Design, Fabrication and Performance Evaluation of an Impedimetric Urea Biosensor System

An impedance bioanalyzer system comprising an in-vitro biotransducer, instrumentation and control software for the measurement of urea, potentially in blood dialysate, has been developed. The biotransducer comprises of a microlithographically fabricated interdigitated microsensor electrode (IME) onto which was cast a biorecognition layer conferred with the specificity of the enzyme urease. Urease hydrolysis of urea produces NH4+, HC03- and OH- ions that decrease the device's impedance. The temporal rate of change (kinetic) and the extent of change (equilibrium) of ion concentration were measured as the sensor's response. Five formats: [i) unPEGylated urease-containing poly(hydroxyethylmethacrylate) [p(HEMA)] hydrogel, ii) PEGylated urease-containing p(HEMA) hydrogel, iii) via glutaraldehyde crosslinking in the presence of albumin, iv) the direct covalent immobilization of urease to the IME, and v) solution borne urease]. Michaelis-Menten parameters KM, ZMAX and kcat revealed the following rank: PEGylated urease-Gel >> Free Urease > unPEGylated urease-Gel = BSA in Glutaraldehyde > covalently immobilized urease. The unPEGylated-urease sensor provided a higher enzyrne- substrate binding rate and catalysis rate than PEGylated and thus provided a faster impedimetric response to various molar concentrations of urea. Long-term stability (one month) of the PEGylated-urease hydrogel was favorable. A dedicated three-element array impedimetric instrument, the 3EIC BioAnalyzer was designed and produced. A pair of demodulating logarithmic amplifiers (AD8302) was used to calculate the change in phase and amplitude corresponding to the impedimetric response to a 4.0 kHz, 50 mVPP sine wave from a function generator (MAX038). A graphic user interface (GUI), programmed in LabVIEW 7.0 established instrument control, data acquisition via a USB-48A-30A16 μDAQ and graphical data presentation of temporal impedimetric responses.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Chemical Engineering

Year dc:date.available

2005

Author dc:creator

• Gupta, Vandana

Contributors dc:contributor

• Dr. Anthony Guiseppi

• cell circuit
• biotransducer
• bioanalyzer
• hydrogel
• biosensor
• dialysis
• impedimetric detection
• electrochemical impedance
• IME
• Chemical Engineering
• Engineering

Statement dc:rights

• © The Author

Identifier

https://scholarscompass.vcu.edu/etd/890

OAI identifier oai:identifier

oai:scholarscompass.vcu.edu:etd-1889