Multifunctional Cu-MSN@GCDs Nanocomposites Integrating Environment-Responsive Antibacterial Activity and Real-Time Fluorescence Monitoring

Abstract

In this study, Cu²⁺-doped mesoporous silica nanoparticles (MSNs) (Cu-MSNs) were synthesized via a hydrothermal method, using MSNs as the host matrix. Subsequently, green-emissive carbon dots (GCDs) were covalently grafted onto the surface of Cu-MSNs through an amidation reaction, yielding a nanocomposite denoted as Cu-MSN@GCDs. Cu-MSN@GCDs were designed to combine antibacterial and cellular imaging functions. The GCDs, derived from sodium citrate and formamide, exhibited fluorescence stability in a pH range of 3.0-10.0 and possessed a specific Cu²⁺fluorescence quenching property, enabling the detection of micromolar Cu²⁺. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses confirmed that Cu-MSN@GCDs nanocomposites were successfully constructed. In vitro experiments showed that Cu-MSN@GCDs underwent significant degradation and released Cu²⁺under acidic conditions (pH=4.8), and effectively inhibited the growth of Staphylococcus aureus (S. aureus), with a minimum inhibitory concentration (MIC) of 0.500 mg/mL. Additionally, the fluorescence imaging test showed a good multichannel color rendering ability in 4T1 cells. The nanocomposite combines environment-responsive antibacterial activity and real-time fluorescence monitoring function, providing a new strategy for the development of multifunctional nano-drug delivery systems.

Keywords

mesoporous silica nanoparticle (MSN) / carbon dots doping / Cu²⁺quenching / antibacterial property / cellular imaging