A sequential dual-drug delivery system for multi-target inhibition of subretinal fibrosis

BACKGROUND: Subretinal fibrosis (SRF), a severe vision-threatening complication secondary to neovascular age-related macular degeneration (nAMD), remains a major clinical challenge due to its complex pathogenesis and prolonged disease course. The fibrotic process is driven by multiple synergistic factors, including chronic inflammation, hypoxia, epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells, and pathological neovascularization, which collectively lead to the ineffectiveness of conventional anti-vascular endothelial growth factor (VEGF) monotherapies in halting disease progression. RESULTS: This study developed a sequential dual-drug delivery system based on the terpolymer P(NIPAM-co-AA-co-HEMA) hydrogel (NAHGel), designed to achieve multi-targeted regulation from the pathological microenvironment to downstream fibrotic processes. NAHGel exhibits excellent thermal responsiveness, biomechanical stability, and biodegradability, and is co-loaded with matrine (MT) and cRGD-modified sorafenib liposomes (SF/cLP). The hydrogel undergoes thermal contraction to enable the rapid release of hydrophilic MT, exerting anti-inflammatory and anti-hypoxic effects. As the hydrogel progressively degrades, SF/cLP is released in a delayed manner and, under cRGD mediation, is targeted to RPE cells and vascular endothelial cells. This enables modulation of key pathways including TGF-β2/MEK1/2/ERK1/2 and HIF-α/VEGF/PDGF, thereby inhibiting EMT and endothelial proliferation. In a laser-induced SRF mouse model, MT + SF/cLP@NAHGel formed a stable in situ gel within 24 h after intravitreal injection and remained structurally intact in the dynamic vitreous environment, enabling sustained retention for up to 8 months. Imaging and histological analyses demonstrated that, compared with aflibercept and other group, this system significantly reduced choroidal neovascularization and fibrotic lesion areas. Transcriptomic analysis further confirmed its broad inhibition of signaling pathways related to inflammation, angiogenesis, and fibrosis, with marked downregulation of key mediators including VEGFA, TGF-β2, TNF-α, and HIF-1α. CONCLUSION: MT + SF/cLP@NAHGel achieves sequential drug release and multi-targeted synergy to intervene in key pathological processes such as inflammation, hypoxia, EMT, and pathological neovascularization, thereby effectively halting SRF progression. Combining sustained therapeutic efficacy with excellent biosafety, this system holds strong translational potential as a long-acting treatment strategy for SRF and other multifactorial retinal diseases.