Incorporation of PEG Diacrylates (PEGDA) Generates Hybrid Fmoc-FF Hydrogel Matrices

Generated by a hierarchical and multiscale self-assembling phenomenon, peptide-based
hydrogels (HGs) are soft materials useful for a variety of applications. Short and ultra-short pep-
tides are intriguing building blocks for hydrogel fabrication. These matrices can also be obtained
by mixing low-molecular-weight peptides with other chemical entities (e.g., polymers, other pep-
tides). The combination of two or more constituents opens the door to the development of hybrid
systems with tunable mechanical properties and unexpected biofunctionalities or morphologies.
For this scope, the formulation, the multiscale analysis, and the supramolecular characterization
of novel hybrid peptide-polymer hydrogels are herein described. The proposed matrices contain
the Fmoc-FF (N?-fluorenylmethyloxycarbonyl diphenylalanine) hydrogelator at a concentration of
0.5 wt% (5.0 mg/mL) and a diacrylate ?-/?-substituted polyethylene-glycol derivative (PEGDA).
Two PEGDA derivatives, PEGDA 1 and PEGDA2 (mean molecular weights of 575 and 250 Da, respec-
tively), are mixed with Fmoc-FF at different ratios (Fmoc-FF/PEGDA at 1/1, 1/2, 1/5, 1/10 mol/mol).
All the multicomponent hybrid peptide-polymer hydrogels are scrutinized with a large panel of
analytical techniques (including proton relaxometry, FTIR, WAXS, rheometry, and scanning electronic
microscopy). The matrices were found to be able to generate mechanical responses in the 2-8 kPa
range, producing a panel of tunable materials with the same chemical composition. The release of
a model drug (Naphthol Yellow S) is reported too. The tunable features, the different topologies,
and the versatility of the proposed materials open the door to the development of tools for different
applicative areas, including diagnostics, liquid biopsies and responsive materials. The incorporation
of a diacrylate function also suggests the possible development of interpenetrating networks upon
cross-linking reactions. All the collected data allow a mutual comparison between the different
matrices, thus confirming the significance of the hybrid peptide/polymer-based methodology as a
strategy for the design of innovative materials.