Assembly of Multifunctional Materials Using Molecular Cluster Building Blocks

This thesis explores the synthesis, properties, and potential applications of molecular clusters and the hierarchical solids that form when complementary clusters are combined. Chapter 1 introduces the diverse set of molecular clusters that I employ as nanoscale building blocks in the assembly of multifunctional materials. The core structure of the molecular clusters is closely related to the superconducting Chevrel phases. In discrete clusters, however, the core is passivated by organic ligands, which add stability and important functionalities. The molecular clusters have rich physical and chemical properties of their own, and I present some of the techniques used to investigate their intrinsic electronic properties. Finally, I review some of the modes by which the molecular clusters interact with another to assemble into hierarchical solids. The structural tunability and complexity embedded in the molecular clusters will enable the design of modular, well-defined, multifunctional materials with desirable electronic and magnetic properties. Chapter 2 details the synthesis and characterization of a family of manganese telluride molecular clusters. By varying the ligands that decorate the surface of the inorganic core, I show that the core structures can be tuned. The study of molecular clusters provides insight into how extended solids form. As such, I make structural comparisons of the clusters to known solid-state compounds. Being structurally varied and chemically flexible, the clusters reported in this chapter present an exciting new class of building blocks for the assembly of solid-state compounds. In Chapters 3-4, I present a nanoscale approach to investigate the electronic behaviors of individual molecular clusters. By using a scanning tunneling microscope-based break-junction technique and density-functional theory calculations, I study the effects of the junction environment and the redox properties of the molecular clusters on the conductance of single-cluster junction. Importantly, current blockade effect is observed at room temperature in the single-cluster junctions, allowing for the conductance to be turned on or off by varying the bias potential. Chapters 5-7 explore the synthesis and properties of the hierarchical solids comprised of molecular cluster building blocks. Chapter 5 unveils an approach to create a three-dimensional (3D) coordination network of molecular clusters by using a bifunctional cyanide ligand. The cyanide ligand is appended to the metal sites of the cluster through the carbon terminus, leaving the nitrogen end available for coordination by a divalent metal cation. Whereas the molecular cluster itself is paramagnetic across a temperature range of 3-300 K, the 3D coordination compound shows a ferromagnetic transition at ~25 K. In Chapter 6, I describe the importance of a molecular recognition feature on the molecular cluster that contributes to the assembly of a layered, van der Waals solid. The bulk material contains monolayers of fullerene and can be mechanically exfoliated to thinner layers, providing a key templated strategy to isolate free monolayers of fullerene. Lastly, Chapter 7 details layered, van der Waals solids of rhenium and molybdenum synthesized using traditional solid-state reactions. Because the neighboring cluster units are covalently bound together, the inter-cluster coupling is much stronger in the plane of these materials than that of the self-assembled solid described in Chapter 6. The strong two-dimensional (2D) character in these layered materials allows for the exfoliation of bulk crystals into robust, low-defect monolayers. The surfaces of these monolayers are covered with substitutionally labile ligands, which is an atypical yet valuable feature among 2D materials. I demonstrate that the electronic properties of the monolayers can be tuned by exchanging the surface ligands

LI-RADS Category Can Be a Post-Surgical Prognostic Factor for Intrahepatic Cholangiocarcinoma in Patients with Liver Cirrhosis or Chronic Hepatitis B

Introduction: The Liver Imaging Reporting and Data System (LI-RADS) categorization has been proposed as a potential prognostic indicator for primary liver neoplasms in patients with liver cirrhosis or chronic hepatitis B. This multicenter study aimed to determine whether LI-RADS categorization can offer additional post-surgical prognostic value for intrahepatic cholangiocarcinoma (ICCA) when used in conjunction with the American Joint Committee on Cancer (AJCC) guidelines. Methods: Patients with high risk for hepatocellular carcinoma, surgically confirmed ICCAs, and available preoperative MRI were enrolled. LI-RADS categorization of ICCAs was performed using MRI features, and multivariate analyses were conducted incorporating LI-RADS category, AJCC staging, and clinicopathologic factors to evaluate their predictive value for postoperative recurrence-free survival (RFS) and overall survival (OS). In patients with early recurrence (<2 years), the percentages of AJCC stage I and LR-M or LR tumor-in-vein (TIV) were calculated, respectively. Results: Among the 166 ICCAs analyzed, 13.3% (22/166) were classified as LR-4/5, 77.7% (129/166) as LR-M, and 9.0% (15/166) as LR TIV. Classifications according to the 8th AJCC guidelines for patients with available post-surgical pathologic data and follow-up imaging were 40.6% (63/155) stage I tumors, 23.9% (37/155) stage II, and 35.5% (55/155) stage III. Multivariate analysis revealed that LI-RADS category (LR-M or LR-TIV) was a significant factor for predicting both RFS (hazard ratio [HR] = 2.86, p = 0.02) and OS (HR = 3.18, p = 0.03). Additionally, AJCC staging (II or III) was a significant factor for RFS (HR = 3.90, p < 0.001) and OS (HR = 3.29, p < 0.001), male sex was a significant factor for RFS (HR = 1.89, p = 0.006) and OS (HR = 2.23, p = 0.002), and positive resection margin was a significant factor for OS (HR = 1.91, p = 0.03). Among the 80 patients with early recurrence, 97.5% displayed LR-M or LR-TIV features, while 11.3% were AJCC stage I patients. Conclusion: The MRI-based preoperative LI-RADS categorization of ICCA provides additional post-surgical prognostic value beyond the AJCC guidelines, with significant implications for both RFS and OS

