Post-functionalization of sulfur quantum dots and their aggregation-dependent antibacterial activity

Area of Science:

• Nanomaterials Science
• Biomedical Engineering
• Materials Chemistry

Background:

• Sulfur quantum dots (SQDs) are luminescent nanomaterials with promising physiochemical and optoelectronic properties.
• Limited surface functionalization hinders the biomedical applications of SQDs.
• Developing effective antibacterial agents requires novel nanomaterial strategies.

Purpose of the Study:

• To explore surface functionalization of SQDs using thiol ligands with tuneable properties.
• To evaluate the antibacterial efficacy of functionalized SQDs.
• To investigate the relationship between surface hydrophobicity and antibacterial activity.

Main Methods:

• Surface functionalization of SQDs with various thiol ligands.
• Assessment of antibacterial activity through minimum inhibitory concentration (MIC) determination.
• Evaluation of SQD aggregation and its effect on antibacterial efficacy.
• In vivo antibacterial assessments.

Main Results:

• Functionalized SQDs exhibited significantly higher antibacterial activity (10-25 ng/mL) compared to nonfunctionalized SQDs (10^5 times increase).
• A reverse trend was observed: increased surface hydrophobicity correlated with enhanced antibacterial activity.
• Higher surface hydrophobicity led to SQD aggregation, which consequently reduced antibacterial efficacy.
• In vivo studies corroborated the in vitro findings regarding hydrophobicity and aggregation effects.

Conclusions:

• Surface modification is crucial for enhancing the antibacterial potential of SQDs.
• Surface hydrophobicity plays a key role in the antibacterial efficacy of functionalized SQDs.
• Balancing surface hydrophobicity is essential to prevent aggregation and maximize antibacterial performance.