Nanoscale imaging and force probing of biomolecular systems using atomic force microscopy: from single molecules to living cells

Due to the lack of adequate tools for observation, native molecular behaviors at the nanoscale have been poorly understood. The advent of atomic force microscopy (AFM) provides an exciting instrument for investigating physiological processes on individual living cells with molecular resolution, which attracts the attention of worldwide researchers. In the past few decades, AFM has been widely utilized to investigate molecular activities on diverse biological interfaces, and the performances and functions of AFM have also been continuously improved, greatly improving our understanding of the behaviors of single molecules in action and demonstrating the important role of AFM in addressing biological issues with unprecedented spatiotemporal resolution. In this article, we review the related techniques and recent progress about applying AFM to characterize biomolecular systems in situ from single molecules to living cells. The challenges and future directions are also discussed.

Atomic Force Microscopy in Characterizing Cell Mechanics for Biomedical Applications: A Review

Cell mechanics is a novel label-free biomarker for indicating cell states and pathological changes. The advent of atomic force microscopy (AFM) provides a powerful tool for quantifying the mechanical properties of single living cells in aqueous conditions. The wide use of AFM in characterizing cell mechanics in the past two decades has yielded remarkable novel insights in understanding the development and progression of certain diseases, such as cancer, showing the huge potential of cell mechanics for practical applications in the field of biomedicine. In this paper, we reviewed the utilization of AFM to characterize cell mechanics. First, the principle and method of AFM single-cell mechanical analysis was presented, along with the mechanical responses of cells to representative external stimuli measured by AFM. Next, the unique changes of cell mechanics in two types of physiological processes (stem cell differentiation, cancer metastasis) revealed by AFM were summarized. After that, the molecular mechanisms guiding cell mechanics were analyzed. Finally the challenges and future directions were discussed.

Performance Investigation of Multilayer MoS2 Thin-Film Transistors Fabricated via Mask-free Optically Induced Electrodeposition

Transition metal dichalcogenides, particularly MoS₂, have recently received enormous interest in explorations of the physics and technology of nanodevice applications because of their excellent optical and electronic properties. Although monolayer MoS₂ has been extensively investigated for various possible applications, its difficulty of fabrication renders it less appealing than multilayer MoS₂. Moreover, multilayer MoS₂, with its inherent high electronic/photonic state densities, has higher output driving capabilities and can better satisfy the ever-increasing demand for versatile devices. Here, we present multilayer MoS₂ back-gate thin-film transistors (TFTs) that can achieve a relatively low subthreshold swing of 0.75 V/decade and a high mobility of 41 cm²·V^-1·s^-1, which exceeds the typical mobility value of state-of-the-art amorphous silicon-based TFTs by a factor of 80. Ag and Au electrode-based MoS₂ TFTs were fabricated by a convenient and rapid process. Then we performed a detailed analysis of the impacts of metal contacts and MoS₂ film thickness on electronic performance. Our findings show that smoother metal contacts exhibit better electronic characteristics and that MoS₂ film thickness should be controlled within a reasonable range of 30-40 nm to obtain the best mobility values, thereby providing valuable insights regarding performance enhancement for MoS₂ TFTs. Additionally, to overcome the limitations of the conventional fabrication method, we employed a novel approach known as optically induced electrodeposition (OIE), which allows the flexible and precise patterning of metal films and enables rapid and mask-free device fabrication, for TFT fabrication.

Characterization of Carbon Nanotube Based Infrared Photodetector Using Digital Microscopy

The state-of-the-art infrared camera suffers from the trade-off between sensitivity and cost. The bolometer infrared sensors are low resolution and slow speed while the quantum photodetectors are bulky and expensive. In this paper, the novel low dimensional material Carbon Nanotube (CNT) based non-cryogenic photodetector is proposed to detect infrared (IR) irradiance. The photoconductance and photovoltaic effect need to be distinguished to fully understand and improve nano IR detector performance. The robust test bench using digital microscope and precise five axis substage is used to measure detector photoresponse. The relative position between nanoscale sensor and IR beam is localized by mapping the photocurrent on laser spot. The distance between photodetector and infrared laser lens is leveraged by digital microscope. The experimental results show photovoltaic quantum effect dominates CNT-Metal Schottky based IR detector and the photoresponse is dependent on contact size and metal materials. The photoresponsivity can reach to 16.8 μA/mW at 808 nm wavelength. The proposed method will be applicable for 1D/2D nanoscale material based photodiode characterization.

