Biophysical Society Thematic Meeting | Bucharest 2026

Biophysics of Membrane Reactions in Brian

Tuesday Speaker Abstracts

PH-RESPONSIVE PEPTIDE NANOPARTICLES DELIVER MACROMOLECULES TO CELLS VIA ENDOSOMAL MEMBRANE NANOPORATION Eric Wu 1 ; Ace Ellis 1 ; Keynon Bell 2 ; Ana-Nicoleta Bondar 3,4 ; Kalina Hristova 2 ; William C. Wimley 1 ; 1 Tulane University School of Medicine, Biochemistry and Mol. Biol., New Orleans, LA, USA 2 Johns Hopkins University, Materials Science, Baltimore, MD, USA 3 University of Bucharest, Physics, Bucharest, Romania 4 Forschungszentrum Jülich, Institute of Computational Biomedicine, Jülich, Germany The ability to transport proteins and other macromolecular cargos into cells and across cellular barriers remains a significant challenge for therapeutic development. The synthetically evolved pHD family of peptides addresses this challenge through a pH-responsive mechanism that enables membrane permeabilization, but only under acidic conditions. Members of this family self-assemble into macromolecule-sized nanopores (2–10 nm diameter) in lipid bilayers at pH values below ~6. Here, we show that the representative peptide pHD108 exhibits the same pH dependent nanopore-forming activity in the endosomal membranes of living human cells, triggered by endosomal acidification, thereby enabling efficient cytosolic delivery of endocytosed proteins and other large cargos. Addition of acyl groups to either peptide terminus significantly improves delivery efficiency without cytotoxicity. Peptides modified with longer acyl chains are more potent. The most active variant, N-terminally palmitoylated C16-pHD108, delivers diverse macromolecular cargos, including enzymes, fluorescent proteins, and dye labeled dextrans, to the cytosol of human cells. At neutral pH, C16-pHD108 assembles into stable, monodisperse micellar nanoparticles (~30 nm diameter) that are non-lytic and non-toxic. Acidification destabilizes these nanoparticles and promotes membrane binding and nanopore formation. These results support a delivery mechanism in which passive uptake of cargo and peptide nanoparticles is followed by acidification-triggered activation of nanoporation in endosomal membranes, enabling macromolecular cargo to escape into the cytosol. This system provides a general platform for intracellular and trans-barrier delivery of large biological cargos, with potential relevance to challenging targets such as the blood–brain barrier.

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