Direct chiral-selective detection of (3S,3'S)-astaxanthin using hydrogel-based SERS chips.

(3S,3'S)-astaxanthin ((3S,3'S)-AST) with excellent physiological activity demands accurate chiral-selective detection, yet conventional methods have inherent limitations and SERS technology lacks relevant applications here. In this study, a chiral-selective hydrogel-based SERS chip was prepared by immobilizing aggregated silver nanocages (a-AgNCs) in polyvinyl alcohol (PVA) hydrogel for specific and sensitive (3S,3'S)-AST detection. The hydrogel realized selective adsorption of (3S,3'S)-AST, and a-AgNCs provided strong SERS enhancement via electromagnetic-chemical synergistic effect. The sensing system showed excellent stability (intra/inter-chip RSD < 4.22%, signal loss <5% in 6 weeks), a semi-logarithmic linear response for (3S,3'S)-AST in 0.5-500 ng/g. Practical detection in Haematococcus pluvialis (HP) and Phaffia rhodozyma yeast (PRY) powders confirmed no (3S,3'S)-AST in PRY, and the detected contents in HP samples were consistent with HPLC results. This chip establishes a rapid and reliable chiral-selective detection method for (3S,3'S)-AST, and expands SERS application in chiral analysis of food-related natural products.