Online Determination of Graphene Lattice Orientation Through Lateral Forces

Rapid progress in graphene engineering has called for a simple and effective method to determine the lattice orientation on graphene before tailoring graphene to the desired edge structures and shapes. In this work, a wavelet transform-based frequency identification method is developed to distinguish the lattice orientation of graphene. The lattice orientation is determined through the different distribution of the frequency power spectrum just from a single scan line. This method is proven both theoretically and experimentally to be useful and controllable. The results at the atomic scale show that the frequencies vary with the lattice orientation of graphene. Thus, an adjusted angle to the desired lattice orientation (zigzag or armchair) can easily be calculated based on the frequency obtained from the single scan line. Ultimately, these results will play a critical role in wafer-size graphene engineering and in the manufacturing of graphene-based nanodevices.

Nonconvex compressive video sensing

High-speed cameras explore more details than normal cameras in the time sequence, while the conventional video sampling suffers from the trade-off between temporal and spatial resolutions due to the sensor's physical limitation. Compressive sensing overcomes this obstacle by combining the sampling and compression procedures together. A single-pixel-based real-time video acquisition is proposed to record dynamic scenes, and a fast nonconvex algorithm for the nonconvex sorted ℓ₁ regularization is applied to reconstruct frame differences using few numbers of measurements. Then, an edge-detection-based denoising method is employed to reduce the error in the frame difference image. The experimental results show that the proposed algorithm together with the single-pixel imaging system makes compressive video cameras available.

[Determination of Trace Elements in the Melon of Indo-Pacific Humpback Dolphins (Sousa chinensis) with ICP-MS]

The Indo-Pacific humpback dolphins (Sousa chinensis) with long life-span are top predators in marine ecosystem -and they could accumulate heavy metals and persistent organic pollutants in their tissues, while the melon is a unique lipid-rich structure within the cetacean forehead that functions in the transmission of echolocation signals. To explore the baseline levels and the main characteristics of the components, the concentrations of vanadium (V), nickel (Ni), chromium (Cr), manganese (Mn), copper (Cu), arsenic (As), zinc (Zn), mercury (Hg), selenium (Se), cadmium (Cd) and lead (Pb) were determined in the melon of the Indo-Pacific humpback dolphins with inductively coupled plasma mass spectrometry (ICP-MS). The results showed that this method was quite suitable for the determination of trace elements in the melon of Indo-Pacific humpback dolphins with highly accuracy and precision, and the trace elements in melon existed individual differences. The average contents were in the order of Zn>As>Cu>Mn>Se>Hg>Cr>Ni>V>Pb>Cd. It is worth noting that the within (1.158 μg·g-1 ww), non-essential toxic trace element may cause toxic effect on the dolphins. Spearman correlation analysis showed positively significant correlations between As, Cd, Hg and body length, indicating that the concentrations of As, Cd, Hg may increase with age. Moreover, Cr and Ni were positively correlated (p<0.05), a significant negative correlation was observed between Mn and As (p<0.01), indicating that there are certain correlation among elements. In addition, the principal component analysis results showed that V, Mn, Ni, Se, Cu, Hg are the main characteristics of trace elements for melon. This study presents a reliable method for determination of the trace element analysis in cetacean melon, and this is the first study that reports the trance elements in the melon of the Indo-Pacific humpback dolphins in PRE that could provide reasonable and effective information for its conservation work.

