Anhong Zhou

BRMS1 expression alters the ultrastructural, biomechanical and biochemical properties of MDA-MB-435 human breast carcinoma cells: An AFM and Raman microspectroscopy study

Restoring BReast cancer Metastasis Suppressor 1 (BRMS1) expression suppresses metastasis in MDA-MB-435 human breast carcinoma cells at ectopic sites without affecting tumor formation at orthotopic site in the body. BRMS1 expression induces many phenotypic alterations in 435 cells such as cell adhesion, cytoskeleton rearrangement, and the down regulation of epidermal growth factor receptor (EGFR) expression. In order to better understand the role of cellular biomechanics in breast cancer metastasis, the qualitative and quantitative detection of cellular biomechanics and biochemical composition is urgently needed. In the present work, using atomic force microscopy (AFM) and fluorescent microscopy we revealed that BRMS1 expression in 435 cells induced reorganization of F-actin and caused alteration in cytoarchitectures (cell topography and ultrastructure). Results from AFM observed increase in biomechanical properties which include cell adhesion, cellular spring constant, and Youngs modulus in 435/BRMS1 cells. Raman microspectroscopy showed weaker vibrational spectroscopic bands in 435/BRMS1 cells, implying decrease in concentration of cellular biochemical components in these cells. This was despite the similar spectral patterns observed between 435 and 435/BRMS1 cells. This work demonstrated the feasibility of applying AFM and Raman techniques for in situ measurements of the cellular biomechanics and biochemical components of breast carcinoma cells. It provides vital clues in understanding of the role of cellular biomechanics in cancer metastasis, and further the development of new techniques for early diagnosis of breast cancer.

The prolongevity effect of resveratrol depends on dietary composition and calorie intake in a tephritid fruit fly

Several studies have shown that resveratrol can extend lifespan in yeast, worm, fruit fly and short-lived fish, as well as mice under a high-fat diet, probably acting through molecular pathways similar to dietary restriction. However, the putative prolongevity effect of resveratrol has not been observed in other studies. To evaluate the robustness of the prolongevity effects of resveratrol, we designed a nutritional study to address the question, Under what nutritional conditions does resveratrol affect lifespan and reproduction? We fed 2592 individual tephritid fruit fly of the species, Anastrepha ludens, 24 diets of different sugar:yeast ratios supplemented with or without 100 microM resveratrol. Sex-specific survival and daily egg laying in females were recorded. Resveratrol was found to have no or little effect on lifespan of males in all the treatments, as well as on lifespan and reproduction of females. Only under one diet combination, resveratrol appears to increase mean lifespan of females but not at a statistically significant level after multiple comparison adjustment. These findings suggest that the prolongevity effect of resveratrol is at most limited to a narrow range of dietary composition and calorie content in this fruit fly. Coupled with a recent study indicating that resveratrol does not extend lifespan of mice fed the standard diet, our findings further question the ability of resveratrol to increase lifespan in organisms under normal conditions.

An improved Hurst parameter estimator based on fractional Fourier transform

A fractional Fourier transform (FrFT) based estimation method is introduced in this paper to analyze the long range dependence (LRD) in time series. The degree of LRD can be characterized by the Hurst parameter. The FrFT-based estimation of Hurst parameter proposed in this paper can be implemented efficiently allowing very large data set. We used fractional Gaussian noises (FGN) which typically possesses long-range dependence with known Hurst parameters to test the accuracy of the proposed Hurst parameter estimator. For justifying the advantage of the proposed estimator, some other existing Hurst parameter estimation methods, such as wavelet-based method and a global estimator based on dispersional analysis, are compared. The proposed estimator can process the very long experimental time series locally to achieve a reliable estimation of the Hurst parameter.

