Direct investigations of interactions between nucleolins and aptamers on pancreatic cancer and normal cells by atomic force microscopy.

Nucleolin is overexpressed on the surface of pancreatic cancer cells and are regarded as the remarkable therapeutic target. Aptamers are capable of binding the external domain of nucleolin on the cell surface with high affinity and specificity. But nucleolin has not been localized on pancreatic cancer cells at very high spatial resolution, and the interactions between nucleolin and aptamers have not been investigated at very high force resolution level. In this work, nucleolin was localized on pancreatic cancer and normal cells by aptamers (9FU-AS1411-NH2, AS1411-NH2 and CRONH2) in Single Molecule Recognition Imaging mode of Atomic Force Microscopy. There are plenty of nucleolin on the surfaces of pancreatic cancer cells (area percentage about 5 %), while there are little nucleolin on the surfaces of normal cells. The interactions between three types of aptamers and nucleolins on the surfaces of pancreatic cancer cells were investigated by Single Molecule Force Spectroscopy. The unbinding forces of nucleolins-(9FU-AS1411-NH2) are larger than nucleolins-(AS1411-NH2). The dissociation activation energy on nucleolin-(9FU-AS1411-NH2) is higher than nucleolin-(AS1411-NH2), which indicates that the former complex is more stable and harder to dissociate than the later complex. There are no unbinding forces between nucleolin and CRONH2. All these demonstrate that nucleolin was localized on pancreatic cancer and normal cells at single molecule level quantitatively, and the interactions (unbinding forces and kinetics) between nucleolin and aptamers were studied at picoNewton level. The approaches and results of this work will pave new ways in the investigations of nucleolin and aptamers, and will also be useful in the studies on other proteins and their corresponding aptamers.

Atomic force microscopy correlates mechanical and electrical properties of HepG2 cells with curcumin concentration.

Hepatocellular carcinoma (HCC) is a highly prevalent cancer with a significant impact on human health. Curcumin, a natural compound, induces cytoskeletal changes in liver cancer cells and modifies the distribution of lipids, proteins, and polysaccharides on plasma membranes, affecting their mechanical and electrical properties. In this study, we used nanomechanical indentation techniques and Kelvin probe force microscopy (KPFM) based on atomic force microscopy (AFM) to investigate the changes in surface nanomechanical and electrical properties of nuclear and cytoplasmic regions of HepG2 cells in response to increasing curcumin concentrations. CCK-8 assays and flow cytometry results demonstrated time- and concentration-dependent inhibition of HepG2 cell proliferation by curcumin. Increasing curcumin concentration led to an initial increase and then decrease in the mechanical properties of nuclear and cytoplasmic regions of HepG2 cells, represented by the Young's modulus (E), as observed through nanoindentation. KPFM measurements indicated decreasing trends in both cell surface potential and height. Fluorescence microscopy results indicated a positive correlation between curcumin concentration and phosphatidylserine translocation from the inner to the outer membrane, which influenced the electrical properties of HepG2 cells. This study provides valuable insights into curcumin's mechanisms against cancer cells and aids nanoscale evaluation of therapeutic efficacy and drug screening.

Direct investigations of the effects of nicardipine on calcium channels of astrocytes by Atomic Force Microscopy.

Calcium channel blockers (CCB) of astrocytes can blockade the calcium ions entry through the voltage gated calcium channels (VGCC), and is widely used in the diseases related with VGCC of astrocytes. But many aspects of the interaction mechanisms between the CCB and VGCC of astrocytes still remain unclear due to the limited resolution of the approaches. Herein the effects of the nicardipine (a type of CCB) on VGCC of astrocytes were investigated at very high spatial, force and electrical resolution by multiple modes of Atomic Force Microscopy (AFM) directly. The results reveal that after the addition of nicardipine, the recognition signals of VGCC disappeared; the specific unbinding forces vanished; the conductivity of the astrocytes decreased (the current decreased about 2.9 pA and the capacitance was doubled); the surface potential of the astrocytes reduced about 14.2 mV. The results of electrical properties investigations are consistent with the simulation experiments. The relations between these biophysical and biochemical properties of VGCC have been discussed. All these demonstrate that the interactions between nicardipine and VGCC have been studied at nanometer spatial resolution, at picoNewton force resolution and very high electrical signal resolution (pA in current, pF in capacitance and 0.1 mV in surface potential) level. The approaches are considered to be high resolution and high sensitivity, and will be helpful and useful in the further investigations of the effects of other types of CCB on ion channels, and will also be helpful in the investigations of mechanisms and therapy of ion channelopathies.

