Dielectrophoretic immobilization of proteins: Quantification by atomic force microscopy

Area of Science:

• Biophysics
• Nanotechnology
• Surface Science

Background:

• Dielectrophoretic force enables protein immobilization using alternating electric fields and nanoelectrodes.
• Accurate quantification of immobilized proteins is crucial for understanding and optimizing this process.

Purpose of the Study:

• To introduce and validate atomic force microscopy (AFM) as a quantification method for dielectrophoretic protein immobilization.
• To compare AFM with fluorescence microscopy for protein immobilization analysis.
• To investigate the influence of experimental parameters on protein immobilization.

Main Methods:

• Dielectrophoretic force applied via nanometer-sized electrodes.
• Protein immobilization experiments with systematic variation of voltage and duration.
• Quantification using Atomic Force Microscopy (AFM) and Fluorescence Microscopy.
• Calculation of electric field distribution.

Main Results:

• AFM revealed a linear correlation between immobilized protein amount and field application duration.
• Both AFM and fluorescence microscopy showed a square dependence of immobilized protein amount on applied voltage.
• AFM detected proteins obscured in fluorescence images due to low signal-to-noise ratio.
• AFM's high spatial resolution visualized protein distribution on single nanoelectrodes.
• Calculated electric field distribution agreed well with AFM measurements.

Conclusions:

• AFM is a powerful tool for quantifying dielectrophoretic protein immobilization, offering higher resolution and sensitivity than fluorescence microscopy.
• Understanding the relationship between experimental parameters and immobilization is key for optimizing nanodevices.
• AFM provides detailed insights into protein distribution at the nanoscale, crucial for applications in biosensing and nanotechnology.