Synthesis and application of exopolysaccharide-selenium nanocomposite produced by Pseudoduganella armeniaca ZMN-3.

This study investigated the antioxidant and anticancer activities of selenium nanoparticles stabilized by exopolysaccharides from Pseudoduganella armeniaca ZMN-3 (EPS‑SeNPs). The synthesized EPS‑SeNPs had an average size of 145 nm and were thoroughly characterized. In vitro antioxidant assays revealed that at 4 mg/mL, EPS‑SeNPs scavenged 86.49 ± 0.53% of DPPH radicals, 82.96 ± 0.32% of ABTS radicals, and 36.41 ± 0.77% of hydroxyl radicals. The reducing power assay showed that, at the same concentration, EPS‑SeNPs exhibited an absorbance value of 1.28 ± 0.029, which was higher than that of the other groups. The EPS‑SeNPs composite exhibited pronounced time- and concentration-dependent antiproliferative effects against the two selected cancer cell lines, MCF‑7 and SMMC. After 48 h of treatment at the highest concentration (250 µg/mL), the inhibition rates reached 52.88% for SMMC cells and 54.41% for MCF-7 cells. This effect was significantly stronger than that of EPS or SeNPs alone, indicating a marked enhancement. Cytokine analysis further revealed that even at a low concentration (31.25 µg/mL), a measurable effect was observed. The levels of TNF‑α released by SMMC and MCF‑7 cells reached their highest values at the high concentration of 250 µg/mL, namely 344.79 pg/mL and 132.6 pg/mL, respectively. This promoting effect exceeded that of the positive control (LPS group) and was notably stronger than the effects of SeNPs or EPS alone, with the enhancement being particularly prominent in SMMC cells. Collectively, EPS-SeNPs exhibit both antioxidant and in vitro anti-tumor activity, warranting further investigation.