Current Understanding of Methamphetamine-Associated Metabolic Changes Revealed by the Metabolomics Approach

Metabolomics is a powerful tool used in the description of metabolic system perturbations caused by diseases or abnormal conditions, and it usually involves qualitative and/or quantitative metabolome determination, accompanied by bioinformatics assessment. Methamphetamine is a psychostimulant with serious abuse potential and due to the absence of effective pharmacotherapy and a high recurrence potential, methamphetamine addiction is a grave issue. Moreover, its addiction mechanisms remain unclear, probably due to the lack of experimental models that reflect personal genetic variances and environmental factors determining drug addiction occurrence. The metabolic approach is only recently being used to study the metabolic effects induced by a variety of methamphetamine exposure statuses, in order to investigate metabolic disturbances related to the adverse effects and discover potential methamphetamine addiction biomarkers. To provide a critical overview of methamphetamine-associated metabolic changes revealed in recent years using the metabolomics approach, we discussed methamphetamine toxicity, applications of metabolomics in drug abuse and addiction studies, biological samples used in metabolomics, and previous studies on metabolic alterations in a variety of biological samples—including the brain, hair, serum, plasma, and urine—following methamphetamine exposure in animal studies. Metabolic alterations observed in animal brain and other biological samples after methamphetamine exposure were associated with neuronal and energy metabolism disruptions. This review highlights the significance of further metabolomics studies in the area of methamphetamine addiction research. These findings will contribute to a better understanding of metabolic changes induced by methamphetamine addiction progress and to the design of further studies targeting the discovery of methamphetamine addiction biomarkers and therapeutic targets

Flexible Plasmonic Color Filters Fabricated via Nanotransfer Printing with Nanoimprint-Based Planarization

We investigated the preparation and performance of large-area transmission-type flexible plasmonic color filters (PCFs). These large-area PCFs were fabricated based on a nanotransfer printing (nTP) process that involves nanoimprint-based planarization. This process is a simple surface treatment for easy transfer of a metal to a flexible plastic substrate and formation of patterned aluminum nanodots and nanoholes on a substrate surface with poor roughness. Rabbit-ear structures can form during the nTP process, and this phenomenon was analyzed by numerical simulation. As defects were not detected in a 10 000-round bending test, the PCFs fabricated using this nTP process have excellent mechanical properties

Clinical Implication of Liquid Biopsy in Colorectal Cancer Patients Treated with Metastasectomy

Background & Aims: The application of circulating tumor DNA (ctDNA) has been studied for predicting recurrent disease after surgery and treatment response during systemic treatment. Metastasectomy can be curative for well-selected patients with metastatic colorectal cancer (mCRC). This prospective study investigated the ctDNA level before and after metastasectomy in patients with mCRC to explore its potential as a predictive biomarker. Methods: We collected data on 98 metastasectomies for mCRC performed from March 2017 to February 2020. Somatic mutations in the primary and metastatic tumors were identified and tumor-informed ctDNAs were selected by ultra-deep targeted sequencing. Plasma samples were mandatorily collected before and 3–4 weeks after metastasectomy and serially, if patients agreed. Results: Data on 67 of 98 metastasectomies (58 patients) meeting the criteria were collected. ctDNA was detected in 9 (29%) of 31 cases treated with upfront metastasectomy and in 7 (19.4%) of 36 cases treated with metastasectomy after upfront chemotherapy. The detection rate of ctDNA was higher in liver metastasis (p = 0.0045) and tumors measuring ≥1 cm (p = 0.0183). ctDNA was less likely to be detected if the response to chemotherapy was good. After metastasectomy, ctDNA was found in 4 (6%) cases with rapid progressive disease. Conclusion: The biological factors affecting the ctDNA shedding from the tumor should be considered when applying ctDNA assays in a clinical setting. After metastasectomy for oligometastatic lesions in good responders of chemotherapy, most ctDNA was cleared or existed below the detection level. To assist clinical decision making after metastasectomy for mCRC using ctDNA, further studies for improving specific outcomes are needed