Cationic Polymer Brushes Functionalized with Carbon Dots and Boronic Acids for Bacterial Detection and Inactivation

Abstract

Drug-resistant bacterial infections are among the most severe physiological challenges facing human health. Therefore, the detection and inactivation of pathogenic bacteria remains a crucial therapeutic goal in modern society. In this study, we design multifunctional nanocomposites aimed at bacterial binding, fluorescence labeling, and synergistic antibacterial treatment. These nanocomposites are prepared by introducing cationic polymers with quaternary ammonium compounds onto silica nanoparticles using surface-initiated atom transfer radical polymerization, followed by incorporation of copper-doped carbon dots and modification of boronic acid. The cationic polymer units and boronic acid end groups enhance the bacterial binding capacity and synergistic bactericidal effects in cooperation with the carbon dots. Due to the stable fluorescent properties of carbon dots, the nanocomposites can generate fluorescence signals around bacteria, enabling bacterial fluorescence imaging. Overall, this study demonstrates a multifunctional nanocomposite-assisted strategy for bacterial labeling, imaging, and deactivation, providing a novel approach for bacterial detection and synergistic treatment.

Scheme 1. Schematic Illustration for the Synthesis of the Multifunctional Nanocomposite Si@co@BA and Application of the Material for Binding, Detection, and Inactivation of Bacteria

Figure 1

SEM and TEM images of (a,d) Si@BiBB, (b,e) Si@co, and (c,f) Si@co@BA. Scale bar in (a–c): 100 nm; (d–f): 50 nm.

Figure 2

TGA analysis of Si@BiBB and Si@co.

Figure 3

(a) UV–vis spectra of CDs. (b) Maximum fluorescence excitation and emission fluorescent spectra of CDs (excitation: 400 nm). (c) Excitation wavelength dependence of CDs.

Figure 4

(a) FTIR spectra of Si@BiBB, Si@co, and Si@co@BA. (b) Zeta potential of Si@NH₂, Si@BiBB, Si@co, Si@co@CDs, Si@co@BA, and CDs.

Figure 5

(a) Photographs and (b) corresponding cell survival rate of Escherichia coli treated with different concentrations of Si@co@BA.

Figure 6

(a) Photographs and (b) corresponding cell survival rate of E. coli treated with 1 mg/mL of Si@co, Si@co@CDs, Si@co@BA, and 200 μg/mL of CDs.

Figure 7

(a–c) Photographs and (d) corresponding residual rate of remaining E. coli in the medium after treatment with Si@co@CDs and Si@co@BA. TEM images of E. coli mixed with (e) Si@co@CDs and (f) Si@co@BA. Scale bar: 1 μm.

Figure 8

Fluorescent microscope images of E. coli treated with Si@co@CDs and Si@co@BA (scale bar: 20 μm; excitation: 405 nm).