions helped to ensure that the papers accepted for this special issue of ABC meet the highest scientific standards. We hope that this topical collection will become a useful source of information for sensor scientists and help advance the field of direct optical sensing in a world full of opportunities and challenges.

Biographies

Antje Baeumner

is Director of the Institute of Analytical Chemistry, Chemo- and Biosensors at the University of Regensburg. Prior to returning to Germany, she was Professor and Director of Graduate Studies in the Department of Biological and Environmental Engineering at Cornell University in Ithaca, NY, USA. She is an Editor of the Springer Nature Journal Analytical and Bioanalytical Chemistry (ABC) and President of the International Association of Environmental Analytical Chemistry (IAEAC). Her research is focused on the development of biosensors and microTotal Analysis Systems for the detection of pathogens and toxins in food, the environment and for clinical diagnostics. Her research includes the development of novel nanomaterials such as liposomes, nanofibers and nanoparticles, microfluidic biosensors, sample preparation strategies, and point-of-care devices. She has chaired the Gordon Research Conference (GRC) on Bioanalytical Sensors in 2010 and is co-chair for the GRC on Nanoscale Science and Engineering for Agricultural and Food Systems in 2022. She has also organized and chaired the international biosensor conference BBMEC in 2001 and 2015. She has received numerous awards for her research including being a finalist of the Blavatnik Award, senior fellow of the Alexander-von-Humboldt Foundation, and Mercator Professor of the German Science Foundation; and numerous teaching awards.

Günter Gauglitz

is Senior Professor at the Eberhard Karls University of Tübingen working on analytical and physical chemistry. He was the Chairman of the Division of Analytical Chemistry of the German Chemical Society, and chaired the Europt(r) ode VIII meeting. For more than 25 years, his main scientific interests have centered on research and development in chemical and biochemical sensors, with special focus on the characterization of interfaces of polymers and biomembrane surfaces, spectroscopic techniques, use of spectral interferometry to monitor changes in the optical thickness of thin layers, and the effects of Fresnel reflectivity at interfaces. He has been an Editor of Analytical and Bioanalytical Chemistry since 2002.

Jiří Homola

is Director of the Institute of Photonics and Electronics, Prague (Czech Republic). He also is Professor at Charles University in Prague and Affiliate Professor at the University of Washington, Seattle (USA). He received his MS (1988) from the Czech Technical University and PhD (1993) and DSc (2009) degrees from the Czech Academy of Sciences. His research interests are in photonics and biophotonics, in particular in optical sensors and biosensors. He investigates photonic and plasmonic phenomena and pursues development of sensor instrumentation, microfluidic devices, and functional coatings for optical biosensors for molecular biology, medical diagnostics, food safety, and security. He has chaired multiple international conferences and symposia (Europtrode X, SPIE Optics and Optoelectronics) and serves as Associate Editor of Biosensors and Bioelectronics (Elsevier). He has received numerous awards, including the Roche Diagnostics Prize for Sensor Technology, Award for Outstanding Research of the Ministry of Education, Youth and Sports of the Czech Republic, Premium Academiae of the Czech Academy of Sciences, and Czech Head. He has been elected Fellow of the Learned Society of the Czech Republic and Fellow of the International Society for Optical Engineering (SPIE).

Funding information

Open Access funding provided by Projekt DEAL.