Glucose oxidase-like activity of cerium oxide nanoparticles: use for personal glucose meter-based label-free target DNA detection

Recently, personal glucose meter (PGM) has been utilized for the detection of non-glucose targets for point-of-care (POC) testing. Aimed at this goal, we herein developed a new PGM-based label-free read-out method for polymerase chain reaction (PCR) based on our novel finding that cerium oxide nanoparticles (CeO₂ NPs) exhibit glucose oxidase-like activity comparable to the natural glucose oxidase enzyme. Methods: In principle, DNA amplicons produced by PCR in the presence of target DNA electrostatically bind to CeO₂ NPs, leading to their aggregation and reducing the efficiency for CeO₂ NP-catalyzed glucose oxidation reaction. Thus, glucose is hardly oxidized to gluconic acid, resulting in the maintenance of initial high glucose level. On the contrary, in the absence of target DNA or presence of non-target DNA, DNA amplicons are not produced and glucose is effectively oxidized by the glucose oxidase-like activity of CeO₂ NPs, leading to the significant reduction of glucose level. Finally, the resulting glucose level is simply measured by using PGM. Results: With this strategy, DNA amplicons were quantitatively examined within 5 min, realizing ultrafast analysis of PCR results without any cumbersome and labor-intensive procedures. In addition, the target genomic DNA derived from Escherichia coli (E. coli) was sensitively determined down to 10 copies with high selectivity. Conclusion: Importantly, the use of PGM as a detection component enables its direct application in POC settings. Based on the meritorious features of PGM such as rapidity, simplicity, and cost-effectiveness, we expect that the devised system could serve as a core platform for the on-site read-out of PCR amplification.