Single-Droplet/cell electrochemistry

biophysical electrochemistry

protein aggregation and condensation

antimicrobial susceptibility

Education

• Ph.D., University of Miami, Coral Gables, FL., 2000
• M.S., Universidad del Valle, Cali, Colombia, 1996
• B.S., Universidad del Tolima, Ibague, Colombia, 1989

Research Interests

Research in our lab centers around problems in biomedicine and technology wherein we apply electrochemistry to systems in which present approaches are insufficient to extract quantitative information from electrochemical measurements. For example, in viscoelastic fluids the dual liquid-solid behavior caused by polymers (e.g. proteins) precludes extracting bulk and molecular parameters from electrochemical currents
because Fick’s laws of diffusion are inapplicable to viscoelastic media (e.g. biological  fluids, tissues, polymer materials). Recently, we discovered that a decelerated mode of Non-Fickian diffusion called sub-diffusion can be measured electrochemically in viscoelastic protein hydrogels. We want to correlate sub-diffusion with the
degree of protein aggregation that occurs in neurodegenerative diseases (e.g. Alzheimer’s, Parkinson’s). Our goal is to reveal mechanisms of protein aggregation to test therapeutic hypotheses and develop diagnostic methods. We also want to study conventional polymer fluids to disclose diffusion-structure relationships for
applications in materials, food, and biotech industry.

Another research area in our lab revolves around using single-entity electrochemistry to characterize microscopic particles (e.g. microbial cells, microdroplets) as they collide in real time with miniaturized electrodes. We aim to relate the electrochemical current rendered by individual particles to their properties and physicochemical processes occurring inside and around them. For example, coupled with fluorescence microscopy we want to uncover mechanisms by which droplets divide spontaneously (and grow) in solution and when they collide with the surface of microscopic electrodes. This research will provide insights on how life-like behaviors might have arisen from non-living matter before the origin of life.

Select Publications

Wu, L., Ramirez, A., Vo, I.D., Haglund, E., Alvarez, J.C. “Can Electroactive Tracer Molecules Reveal Viscoelastic Structure by Measuring Non-Fickian Diffusion”, Angew. Chem. Int. Ed. 2025, e202425114.

Tubbs, A., Ahmed, J. U., Christopher, J., Alvarez, J.C., “Savitzky-Golay Processing and Bidemensional Plotting of Current-Time Signals from Stochastic Blocking Electrochemistry to Analyze Mixtures of Rod-Shaped Bacteria,” Anal. Methods, 2024, 16, 6570-6576.

Lutkenhaus, J.A., Ahmed, J.U., Hasan, M., Prosser, D. C., Alvarez, J.C., “Average Collision Velocity of Single Yeast Cells during Electrochemically Induced Impacts”, Analyst, 2024, 149, 3214-3223.

Ahmed, J.U., Lutkenhaus, J.A., Tubbs, A., Nag, A., Christopher, J., and Alvarez, J.C.,
“Estimating Average Velocities of Particle Arrival Using the Time Duration of the Current Signal in Stochastic Blocking Electrochemistry”, Anal. Chem., 2022, 94, 16560-16569.

Ahmed, J.U., Lutkenhaus, J.A., Alam, M.S., Marshall, I., Paul, D.K., Alvarez, J.C., “Dynamics of Collisions and Adsorption in the Stochastic Electrochemistry of Emulsion Microdroplets”, Anal. Chem., 2021, 93, 7993-8001.

Awards

• National Science Foundation Career Award 2007
• Excellence in Scholarship Award, College of Humanities and Sciences, VCU, 2007
• Outstanding Graduate Student Award, University of Miami, 2000