Bio-syncretic tweezers actuated by microorganisms: modeling and analysis

Advancements in micro-/nano-technology have led to the development of micro-manipulators. However, some challenges remain; for instance, the efficiency, precision and flexibility of micro-manipulators restrain their applications. This paper proposes a bio-tweezer system to flexibly manipulate micro-objects with bio-actuation via local light-induced high-concentration microorganisms in two different manipulation modes: light-spot induced mode and geometric shape-induced mode. Depending on the shape of micro-objects, either 2-dimensional translation or 1-dimensional rotation can be achieved. Based on the Langevin equation, a mathematical model considering both hydrodynamics and mimicked Brownian motion is proposed to analyze the bio-manipulation performance of the microorganisms; the model was validated by experiments to translate micro-particles in a two-dimensional plane and to rotate a micro-gear structure around its axis. This paper will aid in the development of micro-manipulators and the quantitative understanding of micro-/nano-manipulation actuated by microorganisms.

Modeling and analysis of bio-syncretic micro-swimmers for cardiomyocyte-based actuation

Along with sensation and intelligence, actuation is one of the most important factors in the development of conventional robots. Many novel achievements have been made regarding bio-based actuators to solve the challenges of conventional actuation. However, few studies have focused on methods for controlling the movement performance of bio-syncretic robots by designing robotic structures and programming actuation bio-entities. In this paper, a theoretical model was derived considering kinematics and hydromechanics to describe the dynamics of a dolphin-shaped microstructure and to control the bio-syncretic swimmer movement by establishing the relationships between the swimming velocity of the bio-swimmer, the cell seeding concentration and the cell contractility. The proposed theoretical model was then verified with the fabricated biomimetic swimmer prototype actuated by equivalent external magnetism replacing the bio-entity force based on the study of living, beating cardiomyocyte contractility. This work can improve the development of bio-syncretic robots with an approach to preplanning the seeding concentration of cells for controlling the movement velocity of microstructures, and is also meaningful for biomimetic robots, medical treatments and interventional therapy applications.

Integrated Task Planning and Control for Mobile Manipulators

In this paper we present an approach to decoupled force/position control of the end-effector along the same direction for redundant robots, and an approach to nonholonomic cart pushing with mobile manipulators. The mobile manipulator is considered as a redundant robot, and a unified dynamic model for an integrated mobile platform and on-board manipulator is developed. The dynamic model is decoupled and linearized using the nonlinear feedback technique in a unified frame. Combining the event-based planning and control method with singularity analysis of the robot arm, a task level action controller is designed and an online kinematic redundancy resolution scheme is developed. The system is stable during normal operation as well as at the occurrence of unexpected obstacles. In addition, explicit force/position control along the same task direction for redundant robots is proposed. The kinematic redundancy of mobile manipulators enables independent control of force and position along the same task directions. To verify the decoupled force/postion scheme, an integrated task planning and control approach is further proposed for the mobile manipulator to complete complicated tasks by regulating its output force. A cart pushing task, which requires both force and position control along the same task direction, is discussed. The cart manipulation task fully integrates trajectory and force planning of the cart, and planning and control of the mobile manipulators. The approaches have been tested on a mobile manipulator consisting of a Nomadic XR4000 and a Puma 560 robot arm. The experimental results demonstrate the efficacy of the approach for the mobile manipulation of a nonholonomic cart.

Supermedia Interface for Internet-based Telediagnostics of Breast Pathology

We present our development of a supermedia interface for telediagnostics of breast pathology via the Internet. Supermedia is the incorporation of multiple media and data streams, such as audio, video, ultrasound images, and tactile and haptic sensor data for enhanced telepresence capabilities. Our supermedia interface comprises an anthropomorphic arm/hand equipped with haptic and tactile sensing, ultrasound imaging capabilities, a physician interface capable of rendering both haptic and tactile information, and two-way audio and video. The supermedia interface was tested via the Internet and enables telediagnostics. Preliminary experiments with silicone breast models have demonstrated the e fectiveness of the supermedia interface for telediagnostics. The interface is expected to enhance and improve the diagnostic performance of breast pathology as well as promote telediagnostics in remote areas and for patients with cultural barriers.

