Preparation, characterization and antioxidant activity of cobalt polysaccharides from Qingzhuan Dark Tea

The paradoxical effects of cobalt in biological processes have caused controversy regarding the application of cobalt-based biomaterials. Cobalt has recently been shown to be a trace element that promotes bone growth. Qingzhuan Dark Tea polysaccharides (TPS) has been shown to be a biomaterial with antioxidant and immunomodulatory effects. In order to develop a novel immunomodulatory biomaterial, we synthesized polysaccharide cobalt complex (TPS-Co) to prevent the paradoxical effects of cobalt while maintaining its beneficial effects, and evaluated its morphology, structure, and antioxidant activity. Fourier-transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy demonstrated that cobalt complexed successfully with TPS. Scanning electron microscopy and atomic mechanical microscopy demonstrated that TPS-Co has a more homogeneous and concentrated morphological distribution compared to TPS. Thermal performance analysis demonstrated that TPS-Co has higher thermal stability. Atomic absorption spectroscopy showed a cobalt content of 3.8%. Ultraviolet spectroscopy indicated that TPS-Co does not contain nucleic acids and proteins. Antioxidant activity assays showed that TPS-Co has better antioxidant activity than TPS in the concentration range of 0.4–2 mg/mL. Proliferation assay of MC3T3-E1 cells demonstrated that TPS-Co has the best cell proliferation effect at a cobalt concentration of 2 ppm. Therefore, TPS-Co may have potential applications in bone regeneration.