Human monocyte morphology is affected by local substrate charge heterogeneity

Area of Science:

• Cell Biology
• Biophysics
• Materials Science

Background:

• Cell-substrate interactions are influenced by topological, chemical, and electrical properties.
• Previous research often overlooked or confounded electrical effects in cell-surface studies.
• Nanofabrication enables precise control over substrate properties, including surface charge density.

Purpose of the Study:

• To investigate the response of human monocytes to controlled surface charge heterogeneity.
• To determine if electrical surface properties alone can influence cell behavior.
• To explore the role of local surface charge in cell morphology and function.

Main Methods:

• Utilized nanofabrication to create optically transparent polystyrene surfaces with patterned charge domains (3.3 microns wide).
• Incubated human monocytes on these patterned substrates under charge-neutral conditions.
• Challenged cells with phagocytic triggers (opsonized zymosan particles) and analyzed cell area and perimeter.
• Conducted ultrastructural studies on silicon dioxide substrates to assess morphological changes.

Main Results:

• Human monocytes showed a greater than twofold increase in cell area and perimeter in response to patterned surface charges.
• These cellular responses were time-dependent and linked to significant charge density.
• Ultrastructural analysis revealed charge-density-dependent qualitative morphological differences in monocytes.
• Cellular responses occurred in the absence of variations in substrate topology and composition.

Conclusions:

• Human monocytes are sensitive to local surface charge heterogeneity.
• Electrical properties of substrates play a significant role in cell behavior and morphology.
• This study establishes a novel method for studying cell-electrical surface interactions independently.