Mixed-Charge Surface Based on Conjugated Polymer Nanoparticles Enables Controllable Antibacterial Activity

Area of Science:

• Biomaterials Science
• Nanotechnology
• Antimicrobial Research

Background:

• Effective photodynamic antibacterial strategies require close contact between photosensitizers and bacteria.
• Cationic groups improve bacterial binding but cause membrane disruption and dark toxicity.

Purpose of the Study:

• To engineer mixed-charge surfaces on conjugated oligomer nanoparticles for controllable antibacterial performance.
• To investigate the impact of surface charge engineering on nano-bio interactions and photodynamic efficacy.

Main Methods:

• Assembly of photofunctional nanoparticles (OFTFNPs) using charge-complementary conjugated oligomers (OFTF(+) and OFTF(-)) at varying molar ratios.
• Characterization of interfacial interactions, reactive oxygen species generation (Type II mechanism), bacterial eradication, dark toxicity, and cytocompatibility.

Main Results:

• Mixed-charge OFTFNPs achieved stable bacterial binding with reduced nonspecific damage compared to purely cationic nanoparticles.
• Balanced nano-bio interface facilitated Type II reactive oxygen species generation upon light irradiation.
• OFTFNPs demonstrated potent photodynamic antibacterial activity with significantly reduced dark toxicity and improved cytocompatibility.

Conclusions:

• Mixed-charge surface engineering on nanoparticles provides a strategy for tunable antibacterial efficacy.
• This approach successfully decouples potent photodynamic antibacterial activity from undesirable cationic dark cytotoxicity.
• The findings offer a promising platform for developing safer and more effective photodynamic antibacterial agents.