Rapid detection of <i>Fusobacterium nucleatum</i> in saliva using magnetic flux change

We have developed a low-cost, rapid, and highly sensitive antigen test for Fusobacterium Nucleatum that utilizes the antigen-antibody reaction between magnetic nanoparticles and biological materials (antigens), which changes the magnetic flux passing through the small pickup coil. The magnetic flux of the pickup coil decreased with increasing antigen concentration because the density of magnetic nanoparticles decreased with increasing antigen concentration. The driving coil was air-cooled to reduce thermal drift, and the size of the differential pickup coil was reduced to achieve a high signal-to-noise ratio in magnetic flux measurements. After the antigen-antibody reaction, the magnetic nanoparticles and antigens are agglutinated by magnetic force, reducing the influence of contaminants and allowing the concentration of Fusobacterium Nucleatum to be evaluated without a washing step. The method was validated using samples collected from 28 individuals. The results showed a strong correlation with qPCR analysis (correlation coefficient = 0.69, p &amp;lt; 0.0001), highlighting the accuracy and precision comparable to conventional qPCR systems. The proposed approach offers several advantages for bacterial detection: low cost, rapid evaluation, high sensitivity, and minimal interference from contaminants.