Immobilization, hybridization, and oxidation of synthetic DNA on gold surface: Electron transfer investigated by electrochemistry and scanning tunneling microscopy

Fundamental understanding of interfacial electron transfer (ET) among electrolyte/DNA/solid-surface will facilitate the design for electrical detection of DNA molecules. In this report, the electron transfer characteristics of synthetic DNA (sequence from pathogenic Cryptosporidium parvum) self-assembled on a gold surface was electrochemically studied. The effects of immobilization order on the interface ET related parameters such as diffusion coefficient (D0), surface coverage (thetaR), and monolayer thickness (d(i)) were determined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). DNA surface density (Gamma(DNA)) was determined by the integration of the charge of the electro-oxidation current peaks during the initial cyclic voltammetry scans. It was found that the DNA surface densities at different modifications followed the order: Gamma(DNA) (dsS-DNA/Au) > Gamma(DNA) (MCH/dsS-DNA/Au) > Gamma(DNA) (dsS-DNA/MCH/Au). It was also revealed that the electro-oxidation of the DNA modified gold surface would involve the oxidation of nucleotides (guanine and adenine) with a 5.51 electron transfer mechanism and the oxidative desorption of DNA and MCH molecules by a 3 electron transfer mechanism. STM topography and current image analysis indicated that the surface conductivity after each surface modification followed the order: dsS-DNA/Au < MCH/dsS-DNA/Au < oxidized MCH/dsS-DNA/Au < Hoechst/oxidized MCH/dsS-DNA/Au. The results from this study suggested a combination of variations in immobilization order may provide an alternative approach for the optimization of DNA hybridization and the further development for electrical detection of DNA.

Characterization and analysis of mycobacteria and Gram-negative bacteria and co-culture mixtures by Raman microspectroscopy, FTIR, and atomic force microscopy

AbstractThe molecular composition of mycobacteria and Gram-negative bacteria cell walls is structurally different. In this work, Raman microspectroscopy was applied to discriminate mycobacteria and Gram-negative bacteria by assessing specific characteristic spectral features. Analysis of Raman spectra indicated that mycobacteria and Gram-negative bacteria exhibit different spectral patterns under our experimental conditions due to their different biochemical components. Fourier transform infrared (FTIR) spectroscopy, as a supplementary vibrational spectroscopy, was also applied to analyze the biochemical composition of the representative bacterial strains. As for co-cultured bacterial mixtures, the distribution of individual cell types was obtained by quantitative analysis of Raman and FTIR spectral images and the spectral contribution from each cell type was distinguished by direct classical least squares analysis. Coupled atomic force microscopy (AFM) and Raman microspectroscopy realized simultaneous measurements of topography and spectral images for the same sampled surface. This work demonstrated the feasibility of utilizing a combined Raman microspectroscopy, FTIR, and AFM techniques to effectively characterize spectroscopic fingerprints from bacterial Gram types and mixtures. FigureAFM deflection images, Raman spectra, SEM images, and FTIR of Mycobacterium sp. KMS

Non-invasive detection of biomechanical and biochemical responses of human lung cells to short time chemotherapy exposure using AFM and confocal Raman spectroscopy

Cellular biomechanical properties including cell elasticity and cell adhesion are regarded as criteria to differentiate cancer cells and normal cells. In this study, the biomechanical properties including the Youngs modulus and adhesion force of human lung adenocarcinoma epithelial cell line A549 and non-cancerous human primary small airway epithelial cells (SAECs) were measured by using atomic force microscopy (AFM). It was found that primary SAECs are stiffer and more adhesive than cancerous A549 cells. Upon treatment with anti-cancer drug doxorubicin (DOX) for a short time (4 hours), both biomechanical properties of A549 cells were found to be increased while those of SAECs were decreased, implying that DOX-induced response mechanisms are different between these two types of cells (cancerous vs. primary cells). Using confocal Raman spectroscopy, we measured the changes in (sub)cellular biochemical compositions of both cell types before and after DOX exposure. Our ultimate goal is to find out the potential relationship between the changes in biomechanics and biochemical compositions of lung epithelial cells in response to anti-cancer drugs.

