CAREER: Engineering Bimetallic Nanostructures as Peroxidase Mimics for Diagnostic Applications

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A strategy chemists often employ in sensor design is to use a chemical called a "catalyst", a substance that can bring about a chemical change. In the present project the desired change is the formation of colored products from uncolored chemicals for detection purposes. The presence of the targeted chemical can then be detected by colorimetric assay which quantifies the intensity of the colored product. While colorimetric technology is easy to use without lengthy training and with inexpensive equipment, the detection sensitivity of colorimetric assays can be less than optimum. In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Professor Xiaohu Xia of Michigan Technological University is studying bimetallic nanostructures as the active component of chemical sensors for properties that result from their very small particle size and their chemical composition. Their behavior mimics that of naturally-occurring peroxidases, a type of enzyme that is good at transforming biological disease markers into colored products but which suffers from low reactivity. Investigation of the synthesis and fundamental catalytic behavior of the bimetallic nanoparticles are evaluated by their use in sensitive and reliable colorimetric assays for disease biomarkers. Broader impacts of the research result from the creation of simple and affordable sensor technologies which can greatly improve our standard of living through better disease biomarker detection. Broader impacts are also made in education and outreach activities, which engage graduate and undergraduate students, especially women and minorities, in fundamental research. The research is integrated into outreach activities for K-12 students from the Upper Peninsula of Michigan. The well-defined nanocrystals, with striking shapes and uniform sizes, serve as vivid examples that are particularly appropriate for the K-12 level students to foster their interests and curiosities in modern nanoscience and nanotechnology.In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Professor Xiaohu Xia of Michigan Technological University is studying bimetallic nanostructures as the active component of chemical sensors for their ability to act as peroxidase mimics toward targeted disease marker molecules. The research engineers the bimetallic nanoparticles in a unique Pd@M_nL core@shell structure, where M is composed of Pt, Ir, Rh, Ru, or Au and with the number of nanolayers (nL) equal to 1-10 atomic layers. By carefully controlling the crystallographic plane and elemental composition of the surface, Dr. Xia is able to maximize the efficiency of the bimetallic particles for improved detection limits in colorimetric assays. By coupling atomic-level electron microscopy imaging with theoretical simulations, this research addresses scientific questions of the structure-property relationships of bimetallic nanoparticle peroxidase mimics that are presently only poorly understood. Broader impacts of the research result from improved sensor technology, since as alternatives to natural peroxidase, these highly efficient mimics are straightforwardly to use for in-vitro diagnostics of disease biomarkers. Broader impacts are also made in education and outreach activities, which benefit in the engagement of graduate and undergraduate students, especially women and minorities, in fundamental research. The research is integrated into outreach activities for K-12 students from the Upper Peninsula of Michigan. The well-defined nanocrystals, with striking shapes and uniform sizes, serve as vivid examples that are particularly appropriate for the K-12 level students to foster their interests and curiosities in modern nanoscience and nanotechnology.