High-resolution imprint and soft lithography for patterning self-assembling systems

This thesis contributes to the continuous development of patterning strategies in several different areas of unconventional nanofabrication. A series of soft lithography approaches (microcontact printing, nanomolding in capillaries), nanoimprint lithography (NIL), and capillary force lithography (CFL) combined with different surface chemistry have been used to pattern or process different self-assembling systems (e.g. self-assembled monolayers, nanoparticles, (bio)molecules, and polymers) on surfaces. A focus is on high resolution and high materials versatility. In Chapter 3, the formation of bifunctional, chemically patterned flat PDMS stamps improved the compatibility of the PDMS with polar inks by having hydrophilic patterns on the PDMS surface. In chapter 4 and 5, the combination of nanoimprint lithography or capillary force lithography with flat stamp concept opens new ways to fabricate chemical patterns on flat PDMS and improves the printing resolution down to sub-100 nm. In chapter 6 and 7, the use of a hybrid PDMS nanomold as a template for a wet lithography approach has created a simple but powerful tool to pattern different kinds of material at the nanoscale. These high-resolution soft lithography approaches developed in this thesis are ready to be used in normal research labs as tools to pattern different molecules or nanomaterials to functional nanostructures especially, when combined with the large chemical versatility of soft lithography. I also believe these tools are valuable to fabricate future nano-electronic or bio-sensing devices

High-Resolution Contact Printing with Chemically Patterned Flat Stamps Fabricated by Nanoimprint Lithography

Chemically patterned flat stamps provide an effective solution to avoid mechanical stamp-stability problems currently encountered in microcontact printing. A new method is developed to fabricate chemical patterns on a flat PDMS stamp using nanoimprint lithography. Sub-100 nm gold patterns are successfully replicated by these chemically patterned flat PDMS stamps. \ud \u

Outdoor particulate matter exposure affects metabolome in chronic obstructive pulmonary disease: Preliminary study

IntroductionThe metabolomic changes caused by airborne fine particulate matter (PM2.5) exposure in patients with chronic obstructive pulmonary disease (COPD) remain unclear. The aim of this study was to determine whether it is possible to predict PM2.5-induced acute exacerbation of COPD (AECOPD) using metabolic markers.MethodsThirty-eight patients with COPD diagnosed by the 2018 Global Initiative for Obstructive Lung Disease were selected and divided into high exposure and low exposure groups. Questionnaire data, clinical data, and peripheral blood data were collected from the patients. Targeted metabolomics using liquid chromatography-tandem mass spectrometry was performed on the plasma samples to investigate the metabolic differences between the two groups and its correlation with the risk of acute exacerbation.ResultsMetabolomic analysis identified 311 metabolites in the plasma of patients with COPD, among which 21 metabolites showed significant changes between the two groups, involving seven pathways, including glycerophospholipid, alanine, aspartate, and glutamate metabolism. Among the 21 metabolites, arginine and glycochenodeoxycholic acid were positively associated with AECOPD during the three months of follow-up, with an area under the curve of 72.50% and 67.14%, respectively.DiscussionPM2.5 exposure can lead to changes in multiple metabolic pathways that contribute to the development of AECOPD, and arginine is a bridge between PM2.5 exposure and AECOPD

Short-term exposure to fine particulate matter and genome-wide DNA methylation in chronic obstructive pulmonary disease: A panel study conducted in Beijing, China

BackgroundFine particulate matter (PM2.5) is a crucial risk factor for chronic obstructive pulmonary disease (COPD). However, the mechanisms whereby PM2.5 contribute to COPD risk have not been fully elucidated. Accumulating evidence suggests that epigenetics, including DNA methylation, play an important role in this process; however, the association between PM2.5 exposure and genome-wide DNA methylation in patients with COPD has not been studied.ObjectiveTo evaluate the association of personal exposure to PM2.5 and genome-wide DNA methylation changes in the peripheral blood of patients with COPD.MethodsA panel study was conducted in Beijing, China. We repeatedly measured and collected personal PM2.5 data for 72 h. Genome-wide DNA-methylation of peripheral blood was analyzed using the Illumina Infinium Human Methylation BeadChip (850 k). A linear-mixed effect model was used to identify the differentially methylated probe (DMP) associated with PM2.5. Finally, we performed a functional enrichment analysis of the DMPs that were significantly associated with PM2.5.ResultsA total of 24 COPD patients were enrolled and 48 repeated DNA methylation measurements were associated in this study. When the false discovery rate was < 0.05, 19 DMPs were significantly associated with PM2.5 and were annotated to corresponding genes. Functional enrichment analysis of these genes showed that they were related to the response to toxic substances, regulation of tumor necrosis factor superfamily cytokine production, regulation of photosensitivity 3-kinase signaling, and other pathways.ConclusionThis study provided evidence for a significant relationship between personal PM2.5 exposure and DNA methylation in patients with COPD. Our research also revealed a new biological pathway explaining the adverse effects of PM2.5 exposure on COPD risk