Biophysical assessment of single cell cytotoxicity: Diesel exhaust particle-treated human aortic endothelial cells

Exposure to diesel exhaust particles (DEPs), a major source of traffic-related air pollution, has become a serious health concern due to its adverse influences on human health including cardiovascular and respiratory disorders. To elucidate the relationship between biophysical properties (cell topography, cytoskeleton organizations, and cell mechanics) and functions of endothelial cells exposed to DEPs, atomic force microscope (AFM) was applied to analyze the toxic effects of DEPs on a model cell line from human aortic endothelial cells (HAECs). Fluorescence microscopy and flow cytometry were also applied to further explore DEP-induced cytotoxicity in HAECs. Results revealed that DEPs could negatively impair cell viability and alter membrane nanostructures and cytoskeleton components in a dosage- and a time-dependent manner; and analyses suggested that DEPs-induced hyperpolarization in HAECs appeared in a time-dependent manner, implying DEP treatment would lead to vasodilation, which could be supported by down-regulation of cell biophysical properties (e.g., cell elasticity). These findings are consistent with the conclusion that DEP exposure triggers important biochemical and biophysical changes that would negatively impact the pathological development of cardiovascular diseases. For example, DEP intervention would be one cause of vasodilation, which will expand understanding of biophysical aspects associated with DEP cytotoxicity in HAECs.

AN OVERVIEW OF FRACTIONAL ORDER SIGNAL PROCESSING (FOSP) TECHNIQUES

This paper presents a brief overview of some existing fractional order signal processing (FOSP) techniques where the developments in the mathematical communities are introduced; relationship between the fractional operator and long-range dependence is demonstrated, and fundamental properties of each technique and some of its applications are summarized. Specifically, we presented a tutorial on 1) fractional order linear systems; 2) autoregressive fractional integrated moving average (ARFIMA); 3) 1/fα noise; 4) Hurst parameter estimation; 5) fractional order Fourier transformation (FrFT); 6) fractional order linear transforms (Hartley, Sine, Cosine); 7) fractal; 8) fractional order splines; 9) fractional lower order moments (FLOM) and 10) fractional delay filter. Whenever possible, we indicate the connections between these FOSP techniques.Copyright

Toxicity effects of short term diesel exhaust particles exposure to human small airway epithelial cells (SAECs) and human lung carcinoma epithelial cells (A549).

In this study, confocal Raman spectroscopy, atomic force microscope (AFM) and multiplex ELISA were applied to analyze the biophysical responses (biomechanics and biospectroscopy) of normal human primary small airway epithelial cells (SAECs) and human lung carcinoma epithelial A549 cells to in vitro short term DEP exposure (up to 2h). Raman spectra revealed the specific cellular biomolecular changes in cells induced by DEP compared to unexposed control cells. Principal component analysis was successfully applied to analyze spectral differences between control and treated groups from multiple individual cells, and indicated that cell nuclei are more sensitive than other cell locations. AFM measurements indicated that 2h of DEP exposure induced a significant decrease in cell elasticity and a dramatic change in membrane surface adhesion force. Cytokine and chemokine production measured by multiplex ELISA demonstrated DEP-induced inflammatory responses in both cell types.

Probing nanostructures of bacterial extracellular polymeric substances versus culture time by Raman microspectroscopy and atomic force microscopy.

The structure of a bacterial cell wall may alter during bacterial reproduction. Moreover, these cell wall variations, on a nanoscale resolution, have not yet fully been elucidated. In this work, Raman spectroscopy and atomic force microscopy (AFM) technique are applied to evaluate the culture time-dependent cell wall structure variations of Pseudomonas putida KT2440 at a quorum and single cell level. The Raman spectra indicate that the appearance of DNA/RNA, protein, lipid, and carbohydrates occurs till 6 h of cultivation time under our experimental conditions. AFM characterization reveals the changes of the cellular surface ultrastructures over the culture time period, which is a gradual increase in surface roughness during the time between the first two and eight hours cultivation time. This work demonstrates the feasibility of utilizing a combined Raman spectroscopy and AFM technique to investigate the cultivation time dependence of bacterial cellular surface biopolymers at single cell level.