Speakers 2023

Lihi Adler-Abramovich Adelung
Tel Aviv University, Israel

The emerging demand for tissue engineering scaffolds capable of inducing bone regeneration using minimally invasive techniques prompts the need for the development of new biomaterials. One promising route is molecular self-assembly, a key direction in current nanotechnology and material science. In this approach, the physical properties of the formed supramolecular assemblies are directed by the inherent characteristics of the specific building blocks. Molecular co-assembly at varied stoichiometry substantially increases the structural and functional diversity of the formed assemblies, thus allowing tuning of their architecture and physical properties.

Here, in line with polymer chemistry paradigms, we applied a co-assembly approach using hydrogel-forming peptides, resulting in a synergistic modulation of their mechanical properties to form extraordinarily rigid hydrogels which supported osteogenic differentiation based on cells-mechanosensing. Furthermore, we designed a multi-component scaffold composed of polysaccharides, short self-assembling peptides, and bone minerals. We demonstrate the formation of a rigid, yet injectable and printable hydrogel without the addition of cross-linking agents. The formed composite hydrogel displays a nanofibrous structure, which mimics the extracellular matrix and exhibits thixotropic behavior and a high storage modulus. This composite scaffold can induce osteogenic differentiation and facilitate calcium mineralization.

This work provides a conceptual framework for the utilization of co-assembly strategies to push the limits of nanostructure physical properties obtained through self-assembly for the design of new biomaterials for tissue engineering and personalized medicine applications.

Annelise Barron
Stanford University, USA

Eva Blasco
Heidelberg University, Germany

Uwe Bunz
Heidelberg University, Germany

Martina Delbianco
Max Planck Institute of Colloids and Interfaces, Germany

Polysaccharides are the most abundant organic materials in nature, yet correlations between their three-dimensional structures and macroscopic properties have not been established. With automated glycan assembly (AGA), we prepared well-defined oligo- and polysaccharides resembling natural as well as unnatural structures.[1] These synthetic glycans are ideal probes for the fundamental study of polysaccharides, shedding light on how the primary sequence affects the polysaccharide properties (i.e. solubility and crystallinity). Molecular dynamics simulations, NMR spectroscopy, and single molecule imaging allowed for the visualization of polysaccharides’ conformation and revealed that some polymers form helices while others adopt rod-like structures.[2] Modifications in specific positions of the oligosaccharide chains permitted to tune the three-dimensional structures and solubility of such compounds.[3] These synthetic oligosaccharides self-assembled into nanostructures of varying morphologies.[4] Differences in chain length, monomer modification, and aggregation methods yielded glycomaterials with distinct shapes and chirality, offering valuable models to study the aggregation of natural polysaccharides.

Daniela Duarte-Campos
Heidelberg University, Germany

Makota Fujita
University of Tokyo, Japan

Self-assembly of gigantic polyhedral complexes from a number of metal ions and small organic molecules will be discussed. The organic components can be either simple and rigid bridging ligands or oligopeptides that adopt fixed conformation when folded.

Frauke Gräter
Heidelberg University, Germany

Ian Hamley
University of Reading, UK

Peptides offer outstanding potential as bioactive and biocompatible nanomaterials that can be programmed with unique properties. I will review work from our group on peptides, lipopeptides (peptide amphiphiles) and polymer-peptide conjugates. This includes a diversity of designed or bio-inspired or bio-derived systems that self-assemble into micelles, vesicles, fibrils, nanotapes, and other nanostructures in solution and as hydro- or organo-gels. A remarkable range of biofunctionality has been demonstrated, including use as antimicrobial materials, scaffolds for regenerative medicine and tissue engineering, as amyloid functional materials and potential therapeutics, in gene delivery, and in other biomedical applications.

Stefan Hecht
RWTH Aachen, Germany

The presentation will highlight xolography as a new and powerful volumetric 3D printing technique. It is based on the use of dual color photoinitiators that enable the precise confinement of the polymerization process into regions defined by two different light sources consisting of an UV/blue light sheet and an orthogonal visible light projector. The linear nature of the process in combination with the high-definition of the projection allow for rapid printing of homogeneous materials and complex multicomponent objects in high resolution without the need for support structures. Advantages and disadvantages as well as opportunities will be discussed.

Light-based additive manufacturing techniques offer various advantages based on their superior speed and resolution. Until now this great potential has not fully been harnessed due slow build rates and material inhomogeneities caused by point-wise or layered object generation common for methods including stereolithography and digital light processing. Volumetric 3D printing is the next evolutionary step to realize a fast and continuous printing process. However, both currently established methods, two-photon photopolymerization and computed axial lithography, suffer from low volume generation rates and limited resolution, respectively.

