Charge guides pathway selection in β-sheet fibrillizing peptide co-assembly

Abstract

Peptide co-assembly is attractive for creating biomaterials with new forms and functions. Emergence of these properties depends on the peptide content of the final assembled structure, which is difficult to predict in multicomponent systems. Here using experiments and simulations we show that charge governs content by affecting propensity for self- and co-association in binary CATCH(+/−) peptide systems. Equimolar mixtures of CATCH(2+/2−), CATCH(4+/4−), and CATCH(6+/6−) formed two-component β-sheets. Solid-state NMR suggested the cationic peptide predominated in the final assemblies. The cationic-to-anionic peptide ratio decreased with increasing charge. CATCH(2+) formed β-sheets when alone, whereas the other peptides remained unassembled. Fibrillization rate increased with peptide charge. The zwitterionic CATCH parent peptide, “Q11”, assembled slowly and only at decreased simulation temperature. These results demonstrate that increasing charge draws complementary peptides together faster, favoring co-assembly, while like-charged molecules repel. We foresee these insights enabling development of co-assembled peptide biomaterials with defined content and predictable properties.

Injectable nanofibrillar hydrogels based on charge-complementary peptide co-assemblies

“…The observed net neutral ζ-potential for CATCH (4+/4−) and CATCH(6+/6−) nanofibers may be explained by recently published NMR measurements and computational simulations, which suggest that the cationic peptides are present in stoichiometric excess of the anionic peptides in CATCH nanofibers. 34,35 Here, ζ-potential measurements indicated that lysine-rich CATCH(+) peptides have a relatively low absolute charge when alone, especially when compared to the CATCH(−) peptides. We propose that this increases the prob-…”

“…S4df †), which is near or above the critical concentration of fibrillization. 35 While these measurements could explain the aggregation prone behaviour of the CATCH(4+/4−) pair, they do not explain the behaviour of the CATCH(6+/6−) pair, which formed dispersed nanofibers at low concentrations and weaker porous gels at higher concentrations. Likewise, these measurements cannot explain the differences in pore size and wall thickness of CATCH(4+/6−) and CATCH(6+/4−) hydrogel networks.…”

“…Indeed, recent reports have shown that the cationic CATCH peptides have greater propensity for self-association than their anionic counterparts, especially at high and low ionic strength. 35 Collectively, these observations demonstrate that the interplay between CATCH peptide charge, β-sheet assembly, and nanofiber composition is highly complex, and suggest that advancing our understanding of the rheological behaviour of CATCH peptide hydrogels will require greater knowledge of these molecular-level aspects of the system. Based on their similar rheological properties, network architectures, and lack of cytotoxicity, we characterized the host response to CATCH(4+/6−) and CATCH(6+/4−) hydrogels after injection into the subcutaneous space.…”

“…31,37 Further, peptide sequence and nanofiber charge can influence biocompatibility and immunogenicity. 38 Although all complementary CATCH pairs can co-assemble into β-sheet nanofibers, 35 how the peptide sequence and peptide charge contribute to the biophysical properties of CATCH hydrogel networks is not well understood. Using a combination of oscillatory rheology, transmission electron microscopy, cryogenic-scanning electron microscopy, and ζ-potential measurements, we studied relationships between CATCH peptide pairings, hydrogel rheology, and biocompatibility.…”

Controlling hydrogel properties by tuning non-covalent interactions in a charge complementary multicomponent system

“…10,11,[15][16][17][18][19][20] In these gels, the electrostatic interactions between the positively and negatively charged groups act as the key driving force to build up the underlying network. 12,[20][21][22][23] Additionally, tuning of material properties is possible simply by controlling the surface charge on the bres through pH change. 22 Many natural systems and processes such as assembly of proteins and silk brils involve multicomponent ionic interactions.…”