Effects of surface properties of GaN semiconductors on cell behavior.

In recent years, semiconductors have aroused great interest in connecting, observing and influencing the behavior of biological elements, and it is possible to use semiconductor-cell compound interfaces to discover new signal transduction in the biological field. Among them, III-V nitride semiconductors, represented by gallium nitride (GaN), are used as substrates to form semiconductor-biology interfaces with cells, providing a platform for studying the effects of semiconductors on cell behavior. The interfaces between GaN substrate and cells play an important role in detecting and manipulating cell behaviors and provide a new opportunity for studying cell behavior and developing diagnostic systems. Hence, it is necessary to understand how the properties of the GaN substrate directly influence the behavior of biological tissues, and to create editable biological interfaces according to the needs. This paper reviews the synergism between GaN semiconductors and biological cells. The electrical properties, persistent photoconductivity (PPC), nanostructures, and chemical functionalization of GaN on the promotion of cell behaviors, such as growth, adhesion, differentiation, and signal transduction, are emphatically introduced. The purpose of this study is to provide guidance to explore the detection and regulation methods of cell behavior based on semiconductors and promote the application of them in the field of bioelectronics, such as biochips, biosensors, and implantable systems.

Construct of qualitative diagnostic biomarkers specific for glioma by pairing serum microRNAs.

BACKGROUND: Serum microRNAs (miRNAs) are promising non-invasive biomarkers for diagnosing glioma. However, most reported predictive models are constructed without a large enough sample size, and quantitative expression levels of their constituent serum miRNAs are susceptible to batch effects, decreasing their clinical applicability. METHODS: We propose a general method for detecting qualitative serum predictive biomarkers using a large cohort of miRNA-profiled serum samples (n = 15,460) based on the within-sample relative expression orderings of miRNAs. RESULTS: Two panels of miRNA pairs (miRPairs) were developed. The first was composed of five serum miRPairs (5-miRPairs), reaching 100% diagnostic accuracy in three validation sets for distinguishing glioma and non-cancer controls (n = 436: glioma = 236, non-cancers = 200). An additional validation set without glioma samples (non-cancers = 2611) showed a predictive accuracy of 95.9%. The second panel included 32 serum miRPairs (32-miRPairs), reaching 100% diagnostic performance in training set on specifically discriminating glioma from other cancer types (sensitivity = 100%, specificity = 100%, accuracy = 100%), which was reproducible in five validation datasets (n = 3387: glioma = 236, non-glioma cancers = 3151, sensitivity> 97.9%, specificity> 99.5%, accuracy> 95.7%). In other brain diseases, the 5-miRPairs classified all non-neoplastic samples as non-cancer, including stroke (n = 165), Alzheimer's disease (n = 973), and healthy samples (n = 1820), and all neoplastic samples as cancer, including meningioma (n = 16), and primary central nervous system lymphoma samples (n = 39). The 32-miRPairs predicted 82.2 and 92.3% of the two kinds of neoplastic samples as positive, respectively. Based on the Human miRNA tissue atlas database, the glioma-specific 32-miRPairs were significantly enriched in the spinal cord (p = 0.013) and brain (p = 0.015). CONCLUSIONS: The identified 5-miRPairs and 32-miRPairs provide potential population screening and cancer-specific biomarkers for glioma clinical practice.

