A research team in the Department of Chemical and Biomolecular Engineering led by Professor Jinwoo Lee has successfully developed a graphene-based peroxidase-mimicking nanomaterial.
Peroxidase enzymes have been a regular topic of research due to their importance in a large number of biological processes. A specific type of peroxidase called horseradish peroxidase (HRP), often used in bioassays, is generally found in plants. A bioassay is an analytical process aimed at finding the concentration of a substance by examining its effect on living cells. As a signaling enzyme, HRP’s small size, high turnover rate, and easy attachment to other biological receptors make it a topic of interest, while its instability and difficult extraction process make it quite expensive.
Nanomaterials, materials consisting of single units with a nano-ranged size, that act as enzymes (nanozymes) can be an alternative to such natural peroxidases. While such nanozymes are usually stable and cheaper, their catalytic activity is usually inferior to that of a natural peroxidase. Thus, the main goal for the researchers was to create a nanozyme with high peroxidase activity and low oxidase activity. High oxidase activity means that the presence of hydrogen peroxide — a crucial component for biosensing systems — cannot be selectively detected.
Nanomaterials of carbon such as graphene oxide are good candidates for such a purpose. However, their lower catalytic activity had to be improved upon for them to become practical. The research team developed a nitrogen and boron co-doped reduced graphene oxide (NB-rGO). This nanozyme has a much higher catalytic activity than those of conventional carbon-based nanozymes and HRP. The researchers were also able to theoretically prove the increased catalytic activity of the new nanozyme with the density functional theory.
One major application of NB-rGO-based bioassays is the detection of acetylcholine, a chemical whose low levels can indicate neural disorders such as Alzheimer’s disease, Parkinson’s disease, schizophrenia, and more. Furthermore, C-reactive protein (CRP) is also crucial in indicating inflammation, tissue damage, and cardiovascular diseases. Through experiments, NB-rGO-based assay systems showed higher sensitivity to acetylcholine than HRP-based or Pt nanoparticles-based assay systems do. The lower limit of CRP detection with NB-rGO was also around one-third of the limit using HRP.
With catalytic efficiency of co-doped nanozyme being up to three orders of magnitude higher than that of a regular one, and experiments indicating high sensitivity to molecules, this new material shows promise for improved identification of biomolecules. This new research can prove to be critical for improving efficiency of the detection of different disorders as well as reducing the cost of such detections.