Flexible Radioactive Patch: Reshaping the Paradigm for Scar and Cutaneous Tumor Treatment

Abstract The treatment of skin diseases, including hypertrophic scars and cutaneous melanoma, remains clinically challenging. Conventional radionuclide (e.g., 90Sr, 32P) patches for beta-ray external beam radiotherapy suffer from rigid structures, leading to off-target irradiation, uneven radionuclide distribution, inconsistent dosing, and potential leakage risks. To address these limitations, we developed an innovative, flexible radioactive patch (32P-RU) by integrating 32P-loaded resin microspheres with boric acid-modified flexible polydimethylsiloxane (PBDMS) gel (P4U), enabling robust adsorption of H32PO42-, homogeneous distribution, and precise, repeated reshaping to conform to irregular lesions. As a pure beta emitter, 32P (Emax = 1.71 MeV, T1/2 = 14.28 d, tissue penetration depth = 4 mm) minimizes damage to adjacent normal tissues. In preclinical models, 32P-RU demonstrated significant therapeutic efficacy: in rabbit ear hypertrophic scar models, five 4 Gy fractions reduced scar volume and improved collagen organization; in murine subcutaneous melanoma models, five 8 Gy fractions effectively suppressed tumor growth. Notably, combining 32P-RU with the immune checkpoint inhibitor (anti-PD-L1) synergistically enhanced anti-tumor effect, promoting dendritic cell maturation, increasing CD8+ T cell infiltration, and suppressing both primary and distant tumors. This conformal, safe, and effective 32P-RU patch offers a strategy for the precise treatment of superficial skin diseases, including refractory cutaneous malignancies.