Nano-Biomedical Engineering

Researches regarding nanozyme (nanomaterial-based artificial enzyme) are emerging nowadays. Based on the enzyme-mimicking activity of nanozymes, we are developing novel biosensing platform technology. First, we have developed a new and simple colorimetric strategy for the detection of nucleic acids, which relies on target DNA-induced shielding action against the peroxidase mimicking activity of magnetic nanoparticles (MNPs). Second, we have developed a nanostructured multi-catalyst system consisting of MNPs as peroxidase mimetics and oxidative enzyme entrapped in large pore sized mesoporous silica. The nanocomposite concept was successfully demonstrated by very conveniently detecting target glucose or cholesterol revealing excellent reusability and stability. Besides, we developed highly efficient electrochemical biosensing system by employing conductive nanocomposite and ultrafast colorimetric immunoassay system by employing a nanocomposite entrapping magnetic and platinum nanoparticles. Finally, we are developing colorimetric biosensors based on new peroxidase mimetics including Fe-aminoclay and Cu-nanoflower. These achievements should accelerate and widen the utility of nanomaterial-based enzyme mimetics as next-generation alternatives to natural enzymes.

We have developed a solid-phase multiplexed amino acid array, which comprises 16 different amino acid E. coli auxotrophs yielding rapid, specific, and sensitive cell growth as a direct response to the concentration of corresponding amino acids. To obtain the resulting cell-based signal, bioluminescence or fluorescence-based measurement of cell density was employed. As a result, amino acid concentration-dependent response was produced. Such an approach is extending to rapid cell-based sensing of homocysteine and galactose that are relevant to human disease.

Nanozymes have also been extensively employed for the colorimetric detection of fungal toxins. Lai et al. developed a nanozyme-mediated strategy to visually detect AFB1. The method was based on the dissolution of MnO₂ nanoflakes, which originally showed peroxidase-like activity, into Mn²⁺ in the presence of ascorbic acid, leading to the loss of activity. Specifically, free AFB1 in the sample and immobilized AFB1 on BSA-modified magnetic beads (AFB1-MB) were competitive antigens for the AFB1 antibody, which was immobilized on ascorbate oxidase-conjugated AuNPs (Ab-AuNPs-AOx). As the concentration of AFB1 in the sample increased, the amount of conjugate between AFB1-MB and Ab-AuNPs-AOx decreased, resulting in less AOx captured by magnetic separation. With less-captured AOx, the degradation of ascorbic acid was hindered and a relatively higher concentration of ascorbic acid remained, leading to the effective dissolution of MnO₂ nanoflakes, thus inhibiting their peroxidase activity.