Hydrophobic surface induced pro-metastatic cancer cells for in vitro extravasation models

In vitro vascularized cancer models utilizing microfluidics have emerged as a promising tool for mechanism study and drug screening. However, the lack of consideration and preparation methods for cancer cellular sources that are capable of adequately replicating the metastatic features of circulating tumor cells contributed to low relevancy with in vivo experimental results. Here, we show that the properties of cancer cellular sources have a considerable impact on the validity of the in vitro metastasis model. Notably, with a hydrophobic surface, we can create highly metastatic spheroids equipped with aggressive invasion, endothelium adhesion capabilities, and activated metabolic features. Combining these metastatic spheroids with the well-constructed microfluidic-based extravasation model, we validate that these metastatic spheroids exhibited a distinct extravasation response to epidermal growth factor (EGF) and normal human lung fibroblasts compared to the 2D cultured cancer cells, which is consistent with the previously reported results of in vivo experiments. Furthermore, the applicability of the developed model as a therapeutic screening platform for cancer extravasation is validated through profiling and inhibition of cytokines. We believe this model incorporating hydrophobic surface-cultured 3D cancer cells provides reliable experimental data in a clear and concise manner, bridging the gap between the conventional in vitro models and in vivo experiments.

Monitoring lipid alterations in Drosophila heads in an amyotrophic lateral sclerosis model with time-of-flight secondary ion mass spectrometry

Lipid alterations in the brain are well-documented in disease and aging, but our understanding of their pathogenic implications remains incomplete. Recent technological advances in assessing lipid profiles have enabled us to intricately examine the spatiotemporal variations in lipid compositions within the complex brain characterized by diverse cell types and intricate neural networks. In this study, we coupled time-of-flight secondary ion mass spectrometry (ToF-SIMS) to an amyotrophic lateral sclerosis (ALS) Drosophila model, for the first time, to elucidate changes in the lipid landscape and investigate their potential role in the disease process, serving as a methodological and analytical complement to our prior approach that utilized matrix-assisted laser desorption/ionization mass spectrometry. The expansion of G4C2 repeats in the C9orf72 gene is the most prevalent genetic factor in ALS. Our findings indicate that expressing these repeats in fly brains elevates the levels of fatty acids, diacylglycerols, and ceramides during the early stages (day 5) of disease progression, preceding motor dysfunction. Using RNAi-based genetic screening targeting lipid regulators, we found that reducing fatty acid transport protein 1 (FATP1) and Acyl-CoA-binding protein (ACBP) alleviates the retinal degeneration caused by G4C2 repeat expression and also markedly restores the G4C2-dependent alterations in lipid profiles. Significantly, the expression of FATP1 and ACBP is upregulated in G4C2-expressing flies, suggesting their contribution to lipid dysregulation. Collectively, our novel use of ToF-SIMS with the ALS Drosophila model, alongside methodological and analytical improvements, successfully identifies crucial lipids and related genetic factors in ALS pathogenesis.

Time-sequential fibroblast-to-myofibroblast transition in elastin-variable 3D hydrogel environments by collagen networks

BACKGROUND

Fibrosis plays an important role in both normal physiological and pathological phenomena as fibroblasts differentiate to myofibroblasts. The activation of fibroblasts is determined through interactions with the surrounding extracellular matrix (ECM). However, how this fibroblast-to-myofibroblast transition (FMT) is regulated and affected by elastin concentration in a three-dimensional (3D) microenvironment has not been investigated.

METHODS

We developed an insoluble elastin-gradient 3D hydrogel system for long-lasting cell culture and studied the molecular mechanisms of the FMT in embedded cells by nanoflow LC-MS/MS analysis along with validation through real-time PCR and immunofluorescence staining.

RESULTS

By optimizing pH and temperature, four 3D hydrogels containing fibroblasts were successfully fabricated having elastin concentrations of 0, 20, 50, and 80% in collagen. At the low elastin level (20%), fibroblast proliferation was significantly increased compared to others, and in particular, the FMT was clearly observed in this condition. Moreover, through mass spectrometry of the hydrogel environment, it was confirmed that differentiation proceeded in two stages. In the early stage, calcium-dependent proteins including calmodulin and S100A4 were highly associated. On the other hand, in the late stage after several passages of cells, distinct markers of myofibroblasts were presented such as morphological changes, increased production of ECM, and increased α-SMA expression. We also demonstrated that the low level of elastin concentration induced some cancer-associated fibroblast (CAF) markers, including PDGFR-β, and fibrosis-related disease markers, including THY-1.

