Modeling microelectrode biosensors: free-flow calibration can substantially underestimate tissue concentrations

Area of Science:

• Biosensing and electrochemical analysis
• Biomedical engineering
• Neuroscience

Background:

• Microelectrode amperometric biosensors are crucial for measuring analytes like glucose and glutamate in biological samples.
• Current calibration methods often overlook the complex tissue environment, potentially leading to inaccurate measurements.
• The influence of the macroscopic tissue environment on biosensor performance requires further investigation.

Purpose of the Study:

• To identify and quantify the underestimation of analyte concentrations in tissue due to standard biosensor calibration methods.
• To develop a more accurate model for biosensor calibration in complex tissue environments.
• To experimentally validate the proposed modeling approach.

Main Methods:

• Mathematical modeling of analyte diffusion and enzymatic reaction within the biosensor and surrounding tissue.
• Experimental verification of model predictions using biosensors in controlled diffusive environments.
• Comparison of biosensor responses under free-flow versus simulated tissue conditions.

Main Results:

• Standard free-flow calibration leads to underestimation of analyte concentrations in tissue.
• Analyte diffusion and enzymatic breakdown create a concentration gradient near the biosensor surface in tissue.
• Tissue properties like porosity and tortuosity further exacerbate the underestimation.

Conclusions:

• Naive free-flow calibration of microelectrode biosensors is inadequate for accurate tissue analyte concentration determination.
• The developed mathematical models provide a better quantification of the discrepancy between calibration and tissue environments.
• Experimental validation confirms the significant impact of the tissue environment on biosensor measurements.