The Complexation Properties of Self-Defensive Microgel-Modified Antimicrobial Surfaces

Area of Science:

• Biomaterials Science
• Surface Chemistry
• Antimicrobial Technology

Background:

• Biomaterial surfaces can be engineered for self-defense against bacterial colonization.
• Contact-activated antimicrobial release from microgels is a promising strategy.
• Understanding the complexation of antimicrobials with microgels is crucial for optimizing this strategy.

Purpose of the Study:

• To investigate the complexation of cationic antimicrobials (colistin and Sub5 antimicrobial peptide) with polyanionic poly(acrylic acid) microgels.
• To determine how this complexation influences the self-defensive properties of biomaterial surfaces.
• To elucidate the factors governing antimicrobial transfer from microgels to bacteria.

Main Methods:

• Synthesis of poly(acrylic acid) microgels via membrane emulsification.
• Electrostatic deposition of microgels onto polycaprolactone and glass surfaces.
• Loading microgels with colistin and Sub5 antimicrobial peptide.
• Coarse-grained molecular dynamics (CGMD) simulations.
• Small-Angle X-ray Scattering (SAXS) experiments.
• In vitro bacterial colonization assays and cell viability tests.

Main Results:

• Microgel loading with antimicrobials caused deswelling; Sub5 remained sequestered while colistin was released.
• CGMD simulations confirmed stronger Sub5/poly(acrylic acid) complexation compared to colistin.
• Sub5 antimicrobial peptide formed dimers and higher-order structures, enhancing complexation strength entropically.
• CGMD simulations showed a thermodynamic driving force for Sub5 transfer from microgels to Staphylococcus aureus membranes.
• Self-defensive surfaces reduced S. aureus colonization by over 90% and were cytocompatible.

Conclusions:

• The supramolecular structure of antimicrobial peptides significantly impacts their complexation strength with polyanionic microgels.
• Enhanced complexation, driven by factors like counterion release and peptide self-assembly, leads to effective, non-elutive antimicrobial surfaces.
• This strategy offers a promising approach for developing self-defensive biomaterials with reduced bacterial colonization and preserved cytocompatibility.