Halogen-Controlled Aromatic Interactions Drive the Self-Assembly and Mechanics of Peptide Hydrogels.
Peptide hydrogels just got a major upgrade—thanks to halogen chemistry. Researchers from the University of Naples have cracked open how swapping different halogens onto aromatic residues lets scientists dial in the self-assembly, strength, and architecture of peptide-based hydrogels. Forget one-size-fits-all. Now, you can tune peptide materials from the molecular level up.
ACS Appl Bio Mater
by La Manna S, Florio D, Santoro F et al.
“Halogen-Controlled Aromatic Interactions Drive the Self-Assembly and Mechanics of Peptide Hydrogels. La Manna S(1), Florio D(2), Santoro F(1), Pota G(1), Panzetta V(3)(4), Gallo E(2), Netti PA(3)(4), Carotenuto A(1), Marasco D(1). Author information: (1)Department of Pharmacy, University of Naples Federico II, Via D. Montesano 49, Naples 80131, Italy. (2)IRCCS SYNLAB SDN, Via G. Ferraris 144, Naples 80146, Italy. (3)Department of Chemical, Materials and Production Engineering, University of Naples Federico II, Piazzale V. Tecchio 80, Naples 80125, Italy. (4)Interdisciplinary Research Centre on Biomaterials (CRIB), University of Naples Federico II, Italian Institute of Technology, Naples 80125, Italy. Halogenation of aromatic residues represents a powerful strategy to modulate the self-assembly and material properties of peptide-based hydrogels. In this study, we investigate the effect of para-halogen substitution (F, Cl, Br, I) on the phenylalanine residue of the amyloidogenic hexapeptide FINyVK, derived from the C-terminal domain of nucleophosmin 1 (NPM1). A systematic combination of spectroscopic, rheological, morphological, and biological analyses was employed to elucidate how halogen identity influences peptide aggregation and hydrogel formation across multiple length scales. All halogenated analogues exhibited a marked decrease in critical aggregation concentration (CAC) with increasing halogen size, reflecting enhanced hydrophobic and aromatic interactions, while the minimum gelling concentration (MGC) showed only moderate variation, indicating a partial decoupling between early aggregation events and macroscopic gelation behavior. Circular dichroism revealed increasingly cooperative and ordered supramolecular assembly from fluorinated to iodinated peptides, driven primarily by enhanced exciton coupling between aromatic residues. Rheological measurements revealed a nonlinear modulation of hydrogel mechanics across the halogen series, with storage moduli ranging from ∼0.4 kPa for the iodinated system to ∼1.5 kPa for the brominated analogue, reflecting the balance between local supramolecular ordering and higher-order network connectivity. All hydrogels displayed good cytocompatibility toward both NIH/3T3 fibroblasts and HaCaT keratinocytes, maintaining cell viability above 70%. NMR studies of the iodinated analogue provided molecular-level insight into early aggregation, supporting the formation of antiparallel dimeric nuclei as initial assembly intermediates. Overall, these results demonstrate that halogenation provides a tunable and systematic approach to control peptide self-assembly, enabling modulation of supramolecular organization, mechanical properties, and network architecture. This work establishes halogen-dependent aromatic interactions as a key design parameter for the development of peptide hydrogels with tailored properties for potential biomedical and materials applications.”
Here’s the key: The team modified the phenylalanine residue in a hexapeptide (FINyVK) with four halogens—fluorine, chlorine, bromine, and iodine. Each swap changed how the peptide chains stick together and build up into larger networks.
What did they find?
Bigger halogens (like iodine) pulled the peptides together at lower concentrations—hydrophobic and aromatic interactions did the heavy lifting.
But the minimum amount needed to form a stable hydrogel (the minimum gelling concentration) barely budged. Early aggregation and full gelation aren’t always tied together.
Structure matters: As the halogen got heavier, peptide assembly became more cooperative and ordered. Circular dichroism showed those aromatic groups really interact.
Mechanics are tunable: The bromine version created the stiffest hydrogel (up to 1.5 kPa storage modulus), while iodine made a softer gel (0.4 kPa). That means you can design for soft tissue or firmer scaffolds—your choice.
Cytocompatibility? All versions kept cell viability above 70% for fibroblasts and keratinocytes. That’s promising for real-world applications.
The big takeaway: Halogenation gives researchers a precise toolkit for designing peptide hydrogels with custom aggregation, structure, and mechanics. This could mean smarter scaffolds, injectable gels, or materials that adapt to their environment.
Want to dive deeper into tailoring peptide materials? Check the peptide research index for more breakthroughs. Researchers looking to experiment can find suppliers in the vendor directory. The era of designer peptide hydrogels is here—pick your halogen, pick your properties.
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