Preparation and Antitumor Activity of METTL3 SiRNA Nanoparticles Carried by Hypoxia Sensitive Polymer (mPEG-Azo-PEI)

Purpose: The clinical application of small interfering RNA (siRNA) therapy is limited by instability, inefficient tumor targeting, and inadequate responsiveness to the hypoxic tumor microenvironment. Therefore, this study aimed to construct a hypoxia-sensitive polymer-based nanocarrier to improve siRNA delivery efficiency and enhance antitumor effects in colorectal cancer (CRC). Methods: A hypoxia-sensitive polymer (mPEG-Azo-PEI) was synthesized and its cytotoxicity was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The polymer was loaded with siRNA targeting the METTL3 gene to form nanoparticles, which were then optimized and characterized. Coumarin-loaded nanoparticles were also prepared to study the cellular uptake in HCT116 cells under hypoxic conditions. The Antitumor effects were evaluated via MTT and real-time polymerase chain reaction (RT-PCR) in vitro and in vivo, and a rectal cancer model was established using HCT116 cells in nude mice. Tumor size, weight, and histology (HE staining) were assessed, and RT-PCR analyzed METTL3 ex-pression. Results: The CMC of mPEG-Azo-PEI was 0.001687 mg/mL, indicating good self-assembly stability under dilution conditions. The optimized mPEG-Azo-PEI@siRNA2 nanoparticles exhibited a mean particle size of 141.34 ± 2.31 nm, a PDI of 0.213 ± 0.011, and a zeta potential of +21.76 ± 1.76 mV. Hypoxia-triggered release reached ~95% within 24 h, compared with ~10% under normoxic conditions. Coumarin uptake by HCT116 cells was enhanced under hypoxic conditions, indicating improved intracellular delivery. In vitro, the nanoparticles inhibited tumor cell proliferation, with IC50 values of 1.133 (normoxia) and 0.481 (hypoxia) nM. In vivo, mPEG-Azo-PEI@siRNA2 significantly suppressed tumor growth and improved body weight. RT-PCR confirmed the downregulation of METTL3, aligning with tumor suppression. Conclusion: These results demonstrated that hypoxia-sensitive mPEG-Azo-PEI@siRNA2 nanoparticles effectively delivered siRNA2 and inhibited HCT116 cell proliferation, offering a promising hypoxia-activated targeting strategy for colon cancer therapy.