Single molecule localizations of voltage-gated sodium channel NaV1.5 on the surfaces of normal and cancer breast cells.

Voltage-gated sodium channels (VGSCs) are widely expressed in various types of tumor and cancer cells, and NaV1.5 is overexpressed in highly metastatic breast cancer cells. There may be positive relations between the expression levels of NaV1.5 and breast cancer recurrence and metastasis. Herein, NaV1.5 was detected and localized on the surfaces of normal and cancer breast cells by the single molecule recognition imaging (SMRI) mode of atomic force microscopy (AFM). The results reveal that NaV1.5 was irregularly distributed on the surfaces of normal and cancer breast cells. The NaV1.5 has an area percentage of 0.6% and 7.2% on normal and cancer breast cells, respectively, which indicates that there is more NaV1.5 on cancer cells than on normal cells. The specific interaction forces and binding kinetics in the NaV1.5-antibody complex system were investigated with the single molecule force spectroscopy (SMFS) mode of AFM, indicating that the stability of the NaV1.5-antibody on normal breast cells is higher than that on cancer breast cells. All these results will be useful to study the interactions of other ion channel-antibody systems, and will also be useful to understand the role of sodium channels in tumor metastasis and invasion.

Identification of an Individualized Prognostic Biomarker for Serous Ovarian Cancer: A Qualitative Model.

Serous ovarian cancer is the most common type of ovarian epithelial cancer and usually has a poor prognosis. The objective of this study was to construct an individualized prognostic model for predicting overall survival in serous ovarian cancer. Based on the relative expression orderings (Ea > Eb/Ea ≤ Eb) of gene pairs closely associated with serous ovarian prognosis, we tried constructing a potential individualized qualitative biomarker by the greedy algorithm and evaluated the performance in independent validation datasets. We constructed a prognostic biomarker consisting of 20 gene pairs (SOV-P20). The overall survival between high- and low-risk groups stratified by SOV-P20 was statistically significantly different in the training and independent validation datasets from other platforms (p < 0.05, Wilcoxon test). The average area under the curve (AUC) values of the training and three validation datasets were 0.756, 0.590, 0.630, and 0.680, respectively. The distribution of most immune cells between high- and low-risk groups was quite different (p < 0.001, Wilcoxon test). The low-risk patients tended to show significantly better tumor response to chemotherapy than the high-risk patients (p < 0.05, Fisher's exact test). SOV-P20 achieved the highest mean index of concordance (C-index) (0.624) compared with the other seven existing prognostic signatures (ranging from 0.511 to 0.619). SOV-P20 is a promising prognostic biomarker for serous ovarian cancer, which will be applicable for clinical predictive risk assessment.

Fast ionic transport in SrTiO3/LaAlO3 heterostructure.

SrTiO3/LaAlO3 heterostructures were constructed, which achieved a high ionic conductivity of 0.24 S cm-1 and fuel cell power output of 675 mW cm-2 at 520 °C. Theoretical calculations and experimental determinations found that the resultant built-in electric field plays an important role in fast ionic conduction through the interface with the electron accumulation layer in the interface region.

Predict ovarian cancer by pairing serum miRNAs: Construct of single sample classifiers.

