Wide-range direct detection of 25-hydroxyvitamin D₃ using polyethylene-glycol-free gold nanorod based on LSPR aptasensor

Vitamin D is associated with various diseases such as obesity, digestive problems, osteoporosis, depression, and infections, which has emerged as an interest in public healthcare. Recently, vitamin D has received more attention because of the potential implication with coronavirus disease 2019. In this study, we developed a localized surface plasmon resonance (LSPR) aptasensor based on polyethylene-glycol(PEG)-free gold nanorods (AuNRs) for the wide-range and direct detection of 25-hydroxyvitamin D₃. The surfactant on AuNRs was removed by exchanging with polystyrene sulfonate (PSS) instead of PEG then the PSS was exchanged with citrate. By exchanging the stabilizer of AuNRs from PEG to PEG-free (i.e., citrate), the sensing efficiency of LSPR aptasensor was significantly improved. Additionally, LSPR aptasensor was functionalized with aptamer and blocking agent to enhance the sensing performance. The LSPR aptasensor achieved the direct, highly sensitive, and selective detection of 25-hydroxyvitamin D₃ over a wide concentration range (0.1–10⁵ ng/mL), with a limit of detection of 0.1 ng/mL. This detection range included the concentration of vitamin D from deficiency to excess. The PEG-free AuNR-based LSPR aptasensor affords a new avenue for the development of robust sensing technology for vitamins.