To overcome this limitation, we have developed xolography as a new and powerful volumetric 3D printing technique. It is based on the use of photoswitchable photoinitiators that require a sequence of two one-photon processes taking place at distinctly different wavelengths. Therefore, these dual color photoinitiators enable the precise confinement of the polymerization into regions defined by two different light sources consisting of an activating UV/blue light sheet and an orthogonal visible light projector. Since the crossing (x) light beams generate an entire (holos) object by this printing process, we refer to it as xolography. The linear nature of the process in combination with the high-definition of the projection allow for rapid printing of homogeneous materials and complex multicomponent objects in high resolution and without the need for support structures.

The presentation will highlight the action principle of xolography and discuss advantages and disadvantages with regard to build speed and resolution, object dimensions and complexity, as well as employable materials.

Nature 588, 620-624 (2020). DOI: 10.1038/s41586-020-3029-7

Ivan Huc
Ludwig-Maximilians-University, Germany

Aromatic oligoamides constitute a distinct and promising class of synthetic foldamers – oligomers that adopt stable folded conformations. Single helical structures are predictable, show unprecedented conformational stability, and constitute convenient building blocks to elaborate synthetic, very large (protein-sized) abiotic architectures[1] and peptide-foldamer hybrid structures.[2] They possess a high propensity to assemble into double, triple and quadruple helices, or to fold into sheet-like structures.[3] Cavities can be designed within such synthetic molecules that enable them to act as artificial receptors[4] and molecular motors.[5] Water soluble analogues of these foldamers show promise in protein recognition.[6] This lecture will give an overview of the design principles of these functional molecular architectures it will highlight recent developments and emphasize key methodologies.

1.   S. De, C. Chi, T. Granier, T. Qi, V. Maurizot, I. Huc, Nat. Chem., 2018, 10, 51.

2.   J. M. Rogers, S. Kwon, S. J. Dawson, P. K. Mandal, H. Suga, I. Huc., Nat. Chem., 2018, 10, 405

3. B. Gole, B. Kauffmann, A. Tron, V. Maurizot, N. McClenaghan, I. Huc, Y. Ferrand, J. Am. Chem. Soc. 2022, 144, 6894.

4. P. Mateus, N. Chandramouli, C. D. Mackereth, B. Kauffmann, Y. Ferrand, I. Huc, Angew. Chem. Int. Ed. 2020, 59, 5797.

5.  V. Koehler, A. Roy, I. Huc, Y. Ferrand, Acc. Chem. Res. 2022, 55, 1074.

6. K. Ziach, C. Chollet, V. Parissi, P. Prabhakaran, M. Marchivie, V. Corvaglia, P. Pratim Bose, K. Laxmi-Reddy, F. Godde, J.-M. Schmitter, S. Chaignepain, P. Pourquier, I. Huc, Nat. Chem., 2018, 10, 251.

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Laura Kiessling
Massachusetts Institute of Technology, USA

Milan Kivala
Heidelberg University, Germany

Triarylamines have in the meanwhile become ubiquitous in the area of organic electronics owing to their appreciable electron donor and hole transport properties. In our research we employ various structurally relatively simple triarylamines for the construction of unprecedented nitrogen-doped p-conjugated scaffolds upon introduction of different bridging moieties. In these compounds the nitrogen atom readily adopts a planar sp2-hybridized geometry to provide for efficient electronic communication with the surrounding p system. The resulting electron-rich compounds are highly attractive both as objects for fundamental studies and functional materials for diverse applications. Our recent achievements in this area will be presented herein.

Regine von Klitzing
Technical University of Darmstadt, Germany

Tuomas Knowles
University of Cambridge, UK

Mariana Kozlowska (tbd)
Karlsruhe Institute of Technology (KIT), Germany

Barbara Lechner
Technical University of Munich, Germany

Sub-nanometer metal clusters exhibit particular chemical and physical properties which often change non-monotonically with cluster size. Such clusters are used in heterogeneous catalysis, plasmonic devices, biosensors or coatings, to name just a few examples. We produce size-selected clusters and soft-land them on oxide supports to investigate the dynamics inherent to such systems experimentally and correlate functionality with structural dynamics. Pt clusters, for example, typically become encapsulated by reducible supports such as Fe3O4 or TiO2, altering the available active sites for catalytic reactions. Moreover, the cluster sinter by atom or cluster diffusion, depending on initial cluster size. By combining atomically resolved movie-rate scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy in pressures from ultra-high vacuum to near-ambient conditions, we investigate dynamic phenomena including cluster fluxionality, diffusion and sintering as well as support etching and growth, cation dynamics, and adsorbate spillover on a fundamental level.

