Sandwich-Type SERS Aptasensor Based on Aptamer-functionalized Magnetic Capture Probe and AuNPs@MIL-101 Signal Enhancement Probe for Ultrasensitive Detection of Bifidobacterium bifidum

Rapid and on-site detection of Bifidobacterium bifidum (B. bifidum) throughout the food manufacturing process serves as an essential sentinel for assessing product quality and healthy potency. Herein, we introduce a sandwich-type surface-enhanced Raman scattering (SERS) aptasensor for B. bifidum quantification, which integrates aptamer-functionalized magnetic beads (Apt-Fe₃O₄) for target-specific capture and aptamer-modified gold nanoparticles/metal-organic framework composites (Apt-AuNPs@MIL-101) for SERS-based signal amplification. Experimental results revealed a strong linear correlation between the intensity of the characteristic Raman peak and the logarithmic of the B. bifidum concentrations within the range of 2.0 × 10¹ to 2.0 × 10⁶ CFU/mL, and the limit of detection was as low as 2.5 CFU/mL. In addition to superior sensitivity, the proposed approach demonstrated exceptional specificity against non-target bacterial strains, particularly in multi-strain coexistent systems. The method further demonstrated great potential in analysis of B. bifidum in commercial samples, showing high consistency with the results obtained from the classic qPCR method. The study established an innovative analytical platform for rapid and on-site probiotic assessment, highlighting its applicability in probiotic food products’ quality control and evaluation.