Transferrin-Functionalized Conjugated Polymer Nanoparticles for Enhanced Photodynamic Therapy of Glioblastoma

Glioblastoma (GBM) remains one of the most lethal primary brain tumors due to its highly infiltrative nature, pronounced intratumoral heterogeneity, and the restrictive blood-brain barrier (BBB), which severely limit the efficacy of conventional therapies. Photodynamic therapy (PDT) offers a spatially and temporally controllable treatment modality; however, its clinical translation for GBM is hindered by insufficient tumor selectivity and suboptimal photosensitizer delivery to intracranial lesions. The purpose of this study was to develop and preclinically evaluate transferrin-functionalized conjugated polymer nanoparticles (CPNs) as a receptor-targeted nanoplatform to enhance BBB traversal, tumor cell uptake, and photodynamic therapeutic efficacy in GBM.

F8BT-based CPNs doped with platinum(II) octaethylporphyrin (PtOEP) and stabilized with poly(styrene-co-maleic anhydride) (PSMA) were synthesized by controlled nanoprecipitation and covalently conjugated to holo-transferrin (holo-Tf) using EDC/NHS chemistry. Nanoparticles were characterized by dynamic light scattering, zeta potential, UV-visible and fluorescence spectroscopy, transmission electron microscopy, electrophoretic mobility, and protein quantification assays. Cellular uptake, receptor specificity, and photodynamic cytotoxicity were evaluated in GBM cell lines. Therapeutic efficacy was further assessed in an orthotopic U87MG-tdiRFP glioblastoma mouse model.

Holo-Tf functionalization increased nanoparticle hydrodynamic diameter, reduced surface charge magnitude, and introduced a protein-specific absorbance feature, while preserving colloidal stability and optical properties. Protein quantification assays confirmed retention of more than 70% of the input holo-Tf. In vitro, holo-Tf CPNs showed significantly enhanced uptake in TfR-high U87MG cells compared with non-functionalized CPNs (42% vs 18% nanoparticle-positive cells at 1 h; gMFI 211 vs 73 at 4 h), which was reduced by excess free holo-Tf, indicating receptor-mediated uptake. PDT mediated by holo-Tf CPNs produced greater phototoxicity in vitro and, in vivo, reduced tumor fluorescence and prolonged survival relative to controls.

Transferrin functionalization enhances receptor-directed delivery and PDT efficacy of conjugated polymer nanoparticles in GBM, supporting their further optimization and translational development.