Objective: The accuracy of CA125 or clinical examination in ovarian cancer (OVC) screening is still facing challenges. Serum miRNAs have been considered as promising biomarkers for clinical applications. Here, we propose a single sample classifier (SSC) method based on within-sample relative expression orderings (REOs) of serum miRNAs for OVC diagnosis. Methods: Based on the stable REOs within 4,965 non-cancer serum samples, we developed the SSC for OVC in the training cohort (GSE106817: OVC = 200, non-cancer = 2,000) by focusing on highly reversed REOs within OVC. The best diagnosis is achieved using a combination of reversed miRNA pairs, considering the largest evaluation index and the lowest number of miRNA pairs possessed according to the voting rule. The SSC was then validated in internal data (GSE106817: OVC = 120, non-cancer = 759) and external data (GSE113486: OVC = 40, non-cancer = 100). Results: The obtained 13-miRPairs classifier showed high diagnostic accuracy on distinguishing OVC from non-cancer controls in the training set (sensitivity = 98.00%, specificity = 99.60%), which was reproducible in internal data (sensitivity = 98.33%, specificity = 99.21%) and external data (sensitivity = 97.50%, specificity = 100%). Compared with the published models, it stood out in terms of correct positive predictive value (PPV) and negative predictive value (NPV) (PPV = 96.08% and NPV=95.16% in training set, and both above 99% in validation set). In addition, 13-miRPairs demonstrated a classification accuracy of over 97.5% for stage I OVC samples. By integrating other non-OVC serum samples as a control, the obtained 17-miRPairs classifier could distinguish OVC from other cancers (AUC>92% in training and validation set). Conclusion: The REO-based SSCs performed well in predicting OVC (including early samples) and distinguishing OVC from other cancer types, proving that REOs of serum miRNAs represent a robust and non-invasive biomarker.

Direct investigations of the electrical conductivity of normal and cancer breast cells by conductive atomic force microscopy.

Breast cancer is one of the most commonly diagnosed malignant cancers that threatens the health of women severely. The pathogenesis has not been revealed exhaustively due to the complex mechanisms. Evidences suggest that electrical conductivity properties play critical roles in cellular functions and activities. But the roles of electrical conductivity in pathogenesis of breast cancer cells have not been studied clearly at the nanometer level yet. In the present work, the electrical conductivity and electron transport of two normal and one cancer breast cell lines were investigated and compared at nanometer spatial level and picoampere current level by Conductive Atomic Force Microscopy (CAFM). The cell bodies of normal and cancer breast cells show the typical capacitor behaviors with little conductivity capability for electricity. The capacitance of cell bodies of the cancer breast cells is less than the normal breast cells. The conductivity of the processes of normal and cancer breast cells has also been investigated. The processes of the normal breast cells also exhibit the capacitor behavior. While the processes of the breast cells are electrically conductive along micrometer length scales, and show the semiconductor like conductive characteristics with Schottky barrier of 0.8391 V. All these demonstrate that the electrical conductivity of the cancer breast cells is better than the normal breast cells. This work will be helpful in the further investigations of electrical conductivity of normal and cancer cells at nanometer level, and will also pave new way in the distinguishing the cancer cells and tissues from the normal cells and tissues.

Rapid Gelling of Guar Gum Hydrogel Stabilized by Copper Hydroxide Nanoclusters for Efficient Removal of Heavy Metal and Supercapacitors.

In this paper, guar gum (GG) hydrogel has been successfully prepared by adding GG and Cu2+ mixture into an alkaline medium. The formation mechanism of the hydrogel has been investigated through various techniques. Results reveal GG facilitates the formation of ultrafine copper hydroxide clusters with a diameter of ∼3 nm. Moreover, these nanoclusters bring about a rapid gelling of GG within 10 ms. The synthesized hydrogel is applied to the adsorption of heavy metal ions from wastewater. The hydrogel shows excellent removal efficiency in removing various heavy metal ions. Besides, the hydrogel derived porous carbon exhibits high specific capacitance (281 F/g at 1 A/g) and excellent rate capacity. The high contaminant removal efficiency character and excellent electrochemical performance endow GG hydrogel with potential applications in the environmental and energy storage field.

Recent Advances in Understanding the Role of Cartilage Lubrication in Osteoarthritis.

