Development of efficient nanozymes for biosensing and degrading biofilms

다국어 초록 (Multilingual Abstract)

In the first study, copper-anchored nitrogen-doped graphene quantum dots (Cu@N-GQDs) were developed as multifunctional nanozymes exhibiting dual-mode optical sensing capabilities. Through one-pot hydrothermal synthesis, Cu2O species were uniformly anchored onto N-GQDs, yielding nanocomposites (3.2 ± 0.4 nm) with preserved fluorescence emission and enhanced peroxidase-like activity. The Cu@N- GQDs enabled highly sensitive and selective detection of sulfide ions (S2-) via two complementary mechanisms: fluorescence quenching (LOD: 0.5 µM) and suppression of catalytic TMB oxidation (LOD: 3.5 µM), both triggered by Cu-S complex formation. The sensing platform demonstrated excellent selectivity against common interferents and achieved recovery rates of 95.4-104.6% in spiked tap water samples, validating its practical applicability for environmental monitoring. In the second study, L-arginine-functionalized zirconium-based metal-organic framework (Arg-ZrMOF) was synthesized to combat bacterial biofilms through enhanced hydrolase-like activity. A controlled three-step approach-solvothermal synthesis, acid-induced defect engineering (1M HCl, 4h), and post-synthetic Arginine modification yielded a stable material with preserved MOF-808 topology and substantially improved catalytic performance. Arg-ZrMOF exhibited DNase- mimicking phosphodiesterase activity with Michaelis-Menten kinetics (Km = 0.54 mM for BnPP), representing markedly higher substrate affinity than pristine MOF- 808. The cationic guanidinium groups of arginine enhanced electrostatic substrate recruitment while simultaneously disrupting bacterial adhesion. Biofilm assays against Escherichia coli demonstrated concentration-dependent efficacy, achieving up to 80% inhibition of biofilm formation and 70% degradation of mature biofilms at 1.0 mg/mL. SEM, crystal violet staining, and fluorescence microscopy confirmed substantial disruption of biofilm architecture and EPS matrix. Arg-ZrMOF maintained catalytic activity across harsh pH (4-10) and temperature (4-90°C) conditions, significantly outperforming natural enzymes. Collectively, this research demonstrates how compositional design, defect engineering, and surface functionalization can be strategically integrated to develop nanozymes with tailored catalytic properties. Cu@N-GQDs exemplify the integration of fluorescence and catalytic functions for dual-mode chemical sensing, while Arg- ZrMOF showcases synergistic mechanisms combining hydrolytic degradation with anti-adhesion properties for biofilm control. These findings advance the fundamental understanding of nanozyme design principles and establish practical platforms for environmental diagnostics and antimicrobial applications. The insights gained provide a foundation for developing next-generation multifunctional nanozymes capable of addressing diverse challenges in analytical chemistry, biomedical engineering, and environmental science.

목차 (Table of Contents)

• CHAPTER 1. Introduction 1
• 1.1 Nanozymes and their applications in biosensing and degrading biofilm. 1
• 1.2 Focus on current research 3
• CHAPTER 2. Dual-mode optical sulfide sensing enabled by copper-anchored N-doped graphene quantum dot nanozymes 7
• 2.1 Introduction 7
• 2.2 Experimental details. 9
• 2.2.1 Characterization of samples 9
• 2.2.2 Preparation of nanozymes 9
• 2.2.3 Sulfide ion detection via Cu@N-GQDs 10
• 2.2.4 Dual-mode optical sensing (colorimetric and fluorometric) 10
• 2.2.5 Sulfide ion detection in environmental samples 11
• 2.3 Results and discussion 12
• 2.3.1 Cu@N-GQDs nanozyme construction 12
• 2.3.2 Sulfide ion detection via fluorometric assay 18
• 2.3.3 Sulfide ion detection via colorimetric Assay 19
• 2.3.4 Application in environmental samples 21
• 2.4 Summary 22
• CHAPTER 3. L-Arginine-functionalized ZrMOF for enhanced biofilm degradation via hydrolase-like activity 28
• 3.1 Introduction 28
• 3.2 Experimental details 30
• 3.2.1 Synthesis and characterization of L-Arginine-functionalized ZrMOF 30
• 3.2.2 Characterization methods 31
• 3.2.3 Catalytic activity assays 31
• 3.2.4 Biofilm formation and degradation studies 32
• 3.3 Results and discussion 34
• 3.3.1 Arg-ZrMOF synthesis and characterization 34
• 3.3.2 Hydrolase-like activity of Arg-ZrMOF 38
• 3.3.3 Biofilm degradation efficiency 41
• 3.4 Summary 44
• CHAPTER 4. Conclusion 49
• Acknowledgement 50