RGD-Modified Gold Nanoparticles Loaded with SAHA Remodel the Hypoxic Inflammatory Microenvironment via Inhibiting HIF-1α-VEGF Signaling to Enhance Radiosensitivity in NSCLC.

[OBJECTIVE] This research explored the effectiveness of RGD peptide-functionalized gold nanoparticles (AuNPs) loaded with the histone deacetylase inhibitor SAHA (suberoylanilide hydroxamic acid) to enhance the radiosensitivity of non-small cell lung cancer (NSCLC) by suppressing hypoxia signaling, thereby mitigating oxidative stress and inflammatory responses.

[METHODS] RGD-AuNPs-SAHA was synthesized via citrate reduction, thiol-gold bonding for RGD modification, and SAHA loading. Structural and chemical characteristics were assessed via dynamic light scattering (DLS), transmission electron microscopy (TEM), UV-Vis spectroscopy, high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Elemental distribution was mapped using TEM-EELS. Drug release behavior was evaluated under neutral and acidic conditions (pH 7.4 and 5.5). SAHA release kinetics were assessed at pH 7.4 and 5.5. Cellular uptake and biodistribution were evaluated in A549 cells and xenograft mice using fluorescence labeling and flow cytometry. Therapeutic efficacy was examined via tumor volume measurement, serum cytokine profiling (TNF-α, IL-6, IL-10), oxidative stress markers (SOD, CAT, MDA), and molecular analyses (IHC, IF, Western blot, RT-PCR). DNA damage and apoptosis were quantified using TUNEL and γ-H2AX staining.

[RESULTS] RGD-AuNPs-SAHA exhibited uniform size (~20 nm), high SAHA encapsulation (85.2%), and pH-responsive release (60% at pH 5.5 vs 35% at pH 7.4). XPS and EELS mapping further verified the formation of Au-S bonds between thiol-modified RGD and the AuNP surface. Quantitative analysis of surface-bound RGD peptides was performed using UV-Vis spectroscopy combined with the Levenberg-Marquardt algorithm. In vivo, RGD-AuNPs-SAHA reduced tumor volume by 60% and modulated inflammatory cytokines (↓TNF-α/IL-6, ↑IL-10). Oxidative stress markers improved significantly (SOD: 110 U/mL; CAT: 85 U/mL; MDA: ↓2 nmol/mL). Hypoxia signaling proteins HIF-1α and VEGF decreased by 50% and 40%, respectively, confirmed by Western blot and RT-PCR. Apoptosis and DNA damage markers increased by 70% (TUNEL) and 65% (γ-H2AX), demonstrating enhanced radiosensitization.

[CONCLUSION] RGD-AuNPs-SAHA effectively remodeled the hypoxic tumor microenvironment, attenuated oxidative stress, and suppressed pro-tumorigenic signaling, leading to significant apoptosis and DNA damage. These findings highlight its potential as a radiosensitizer for NSCLC, offering a promising strategy to improve radiation therapy outcomes.