PET Imaging of Inflammation and Nanoparticle Distribution using Radiolabeled Sorbitol and PLGA Nanoparticles = 방사성 표지 솔비톨 및 PLGA 나노입자를 이용한 염증 PET 영상화 및 나노입자 분포에 관한 연구

다국어 초록 (Multilingual Abstract)

Medical imaging has become a crucial tool for the early diagnosis of diseases, monitoring disease progression, elucidating pathological mechanisms, and accelerating drug development. Positron Emission Tomography (PET) is a molecular imaging technology that visualizes pathological changes induced by diseases using radiopharmaceuticals, allowing for early diagnosis and real-time assessment of treatment efficacy. One of the most commonly used radiopharmaceuticals in PET imaging, 18F-Fluorodeoxyglucose (18F-FDG), primarily utilizes the differences in glucose metabolism between normal tissues and lesions to visualize cancer and inflammation. However, the uptake of 18F-FDG poses challenges in differentiating between cancer and inflammation, as it also accumulates in tissues with high glucose metabolism such as the brain, heart, and muscles, leading to false positives. Therefore, there is an increasing necessity for the development of safe and inflammation-specific radiopharmaceuticals as alternatives to 18F-FDG.
Sorbitol, a sugar alcohol with a structure similar to glucose, is a safe substance found in fruits and has recently shown successful imaging in studies of bacterial infections and cancers. The characteristic of sorbitol, as an energy source absorbed by both bacteria and potentially as an inflammation-specific radiopharmaceutical, presents significant promise.
While fluorescent or luminescent imaging techniques are commonly employed to analyze the in vivo behavior of biological substances, they have critical limitations in quantitative analysis due to high background noise and signal loss. In nanomedicine, these limitations continue to pose obstacles in the development of drug delivery systems. The high energy of radiation used in PET imaging provides an advantage for accurately visualizing the location of lesions without signal loss, allowing for the quantification of the exact location and delivery efficiency of administered drug delivery systems. Therefore, in this study, PET imaging was utilized to report the inflammation-specific applicability of sorbitol. In addition, the systemic distribution and immune cell uptake of nanoparticles were evaluated depending on the route of administration.
Inflammation-specific uptake of radiolabeled sorbitol was visualized in real-time in a murine inflammation model using PET imaging. For inflammation imaging, sorbitol was stably labeled with radioactive zirconium via the Diethylenetriamine pentaacetate (DTPA) chelator, maintaining binding stability over 24 hours. The radiolabeled sorbitol administered to the acute inflammation mouse model was rapidly taken up in the inflamed tissues immediately after administration, with the highest inflammation-to-background signal confirmed by PET imaging at 1 hour post-injection. In contrast, in the brain, heart, and muscles, the radiolabeled sorbitol was rapidly cleared after initial administration and not re-absorbed. Finally, comparative studies with groups treated with anti-inflammatory drugs indicated a significantly lower signal of radiolabeled sorbitol in inflamed sites. These findings confirmed that sorbitol can be applied to evaluate the efficacy of various anti-inflammatory drugs.
Poly(lactic-co-glycolic acid (PLGA) nanoparticles designed for efficient phagocytic uptake were synthesized, and their biodistribution was quantitatively evaluated via various administration routes using zirconium radiolabeling. In vitro experiments confirmed that nanoparticles smaller than 1 micrometer were internalized into cells in a phagocytosis-dependent manner as their size increased to 900 nm. In vivo studies showed that nanoparticles administered intranasally demonstrated the highest pulmonary delivery and retention for up to 6 days, whereas intravenously administered nanoparticles were rapidly cleared from the lungs within hours. Additionally, the 900 nm nanoparticles delivered to the lungs exhibited a higher uptake preference by myeloid immune cells compared to lymphoid immune cells, demonstrating the potential for selective drug delivery through size modulation of nanoparticles.
In conclusion, this study provides evidence for the inflammation-specific uptake of sorbitol and the systemic distribution of nanoparticle-based drug delivery systems through PET imaging. Overall, these findings suggest that sorbitol is a promising tool for inflammation diagnostics and facilitating anti-inflammatory drug development, while optimizing drug delivery efficiency through tailored administration routes for nanoparticle-based systems.