Experimental study and modeling of atomic-scale friction in zigzag and armchair lattice orientations of MoS2

Physical properties of two-dimensional materials, such as graphene, black phosphorus, molybdenum disulfide (MoS₂) and tungsten disulfide, exhibit significant dependence on their lattice orientations, especially for zigzag and armchair lattice orientations. Understanding of the atomic probe motion on surfaces with different orientations helps in the study of anisotropic materials. Unfortunately, there is no comprehensive model that can describe the probe motion mechanism. In this paper, we report a tribological study of MoS₂ in zigzag and armchair orientations. We observed a characteristic power spectrum and friction force values. To explain our results, we developed a modified, two-dimensional, stick-slip Tomlinson model that allows simulation of the probe motion on MoS₂ surfaces by combining the motion in the Mo layer and S layer. Our model fits well with the experimental data and provides a theoretical basis for tribological studies of two-dimensional materials.

Effects of temperature and cellular interactions on the mechanics and morphology of human cancer cells investigated by atomic force microscopy

Cell mechanics plays an important role in cellular physiological activities. Recent studies have shown that cellular mechanical properties are novel biomarkers for indicating the cell states. In this article, temperature-controllable atomic force microscopy (AFM) was applied to quantitatively investigate the effects of temperature and cellular interactions on the mechanics and morphology of human cancer cells. First, AFM indenting experiments were performed on six types of human cells to investigate the changes of cellular Young's modulus at different temperatures and the results showed that the mechanical responses to the changes of temperature were variable for different types of cancer cells. Second, AFM imaging experiments were performed to observe the morphological changes in living cells at different temperatures and the results showed the significant changes of cell morphology caused by the alterations of temperature. Finally, by co-culturing human cancer cells with human immune cells, the mechanical and morphological changes in cancer cells were investigated. The results showed that the co-culture of cancer cells and immune cells could cause the distinct mechanical changes in cancer cells, but no significant morphological differences were observed. The experimental results improved our understanding of the effects of temperature and cellular interactions on the mechanics and morphology of cancer cells.

Abstract 789: CT413 is a novel dual Axl/Mer inhibitor that potently inhibited the growth of Axl overexpressed tumors

Receptor tyrosine kinases (RTKs), which play an important role in cell signal transduction, are proven therapeutic targets for the treatment of human cancers. Axl and Mer are members of the TAM family which also includes Tyro-3. Axl has been established as a strong drug target candidate for therapeutic inhibition of cancer invasion and dissemination. As metastatic disease is the most frequent cause of cancer patient mortality, therapeutics specifically aimed at inhibiting metastatic dissemination and colonization would be important additions to the arsenal of drugs in clinical use. Some FDA-approved or in clinical trial molecules block Axl and Mer activity, however, there is no inhibitor clearly designed to inhibit Axl and Mer on the market. As a potential new therapy against malignant tumor, the development of Axl and Mer dual inhibitors is of great significance.

CT413 is a novel, orally bioavailable Axl/Mer inhibitor that is currently in our preclinical development pipeline. In biochemical assay, CT413 potently inhibit Axl and Mer with respective IC50 values of 4 and &lt; 1 nM. Among 97 kinase screened, CT413 inhibited Met and Ron receptor tyrosine kinases with IC50 values of 3 and 9 nM, respectively. Furthermore, CT413 blocked the Axl, Met and Ron autophosphorylation in cells with IC50 values of 13, 34 and 540 nM, respectively, demonstrating high kinase selectivity in both biochemical and cell-based assays. CT413 potently suppressed tumor growth in BALB/cA-nu/nu mice bearing subcutaneous human tumor xenografts. For example, in A549 (NSCLC), SK-OV-3 (ovarian) and K562 (CML) tumor models, CT413 inhibited tumor growth with TGIs of 84%, 110% and 66% dosed orally at 30 mg/kg QD, as compared to the vehicle-treated group. CT413 did not inhibit CYP450 subtype 3A4, 2D6, 1A2, 2C9 and 2C19 (IC50 &gt; 10 μM) and showed no induction effect on CYP450 subtype 1A2, 2B6 and 3A4. Furthermore, the IC50 of CT413 at hERG sodium ion channel was determined to be greater than 30 μM, indicating its minimal cardio-liability. CT413 exhibited good metabolic stability when incubated with human or rat microsome. Pharmacokinetic studies performed in rodents and large animals showed that CT413 had low clearance and high oral exposures across animal species. The oral bioavailability for mice, rats, dogs and monkeys are 133%, 85%, 83% and 68% respectively. The non-GLP 28-day toxicity studies in rats and dogs indicated that CT413 has an excellent therapeutic window. Based on these promising results, CT413 is advanced in our project pipeline as a clinical candidate for cancer therapy.

