Viscoelastic behavior of chemically fueled supramolecular hydrogels under load and influence of reaction side products

Martin Kretschmer,Job Boekhoven,Benjamin Winkeljann,Oliver Lieleg,Brigitte A K Kriebisch

doi:10.1038/s43246-021-00202-6

Abstract

About ten years ago, chemically fueled systems have emerged as a new class of synthetic materials with tunable properties. Yet, applications of these materials are still scarce. In part, this is due to an incomplete characterization of the viscoelastic properties of those materials, which has – so far – mostly been limited to assessing their linear response under shear load. Here, we fill some of these gaps by comparing the viscoelastic behavior of two different, carbodiimide fueled Fmoc-peptide systems. We find that both, the linear and non-linear response of the hydrogels formed by those Fmoc-peptides depends on the amount of fuel driving the self-assembly process – but hardly on the direction of force application. In addition, we identify the concentration of accumulated waste products as a novel, so far neglected parameter that crucially affects the behavior of such chemically fueled hydrogels. With the mechanistic insights gained here, it should be possible to engineer a new generation of dynamic hydrogels with finely tunable material properties that can be tailored precisely for such applications, where they are challenged by mechanical forces.

Highlights

About ten years ago, chemically fueled systems have emerged as a new class of synthetic materials with tunable properties
By comparing results obtained with the full waste product to data obtained with waste-mimetics, we identify hydrophobic and electrostatic interactions between the Fmoc-based peptides and the waste molecules to be the critical forces that challenge the assembly process
When we probe the nonlinear properties of the same set of samples by large amplitude oscillatory shear (LAOS) measurements, we find that all three FmocAVD hydrogel variants show linear material response up to strain levels of ~γ = 1–2% (Fig. 2c)

Summary

Introduction

Chemically fueled systems have emerged as a new class of synthetic materials with tunable properties Applications of these materials are still scarce. Self-assembly is driven by the hydration of a carbodiimide fuel In such Fmoc-based peptide systems, the properties of the self-assembled materials are broadly tunable, and this is achieved by a tailored variation of the conjugated amino acid sequence[29]. It was speculated previously that the reaction waste products might interact with the supramolecular structures and disturb their assembly process[30] To avoid such interference by waste accumulation effects, Sorrenti et al created dynamic selfassemblies in a membrane reactor which allowed waste molecules to leave the microcompartment[31]

Methods

Results

Conclusion