“Self‐Capped” Carbon Dots with Excellent Anti‐Bacteria Effect and an Extremely Low Cytotoxicity Applied for Hand Sanitizer

Self-capped carbon dots (MC-CDs) synthesized from methylene blue and cetyltrimethylammonium chloride show photodynamic antibacterial activity under 660 nm light. Incorporating Zn²⁺ into the MC-CDs improves their antibacterial efficacy even in the absence of light. When formulated into a hand sanitizer, Zn@MC-CDs demonstrate high efficacy and very low cytotoxicity, being potentially as a safe and effective antibacterial agent for healthcare applications.

Abstract

The increasing challenge of antibiotic resistance necessitates the development of novel antibacterial strategies. In this study, a novel kind of self-capped carbon dots is synthesized from methylene blue (MB) and cetyltrimethylammonium chloride (CTAC), and named as MC-CDs that are specifically designed for enhanced photodynamic antibacterial activity. Under 660 nm laser irradiation, MC-CDs demonstrate high inactivation rates of Escherichia coli (96.83%) and Staphylococcus aureus (94.44%) at 14 and 18 µg mL⁻¹ effectively, disrupting bacterial cell membranes. The incorporation of zinc cations (Zn²⁺) doping further enhances the antibacterial potential of MC-CDs, enabling substantial efficacy even in the absence of light due to improved electrostatic interactions with bacterial membranes. In comparison to commercial agents such as salicylic acid, p-chloro-m-xylenol, and triclosan, Zn@MC-CDs exhibit superior antibacterial performance. When formulated into a hand sanitizer, Zn@MC-CDs maintained over 90% efficacy, displaying excellent stability and extremely low cytotoxicity, highlighting their potential for safe and effective use in personal hygiene products. This study introduces self-capped carbon dot as a promising antibacterial agent, addressing a critical need for advanced and reliable solutions in infection control.