14 research outputs found
암진단 및 치료를 위한 고분자 나노입자의 제조와 특성화 연구
Get PDF학위논문 (박사)-- 서울대학교 대학원 : 재료공학부, 2014. 2. 박종래.Optical imaging and photodynamic therapy (PDT) are emerging modalities for cancer diagnosis and therapy. Polymeric nanoparticles (PNPs) have been extensively used as bioimaging probes or PDT drug carriers since PNPs in vivo utility was well-demonstrated in nanoscopic size-motivated tumor targeting efficiency, and as excellent biocompatibility. However, the clinical use of PNPs is limited by some inherent obstacles in both optical imaging and PDT. In particular, the high resolution of PNP-mediated optical imaging can be hindered by photon-limiting interferences such as scattering, absorption, and autofluorescence occurring in biological tissues. PNPs aimed to deliver the PDT drugs are mainly used for small-animal studies and are not generally transferred into the clinic because of the immunogenic response from the body and the inconvenience of further medication for clinical purposes. Therefore, a new type of PNPs is required to develop practical diagnostic/therapeutic agents.
In this thesis, two different types of PNPs are suggested as alternatives to high performance diagnostic/therapeutic agents for a clinic. The first type is photoswitchable PNPs based on the nanocomposite of π-conjugated polymer and photochromophore, which provides high resolution of bioimaging through bistable photoswitching of near-infared (NIR) fluorescence. The second type is PNPs of sugar-based polymers and their amphiphilic derivatives, providing high tumor targeting efficiency and high therapeutic efficacy by taking the virtues of its nanosopic size, biocompatibility, antifouling property, and loading capability of hydrophobic drugs. The aims of this study are to introduce the essential requirements of PNPs through a theoretical approach, design a new type of PNPs of π-conjugated polymer or sugar-based polymer as diagnostic/therapeutic agents, and analyze the biological performance of each PNP used in cancer diagnosis and therapy.
Part I provides a general introduction of PNP-based cancer diagnostic/therapeutic agents regarding the essential requirements for a new type of PNPs. Optical imaging is summarized with an imaging mechanism, multiple performance parameters, and inherent obstacles. Photodynamic therapy is also summarized with a photo-triggered therapy mechanism and performance parameters. The main challenges and issues of the PNPs for the advanced optical imaging/photodynamic therapy are indicated by the state of the art analysis. Throughout the analysis, the aim and scope of this research contains a theoretical study and preparation, and characterization of new PNPs as the diagnostic/therapeutic agents are introduced.
Part II discusses a new type of photoswitchable PNPs based on binary nanocomposite of π-conjugated polymer and photochromophore. The composite PNPs showed bright fluorescence in the NIR region and its high-contrast photoswitching through the efficient intraparticle fluorescence energy transfer (FRET) as well as tiny colloidal size PNPs for in vivo delivery. Consequently, the composite PNPs can allow the dynamic signal to be distinguished from the static autofluorescence of biological tissues to improve the capability of signal identification. By taking the merit of photoswitching, the composite PNPs can be suggested as a new strategy to overcome the inherent limitation of optical imaging.
Part III presents synthesis and biological use of new sugar-based polymers, poly(oxyethylene galactaramide)s (PEGAs), in order to take the combined merits of PEG and polysaccharides such as biocompatibility, antifouling property, and pendant functional groups. PEGAs with hydrogen bond-mediated self-assembly into PNPs and PEGA nanoassemblies (PEGA PNPs) exhibited high tumor targeting efficiency from the virtues of the size-motivated EPR effect and the antifouling effect. PEGA PNPs hold great potential for practical biomedical applications including optical imaging, which is worthy of further exploitation for payload carriage and immunogenicity evaluation.
