Aaron R. Clapp
Assistant Professor
3033 Sweeney Hall
Iowa State University
Ames, IA 50011-2230
Phone (515) 294-9514
Fax (515) 294-2689
clapp
iastate.edu
Education
B.S., Chemical Engineering, University of Minnesota (1996)
M.S., Biomedical Engineering, University of Florida (2000)
Ph.D., Chemical Engineering, University of Florida (2001)
Honors
Ray W. Fahien Teaching Assistant Award,
Dept. of Chemical Engineering, University of Florida, 2000
National Research Council (NRC) Postdoctoral Fellow,
Naval Research Laboratory, 2002-present
Tau Beta Pi
Teaching/Office Hours Schedule
Research Interests
• Optical microscopy techniques (optical trapping, fluorescence, multi-photon, etc.)
• Colloidal behavior and interfacial phenomena
• Measurement of forces and interactions in biological systems
• Nanocrystal synthesis and applications
• Optical spectroscopy
• Energy transfer in molecular systems
• Biosensor development
Research
I am principally interested in the study interfacial phenomena, particularly in biological systems and in size regimes where surface area effects begin to dominate the behavior of materials (i.e., colloids). As a classical example, the stability and rheology of colloidal particles in solution are largely determined by forces that are a result of their surface and bulk material properties. These fundamental interactions govern the stability of colloidal dispersions and are also relevant to far more complex systems like bacteria, eukaryotic cells, and viruses. In biological systems, fundamental interaction forces play a critical role in phenomena such as bacterial adhesion and internal cellular mechanics. Understanding how these forces contribute to the behavior of colloidal or biological systems is a continuing goal in biomedical engineering not only from a fundamental perspective, but also in the rational design of novel biomaterials and engineered systems. Additionally, I am interested in the application of engineered nanomaterials as a novel tool for investigating biological processes.
As a general theme, my research focuses on colloidal phenomena in biological systems. This includes two principal thrusts: 1. synthesis, characterization, and applications of biocompatible nanoparticles (notably luminescent quantum dots) and 2. development of optical microscopy-based techniques for observing nanoscale interactions and processes. Regarding the first thrust, the motivation for synthesizing nanoparticles is to precisely tailor their properties for specific applications (e.g., cell imaging, biosensing, etc.). There is intense interest in studying the fundamental properties of colloidal quantum dots and other related nanomaterials, however I am primarily interested in using these engineered materials for specific experimental investigations. Recently published advances in synthetic reaction schemes now allow relatively simple approaches for generating robust nanoparticles for biological applications. Nanomaterials such as quantum dots have opened new avenues of research and provide truly unique materials for developing diagnostic tools in the biological sciences. Previous work in this area has shown that QDs have vast potential for long-term imaging and biosensing applications due to their small size and unique photophysical properties. Much of the previous literature only hints at the potential of these materials in biotechnology.
With respect to the second thrust, we utilize a highly sensitive, multifunctional optical trapping microscopy system that can probe small-scale interaction forces acting on colloidal scale objects. This system can be used to measure both non-specific and specific forces that arise due to bulk, surface, and biologically specific properties of colloids. Of particular interest are intracellular processes, cell–cell interactions, and biological interactions with relevant surfaces. It can also impart suitably small forces on objects that have covalently attached colloidal “handles” such as oligonucleotides tethered to a polymer sphere or a protein-coated nanoparticle. In addition, the system integrates significant fluorescence capabilities. This includes capabilities for fluorescence cell imaging, single molecule detection, total internal reflection fluorescence (TIRF), multiphoton excitation, energy transfer, and optical spectroscopy. The combination of these capabilities (often used simultaneously) affords us a highly versatile and unique platform for probing relevant biological phenomena, often in vivo, at very small length scales (<1 μm). Methods such as light scattering, interferometry, and fluorescence localization allow us to quantitatively assess interactions occurring on length scales well below the diffraction limit, a domain not typically associated with optical microscopy, while preserving the non-invasive advantages associated with optical techniques.
Selected Publications
A. R. Clapp, I. L. Medintz, H. Mattoussi, “Förster Resonance Energy Transfer Investigations Using Quantum Dot Fluorophores” ChemPhysChem, 7, 47-57 (2006). (invited review)
I. L. Medintz, A. R. Clapp, J. S. Melinger, J. R. Deschamps, H. Mattoussi, “A Reagentless Biosensing Assembly Based on Quantum Dot-Donor Förster Resonance Energy Transfer” Adv. Mater., 17, 2450-2455 (2005).
E. R. Goldman, I. L. Medintz, J. L. Whitley, A. Hayhurst, A. R. Clapp, H. T. Uyeda, J. R. Deschamps, M. E. Lassman, H. Mattoussi, “A Hybrid Quantum Dot-Antibody Fragment Fluorescence Resonance Energy Transfer-Based TNT Sensor” J. Am. Chem. Soc., 127, 684-688 (2005).
A. R. Clapp, I. L. Medintz, B. R. Fisher, and H. Mattoussi, “Can Luminescent Quantum Dots be Efficient Energy Acceptors with Conventional Dye Donors in Fluorescence Resonance Energy Transfer Assays?” J. Am. Chem. Soc., 127, 1242-1250 (2005).
I. L. Medintz, J. H. Konnert, A. R. Clapp, I. Stanish, M. E. Twigg, H. Mattoussi, J. M. Mauro, and J. R. Deschamps, “A Fluorescence Resonance Energy Transfer-Derived Structure of a Quantum Dot- Protein Bioconjugate Nanoassembly” Proc. Nat. Acad. Sci. USA, 101, 9612-9617 (2004).
H. Mattoussi, I. L. Medintz, A. R. Clapp, E. R. Goldman, J. K. Jaiswal, S. M. Simon, and J. M. Mauro, “Luminescent Quantum Dot-Bioconjugates in Immunoassays, FRET, Biosensing and Imaging Applications,” Journal of the Association for Laboratory Automation (JALA), 9, 28-32 (2004).
E. R. Goldman, A. R. Clapp, G. P. Anderson, H. T. Uyeda, J. M. Mauro, I. L. Medintz, and H. Mattoussi, “Multiplexed Toxin Analysis Using Four Colors of Quantum Dot Fluororeagents,” Anal. Chem., 76, 684-688 (2004).
A. R. Clapp, I. L. Medintz, J. M. Mauro, B. R. Fisher, M. G. Bawendi, and H. Mattoussi, “Luminescent Quantum Dot Bioconjugates in Fluorescence Resonance Energy Transfer (FRET) Assays,” J. Am. Chem. Soc., 126, 301-310 (2004).
A. R. Clapp and R. B. Dickinson, “Direct Measurement of Static and Dynamic Forces between a Colloidal Particle and a Flat Surface Using a Single-Beam Gradient Optical Trap and Evanescent Wave Light Scattering” Langmuir, 17, 2182-2191 (2001).