Nanostructure enabled extracellular vesicles separation and detection

Extracellular vesicles (EVs) have recently attracted significant research attention owing to their important biological functions, including cell-to-cell communication. EVs are a type of membrane vesicles that are secreted into the extracellular space by most types of cells. Several biological biomolecules found in EVs, such as proteins, microRNA, and DNA, are closely related to the pathogenesis of human malignancies, making EVs valuable biomarkers for disease diagnosis, treatment, and prognosis. Therefore, EV separation and detection are prerequisites for providing important information for clinical research. Conventional separation methods suffer from low levels of purity, as well as the need for cumbersome and prolonged operations. Moreover, detection methods require trained operators and present challenges such as high operational expenses and low sensitivity and specificity. In the past decade, platforms for EV separation and detection based on nanostructures have emerged. This article reviews recent advances in nanostructure-based EV separation and detection techniques. First, nanostructures based on membranes, nanowires, nanoscale deterministic lateral displacement, and surface modification are presented. Second, high-throughput separation of EVs based on nanostructures combined with acoustic and electric fields is described. Third, techniques combining nanostructures with immunofluorescence, surface plasmon resonance, surface-enhanced Raman scattering, electrochemical detection, or piezoelectric sensors for high-precision EV analysis are summarized. Finally, the potential of nanostructures to detect individual EVs is explored, with the aim of providing insights into the further development of nanostructure-based EV separation and detection techniques

Advances in microfluidic-based DNA methylation analysis

DNA methylation has been extensively investigated in recent years, not least because of its known relationship with various diseases. Progress in analytical methods can greatly increase the relevance of DNA methylation studies to both clinical medicine and scientific research. Microfluidic chips are excellent carriers for molecular analysis, and their use can provide improvements from multiple aspects. On-chip molecular analysis has received extensive attention owing to its advantages of portability, high throughput, low cost, and high efficiency. In recent years, the use of novel microfluidic chips for DNA methylation analysis has been widely reported and has shown obvious superiority to conventional methods. In this review, we first focus on DNA methylation and its applications. Then, we discuss advanced microfluidic-based methods for DNA methylation analysis and describe the great progress that has been made in recent years. Finally, we summarize the advantages that microfluidic technology brings to DNA methylation analysis and describe several challenges and perspectives for on-chip DNA methylation analysis. This review should help researchers improve their understanding and make progress in developing microfluidic-based methods for DNA methylation analysis

Hypersonic poration of supported lipid bilayers

Hypersound (ultrasound of gigahertz (GHz) frequency) has been recently introduced as a new type of membrane-disruption method for cells, vesicles and supported lipid bilayers (SLBs), with the potential to improve the efficiency of drug and gene delivery for biomedical applications. Here, we fabricated an integrated microchip, composed of a nano-electromechanical system (NEMS) resonator and a gold electrode as the extended gate of a field effect transistor (EGFET), to study the effects of hypersonic poration on an SLB in real time. The current recordings revealed that hypersound enabled ion conduction through the SLB by inducing transient nanopores in the membrane, which act as the equivalent of ion channels and show gating behavior. The mechanism of pore formation was studied by cyclic voltammetry (CV), atomic force microscopy (AFM) and laser scanning microscopy (LSM), which support the causality between hypersound-triggered deformation and the reversible membrane disruption of the SLB. This finding contributes to the development of an approach to reversibly control membrane permeability by hypersound

Theoretical and experimental characterizations of gigahertz acoustic streaming in microscale fluids

Even as gigahertz (GHz) acoustic streaming has developed into a multi-functional platform technology for biochemical applications, including ultrafast microfluidic mixing, microparticle operations, and cellar or vesicle surgery, its theoretical principles have yet to be established. This is because few studies have been conducted on the use of such high frequency acoustics in microscale fluids. Another difficulty is the lack of velocimetry methods for microscale and nanoscale fluidic streaming. In this work, we focus on the basic aspects of GHz acoustic streaming, including its micro-vortex generation principles, theoretical model, and experimental characterization technologies. We present details of a weak-coupled finite simulation that represents our current understanding of the GHz-acoustic-streaming phenomenon. Both our simulation and experimental results show that the GHz-acoustic-induced interfacial body force plays a determinative role in vortex generation. We carefully studied changes in the formation of GHz acoustic streaming at different acoustic powers and flow rates. In particular, we developed a microfluidic-particle-image velocimetry method that enables the quantification of streaming at the microscale and even nanoscale. This work provides a full map of GHz acoustofluidics and highlights the way to further theoretical study of this topic. Keywords: Acoustic streaming, Gigahertz, Body force, Microfluidic PI