CONCLUSION

Using our developed 3D elastin-gradient hydrogel system, we evaluated the effect of different elastin concentrations on the FMT. The FMT was induced even at a low concentration of elastin with increasing CAF level via calcium signaling. With this system, we were able to analyze varying protein expressions in the overall FMT process over several cellular passages. Our results suggest that the elastin-gradient system employing nonlinear optics imaging provides a good platform to study activated fibroblasts interacting with the microenvironment, where the ECM plays a pivotal role.

Comparison study of mouse brain tissue by using ToF-SIMS within static limits and hybrid SIMS beyond static limits (dynamic mode)

In the study of degenerative brain diseases, changes in lipids, the main component of neurons, are particularly important because they are used as indicators of pathological changes. One method for the sensitive measurement of biomolecules, especially lipids, is time-of-flight secondary ion mass spectrometry (ToF-SIMS) using pulsed argon cluster ions. In this study, biomolecules including various lipids present in normal mouse brain tissue were measured using ToF-SIMS equipped with pulsed argon cluster primary ions. Based on the ToF-SIMS measurement results, hybrid SIMS (OrbiSIMS), which is a ToF-SIMS system with the addition of an orbitrap mass analyzer, was used to directly identify the biomolecules by the region in the real tissue samples. For this, the results of ToF-SIMS, which measured the tissue samples from a single mouse brain within static limits, were compared with those from OrbiSIMS measured beyond the static limits in terms of the differences in molecular profiling. From this analysis, two types of positive and negative ions were selected for identification, with the OrbiSIMS MS/MS results indicating that the positive ions were glycerophosphocholine and the negative ions were glycerophosphoinositol and sulfatide, a sphingolipid. Then, to confirm the identification of the molecular candidates, lipids were extracted from mirror image tissue samples, and LC-MS/MS also using an orbitrap mass analyzer was performed. As a result, the direct identification of molecular candidate groups distributed in particular regions of the tissue samples via OrbiSIMS was found to be consistent with the identification results by LC-MS/MS for extracted samples.

Quantitative Analysis of Immunosuppressive Drugs Using Tungsten Disulfide Nanosheet-Assisted Laser Desorption Ionization Mass Spectrometry

For organ transplantation patients, the therapeutic drug monitoring (TDM) of immunosuppressive drugs is essential to prevent the toxicity or rejection of the organ. Currently, TDM is done by immunoassays or liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods; however, these methods lack specificity or are expensive, require high levels of skill, and offer limited sample throughput. Although matrix-assisted (MA) laser desorption ionization (LDI) mass spectrometry (MS) can provide enhanced throughput and cost-effectiveness, its application in TDM is limited due to the limitations of the matrixes such as a lack of sensitivity and reproducibility. Here, we present an alternative quantification method for the TDM of the immunosuppressive drugs in the blood of organ transplant patients by utilizing laser desorption ionization mass spectrometry (LDI-MS) based on a tungsten disulfide nanosheet, which is well-known for its excellent physicochemical properties such as a strong UV absorbance and high electron mobility. By adopting a microliquid inkjet printing system, a high-throughput analysis of the blood samples with enhanced sensitivity and reproducibility was achieved. Furthermore, up to 80 cases of patient samples were analyzed and the results were compared with those of LC-MS/MS by using Passing-Bablok regression and Bland-Altman analysis to demonstrate that our LDI-MS platform is suitable to replace current TDM techniques. Our approach will facilitate the rapid and accurate analysis of blood samples from a large number of patients for immunosuppressive drug prescriptions.

