Lee MacKenzie Fischer

An electrochemical-cantilever platform for hybrid sensing applications

This work presents a fully-functional, microfabricated electrochemical-cantilever hybrid platform with flow control. A new cantilever chip format is designed, fabricated, and mounted in a custom polymer flow cell. Issues such as leakage and optical/electrical access are addressed, and combined mechanical and electrochemical performance is investigated. Lastly, a cantilever is “defunctionalized” in situ to create a reference cantilever for differential measurements in detection of Cu2+ ions at concentrations of 10 µM and 100 nM.

An electrochemical-cantilever hybrid sensor for metal ions

In this work we have demonstrated a peptide-functionalized cantilever sensor with integrated electrochemical capabilities. Silicon nitride cantilevers with gold electrodes are functionalized with the chelating peptide Cys-Gly-Gly-His (CGGH) to capture Cu2+ ions from solution. Upon binding the copper ion the peptide folds, creating steric hindrance and causing compressive stress in the monolayer, deflecting the cantilever downward. Ethylenediaminetetraacetic acid (EDTA) was used to remove the copper ions from the peptide, regenerating the layer. A Cysteine monolayer deflected the cantilever upward with Cu2+ ions, indicating tensile stress in the layer, suggesting a different coordination scheme than the CGGH peptide layer.

Exploration of two methods for quantitative Mitomycin C measurement in tumor tissue in vitro and in vivo

Two methods of quantifying Mitomycin C in tumor tissue are explored. A method of ultraviolet-visible absorption microscopy is developed and applied to measure the concentration of Mitomycin C in preserved mouse tumor tissue, as well as in gelatin samples. Concentrations as low as 60 μ M can be resolved using this technique in samples that do not strongly scatter light. A novel method for monitoring the Mitomycin C concentrations inside a tumor is developed, based on microdialysis and ultraviolet-visible spectroscopy. A pump is used to perfuse a microdialysis probe with Ringer’s solution, which is fed to a flow cell to determine intratumor concentrations in real time to within a few μ M. The success and limitations of these techniques are identified, and suggestions are made as to further development. To the authors’ knowledge these are the first attempts made to quantify Mitomycin C concentrations in tumor tissue.