Part IV discusses amphiphilic derivatives of PEGAs synthesized through conjugation of bile/fatty acids to validate the in vivo utility of PEGAs for clinical use, and especially, PDT. PEGA amphiphilies were designed as sugar-based polymeric biosurfactants (SPBs), and self-assembled into PNPs that have a hydrophobic core and a hydrophilic/antifouling exterior. PNPs of PEGA amphiphile exhibited stable loading capability of hydrophobic drugs (or dyes) and the attractive features of PEGAs. Consequently, hydrophobic dyes (rubrene or IR780 iodide)-entrapped PNPs showed high in vitro/vivo tumor selectivity with tumor cells and tumor-bearing mice. Furthermore, the hydrophobic PDT drug (pyropheophorbide-a, PPa)-entrapped PNPs exhibited high efficacy of in vivo PDT with tumor-bearing mice. The improved biological performances are summarized in Part V and clearly show the potentials of new PNPs as alternatives for an advanced cancer diagnostic/therapeutic agents.Part I Basic research on polymeric nanoparticles for cancer diagnosis and therapy
Chapter 1 Introduction......................................................................................2
1.1 General introduction to polymeric nanoparticles for cancer diagnosis and therapy..............................................................................................................................2
1.1.1 Polymeric nanoparticles for cancer diagnosis.................................................4
1.1.1.1 Optical imaging....................................................................................6
1.1.1.2 Magnetic resonance (MR) imaging......................................................9
1.1.1.3 Ultrasound (US) imaging.....................................................................9
1.1.1.4 Nuclear imaging.................................................................................11
1.1.2 Polymeric nanoparticles for cancer therapy..................................................12
1.1.2.1 Chemotherapy....................................................................................13
1.1.2.2 Gene therapy.......................................................................................15
1.1.2.3 Photodynamic therapy (PDT)............................................................17
1.2 Conventional polymeric nanoparticles for cancer diagnosis and therapy................19
1.2.1 Natural polymer based nanoparticles............................................................19
1.2.2 Synthetic polymer based nanoparticles.........................................................22
1.3 Main challenges and issues related to polymeric nanoparticles for cancer diagnosis and therapy.....................................................................................................................23
1.3.1 Polymeric nanoparticles for tumor targeting and delivery............................23
1.3.1.1 Angiogenesis in cancer.......................................................................23
1.3.1.2 Passive tumor targeting......................................................................24
1.3.1.3 Active tumor targeting........................................................................25
1.3.2 Cancer diagnosis: Optical imaging...............................................................27
1.3.1.1 Conventional approaches for polymeric imaging probes..................27
1.3.1.2 Novel approaches for high resolution imaging..................................30
1.3.3 Cancer therapy: Photodynamic therapy........................................................32
1.3.2.1 Conventional approaches for polymeric drug carriers.......................32
1.3.2.2 Novel approaches for high therapeutic efficacy.................................34
1.4 Aim and scope of this research................................................................................37
1.4.1 Preparation and characterization of π-conjugated polymer nanoparticles as photoswitchable nanoprobes for high resolution imaging.....................................37
1.4.2 Preparation and characterization of sugar-based polymeric nanocarriers for cancer diagnosis and therapy..................................................................................38
1.5 References................................................................................................................39
Part II π-Conjugated polymer nanoparticles for high resolution bioimaging
Chapter 2 π-Conjugated polymer/photochromophore binary nanococktails: bistable photoswitching of near-infrared fluorescence for in vivo imaging..............................................................................................................46
2.1 Introduction..............................................................................................................46
2.2 Experimental............................................................................................................49
2.2.1 Materials and instrumentation.......................................................................49
2.2.2 Preparation of nanococktails (NCs)..............................................................49
2.2.3 Photoswitching experiment...........................................................................52
2.2.4 In vitro photoswitching in an in vivo-mimicking model...............................52
2.2.5 In vivo/ex vivo photoswitching......................................................................52
2.2.6 In vivo toxicity study.....................................................................................62
2.3 Results and discussion.............................................................................................54
2.3.1 Preparation of nanococktails (NCs) as photoswitchable nanoprobes...........54
2.3.2 Photoswitching behavior of NCs..................................................................57
2.3.3 In vitro photoswitching of NCs in an in vivo-mimicking model...................67
2.3.4 In vivo photoswitching of NCs in a mouse model........................................69
2.4 Conclusions..............................................................................................................80
2.5 References................................................................................................................81
Part III Sugar-based polymeric nanoparticles for cancer diagnosis
Chapter 3 Poly(oxyethylene sugaramide)s: unprecedented multihydroxyl building blocks for tumor-homing nanoassembly.........................................85
3.1 Introduction..............................................................................................................85
3.2 Experimental............................................................................................................89
3.2.1 Materials and instrumentation.......................................................................89
3.2.2 Synthesis of dimethyl galactarate (DMGA)..................................................90
3.2.3 Synthesis of poly(oxyethylene galactaramide)s (PEGAs)............................90
3.2.4 Conjugation of dyes to PEGA2 and mPEG-amine.......................................92
3.2.5 Conjugation of folic acid (FA) to PEGA2.....................................................93
3.2.6 Cellular Uptake Behavior of PEGA2 Nanoparticles: Cellular fluorescence imaging...................................................................................................................94
3.2.7 Cell attachment onto the surface of 96-well plate.........................................94
3.2.8 In vivo/ex vivo near-infrared fluorescence imaging......................................95
