Electrochemiluminescent/colorimetric monitoring 25(OH)D₃ based on HOFs-g-C₃N₄-CeO₂ functional composite

Vitamin D, mainly in the active form of 25-hydroxy vitamin D₃ (25(OH)D₃), participates in blood circulation and plays a vital role in metabolic homeostasis. Herein, an electrochemiluminescent (ECL)/colorimetric dual-analytical biosensing platform based on HOFs-g-C₃N₄-CeO₂ (HCC) composite was developed for 25(OH)D₃ detection. In the ECL system, electrochemiluminescence-resonance energy transfer (ECL-RET) occurred utilizing HCC as the ECL donor and gold nanorods (Au NRs) as the acceptor. The binding of the complementary aptamer chain (ssDNA) labeled with Au NRs to the aptamer chain VDBA14 immobilized on the surface of HCC quenched the ECL emission via ECL-RET. After adding the target 25(OH)D₃, ECL response was recovered due to the competition for VDBA14 between ssDNA and 25(OH)D₃, resulting in the reduction of Au NRs and attenuation of the ECL-RET on the electrode. In the colorimetric system, VDBA14 immobilized on magnetic beads (MBs) captured ssDNA tagged with HCC through complementary base pairing. VDBA14 could specifically recognize 25(OH)D₃ to release ssDNA competitively, and then, the released HCC was used as the nanozyme to catalyze the chromogenic reaction between tetramethylbenzidine (TMB) and H₂O₂. The bimodal analysis showed a good response to 25(OH)D₃ in the linear range 20 ~ 80 ng/mL, with detection limits of 15.91 ng/mL (for the ECL system) and 7.28 ng/mL (for the colorimetric system). The proposed dual-analytical biosensor improved the reliability of detecting 25(OH)D₃ and performed satisfactorily in practical applications, which is of great significance in immunomodulation, skin physiology, and other important aspects of human health.