SPR immunosensor combined with Ti4+@TiP nanoparticles for the evaluation of phosphorylated alpha-synuclein level

A highly sensitive and specific surface plasmon resonance (SPR) method using one anti-alpha-synuclein antibody (anti-alpha S) and titanium phosphate nanoparticles (Ti4+@TiP) was developed for quantitative evaluation of phosphorylated alpha S level which was defined by the ratio of p-alpha S to total alpha-synuclein (t-alpha S) (p-alpha S/t-alpha S). The close affinities of anti-alpha S to alpha S (0.975 pM(-1)) and p-alpha S (0.938 pM(-1)) were obtained. Based on this fact , both alpha S forms were simultaneously captured and the t-alpha S was quantified using the anti-alpha S immobilized Au chip. With the selective recognition of Ti4+@TiP nanoparticles, the p-alpha S was quantified. The dynamic ranges of our method were 1.0 similar to 20.0 pg mL(-1) for the detection of t-alpha S and 0.1 similar to 10.0 pg mL(-1) for that of p-alpha S. The analysis of alpha S- and p-alpha S-spiked artificial cerebrospinal fluid samples revealed the high accuracy of the method. Furthermore, the concentrations of alpha S and p-alpha S in clinical CSF samples collected from three healthy donors were determined and displayed a high correlation with the results from a commercial ELISA kit, confirming the viability and of the proposed method. The method is convenient, economical, and practical for the evaluation of phosphorylated alpha S level with high sensitivity and selectivity. It is of great significance for the early diagnosis of PD and the evaluation of PD progression.