3.3 Results and discussion.............................................................................................96
3.3.1 Synthesis of poly(oxyethylene galactaramide)s (PEGAs) as hydrogen bondable building blocks.......................................................................................96
3.3.2 Colloidal behavior of PEGA nanoassembly in water..................................101
3.3.3 In vitro antifouling characteristics of PEGA nanoassembly........................106
3.3.4 In vivo antifouling characteristics and tumor homing behaviour of PEGA nanoassembly........................................................................................................112
3.4 Conclusions............................................................................................................119
3.5 References..............................................................................................................120
Part IV Sugar-based polymeric nanoparticles for cancer therapy
Chapter 4 Amphiphilic derivatives of poly(oxythylene sugaramide)s: Sugar-based polymeric biosurfactants as drug carriers with high tumor-homing efficiency........................................................................................... 124
4.1 Introduction............................................................................................................124
4.2 Experimental..........................................................................................................127
4.2.1 Materials and instrumentation.....................................................................127
4.2.2 Synthesis of sugar-based polymeric biosurfactants (SPBs): bile/fatty acid (BA/FA) conjugated PEGA2 ................................................................................127
4.2.3 Determination of critical micelle concentration (CMC) of SPBs...............131
4.2.4 Fluorescence labeling of SPBs....................................................................131
4.2.5 Preparation of hydrophobic dye (or drug)-loaded SPB nanoparticles (NPs).....................................................................................................................131
4.2.6 In vitro fluorescence imaging with tumor cells...........................................132
4.2.7 In vivo fluorescence imaging with tumor-bearing mice..............................132
4.2.8 Photo-induced toxicity evaluation with apoptosis imaging with tumor cells.......................................................................................................................133
4.2.9 Photodynamic therapy with tumor-bearing mice........................................133
4.3 Results and discussion ...........................................................................................135
4.3.1 Synthesis of SPBs.......................................................................................135
4.3. Self-assembly of SPBs into NPs...................................................................140
4.3.3 Intracellular delivery of hydrophobic dye-loaded SPB NPs.......................142
4.3.4 In/ex vivo biodistribution of hydrophobic dye-loaded SPB NPs in tumor-bearing mice.........................................................................................................144
4.3.5 Preparation of pyropheophorbide-a (PPa)-loaded SPB NPs as a nano photosensitizer......................................................................................................150
4.3.6 Photo-induced toxicity of PPa-loaded SPB NPs against tumor cells..........157
4.3.7 Photodynamic therapy of PPa-loaded SPB NPs with tumor-bearing mice ......................................................................................................................161
4.4 Conclusions............................................................................................................164
4.5 References..............................................................................................................165
Part V Conclusions
Chapter 5 Conclusive remarks and the outlook ..........................................169Docto
고 Mn 오스테나이트계 강의 용융아연에 의한 취성
No full textDoctorThe application of TWIP steel in the automotive industry is still limited due to many pending problems. Liquid metal embrittlement caused by Zn is one of the obstacles to be overcome, which is particularly accented when welding TWIP steels. The current study tackles the issue with experimental method as well as numerical one. LME resistivity of different high strength steel grades were investigated for comparative study. It is found that Zn embrittles all the Fe based alloy system regardless of constituent phases. The critical stress for LME has been found to be the one corresponding to strain of 0.4 %, which will cause LME at temperatures over 700 °C. TEM observation revealed that thermo-mechanically assisted diffusion of Zn can occur along grain boundaries of the substrate when strained at high temperatures, which might cause LME. A finite element model has been developed for stress and temperature analysis in welding conditions. It is suggested from FE simulation that tensile stress arises during the cooling stage of the welding, which might cause LME on the weld surface. The level of the tensile stress is dependent on the thermal expansion coefficient of the weld metal, explaining why TWIP steels are vulnerable to LME during resistance spot welding
Spot weldability of TRIP steel with high carbon, high aluminium content
No full textMasterRecent trends towards the integration of strong steels into the automotive industry have accentuated demands on their resistance spot weldability, a technique most widely used for bonding during automotive assembly. However, strong steels are inherently rich in alloying elements. TRIP steels are not exceptions because they require certain level of carbon content and cementite inhibitors such as silicon to maintain austenite stability. The resulting high hardenability makes it difficult to avoid the formation of brittle martensite in the heat affected zone of resistance spot welds. Recent research on TRIP-assisted steel alloy with relatively high carbon and aluminium concentration showed a possible way forward. In this so called δ-TRIP steel, δ-ferrite is stabilized by aluminium and persists in the microstructure at all temperatures after solidification. Soft δ-ferrite can be retained in the martensite that forms. Since it is assumed that avoiding fully martensitic weld nugget may be helpful for better weldability and weld toughness, this idea is promising. Previous research done by Yi et al. reports that δ-ferrite retained after welding process is indeed good for better spot weldabilty, but it is not clear whether the properties achieved are adequate. Expanding on this notion, the effectiveness of δ-ferrite in terms of spot weldability has been qualitatively investigated in this work with alloys newly designed for the purpose. The thesis can be divided into two parts, pre-weld studies and an understanding of the weld. The initial part deals with the optimization of heat treatment conditions itself to acquire the best possible mechanical properties for the alloys. Specimens were tensile tested and analyzed using optical and electron microscopes. The weld study covers microstructure, joint property evaluations and fracture surface analysis. Relations between weld microstructure and fracture mechanisms have been obtained. To further enhance spot weldability, additional heating processes after spot welding with different conditions were applied to assess whether the tempering of martensite in the weld nuggets is advantageous. The procedure was expected to soften the weld nugget and result in better weld integrity