Sijbren Otto
University of Groningen, Netherlands

How the immense complexity of living organisms has arisen is one of the most intriguing questions in contemporary science. We have started to explore experimentally how organization and function can emerge from complex molecular networks in aqueous solution.1 We focus on networks of molecules that can interconvert, to give mixtures that can change their composition in response to external or internal stimuli or internal processes. Noncovalent interactions within molecules in such mixtures can lead to the formation of foldamers.2,3 Molecular recognition between molecules in such mixtures leads to their mutual stabilization, which drives the synthesis of more of the privileged structures (Figure 1), giving rise to self-assembled materials. As the assembly process drives the synthesis of the very molecules that assemble, the resulting materials are self-synthesizing. Intriguingly, in this process the assembling molecules are replicating themselves, where replication is driven by self-recognition of these molecules in the dynamic network.4 The selection rules that dictate which (if any) replicator will emerge from such networks are starting to become clear.5 We have also witnessed spontaneous differentiation (a process akin to speciation as it occurs in biology) in a system made from a mixture of two building blocks.6 When such systems are operated under far-from-equilibrium flow conditions, adaptation of the materials to a changing environment can occur.

Materials that are able to catalyse reactions other than their own formation have also been obtained, representing a first step towards metabolism.7,8 Thus, the prospect of Darwinian evolution of purely synthetic molecules and materials is tantalizingly close and the prospect of synthesizing life de-novo is becoming increasingly realistic.

Ute Schepers
Karlsruhe Institute of Technology (KIT), Germany

Christiane Selhuber-Unkel
Heidelberg University, Germany

Rein Ulijn
Advanced Science Research Center, City University of New York, USA

We are interested in how functionality emerges from interactions and reactions between biomolecules, and subsequently how these functions can be incorporated into materials. Instead of using sequences known in biological systems, we use unbiased computational and experimental approaches to search and map the peptide sequence space for specific interactions and functions, with a focus on side chain, instead of backbone interactions. The talk will explore how to program molecular order and disorder through side chain interactions in short peptides, and how the conformations adopted by these peptides can be exploited to regulate interfacial assembly properties, and liquid-liquid phase separation. We will discuss chemo-mechanical peptide-crystals with connected soft and stiff domains, that change their properties upon changes in hydration states. The last part of the talk will focus on our progress in holistic study of mixtures of molecules that individually are simple and non-functional, but as components of complex interacting systems, however, they give rise to self-organization patterns that are dictated by the environmental conditions.  Collectively, we expect to identify insights that allow the repurposing of nature’s molecules to design new materials beyond those available through biology. 

Helma Wennemers
ETH Zürich, Switzerland

Self-assembly and selective recognition events involving proteins are critical in nature for the function of numerous different processes, for example, catalysis, signal transduction or the controlled formation of structural components such as bones. My group is intrigued by the question whether also peptides with significantly lower molecular weights compared to proteins can fulfill functions for which nature evolved large macromolecules. Specifically, we ask whether peptides can serve as effective asymmetric catalysts, templates for the controlled formation of metal nanoparticles,1 hierarchical supramolecular assemblies,2,3 and synthetic collagen-based assemblies.4,5

The lecture will focus on our research interests in supramolecular assemblies and their application in chemical biology and material sciences.

References

For examples, see:

  1. a) Corra, S.; Lewandowska, U.; Benetti, E. M.; Wennemers. H. Angew. Chem. Int. Ed., 2016, 55, 8542. b) Shoshan, M. S.; Vonderach, T.; Hattendorf, B.; Wennemers, H. Angew. Chem. Int. Ed. 2019, 58, 4901–4905.
  2. Lewandowska, U.; Zajaczkowski, W.; Corra, S.; Tanabe, J.; Borrmann, R.; Benetti, E. M.; Stappert, S.; Watanabe, K.; Ochs, N. A. K.; Schaeublin, R.; Li, C.; Yashima, E.; Pisula, W.; Müllen, K.; Wennemers, H. Nat. Chem., 2017, 9, 1068.
  3. T. Schnitzer, E. Paenurk, N. Trapp, R. Gershoni-Poranne, H. Wennemers,J. Am. Chem. Soc. 2021, 143, 644–648.
  4. Hentzen, N. B.; Smeenk, L. E. J.; Witek, J.; Riniker, S.; Wennemers, H. J. Am. Chem. Soc., 2017, 139, 12815.
  5. Fiala, T.; Barros, E. P.; Ebert, M.-O.; Ruijsenaars, E.; Riniker, S. Wennemers, H. J. Am. Chem. Soc. 2022, in press.

Christof Wöll
Karlsruhe Institute of Technology (KIT), Germany

Omar Yaghi
University of California, USA