Current research efforts in our laboratory are focused on: 1) the design and study of novel electrochemical and optical chemical sensors based on thin polymeric films doped with selective host compounds (especially metal-ligand complexes); 2) the synthesis, characterization and biomedical applications of polymeric materials that release/generate nitric oxide (NO); and 3) development of novel non-separation immunoassay methods.
In the area of chemical sensors we are investigating the use of various metal-ligand complexes (including metalloporphyrins) as anion/gas recognition agents within thin polymeric films to create new electrochemical and optical anion and gas selective sensors. Selective anion or gas molecule coordination to the metal ion center of these complexes can yield changes in membrane potentials (voltage across the polymeric films) and/or the optical absorbance or fluorescence spectra of the complexes within the polymeric phase. Of particular interest is our recent discovery of an interesting dimer-monomer equilibrium of certain metalloporphyrins (In(III), Ga(III), Zr(IV), Sn(IV) octaethyl- and tetraphenyl-porphyrins ) within polymers, with dimers converted to monomers in the presence of anions or volatile species that can coordinate strongly with the central metal ion of the complexes. A large change in the optical properties of the films is associated with this process, and this chemistry provides a completely new transduction mode to devise chemical sensors.
We are also developing methods to improve the biocompatibility of implantable electrochemical/optical gas/ion sensors via use of novel nitric oxide (NO) release polymers. Polymers such as polyurethane, poly(vinyl chloride), and polydimethylsiloxane are being synthesized with pendant diazeniumdiolate functional groups (adducts of NONO with secondary amines). These groups slowly release NO as water is absorbed into the polymer. Owing to the potent anti-platelet aggregating activity of NO, the resulting polymers exhibit a dramatic decrease in platelet adhesion (compared to blank films) during both in vitro and in vivo experiments. New materials that contain immobilized Cu(II)-ligand sites are also being developed as biomimetic catalysts, to generate NO from endogenous nitrite and nitrosothiols already present in blood.
Our efforts in the area of immunoassay technologies are focused on devising rapid, non-separation electrochemical-based immunoassay methods to quantitate a wide range of species, ranging from small environmental analytes (e.g., herbicides) to intact bacterial and viruses. In a collaborative project with researchers in the Electrical Engineering Department, electrically conducting polymers coated on magnetic particles are being used to devise a new generation of conductometric immunosensors for detecting large proteins as well as intact organisms, without any discrete separation of sample components.
Ralph N. Adams Award in Bioanalytical Chemistry, 2013
Rackham Distinguished Faculty Achievement Award, 2011
Charles N. Reilley Award in Electroanalytical Chemistry, 2006
Rackham Distinguished Graduate Mentor Award, 2006
ACS Analytical Chemistry Award in Electrochemistry, 2003
Philip J. Elving Collegiate Professor of Chemistry
M. Pietrzak and M. E. Meyerhoff, “Polymeric Membrane Electrodes with High Nitrite Selectivity Based on Rhodium(III) Porphyrins and Salophens as Ionophores,” Anal. Chem., 81, 3637-3644 (2009).
T. C. Major, D. O. Brant, M. M. Reynolds, R. H. Bartlett, M. E. Meyerhoff, H. Handa, and G. M. Annich, "A Nitric Oxide Releasing Polymer Attenuates Platelet and Monocyte Activation in Rabbit Model of Extracorporeal Circulation," Biomaterials, 31, 2736-2745 (2010).
L. Wang and M. E. Meyerhoff, “Quantitative Determination of High Charge Density Polyanion Contaminants in Biomedical Heparin Preparations Using Potentiometric Polyanion Sensors," Electroanalysis, 22, 26-30 (2010).
K. Gemene and M. E. Meyerhoff, "Reversible Detection of Heparin and Other Polyanions by Pulsed Chronopotentiometric Polymer Membrane Electrode," Anal. Chem., 82, 1612-1615 (2010).
M. M. Reynolds, J. E. Saavedra, B. M. Showalter, C. A. Valdez, A. P. Shanklin, B. K. Oh, L. K. Keefer, and M. E. Meyerhoff, "Tailored Synthesis of Nitric Oxide Releasing Polyurethanes using O2-Protected Diazeniumdiolated Chain Extenders," J. Materials Chem., 20, 3107-3114 (2010).
L. Hofler and M. E. Meyerhoff, "Modeling the Effect of Oxygen on the Amperometric Response of Immobilized Organoselenium-Based S-Nitrosothiol Sensors," Anal. Chem., 83, 619-624 (2011).