HMN 2026: How Novel biosensor enables real-time tracking of iron (II) in living cells

Iron is an essential trace element in biological cells. The concentration of the element and its so-called redox state—it can exist either in a doubly ionized state as iron (II) (Fe²⁺) or a triply ionized state as iron (III) (Fe³⁺)—play a key role in metabolic processes such as cellular respiration and in microbial stress responses.

Dr. Athanasios Papadopoulos, lead author of the study, which has now been published in ACS Sensors: “The ability to observe labile iron in vivo in real time and at a high level of specificity has been extremely limited to date. Our new ‘IronSenseR’ biosensor now makes it possible to conduct such experiments and research the distribution and function of iron in living cells.”

A research team from the Center for Structural Studies (CSS) at HHU has developed a novel, computer-based method called “CoBiSe” to design and produce genetically encoded fluorescence-based biosensors in a rapid and simple approach. The authors now describe the highly selective biosensor “IronSenseR” for iron (II) designed using the method.

The biosensor was successfully inserted into various bacterial systems—including Escherichia coli, Pseudomonas putida and Corynebacterium glutamicum—in order to observe changes in the intracellular iron pool. The application studies were realized in collaboration with the research groups led by Professor Dr. Julia Frunzke, Professor Dr. Thomas Drepper and Professor Dr. Michael Bott, together with the Center for Advanced Imaging (CAi).

“This represents significant progress in the development of biosensors, a process known as biosensor design,” emphasizes corresponding author Professor Dr. Sander Smits. “It enables us to improve our understanding of the dynamics of iron in living cells.”

Dr. Christoph G. W. Gertzen, the second corresponding author, adds, “The biosensor enables precise iron metabolism measurements, which in turn enable further research into iron-related medical conditions, among other things. This successful development offers hope that ‘CoBiSe’ can also be used for the rapid production of genetically encoded biosensors for other metabolites and metal ions, and beyond that, also other tailored proteins such as enzymes.”

New method for biosensor development: ‘CoBiSe—Computational Biosensor Design’

CoBiSe is a computational, structure-based approach. It can be used for the targeted identification of sites on binding proteins—which bind selectively to interesting biological structures—in which biosensor cassettes can subsequently be embedded. These cassettes ultimately carry the fluorescent molecules, which can, for example, be made visible under the microscope, revealing the location of the biological structures being sought. It is important that these biosensor cassettes do not impact the function of the binding proteins.

Smits states, “In comparison with conventional methods, which involve complex and time-consuming experiments, CoBiSe significantly reduces the workload and time required to develop functional biosensors, ensuring they can be used in practice more quickly.”

The iron biosensor IronSenseR developed in this way detects iron (II) with a high level of sensitivity without binding to iron (III) or other metal ions.