목차 (Table of Contents)

• ABSTRACT i
• TABLE OF CONTENTS iv
• LIST OF FIGURES vii
• LIST OF TABLES ix
• LIST OF ABBREVIATION x
• GENERAL INTRODUCTION 1
• LITERATURE REVIEW 4
• CHAPTER Ⅰ Development of a diagnostic and drug evaluation
• system for acute inflammation using a novel [89Zr]DTPA-sorbitol probe 31
• 1 INTRODUCTION 32
• 2 MATERIALS AND METHODS 35
• 2.1 [89Zr] sorbitol DTPA buffer 35
• 2.2 Animals 35
• 2.3 Preparation of DTPA-sorbitol 35
• 2.4 Radiolabeling and Radiochemical yield 36
• 2.5 PET/CT imaging 36
• 2.6 Immunohistology 37
• 2.7 Bio-distribution study 37
• 2.8 PET/CT image analysis 37
• 2.9 Statistical analysis 38
• 3 RESULTS 39
• 3.1 Synthesis and characterization of [89Zr]DTPA sorbitol 39
• 3.2 Visualization of [89Zr]DTPA-sorbitol uptake in acute inflammation sites by real-time PET/CT imaging 45
• 3.3 Assessment of the effect of anti-inflammatory agents on 89Zr-sorbitol uptake in inflammatory lesion using established inflammation-targeting strategies 48
• 4 DISSCUSSION 53
• Chapter Ⅱ Intranasal administration enhances size-dependent
• pulmonary phagocytic uptake of poly(lactic-co-glycolic acid) nanoparticles 56
• 1 INTRODUCTION 57
• 2 MATERIALS AND METHODS 60
• 2.1 Preparation and characterisation of PLGA-NH2
• nanoparticles 60
• 2.2 In vitro cellular uptake study 61
• 2.3 89Zr labelling of PLGA-NH2 nanoparticles 62
• 2.4 Mouse model preparation for in vivo observation 62
• 2.5 PET/CT and quantification 63
• 2.6 Fluorescence-activated cell sorting analysis 64
• 2.7 Statistical analysis 65
• 3 RESULTS 66
• 3.1 Preparation and characterisation of PLGA-NH2 and fluorescently labelled nanoparticles 66
• 3.2 Influence of nanoparticle size on cellular uptake in vitro 66
• 3.3 Biodistribution of 89Zr-labelled PLGA-NH2 nanoparticles in mice 67
• 3.4 Quantification of nanoparticle cellular uptake in the lung tissues 68
• 4 DISSCUSSION 75
• GENERAL DISCUSSION 80
• GENERAL CONCLUSION 87
• REFERENCES 89
• 국문 초록 119
• LIST OF FIGURES
• CHAPTER Ⅰ
• Figure 1.1 Preparation of amino-sorbitol conjugated with
• NCS-DTPA 40
• Figure 1.2 LC-MS and HPLC spectrum of DTPA-sorbitol 41
• Figure 1.3 1H and 13C NMR spectra of DTPA-sorbitol 42
• Figure 1.4 Kinetic analysis of radiolabeled zirconium
• chelation with DTPA with Radio-TLC 43
• Figure 1.5 Radiochemical yield of [89Zr]DTPA-sorbitol labeling monitored by Radio-TLC 44
• Figure 1.6 Cytotoxicity of DTPA-sorbitol 46
• Figure 1.7 PET kinetic imaging study by [89Zr]DTPA-sorbitol 47
• Figure 1.8 Experimental protocol for in vivo study 49
• Figure 1.9 In vivo study of [89Zr]DTPA-sorbitol in CG
• induced inflammation and anti-inflammatory treated mice 50
• Figure 1.10 Histological images from the thigh tissues of mice 51
• Figure 1.11 [18F]FDG PET/CT imaging in carrageenan-
• induced inflammation mice and anti-inflammatory treated mice 52
• Chapter Ⅱ
• Figure 2.1 Preparation and characterisation of PLGA-NH2
• and fluorescently labelled nanoparticles 69
• Figure 2.2 Microscopic examination of uptake of fluorescently
• labelled PLGA-NH2 nanoparticles by RAW264.7 cells after 24 h 70
• Figure 2.3 Biodistribution of 89Zr-PLGA-NH2 nanoparticles
• (900 nm) in mice 71
• Figure 2.4 Preferential uptake of PLGA-NH2 nanoparticles (900 nm) by lung immune cells 72
• Figure 2.5 Radiolabelling efficiency. Radio-TLC analysis of
• 89Zr-PLGA-NH2 nanoparticles 73
• Figure 2.6 Biodistribution of 89Zr-PLGA-NH2 nanoparticles
• (900 nm) in mice 74
• LIST OF TABLES
• LITERATURE REVIEW
• Chapter Ⅰ
• Table 1.1 Major modalities of non-invasive imaging 13
• Table 1.2 Biomarkers for inflammation of PET imaging 19
• Chapter Ⅱ
• Table 2.1 Summary of drug delivery system 26
• Table 2.2 Benefits and challenges of administration routes 30