Global Proteomics to Study Silica Nanoparticle-Induced Cytotoxicity and Its Mechanisms in HepG2 Cells

Silica nanoparticles (SiO₂ NPs) are commonly used in medical and pharmaceutical fields. Research into the cytotoxicity and overall proteomic changes occurring during initial exposure to SiO₂ NPs is limited. We investigated the mechanism of toxicity in human liver cells according to exposure time [0, 4, 10, and 16 h (h)] to SiO₂ NPs through proteomic analysis using mass spectrometry. SiO₂ NP-induced cytotoxicity through various pathways in HepG2 cells. Interestingly, when cells were exposed to SiO₂ NPs for 4 h, the morphology of the cells remained intact, while the expression of proteins involved in mRNA splicing, cell cycle, and mitochondrial function was significantly downregulated. These results show that the toxicity of the nanoparticles affects protein expression even if there is no change in cell morphology at the beginning of exposure to SiO₂ NPs. The levels of reactive oxygen species changed significantly after 10 h of exposure to SiO₂ NPs, and the expression of proteins associated with oxidative phosphorylation, as well as the immune system, was upregulated. Eventually, these changes in protein expression induced HepG2 cell death. This study provides insights into cytotoxicity evaluation at early stages of exposure to SiO₂ NPs through in vitro experiments.

Electro-inductive effect: Electrodes as functional groups with tunable electronic properties

In place of functional groups that impose different inductive effects, we immobilize molecules carrying thiol groups on a gold electrode. By applying different voltages, the properties of the immobilized molecules can be tuned. The base-catalyzed saponification of benzoic esters is fully inhibited by applying a mildly negative voltage of –0.25 volt versus open circuit potential. Furthermore, the rate of a Suzuki-Miyaura cross-coupling reaction can be changed by applying a voltage when the arylhalide substrate is immobilized on a gold electrode. Finally, a two-step carboxylic acid amidation is shown to benefit from a switch in applied voltage between addition of a carbodiimide coupling reagent and introduction of the amine.

Direct Chemical Imaging of Ligand-Functionalized Single Nanoparticles by Photoinduced Force Microscopy

Chemical characterizations of biochemically functionalized single nanoparticles are necessary to optimize the nanoparticle surface functionality in recently advanced nanobiological applications but have not yet been fully explored because of technical difficulties. Exploiting the photoinduced force exerted on a light-illuminated nanoscale tip, nanoscale mid-infrared hyperspectral images with a 10 nm spatial resolution of a monolayer ligand-functionalized single gold nanoparticle under ambient and environmental conditions are presented. We extend our study to the diagnosis of nanoscale heterogeneous chemical contaminants which come from a particle functionalization process but are undetectable in conventional ensemble-averaged imaging technique. High sensitivity and high spatial resolution are achieved via the strongly localized tip-enhanced force at the junction between the gold-coated tip and the functionalized nanoparticle in photoinduced force microscopy, which far exceeds the capability of the conventional methods. The present study paves a new way to directly detect heterogeneous nanochemicals at the single-component level, which is necessary to evaluate nanomaterial safety in biomedical applications.

Probing organic ligands and their binding schemes on nanocrystals by mass spectrometric and FT-IR spectroscopic imaging

We report an analysis method to identify conjugated ligands and their binding states on semiconductor nanocrystals based on their molecular information. Surface science techniques, such as time-of-flight secondary-ion mass spectrometry (ToF-SIMS) and FT-IR spectroscopy, are adopted based on the micro-aggregated sampling method. Typical trioctylphosphine oxide-based synthesis methods of CdSe/ZnS quantum dots (QDs) have been criticized because of the peculiar effects of impurities on the synthesis processes. Because the ToF-SIMS technique provides molecular composition evidence on the existence of certain ligands, we were able to clearly identify n-octylphosphonic acid (OPA) as a surface ligand on CdSe/ZnS QDs. Furthermore, the complementary use of the ToF-SIMS technique with the FT-IR technique could reveal the OPA ligands' binding state as bidentate complexes.

