*Article* **Preparation and Characterization of Nano-Selenium Decorated by Chondroitin Sulfate Derived from Shark Cartilage and Investigation on Its Antioxidant Activity**

**Jianping Chen 1,2,\*, Xuehua Chen 1, Jiarui Li 1, Baozhen Luo 1, Tugui Fan 1, Rui Li 1,2, Xiaofei Liu 1,2, Bingbing Song 1,2, Xuejing Jia 1,2 and Saiyi Zhong 1,2,\***


**Abstract:** In the present study, a selenium-chondroitin sulfate (SeCS) was synthesized by the sodium selenite (Na2SeO3) and ascorbic acid (Vc) redox reaction using chondroitin sulfate derived from shark cartilage as a template, and characterized by SEM, SEM-EDS, FTIR and XRD. Meanwhile, its stability was investigated at different conditions of pH and temperatures. Besides, its antioxidant activity was further determined by the DPPH and ABTS assays. The results showed the SeCS with the smallest particle size of 131.3 ± 4.4 nm and selenium content of 33.18% was obtained under the optimal condition (CS concentration of 0.1 mg/mL, mass ratio of Na2SeO3 to Vc of 1:8, the reaction time of 3 h, and the reaction temperature of 25 ◦C). SEM image showed the SeCS was an individual and spherical nanostructure and its structure was evidenced by FTIR and XRD. Meanwhile, SeCS remained stable at an alkaline pH and possessed good storage stability at 4 ◦C for 28 days. The results on scavenging free radical levels showed that SeCS exhibited significantly higher antioxidant activity than SeNPs and CS, indicating that SeCS had a potential antioxidant effect.

**Keywords:** nanoselenium; chondroitin sulfate derived from shark cartilage; structure characterization; antioxidant activity
