Molecular information processing using reaction networks
Wilhelm Huck

Living cells process information from their environment to detect food and danger, or to communicate with other living cells. They are capable of doing so via intricate reaction networks. Emulating the properties of such networks in synthetic systems would possibly provide a bridge between electronic computers and living systems.

In this tutorial, I will discuss basic principles of reaction network motifs, show examples of synthetic reaction networks with functional properties (oscillations), and illustrate how we can move beyond well-designed motifs and use self-organized reaction networks. Finally, I will discuss how such systems can be used in a new form of neuromorphic computing.

Biofabrication using spider silk proteins
Thomas Scheibel

Proteins reflect one fascinating class of natural polymers with huge potential for technical as well as biomedical applications. One well-known example is spider silk, a protein fiber with excellent mechanical properties such as strength and toughness. We have developed biotechnological methods using bacteria as production hosts which produce structural proteins mimicking the natural ones [1, 2]. Besides the recombinant protein fabrication, we analyzed the natural assembly processes and we have developed spinning techniques to produce protein threads closely resembling natural silk fibers. In addition to fibers, we employ silk proteins in other application forms such as hydrogels, particles or films with tailored properties, which can be employed especially for biomaterials applications [3].

We could e.g. design spider silk-based sheets and scaffolds that prevent adherence of microbes. Without adherence biofilm formation cannot occur, which lowers the frequency of infections in surgical patients. However, the spider silk sheets and scaffolds do not kill any cells. Unlike current treatments they prevent infestation to begin with. The designed spider silk scaffolds are even bio selective, meaning that this designer silk repels microbes while allowing human cell attachment and proliferation [4]. Spider silk hydrogels can be even employed as bioinks for biofabrication (i.e. 3D bioprinting together with cells) [5], but also non-aqueous solvents can be used to 3D-fabricate spider silk scaffolds [6]. Their elastic behavior dominates over the viscous behavior over the whole angular frequency range with a low viscosity flow behavior and good form stability. No structural changes occur during the printing process, and the hydrogels solidify immediately after dispense plotting. Due to the form stability it was possible to directly print multiple layers on top of each other without structural collapse. Cell-loaded spider silk constructs can be easily printed without the need of additional cross-linkers or thickeners for mechanical stabilization. Encapsulated cells show good viability in such spider silk hydrogels. Exemplarily, we use 3D-printed spider silk scaffolds for the growth of heart muscle patches [7, 8] or for generating nerve guiding conduits [9, 10].

[1] Heidebrecht, A., Scheibel T. (2013). Recombinant production of spider silk proteins. Adv. Appl. Microbiol. 82, 115-153

[2] Saric, M., Eisoldt, L., Döring, V., Scheibel, T. (2021) Interplay of Different Major Ampullate Spidroins During Assembly and Implications for Fiber Mechanics. Advanced Materials 33, 2006499

[3] Aigner, T.B., DeSimone, E., Scheibel T. (2018) Biomedical applications of recombinant silk-based materials. Advanced Materials 30, 1704636

[4] Kumari, S., Lang, G., DeSimone, E., Spengler, C., Trossmann, V., Lücker, S., Hudel, M., Jacobs, K., Krämer, N., Scheibel, T. (2020) Engineered spider silk-based 2D and 3D materials prevent microbial infestation. Materials Today, 41, 21-33

[5] Schacht, K., Jüngst, T., Schweinlin, M., Ewald, A., Groll, J., Scheibel, T. (2015) Biofabrication of cell-loaded, 3D recombinant spider silk constructs. Angew. Chem. Int. Ed., 54, 2816-2820

[6] Neubauer, V., Trossmann, V., Jacobi, S., Döbl, A., Scheibel, T. (2021) Aqueous-Organic Solvent Derived Recombinant Spider Silk Gels as Depots for Drugs. Angew. Chem. Int. Ed., 60 DOI:10.1002/anie.202103147

[7] Petzold, J. Aigner, T., Touska, F., Zimmermann, K., Scheibel, T., Engel, F. (2017) Surface features of recombinant spider silk protein eADF4(κ16)-made materials are well-suited for cardiac tissue engineering. Adv. Funct. Mat. 27, 1701427

[8] Kramer, J., Aigner, T., Petzold, J., Roshanbinfar, K., Scheibel, T., Engel, F. (2020) Recombinant spider silk protein eADF4(C16)-RGD coatings are suitable for cardiac tissue engineering. Sci Reports 10, 8789

[9] Pawar, K., Welzel, G., Haynl, C., Schuster, S., Scheibel, T. (2019) Recombinant Spider Silk and Collagen-Based Nerve Guidance Conduits support Neuronal Cell Differentiation and Functionality in vitro. ACS Appl. Bio Mater. 2, 4872-4880

[10] Aigner, T.B., Haynl, C., Salehi, S., O’Connor, A., Scheibel, T. (2020) Nerve guidance conduit design based on self-rolling tubes. Materials Today Bio 5, 100042

Responsive polymers and smart polymeric materials – a tutorial
Brigitte Voit

Polymeric materials that respond to one or several stimuli by changing specific properties e.g. volume, mechanics, optics, shape a.o., can be considered as smart materials with special interest for application in sensorics and as actuator, but also in information technology, optoelectronics, and biomedicine. In this tutorial, after an overview, two major fields of smart polymeric materials will be highlighted. Firstly, responsive hydrogels and soft (multi)compartments will introduced which combine sensoric as well as actuator function. Polymeric hydrogels can be adapted for various stimuli e.g. temperature, pH, light, redox, chemicals a.o. and act usually with a change in volume by swelling or deswelling in water. Examples will be given how this may be used e.g. in microfluidics, microreactors or chemical information processing as well as to control reactions in nanoreactors. The second bigger area which will be covered are smart polymeric composites. Here a function like an electronic, optical or mechanical response will be combined in structural materials, e.g. thermoplastics or elastomers. This is an important part of the field of function integration in structural materials with strong interest for application in robotics, but also in construction and high performance lightweight constructions where it is important to have the ability to monitor the “health” status of the material (structural health monitoring).