A Facile Route for Patterned Growth of Metal-Insulator Carbon Lateral Junction through One-Pot Synthesis

Precise graphene patterning is of critical importance for tailor-made and sophisticated two-dimensional nanoelectronic and optical devices. However, graphene-based heterostructures have been grown by delicate multistep chemical vapor deposition methods, limiting preparation of versatile heterostructures. Here, we report one-pot synthesis of graphene/amorphous carbon (a-C) heterostructures from a solid source of polystyrene via selective photo-cross-linking process. Graphene is successfully grown from neat polystyrene regions, while patterned cross-linked polystyrene regions turn into a-C because of a large difference in their thermal stability. Since the electrical resistance of a-C is at least 2 orders of magnitude higher than that for graphene, the charge transport in graphene/a-C heterostructure occurs through the graphene region. Measurement of the quantum Hall effect in graphene/a-C lateral heterostructures clearly confirms the reliable quality of graphene and well-defined graphene/a-C interface. The direct synthesis of patterned graphene from polymer pattern could be further exploited to prepare versatile heterostructures.

Guided formation of sub-5 nm interstitial gaps between plasmonic nanodisks

To achieve a reliable formation of a surface-enhanced Raman scattering (SERS) sensor with evenly distributed hot spots on a wafer scale substrate, we propose a hybrid approach combining physical nanolithography for preparing Au nanodisks and chemical Au reduction for growing them. During the chemical growth, the interstitial distance between the nanodisks decreased from 60 nm to sub-5 nm. The resulting patterns of the nanogap-rich Au nanodisks successfully enhance the SERS signal, and its intensity map shows only a 5% or less signal variation on the entire sample.

Galvanic synthesis of three-dimensional and hollow metallic nanostructures

We report a low-cost, facile, and template-free electrochemical method of synthesizing three-dimensional (3D) hollow metallic nanostructures. The 3D nanoporous gold (3D-NPG) nanostructures were synthesized by a galvanic replacement reaction (GRR) using the different reduction potentials of silver and gold; hemispherical silver nanoislands were electrochemically deposited on cathodic substrates by a reverse-pulse potentiodynamic method without templates and then nanoporous gold layer replicated the shape of silver islands during the GRR process in an ultra-dilute electrolyte of gold(III) chloride trihydrate. Finally, the wet etching process of remaining silver resulted in the formation of 3D-NPG. During the GRR process, the application of bias voltage to the cathode decreased the porosity of 3D-NPG in the voltage range of 0.2 to -0.62 V. And the GRR process of silver nanoislands was also applicable to fabrication of the 3D hollow nanostructures of platinum and palladium. The 3D-NPG nanostructures were found to effectively enhance the SERS sensitivity of rhodamine 6G (R6G) molecules with a concentration up to 10(-8) M.

One-step large-scale synthesis of micrometer-sized silver nanosheets by a template-free electrochemical method

We have synthesized micrometer-sized Ag nanosheets via a facile, one-step, template-free electrochemical deposition in an ultra-dilute silver nitrate aqueous electrolyte. The nanosheet growth was revealed to occur in three stages: (1) formation of polygonal Ag nuclei on a substrate, (2) growth of {112}-faceted nanowire from the nuclei, and (3) anisotropic growth of (111)-planar nanosheets, approximately 20 to 50 nm in thickness and 10 μm in width, in the <112>-direction. The vertical growth of the facet nanowire was induced by the strong interface anisotropy between the deposit and electrolyte due to the ultra-dilute concentration of electrolyte and high reduction potential. The thickness of Ag nanosheets was controllable by the adjustment of the reduction/oxidation potential and frequency of the reverse-pulse potentiodynamic mode.

Electrochemical release of amine molecules from carbamate-based, electroactive self-assembled monolayers

In this paper, carbamate-based self-assembled monolayers (SAMs) of alkanethiolates on gold were suggested as a versatile platform for release of amine-bearing molecules in response to the electrical signal. The designed SAMs underwent the electrochemical oxidation on the gold surface with simultaneous release of the amine molecules. The synthesis of the thiol compounds was achieved by coupling isocyanate-containing compounds with hydroquinone. The electroactive thiol was mixed with 11-mercaptoundecanol [HS(CH(2))(11)OH] to form a mixed monolayer, and cyclic votammetry was used for the characterization of the release behaviors. The mixed SAMs showed a first oxidation peak at +540 mV (versus Ag/AgCl reference electrode), indicating the irreversible conversion from carbamate to hydroquinone groups with simultaneous release of the amine molecules. The analysis of ToF-SIMS further indicated that the electrochemical reaction on the gold surface successfully released amine molecules.