Plant-derived paclitaxel-loaded ultra-small Fe₃O₄ nanoparticles for MR imaging-mediated antitumor therapy

Precise tumor imaging and effective drug delivery remain significant challenges in cancer therapy. To address these challenges, a novel drug delivery system, Us-Fe NPs/PLA-PEG@PTX, was developed for combined MR imaging and anti-tumor therapy. Ultra-small Fe₃O₄ nanoparticles (Us-Fe NPs) were stabilized with citrate and modified with polylactic acid-polyethylene glycol (PLA-PEG) polymers to enhance biocompatibility and facilitate paclitaxel (PTX) incorporation. PTX was initially extracted from the bark of the Pacific yew tree. The system achieved an encapsulation efficiency of 72.3 % and a loading content of 6.74 %. PTX was released in a controlled manner at both neutral (pH 7.4) and mildly acidic (pH 5.5) conditions. MR imaging studies indicated potential for T1-weighted imaging. Us-Fe NPs/PLA-PEG@PTX demonstrated dose-dependent cytotoxicity (IC₅₀ = 0.06 μg/mL) against MDA-MB-231 cells. PEG modification reduced cellular uptake. Flow cytometry showed G2/M phase arrest and apoptosis induction, and confocal microscopy revealed microtubule disruption. These results suggest that Us-Fe NPs/PLA-PEG@PTX is a promising nano-platform for MR imaging-guided anti-tumor therapy.