Avidity-by-design: spatial control of T7 peptide presentation on polymersomes dictates blood-brain barrier transport fate.
Researchers just rewrote the rules for peptide-based blood-brain barrier (BBB) delivery. By fine-tuning the way T7 peptides are displayed on polymersome nanoparticles, the team demonstrated that spatial arrangement — not just the presence of a peptide — dictates whether a compound crosses the BBB or sticks to its surface.
Drug Deliv Transl Res
by Lopes CDF, Basile M, Barbieri V et al.
“Avidity-by-design: spatial control of T7 peptide presentation on polymersomes dictates blood-brain barrier transport fate. Lopes CDF(#)(1), Basile M(#)(2)(3), Barbieri V(2), Cosenza V(2), Pfeifer P(2), Battaglia G(2)(4). Author information: (1)Institute for Bioengineering of Catalonia (IBEC), Barcelona Institute of Science and Technology (BIST), Carrer Baldiri Reixac, 10-12, 08028, Barcelona, Spain. clopes@ibecbarcelona.eu. (2)Institute for Bioengineering of Catalonia (IBEC), Barcelona Institute of Science and Technology (BIST), Carrer Baldiri Reixac, 10-12, 08028, Barcelona, Spain. (3)Department of Biomedicine, University of Barcelona, Barcelona, Spain. (4)Catalan Institution for Research and Advanced Studies, Passeig de Lluís Companys, Barcelona, Spain. (#)Contributed equally Targeting the transferrin receptor (TfR) holds promise for drug delivery across the blood-brain barrier (BBB), but conventional strategies suffer from competition with endogenous ligands and suboptimal trafficking. To overcome these limitations, we engineered a library of T7 peptide-functionalised pH-responsive polymersomes with precise control over ligand density and ligand insertion depth (δ) within a poly(ethylene glycol) (PEG) corona. We generated nanoparticles with δ values ranging from 0.3 (deeply inserted ligands) to 1.0 (fully exposed ligands), enabling systematic evaluation of how spatial ligand presentation influences BBB interactions. In vitro studies revealed that δ = 1.0 polymersomes exhibited efficient transcytosis, whereas δ = 0.6 polymersomes promoted endothelial retention, a divergence likely linked to differential receptor clustering and trafficking kinetics. Notably, TfR-mediated transport occurred independently of PACSIN2, distinguishing it from tubular transcytosis pathways observed with LRP1-targeted systems. These findings establish avidity-by-design as a strategy to tailor nanocarriers for either BBB penetration or vascular targeting, offering a modular platform for neurological therapeutics. © 2026. The Author(s). Conflict of interest statement: Declarations. Ethics approval and consent to participate: This study was performed using commercially available mouse cell lines, and no ethical approval or consent to participate is required. Consent to publish: This study did not involve human participants, human data, or human tissue. Therefore, consent for publication was not required. Conflict of interests: The authors declare no competing interests.”
Here’s the play-by-play: The team built a set of pH-responsive polymersomes, each loaded up with T7 peptides at varying “depths” within their protective polyethylene glycol (PEG) coating. Think of it like hiding or exposing keys on a keyring — how far the peptide “sticks out” (the δ value) determines what happens next.
Key results:
Polymersomes with fully exposed T7 peptides (δ = 1.0) moved efficiently across BBB models — a big step for delivering research compounds to the brain.
Partially buried peptides (δ = 0.6) didn’t cross; instead, they parked on the endothelial surface, likely due to differences in receptor clustering and the cell’s internal trafficking.
This method worked through the transferrin receptor (TfR), sidestepping the PACSIN2 pathway usually involved in other nanocarrier systems.
What’s the takeaway? Researchers can now use “avidity-by-design” to dial in whether a peptide-laden nanoparticle stays put or makes the jump past the BBB. This modular approach could be a game-changer for neurological research and targeted delivery.
If you’re tracking advances in peptide research, this study is a clear signal: spatial presentation matters just as much as the peptide itself. Watch for more custom-tailored nanocarrier strategies in the near future.
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