Self-Sorting in Multicomponent Supramolecular Gels Using Different Assembly Triggers and Calcium Ion-Induced Diffusion Patterning

This paper investigates self-sorting and triggered assembly of multicomponent gels that combine sorbitol-based low-molecular-weight gelator (LMWG) DBS-CONHNH2 and peptide-based LMWG Nap-FF, with the assembly of Nap-FF being triggered either using glucono-δ-lactone (GdL) to lower pH or CaCl2. Changing triggers alters the way Nap-FF assembles on the molecular scale either as its acid form or its calcium salt, leading to different nanoscale networks and rheological behaviors. The choice of trigger impacts the properties of the two-component gels formed with DBS-CONHNH2. Using either trigger, the LMWGs self-sort on the molecular level into their own distinct assemblies. However, when using a GdL trigger, the sheet-like Nap-FF assemblies encourage DBS-CONHNH2 assembly, with the two assemblies interacting with one another on a network level as a result of interactions between the acylhydrazide and the carboxylic acid. Conversely, when using a CaCl2 trigger, the two fibrillar assemblies are independent of one another on the network level, with the carboxylic acid being bound to calcium in the form of its carboxylate salt, and unable to interact with DBS-CONHNH2. As such, GdL-triggering leads to molecular-level self-sorting and network-level coassembly, while CaCl2-triggering leads to both molecular-level and network-level self-sorting. Injecting the CaCl2 trigger into a preformed DBS-CONHNH2 gel, followed by its diffusion, creates dynamic, evolving, spatially-resolved self-sorted multicomponent gels, with stiffnesses differing by 2 orders of magnitude in different domains. Given the mild, biocompatible nature of CaCl2, it is suggested that this calcium ion diffusion approach to spatiotemporally resolved patterning of multidomain gels may have future relevance in cell-based studies.