Citation Format: Ning Xi, Tingjin Wang, Yanjun Wu, Min Liao, Yanming Feng, Ning Kang, Zhaohe Wang, Yingjun Zhang. CT413 is a novel dual Axl/Mer inhibitor that potently inhibited the growth of Axl overexpressed tumors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 789. doi:10.1158/1538-7445.AM2015-789

Abstract 2659: Discovery of CT365, a highly potent inhibitor of PI3K and mTOR, for cancer treatment

The Phosphatidylinositol 3-kinase (PI3K) regulates essential cellular functions including cell metabolism, growth, migration, survival and angiogenesis. PI3K are divided into three subclasses on the basis of structure, regulation and lipid substrate specificity. The class I subgroup of PI3K, which includes class IA isoforms α, β, δ and class IB isoform γ, is involved primarily in the pathogenesis of human cancer. Thus, activation of the PI3K/AKT/mTOR pathway is commonly observed in human cancer and is critical for tumor progression and resistance to anti-neoplastic drugs, including cytotoxic chemotherapy and targeted drugs. Agents targeted at PI3K/mTOR signaling pathway are believed useful to treat proliferative diseases such as cancers and pulmonary fibrosis. PI3K/mTOR dual inhibitors have enhanced efficacy and a favorable safety profile. With increased understanding of immune modulation, better strategic application of rational combinations, and greater focus on patient selection, this promising class of targeted agents may soon be able to realize its potential to treat human cancers.

Our clinical candidate CT365 is a potent, orally bioavailable small molecule kinase inhibitor against class I subgroup PI3Ks and mTOR. In the biochemical assays, CT365 exhibited nanomolar activities against human PI3 kinase p110α/p85α, p110β/p85α, p110δ/p85αand p120γ, with respective IC50 values of 4, 41, 2, and 6 nM. It also inhibited mTOR with an IC50 of 4 nM. CT365 demonstrated high degree of kinase selectivity when CT365 was profiled in the KinomeScan platform against a panel of 97 kinases, with only 3 kinases showing less than 10% of control binding at 1 μM. CT365 potently suppressed tumor growth in human tumor subcutaneous xenograft models with ED50s in the range of 0.8 ∼ 1.5 mg/kg. In pharmacokinetic analysis, clearance in mice, rats, dogs and cynomolgus monkeys was 0.33, 4.83, 4.50 and 2.67 mL/min/kg; and oral bioavailability in mice, rats, dogs and monkeys was 79, 95, 108 and 60%, respectively. CT365 showed no inhibition against CYP450 subtypes 3A4, 2D6, 1A2, 2C9 and 2C19 at 10 μM and no induction at 1A2, 2B6 and 3A4. The IC50 at hERG sodium channel was also determined to be greater than 30 μM. Non-GLP 28-day toxicological studies in mice and dogs indicated that CT365 has good therapeutic window. Based on the remarkable potencies of CT365 in both in vitro and in vivo studies, and desirable pharmacokinetic and toxicological profiles, CT365 was selected as a clinical candidate for the treatment of cancer.

Citation Format: Ning Xi, Yanjun Wu, Tingjin Wang, Heng Wang, Zhiyong Li, Qingwei Meng, Jing Li, Zhaohe Wang, Yingjun Zhang. Discovery of CT365, a highly potent inhibitor of PI3K and mTOR, for cancer treatment. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2659. doi:10.1158/1538-7445.AM2015-2659

Glow discharge electrolysis plasma initiated preparation of temperature/pH dual sensitivity reed hemicellulose-based hydrogels

The temperature/pH dual sensitivity reed hemicellulose-based hydrogels have been prepared through glow discharge electrolysis plasma (GDEP). The effect of different discharge voltages on the temperature and pH response performance of reed hemicellulose-based hydrogels was inspected, and the formation mechanism, deswelling behaviors of reed hemicellulose-based hydrogels were also discussed. At the same time, infrared spectroscopy (FT-IR), scanning differential thermal analysis (DSC) and scanning electron microscope (SEM) were adopted to characterize the structure, phase transformation behaviors and microstructure of hydrogels. It turned out to be that all reed hemicellulose-based hydrogels had a double sensitivity to temperature and pH, and their phase transition temperatures were all approximately 33 °C, as well as the deswelling dynamics met the first model. In addition, the hydrogel (TPRH-3), under discharge voltage 600 V, was more sensitive to temperature and pH and had higher deswelling ratio.