The remarkable lubrication properties of normal articular cartilage play an essential role in daily life, providing almost frictionless movements of joints. Alterations of cartilage surface or degradation of biomacromolecules within synovial fluid increase the wear and tear of the cartilage and hence determining the onset of the most common joint disease, osteoarthritis (OA). The irreversible and progressive degradation of articular cartilage is the hallmark of OA. Considering the absence of effective options to treat OA, the mechanosensitivity of chondrocytes has captured attention. As the only embedded cells in cartilage, the metabolism of chondrocytes is essential in maintaining homeostasis of cartilage, which triggers motivations to understand what is behind the low friction of cartilage and develop biolubrication-based strategies to postpone or even possibly heal OA. This review firstly focuses on the mechanism of cartilage lubrication, particularly on boundary lubrication. Then the mechanotransduction (especially shear stress) of chondrocytes is discussed. The following summarizes the recent development of cartilage-inspired biolubricants to highlight the correlation between cartilage lubrication and OA. One might expect that the restoration of cartilage lubrication at the early stage of OA could potentially promote the regeneration of cartilage and reverse its pathology to cure OA.

Studying the rhodopsin-like G protein-coupled receptors by atomic force microscopy.

Rhodopsin-like G protein-coupled receptors (GPCRs), widely distributed in microorganisms, invertebrates, and vertebrates, are the largest class in GPCRs, and are involved in many important physiological and pathological processes, including the photosensitivity, regulation of behavior and emotion, and so on. Atomic force microscopy (AFM) is a powerful and multifunctional toolkit in bionanotechnology, as it can image the morphology of membrane proteins at subnanometer spatial resolution and detect forces related with membrane proteins down to piconewton level by single-molecule force spectroscopy (SMFS) mode under physiological conditions. Herein, the achievements of AFM in the study of rhodopsin-like GPCRs, including observing the high-resolution topography and structural changes, revealing the interaction forces, binding kinetics, and mechanical properties (such as modulus), are reviewed and summarized. Finally, the challenges, outlook, and prospects of AFM in the study of rhodopsin-like GPCRs are discussed.

In Operando Mechanism Analysis on Nanocrystalline Silicon Anode Material for Reversible and Ultrafast Sodium Storage.

The electrochemical mechanism of nanocrystalline silicon anode in sodium ion batteries is first studied via in operando Raman and in operando X-ray diffraction. An irreversible structural conversion from crystalline silicon to amorphous silicon takes place during the initial cycles, leading to ultrafast reversible sodium insertion in the newly generated amorphous silicon. Furthermore, an optimized silicon/carbon composite has been developed to further improve its electrochemical performance.

Facile microwave-assisted synthesis of Klockmannite CuSe nanosheets and their exceptional electrical properties.

Klockmannite copper selenide nanosheets (CuSe NSs) are synthesized by a facile microwave-assisted method and fully characterized. The nanosheets have smooth surface and hexagonal shape. The lateral size is 200-500 nm × 400-800 nm and the thickness is 55 ± 20 nm. The current-voltage characteristics of CuSe NS films show unique Ohmic and high-conducting behaviors, comparable to the thermally-deposited gold electrode. The high electrical conductivity of CuSe NSs implies their promising applications in printed electronics and nanodevices. Moreover, the local electrical variation is observed, for the first time, within an individual CuSe NS at low bias voltages (0.1 ~ 3 V) by conductive atomic force microscopy (C-AFM). This is ascribed to the quantum size effect of NS and the presence of Schottky barrier. In addition, the influence of the molar ratio of Cu(2+)/SeO2, reaction temperature, and reaction time on the growth of CuSe NSs is explored. The template effect of oleylamine and the intrinsic crystal nature of CuSe NS are proposed to account for the growth of hexagonal CuSe NSs.

Constant current etching of gold tips suitable for tip-enhanced Raman spectroscopy.

We introduce a setup and method to produce gold tips that are suitable for tip-enhanced Raman spectroscopy by using a single step constant current electrochemical etch. The etching process is fully automated with only three preset parameters: the etching current, the reference voltage and the immersed length of gold wires. By optimizing these parameters, reproducible high quality tips with smooth surface and a radius curvature of about 20 nm can be formed. Tips prepared with this method were examined by tip-enhanced Raman spectroscopy experiments on the samples of single-wall carbon nanotube, p-aminothiophenol, and graphene. In the Raman mapping of single-wall carbon nanotubes, the spatial resolution is about 15 nm.