Sulfated polysaccharides in marine algae exhibit many health beneficial nutraceutical effects such as antioxidant, anticoagulant, and antitumor activities. A semi-continuous system was employed to cultivate the diatom Halamphora sp. (AQ4). Five different cultivation conditions are performed according to different harvesting volumes (2, 3 and 4 L) and with different Na2CO3 content (2 and 10 mMs). The results show that reducing the harvesting volume can increase the polysaccharide content, while increasing the amount of Na2CO3 can increase the cell density. The cell mass concentration can reach 1.2831 g/L and the polysaccharide content can reach 29.1685 mg/g. Furthermore, the addition of Na2CO3 can rise in the cell density but reduce the polysaccharides content. However, it has changed the proportion of polysaccharides. This result can be used as a reference for physiology control of diatom function in the future. Polysaccharides were extracted by ultrasonic-assisted extraction with warm water. Following DEAE Sepharose anion-exchange chromatography, four polysaccharides were eluated at 0, 0.1, 0.5, 1.0 M NaCl concentration (PK0-PK3). The component and FT-IR analysis show that the uronic acid content of AQ4 polysaccharides is 0-15%, the sulfated content is 0-8%, and the molecular weight is 11.87-6.91×103 kDa. Osteoclast plays a key role in the pathogenesis of osteoporosis. The anti-osteogenesis effects of polysaccharides from AQ4 (PK0, PK2, and PK3) was investigated using an in vitro system of receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation. PK3 did not affect the cell viability the murine macrophage (RAW 264.7), but inhibited RANKL-induce osteoclastogenesis in the dosage of 5-10μg/mL. Furthermore, RT-qPCR demonstrated that PK3 inhibited mRNA expression of NFATc-1, TRAP, MMP-9, and cathepsin K, which are four osteoclastogenesis related genes. To simulate the surface modification of bone substitute material, tissue culture plates coated with PK3 at different coating concentration were used to evaluate the effects on RAW264.7 cell viability and osteoclast differentiation. Coating concentration of 0.1-0.5% not only enhanced cell viability but inhibited osteoclast differentiation. These results demonstrated that PK3 may have the potential as an osteoporosis drug, health food, or a novel matrix of bone substitute material.

Anti-osteoclastogenesis activity analysis of diatom polysaccharides produced by a semi-continuous photobioreactor system

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