Phenolic compounds are toxic and can be found in food and beverages (such as whiskey, vegetables, fruits), household products (disinfectants, paints) and in the environment due to industrial waste. They are easily absorbed by the skin, act as carcinogens, and cause damage to the red blood cells and the liver. Inappropriate concentrations of phenolic compounds are responsible for neurodegenerative diseases such as: Parkinson’s or Alzheimer’s.
Current detection methods of phenols, such as chromatographic and spectrophotometric analyses have proven to be costly and labor intensive. Electrochemical methods offer a less expensive approach to attain lower detection limits when compared to traditional methods. This research focuses on electrochemical methods to develop an optimal biosensor that employs a polymer-semiconductor-enzyme junction to detect and catalyze the redox reactions of catechol to quinone. Two biosensors involved in this research consisted of GC|Poly(indole-5-carboxylic acid)|Tyrosinase and GC|Poly(indole-5-carboxylic acid)|CdS|Tyrosinase.
Cyclic voltammetry (CV) was used to characterize the redox processes of the biosensor in various solutions, while chronoamperometry was used to measure how the current of the working electrode changed over time as catechol was added to the solution in small aliquots. Both biosensors were tested in the dark, under illumination, when the enzyme was immobilized to the biosensor's surface and when it was free floating in solution. The data was analyzed and plotted into Michaelis-Menten and Lineweaver-Burke plots and the K_M values were determined under these four conditions mentioned above.
The most optimal biosensor that showed a high efficiency and reliability was the GC|Poly(indole-5-carboxylic acid)|CdS|Tyrosinase under illumination. The K_M values produced under these conditions were lower than the K_M values produced when CdS was not present, when the enzyme was free floating in solution, and when the biosensor was not exposed to illumination.

Matthew Mistretta

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