Synthesis and Characterization of an Amino-oxy-modified Sphingosine-1-Phosphate Derivative that Can Replace Thiolated-S1P in Competitive ELSIA

Sphingosine-1-phosphate (S1P) is a signaling molecule that has various roles in vivo. Recently, S1P has emerged as a biomarker in the early diagnosis of osteoporosis and cancer. A competitive enzyme-linked immunosorbent assay (ELISA) assay kit for detecting S1P in blood or in various samples is now commercially available. Competitive ELISA requires an anti-S1P antibody and S1P-coated microtiter plates. The antigenic derivative used here is the thiolated-S1P in which a sulfur hydryl group is introduced at the terminal end of the S1P hydrophobic chain. However, the sulfur hydryl group is easily oxidized, and its solubility in water is considerably low, making it difficult to handle. In this study, amino-oxy-modified S1P derivatives that can replace thiolated-S1P were synthesized. Amino-oxy groups are easy to attach to proteins and other polymers without any linker, and are easy to handle because they are not easily oxidized, and soluble in water. The synthesized S1P derivative was directly immobilized on a microtiter plate, and an ELISA assay was performed which obtained comparable results with the conventional thiolated-S1P reference. It is expected that the anti-S1P antibody can be easily induced by attaching this amino-oxy-modified S1P to reduced carrier proteins.