Membrane-Context Screening Identifies a Functionally Active Peptide for Targeted Nanodelivery in Triple-Negative Breast Cancer

Ligand binding identified during screening does not necessarily translate into improved nanocarrier delivery. Here, we report a membrane-context screening strategy that uses BT-549 cell membrane-functionalized silica microspheres to identify peptide ligands with preserved nanodelivery activity. From a 7-mer combinatorial library, P1 (KFYVSGT) was selected as a membrane-enriched peptide candidate based on its preferential retention by the membrane-functionalized stationary phase relative to bare silica. After conjugation to PEG–PCL micelles, P1 preserved the nanocarrier’s size, charge, morphology, stability, and drug-loading capacity, yet markedly enhanced biological performance. P1-functionalized micelles increased BT-549 cellular uptake by approximately 5-fold and tumor accumulation by about 3-fold in a BT-549 xenograft model. When loaded with doxorubicin, P1 micelles restrained tumor expansion to 1.96-fold of the initial volume, compared with 4.83-fold for nontargeted micelles, with favorable preliminary systemic tolerance. Competitive uptake, energy depletion, peptide-affinity capture, inhibition, colocalization, and docking analyses suggest that P1 activity is associated with a Galectin-1-related membrane environment. This work establishes membrane-context screening as a practical route to function-preserving peptide ligands for targeted nanodelivery.