<p>Amino-Functionalized Nitrogen-Doped Graphene Quantum Dots for Efficient Enhancement of Two-Photon-Excitation Photodynamic Therapy: Functionalized Nitrogen as a Bactericidal and Contrast Agent</p>

Abstract

Background: Although graphene quantum dots (GQDs) have received considerable research attention for their applications in various fields, the use of GQDs, such as nitrogen-doped GQDs (N-GQDs) and amino-functionalized N-GQDs (amino-N-GQDs), as photosensitizers to facilitate photodynamic therapy (PDT) has received limited research intention. To address this research gap, this study prepared novel amino-N-GQDs and investigated their properties. Methods: The amino-N-GQDs subjected to two-photon excitation (TPE) exhibited remarkable bactericidal capability in PDT. The bonding compositions of nitrogen and the aminofunctionalized group played a critical role in their antimicrobial effects. Results: Compared with amino-group-free N-GQDs and amino-N-free GQDs, the amino-N-GQDs generated a higher amount of reactive oxygen species, demonstrating their superior efficacy for two-photon PDT. Additionally, the intrinsic luminescence properties and high photostability of the amino-N-GQDs demonstrate their suitability as an effective two-photon contrast agent for tracking bacteria during two-photon biomedical imaging. Conclusion: The amino-N-GQD and their remarkable properties may provide an efficient alternative approach for observing and easily eliminating malignant microbes in the future.

Nitrogen Functionalities of Amino-Functionalized Nitrogen-Doped Graphene Quantum Dots for Highly Efficient Enhancement of Antimicrobial Therapy to Eliminate Methicillin-Resistant Staphylococcus aureus and Utilization as a Contrast Agent

“…However, based on the XRD findings, the basal plane was not considerably functionalized. This finding aligns with the theory that, compared with in-plane carbons, graphene has considerably more active edges, and functional groups are present at the amino-N-GQD edges [ 15 ]. The large basal spacing of the amino-N-GQDs is due to the accommodation of several oxygen species, such as epoxy, hydroxyl, and amino groups, and alteration of the carbon hexahedron grid plane, resulting in greater graphene layer spacing.…”

“…The intensity of 1 O2 was measured by monitoring the fluorescence intensity of the singlet oxygen sensor green (SOSG) reagent and trans-1-(2′-methoxyvinyl)pyrene (t-MVP). Moreover, the intensity of O2 − was detected using the 470-nm absorbance of 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) and the absorbance of γ-L-glutamyl-L-cysteinyl-glycine (GSH) after the bacteria were incubated with the material [15,17]. The materials generated 1 O2 The different incubation times had no influence on the bacterial viability; however, the viability level visibly decreased with dose (Table 1).…”

“…This photostability resulted in reduced photobleaching ( Figure 7 e) and high stability in physiological environments, even after 8 weeks ( Table S6 , which corresponds to Figures S8 and S9 ). MRSA viability was determined by fluorescence and quantification ( Figure 8 ) [ 15 ]. After photoexcitation, the generated ROS required additional incubation to effectively process the PDT action.…”

“…In PDT, ROS are formed when molecular oxygen reacts with a photoexcited photosensitizer (PS) exposed to a suitable wavelength of light source and energy [ 15 ]. Photosensitized reactions involving oxygen are categorized as type I or II.…”

Strategies to Improve Photodynamic Therapy Efficacy of Metal-Free Semiconducting Conjugated Polymers

“…First, doping GQDs with heteroatoms N, 123 Cl, 124 F, 125 Eu, Ag, and Se 126 is an effective method, which can change its electronic density and optical properties to improve ROS generation efficiency. Second, PS-doped GQDs could enhance PDT.…”