MC-Au/MSS-Z8 porous network assisted advanced electrochemical immunosensing of 25-hydroxyvitamin D₃

On-site monitoring of vitamin D levels is subject matter of immediate attention owing to the serious aftermath of its long standing deficiency. Therefore, a novel and efficient voltammetric immunosensing of 25-hydroxyvitamin D₃ (25(OH)VD₃) has been experimented based on an advanced sensing platform composed of meso-microporous silica-zeolitic imidazolate framework-8 (MSS-Z8) with highly enhanced surface area (S_{BET, MSS-Z8} (643.4 m²g^-1) > S_{BET, MSS} (49.95 m²g^-1)), embedded with gold particles (mass loading of 82 μg), particularly of microcubic morphology (MC-Au). Further, the MC-Au/MSS-Z8/FTO platform was fashioned with antibody specific to 25(OH)VD₃ via interaction between Au and abundant -SH groups present on the antibody surface. After optimization of operational parameters, the Ab/MC-Au/MSS-Z8/FTO immunosensor was employed for the determination of 25(OH)VD₃ within 0.01-10⁶ pg mL^-1 concentration range through differential pulse voltammetry technique in [Fe(CN)₆]^3-/4-. Thus, 0.01 pg mL^-1 concentration of 25(OH)VD₃ was the experimental limit of detection of the immunosensor. Further, upon examination of various analytical parameters, it turns out that the immunosensor exhibited low theoretical LOD (0.23 pg mL^-1) and LOQ (0.76 pg mL^-1), wide linear range (0.01-10⁶ pg mL^-1), ultra-sensitivity (143.9 μA [log (pg mL^-1)]^-1 cm^-2), adequate reproducibility (RSD ≤1.23%) and acceptable shelf life. Most importantly, the immunosensor presented proficient performance with spiked human serum samples (Recovery = 97.20-100.7%, RSD value < 5.6%), evincing the adequacy of present biosensing approach.