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Multifunctional scanning nanoprobes integrating scanning electrochemical microscopy (SECM), atomic force microscopy (AFM), and scanning nearfield optical microscopy (SNOM) will be developed using microfabrication technology. Novel strategies for the development of a new generation of multifunctional scanning probe tips will extend the application of scanning probe techniques to complex environmental and biological systems at the molecular level. In addition to multiple electrode systems and tip arrays the main focus of this proposal is aimed at integrating multiple smart electrochemical sensing systems for the in-situ analysis of chemical and biochemical processes at the interface between Fe(III)-reducing microorganisms and Fe(III)-containing mineral surfaces. Instead of performing sequential analysis of complex processes between microorganisms and mineral surfaces, we propose to examine these processes simultaneously in space and in time with the newly developed, multifunctional scanning nanoprobes. Attractive energies and electrochemical signals generated by Fe(III)-reducing bacterial cells and specific Fe(III)-reducing enzymes attached to nanoprobe tips will be detected via simultaneous confocal microscopy and scanning probe measurements at the Fe(III) mineral surface. This new technology will enable us to investigate electron transfer mechanisms at the nanometer scale and correlate in-situ measurements with computational simulations of these dynamic processes in the probed volume between the nanoprobe tip and sample surface. Hence, a comprehensive and quantitative theoretical background for integrated scanning nanoprobes as well as data interpretation and correlation will be developed.

The proposed research applies innovative and multifunctional analytical techniques to elucidate complex chemical and biochemical processes at microbe-mineral interfaces. In addition to the development of the first generation of trifunctional scanning nanoprobes [i.e., providing simultaneous (electro)chemical, topographical and optical information in the nearfield regime], correlations with confocal microscopy will provide novel datasets for investigating cellular processes at mineral surfaces. Iron is one of the primary minerals utilized by microorganisms to oxidize organic carbon in soils and sediments. Elucidation of the mechanisms and kinetics of electron transfer to Fe(III) will provide rigorous and comprehensive insights into a globally important, yet poorly understood respiratory process carried out by microorganisms: organic carbon oxidation coupled to anaerobic Fe(III) reduction. This concept can be extended to investigation of a multitude of other complex environmental and biological problems, including biocorrosion, neurophysiology and cellular signaling events. Such investigations require rapid space-and-time resolved information because of the continuous changes associated with biological matrices (e.g., cells). Smart chemical attachment of Fe(III)-reducing whole cells or enzymes to inert tips or electrode surfaces will produce scanning bio-nanoprobes that facilitate studies of cell-surface interactions at unprecedented spatial scales. Mathematical modeling and simulation of the underlying electrochemical and physical processes at the nanometer scale will be based on new models derived from micro- and nanofluid dynamics.

Multifunctional analytical techniques providing information on various parameters correlated in space and time will have a substantial impact on investigation of complex bioprocesses. Besides elucidating biogeochemical pathways, the application of combined and integrated scanning nanoprobes can be expanded to the areas of membrane and tissue processes, neurophysiology, cell signaling, and biomedicine.

An additional goal of this proposal is to promote the interaction between students in science and engineering. We believe this interdisciplinary approach is necessary to foster new advances in research and technology at all levels, and in particular between biologists, chemists, and engineers. This proposal will provide opportunities for the PIs, graduate and undergraduate students, and high-school teachers to engage in joint efforts to promote the excitement of discovery. A new generation of scientists will result from the proposed research and educational activities.

Multifunctional Scanning Nanoprobes for In Situ Analysis of Chemical Processes at Microbe/Mineral Interfaces