PORTFOLIO

Microorganisms are very good at sensing their environment – can we use this capability in a technical or medical sensor? In this project, we intent to build a biosensor platform based on so called living materials, i.e. combinations of materials and organisms, accessible to a sampling area or liquid. The central element is an enclosed, optionally genetically engineered microorganisms. They cannot escape the material, but are still able to communicate with their environment (e.g. sensing and quantifying analytes). In a second part, the sensor platform shall be implemented as an easy, user-friendly readout device.

Our concept of living material was inspired by natural living surfaces such as lichens, and bacterial or fungal biofilms and further developed by adding the sensing function. We have already shown that oligosaccharides (e.g., lactose, galactose) in complex samples can be quantified based in such systems. Minimal equipment requirements and availability to untrained users outside of a laboratory environment make such systems attractive for developing countries.

The objective of this project is to build an inexpensive and fast microorganism-based biosensor platform and additionally tackle questions of storability, biosafety, multiplexing and experimenting with different organisms and reporter systems.

Generally the project aims at an easy use of optionally genetically modified microorganisms to enable an untrained user to exploit their enormous sensing capabilities. Analysis tasks could for example involve the assessment of water and soil quality and food contamination within a complex sample.
Recent work in the field of whole-cell biosensors will be considered and integrated into the new biosensor platform. Innovation comes by combining established biotechnological platforms with modern engineering and cutting edge product development tools resulting in an integrated system.

Previous work of our group has resulted in the creation of a proof of concept living material, which was later modified to possess sensor properties. Oligosaccharide concentrations in a complex sample could be quantified based on diffusion distance in a hydrogel system. This previous work is the starting point of the project described here. The described living material with sensor properties will be validated and optimized as a sensor chip in a new format with a prototype for the readout system. We foresee these first milestones to be achieved within 2017. Complex sensor applications, multiplexing and the transition to a universal user platform will begin in 2018.
Previous work by our research group was based on the bacterium E. coli as a reporter organism. In a first step to move from a living material to a sensor chip, we have switched to use the spore-forming Bacillus subtilis as sensing organism. The change to B. subtilis enabled us to move towards the milestone of finding a material suitable for cell embedding. A mechanically stable polymer hydrogel was identified and tested as a sensor matrix first without and later with cells. Progress is also reported on prototyping a readout system. With 3D-printing as a rapid prototyping method first drafts of a chip suitable for smartphone-readout were built. The current focus is to combine the material with the sensor-microorganisms, optimize the quantification and move towards a user-friendly sensor platform.
After identifying the main components for the platform namely the organism and the carrier material we moved to transfer the batch production of the material to a continuous production using a roll to roll coating device. With this change we are able to produce 1 million sensor units in less than four days, cutting down the material cost to about $ 0.0009. In parallel we tested different bacteria densities incorporated into the material showing that the system is robust towards variations in the bacteria number enclosed regarding its analytic performance. We further tested for batch to batch variations with the results indicating that the analytical performance remains constant between different production runs. Additionally, we investigated the durability of the material in a long-term multi condition stress test showing that the material remains performant in various environmental conditions and over extended periods of time.
Establishment of this platform allowed us to explore the milestone of broadening the detection spectrum of the sensor by using an aptamer-based detection system. A guanine riboswitch coupled to a luminescent reporter system was successfully tested for the quantification the nucleotide with a commercially available smartphone. Proof of the applicability of riboswitch based systems in B. subtilis broadens the detection spectrum of the sensor drastically. To approach the concerns attached to genetically modified organisms in consumer products, a second route for the sensor development was explored. We engineered a non-GMO B. subtilis based system for the detection of plant relevant macronutrients. The exploitation of similar growth requirements for the soil associated bacterium and higher plants allowed for the detection of nutrients in concentrations that are relevant to the plants. The detection range of the sensor aligns with the starvation response
(genetically and physiologically) of A. thaliana. The sensor system was embedded in a shelf-stable, ready-to-use device that can be produced at low cost and can be handled by a layman (submission in progress).

YestroSens, a field-portable S. cerevisiae biosensor device for the detection of endocrine-disrupting chemicals: Reliability and stability, Elsevier ScienceDirect, 15 December 2019
Strategies of Immobilizing Cells in Whole-cell Microbial Biosensor Devices Targeted for Analytical Field Applications, J-STAGE – Analytical Sciences, August 2019
Continuous Production of a Shelf-Stable Living Material as a Biosensor Platform, Advanced Materials Technologies, 11 June 2019
Programmable living material containing reporter micro-organisms permits quantitative detection of oligosaccharides, Biomaterials, 2015
Incorporating microorganisms into polymer layers provides bioinspired functional living materials, PNAS, 2012; featured as Editor’s Choice: Carnivorous Cloth, Science, January 20th 2012, Vol. 335, Issue 6066, pp. 264.
Incorporation of Penicillin-Producing Fungi into Living Materials to Provide Chemically Active and Antibiotic-Releasing Surfaces, Angewandte Chemie, 2012; featured in Nature Chemistry, 4, 960, 2012.