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Enzyme-assisted self-assembly confined within host materials leads to Liesegang-like spatial structuration when precursor peptides are diffusing through an enzyme-functionalized ...hydrogel. It is shown here that playing on peptide and enzyme concentrations results in a transition from continuous self-assembled peptide areas to individual microglobules. Their morphology, location, size and buildup mechanism are described. Additionally, it is also found that the enzymes adsorb onto the peptide self-assemblies leading to co-localization of peptide self-assembled microglobules and enzymes. Finally, we find that large microglobules grow at the expense of smaller ones present in their vicinity in a kind of Ostwald ripening process, illustrating the dynamic nature of the peptide self-assembly process within host hydrogels.
The lord of the rings. The diffusion of a precursor peptide within an enzymatically-active host hydrogel leads to an unexpected non-monotonous self-assembled peptide micropattern. This work ...highlights the potential of the enzyme-assisted self-assembly concept to create spatially localized structures within soft materials based on a Liesegang-like mechanism of reaction-diffusion. Display omitted
Reaction–diffusion (RD) processes are responsible for surface and in-depth micropatterning in inanimate and living matter. Here we show that enzyme-assisted self-assembly (EASA) of peptides is a valuable tool to functionnalize host gels. By using a phosphatase distributed in a host hydrogel, the diffusion of phosphorylated peptides from a liquid/host gel interface leads to the spontaneous formation of a pattern of dephosphorylated peptide self-assembly presenting at least two self-assembly maxima. Variation of enzyme and peptide concentrations change the pattern characteristics. When a peptide drop is deposited on a phosphatase functionalized gel, a self-assembly pattern is also formed both along the gel-solution interface and perpendicular to the interface. This self-assembly pattern induces a local change of the gel mechanical properties measured by nanoindentation. Its appearance relies on the formation of self-assembled structures by nucleation and growth processes which are static in the hydrogel. This process presents great similarities with the Liesegang pattern formation and must be taken into account for the functionalization of hydrogels by EASA. A mechanism based on RD is proposed leading to an effective mathematical model accounting for the pattern formation. This work highlights EASA as a tool to design organic Liesegang-like microstructured materials with potential applications in biomaterials and artificial living systems design.
Hydroxypropylmethylcellulose grafted with silanol groups (Si-HPMC) hydrogels are employed as 3D scaffolds to encapsulate phosphatase-modified silica nanoparticles (AP@NPs). Such hybrid materials are ...catalytically active when enzyme susbtrates are diffusing through the material. Using the enzyme-assisted self-assembly concept, the tripeptide Fmoc-FFY is generated in situ in close vicinity of AP@NPs thanks to the phosphate hydrolysis of the diffusing precursor Fmoc-FFpY. The self-assembly of Fmoc-FFY is spatially concomitant to the presence of AP@NPs. In the Si-HPMC host hydrogel, AP@NPs aggregate and thus limit their diffusion in the material. This feature is used to localize at the micrometre scale the self-assembly within the material: AP@NPs are injected in a defined 3D area within the Si-HPMC gel using an adapted microsyringe. The diffusion of precursor Fmoc-FFpY toward this region leads to a Fmoc-FFY self-assembly exclusively there, an impossible strategy using free AP. Thus, this work allows to spatially control the enzyme-assisted self-assembly of peptides within host materials as an alternative approach for the design of hierarchically structured materials.
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•Supramolecular polymer-peptide dual network hydrogels exhibit micropatterned structures.•Diffusion of phosphatase-modified nanoparticles in a hydroxypropylmethylcellulose hydrogel is strongly limited.•Peptide self-assembly within the polymer host hydrogel is directed from phosphatase-modified nanoparticles.•Localization of phosphatase-modified nanoparticles leads to a 3D spatial control of the peptide self-assembly process.
Composite hydrogels composed of low-molecular-weight peptide self-assemblies and polysaccharides are gaining great interest as new types of biomaterials. Interactions between polysaccharides and ...peptide self-assemblies are well reported, but a molecular picture of their impact on the resulting material is still missing. Using the phosphorylated tripeptide precursor Fmoc-FFpY (Fmoc, fluorenylmethyloxycarbonyl; F, phenylalanine; Y, tyrosine; p, phosphate group), we investigated how hyaluronic acid (HA) influences the enzyme-assisted self-assembly of Fmoc-FFY generated in situ in the presence of alkaline phosphatase (AP). In the absence of HA, Fmoc-FFY peptides are known to self-assemble in nanometer thick and micrometer long fibers. The presence of HA leads to the spontaneous formation of bundles of several micrometers thickness. Using fluorescence recovery after photobleaching (FRAP), we find that in the bundles both (i) HA colocalizes with the peptide self-assemblies and (ii) its presence in the bundles is highly dynamic. The attractive interaction between negatively charged peptide fibers and negatively charged HA chains is explained through molecular dynamic simulations that show the existence of hydrogen bonds. Whereas the Fmoc-FFY peptide self-assembly itself is not affected by the presence of HA, this polysaccharide organizes the peptide nanofibers in a nematic phase visible by small-angle X-ray scattering (SAXS). The mean distance d between the nanofibers decreases by increasing the HA concentration c, but remains always larger than the diameter of the peptide nanofibers, indicating that they do not interact directly with each other. At a high enough HA concentration, the nematic organization transforms into an ordered 2D hexagonal columnar phase with a nanofiber distance d of 117 Å. Depletion interaction generated by the polysaccharides can explain the experimental power law variation d ∼ c − 1 / 4 and is responsible for the bundle formation and organization. Such behavior is thus suggested for the first time on nano-objects using polymers partially adsorbing on self-assembled peptide nanofibers.
Smart stimuli-responsive fluorescent materials are of interest in the context of sensing and imaging applications. In this project, we elaborated multidynamic fluorescent materials made of a ...tetraphenylethene fluorophore displaying aggregation-induced emission and short cysteine-rich C-hydrazide peptides. Specifically, we show that a hierarchical dynamic covalent self-assembly process, combining disulfide and acyl-hydrazone bond formation operating simultaneously in a one-pot reaction, yields cage compounds at low concentration (2 mM), while soluble fluorescent dynamic covalent networks and even chemically cross-linked fluorescent organogels are formed at higher concentrations. The number of cysteine residues in the peptide sequence impacts directly the mechanical properties of the resulting organogels, Young’s moduli varying 2500-fold across the series. These materials underpinned by a nanofibrillar network display multidynamic responsiveness following concentration changes, chemical triggers, as well as light irradiation, all of which enable their controlled degradation with concomitant changes in spectroscopic outputsself-assembly enhances fluorescence emission by ca. 100-fold and disassembly quenches fluorescence emission.