Cellular level robotic surgery: Nanodissection of intermediate filaments in live keratinocytes

We present the nanosurgery on the cytoskeleton of live cells using AFM based nanorobotics to achieve adhesiolysis and mimic the effect of pathophysiological modulation of intercellular adhesion. Nanosurgery successfully severs the intermediate filament bundles and disrupts cell-cell adhesion similar to the desmosomal protein disassembly in autoimmune disease, or the cationic modulation of desmosome formation. Our nanomechanical analysis revealed that adhesion loss results in a decrease in cellular stiffness in both cases of biochemical modulation of the desmosome junctions and mechanical disruption of intercellular adhesion, supporting the notion that intercellular adhesion through intermediate filaments anchors the cell structure as focal adhesion does and that intermediate filaments are integral components in cell mechanical integrity. The surgical process could potentially help reveal the mechanism of autoimmune pathology-induced cell-cell adhesion loss as well as its related pathways that lead to cell apoptosis.

Glow discharge electrolysis plasma induced synthesis of cellulose-based ionic hydrogels and their multiple response behaviors

The cellulose-based hydrogel which was prepared through glow discharge electrolysis plasma showed excellent swelling performance and multiple response behaviors.

Investigating dynamic structural and mechanical changes of neuroblastoma cells associated with glutamate-mediated neurodegeneration

Glutamate-mediated neurodegeneration resulting from excessive activation of glutamate receptors is recognized as one of the major causes of various neurological disorders such as Alzheimer's and Huntington's diseases. However, the underlying mechanisms in the neurodegenerative process remain unidentified. Here, we investigate the real-time dynamic structural and mechanical changes associated with the neurodegeneration induced by the activation of N-methyl-D-aspartate (NMDA) receptors (a subtype of glutamate receptors) at the nanoscale. Atomic force microscopy (AFM) is employed to measure the three-dimensional (3-D) topography and mechanical properties of live SH-SY5Y cells under stimulus of NMDA receptors. A significant increase in surface roughness and stiffness of the cell is observed after NMDA treatment, which indicates the time-dependent neuronal cell behavior under NMDA-mediated neurodegeneration. The present AFM based study further advance our understanding of the neurodegenerative process to elucidate the pathways and mechanisms that govern NMDA induced neurodegeneration, so as to facilitate the development of novel therapeutic strategies for neurodegenerative diseases.

Quality of teleoperator adaptive control for telerobotic operations

Extensive studies have been conducted on telerobotic operations for decades due to their widespread applications in a variety of areas. Most studies have been focused on two major issues: stability and telepresence. Few have studied the influence of the operation status of the teleoperator on the performance of telerobotic operations. As subnormal operation status of the teleoperator may result in insufficient and even incorrect operations, the quality of teleoperator (QoT) is an important impact on the performance of the telerobotic operations in terms of the efficiency and safety even if both the stability and telepresence are guaranteed. Therefore, this paper investigates the online identification of the QoT and its application to telerobotic operations. The QoT is identified based on five QoT indicators which are generated based on the teleoperator’s brain EEG signals. A QoT adaptive control method is designed to adapt the velocity and responsivity of the robotic system to the operation status of the teleoperator such that the teleoperation efficiency and safety can be enhanced. The online QoT identification method was conducted on various teleoperators and the QoT adaptive control method was implemented on a mobile manipulator teleoperation system. The experimental results demonstrated the effectiveness and advantages of the proposed methods.

