Redox Switchable Polydopamine-Modified AFM-SECM Probes: A Probe for Electrochemical Force Spectroscopy

Area of Science:

• Materials Science
• Surface Chemistry
• Biotechnology

Background:

• Polydopamine (PDA) is a versatile thin film material with high potential in biorelevant applications due to its abundant functional groups.
• PDA's surface functionality can be modified, offering opportunities for advanced material design.
• Atomic Force-Scanning Electrochemical Microscopy (AFM-SECM) is a powerful technique for surface analysis and force measurements.

Purpose of the Study:

• To modify conductive AFM-SECM probes with electrochemically deposited PDA for quantitative electrochemical adhesion studies.
• To enable potential-controlled adhesion measurements by altering PDA surface functionality.
• To investigate the influence of surface charges on adhesion interactions with various surfaces and bacterial cells.

Main Methods:

• Electrochemical deposition of PDA onto conductive AFM-SECM probes.
• Utilizing potential control to oxidize or reduce PDA functional groups, switching surface properties.
• Performing electrochemical force spectroscopy on model surfaces (gold, SAMs) and bacterial cells (Pseudomonas fluorescens).

Main Results:

• PDA-modified AFM-SECM probes demonstrated switchable adhesion properties under potential control.
• Adhesion forces varied significantly with probe polarization (e.g., 6.2 ± 2.2 nN for positive vs. 2.6 ± 1.1 nN for negative polarization on gold).
• Switchable probes successfully measured adhesion forces of Pseudomonas fluorescens, showing reduced adhesion with negative polarization (1.1 ± 0.7 nN).

Conclusions:

• Electrochemical control of PDA surface functionality provides a versatile method for quantitative adhesion studies.
• Switchable PDA-modified AFM-SECM probes are effective for investigating surface charge-dependent interactions.
• This technique offers new possibilities for studying cell adhesion and material surface interactions in biorelevant contexts.