Formate Dehydrogenase 기반 MXene 도입 전기화학적 마이크로니들 센서를 활용한 지속적 CO2 모니터링 = MXene-Enhanced Electrochemical Microneedle Sensor based on Formate Dehydrogenase for Continuous CO2 Monitoring

다국어 초록 (Multilingual Abstract)

Chronical obstructive pulmonary disease (COPD) is characterized by impaired gas exchange and the accumulation of carbon dioxide (CO2), and as the disease progresses or during acute exacerbations, it can lead to respiratory failure characterized by hypercapnia. Continuous assessment of CO2 levels in such respiratory failure states is considered an important factor for evaluating the patient's respiratory status and monitoring clinical progression. However, the methods currently used in clinical settings for CO2 assessment have several limitations. Arterial blood gas analysis, the clinical standard for CO2 evaluation, is invasive and therefore unsuitable for repeated or continuous monitoring. In contrast, noninvasive methods such as end-tidal CO2 and transcutaneous CO2 monitoring are limited in measurement consistency and accuracy due to influences from skin condition, peripheral blood flow variations, and respiratory factors.
In this study, an electrochemical microneedle (MN) sensor capable of minimally invasive and continuous CO2 monitoring was developed to address these limitations. The MN surface was modified with amine-functionalized MXene (MXene-NH2) to enhance electrical conductivity and to provide active sites for enzyme immobilization. Formate dehydrogenase (FDH) was immobilized on a gold-based MN electrode modified with MXene-NH2 together with the cofactor NAD+ and the redox mediator neutral red (NR), thereby constructing an enzyme-based electron transfer system that mediates the CO2 reduction reaction.
The developed MN sensor exhibited a clear concentration-dependent current response to changes in CO2 concentration within the physiological range and demonstrated excellent sensitivity, selectivity, reproducibility, and operational stability. This study presents an electrochemical MN platform that enables minimally invasive and continuous monitoring of CO2 status and suggests potential applicability for the diagnosis of hypercapnic respiratory failure and for respiratory status monitoring in COPD patients.

목차 (Table of Contents)

• 1. Introduction 1
• 1.1 COPD and Clinical Significance 1
• 1.2 Physiological and Diagnostic Significance of CO2 2
• 1.3 Current Diagnostic approaches for CO2 measurements 4
• 1.4 MN as Minimally Invasive Sensing Interfaces 6
• 1.5 Electrochemical Sensing Principles and Advantages 8
• 1.6 MXene as Functional Conductive Matrix 11
• 1.7 FDH based CO2 Reduction System 13
• 1.8 Designing a CO2 Sensing System 15
• 2. Materials and Methods 18
• 2.1 Materials and Regents 18
• 2.2 Instrumentations 19
• 2.3 Fabrication of the MN Bionsensor 20
• 2.3.1 Fabrication of the MN-based Electrode Structure 20
• 2.3.2 Synthesis of MXene-NH2 21
• 2.3.3 Preparation of the Enzyme Complex Solution 24
• 2.4 Characterization 25
• 2.4.1 Characterization of MXene 25
• 2.4.2 Characterization of MN morphologies and chemical composition 26
• 2.4.3 Electrochemical characterization of MN 26
• 2.4.4 Preparation of dissolved CO2 solution 27
• 2.4.5 Preparation of aISF 28
• 2.4.6 Preparation of skin mimicking phantom gel 28
• 2.4.7 Statistical Analysis 29
• 3. Results and Discussions 30
• 3.1 Structural and Physicochemical Characterization of MXene-NH2 30
• 3.2 Structural and Surface Compositional Analysis of MNs 38
• 3.3 Optimization of MN sensing performance and electrochemical characterization 43
• 3.4 Performance evaluation of the MN sensor 47
• 3.5 CO2 sensing under simulated physiological conditions 51
• 4. Conclusion 57
• 5. Reference 59