AFM analysis of the multiple types of molecular interactions involved in rituximab lymphoma therapy on patient tumor cells and NK cells

Rituximab is a monoclonal antibody drug approved for the treatment of patients with lymphomas. Rituximab's main killing mechanism is antibody-dependent cellular cytotoxicity (ADCC). During ADCC, rituximab's fragment antigen binding (Fab) region binds to the CD20 antigen on the tumor cell and its fragment crystallizable (Fc) region binds to the Fc receptor (FcR) on the natural killer (NK) cells. In this study, two types of molecular interactions (CD20-rituximab, FcR-rituximab) involved in ADCC were measured simultaneously on cells prepared from biopsy specimens of lymphoma patients by utilizing atomic force microscopy (AFM) with functionalized tips carrying rituximab. NK cells were detected by specific NKp46 fluorescent labeling and tumor cells were detected by specific ROR1 fluorescent labeling. Based on the fluorescence recognition, the binding affinity and distribution of FcRs on NK cells, and CD20 on tumor cells, were quantitatively measured and mapped. The binding affinity and distribution of FcRs (on NK cells) and CD20 (on tumor cells) were associated with rituximab clinical efficacy. The experimental results provide a new approach to simultaneously quantify the multiple types of molecular interactions involved in rituximab ADCC mechanism on patient biopsy cells, which is of potential clinical significance to predict rituximab efficacy for personalized medicine.

Nanoscale imaging and mechanical analysis of Fc receptor-mediated macrophage phagocytosis against cancer cells

Fc receptor-mediated macrophage phagocytosis against cancer cells is an important mechanism in the immune therapy of cancers. Traditional research about macrophage phagocytosis was based on optical microscopy, which cannot reveal detailed information because of the 200-nm-resolution limit. Quantitatively investigating the macrophage phagocytosis at micro- and nanoscale levels is still scarce. The advent of atomic force microscopy (AFM) offers an excellent analytical instrument for quantitatively investigating the biological processes at single-cell and single-molecule levels under native conditions. In this work, we combined AFM and fluorescence microscopy to visualize and quantify the detailed changes in cell morphology and mechanical properties during the process of Fc receptor-mediated macrophage phagocytosis against cancer cells. Lymphoma cells were discernible by fluorescence staining. Then, the dynamic process of phagocytosis was observed by time-lapse optical microscopy. Next, AFM was applied to investigate the detailed cellular behaviors during macrophage phagocytosis under the guidance of fluorescence recognition. AFM imaging revealed the distinct features in cellular ultramicrostructures for the different steps of macrophage phagocytosis. AFM cell mechanical property measurements indicated that the binding of cancer cells to macrophages could make macrophages become stiffer. The experimental results provide novel insights in understanding the Fc-receptor-mediated macrophage phagocytosis.

Nanoscale distribution of CD20 on B-cell lymphoma tumour cells and its potential role in the clinical efficacy of rituximab

Rituximab is an exciting monoclonal antibody drug approved for treating B-cell lymphomas and its target is the CD20 antigen which is expressed on the surface of B cells. In recent years, the variable efficacies of rituximab among different lymphoma patients have become an important clinical issue and urgently need to be solved for further development of antibodies with enhanced efficacies. In this work, atomic force microscopy (AFM) was used to investigate the nanoscale distribution of CD20 on the surface of tumour B cells from lymphoma patients to examine its potential role in the clinical therapeutic effects of rituximab. By performing ROR1 fluorescence labelling (ROR1 is a specific tumour cell surface marker) on the bone marrow cells prepared from B-cell lymphoma patients, the tumour B cells were recognized, and then AFM tips carrying rituximabs via polyethylene glycol crosslinkers were moved to the tumour cells to probe the specific CD20-rituximab interactions. By applying AFM single-molecule force spectroscopy (SMFS) at the local areas (500×500 nm²) on the surface of tumour B cells, the nanoscale distributions of CD20 on the surface of tumour B cells were mapped, visually showing that CD20 distributed heterogeneously on the cell surface. Bone marrow cell samples from three clinical B-cell lymphoma cases were collected to analyze the binding affinity and nanoscale distribution of CD20 on tumour cells. The experimental results showed that CD20 distribution on tumour cells were to some extent related to the clinical therapeutic outcomes while the CD20-rituximab binding forces did not have distinct effects to the clinical outcomes. These results can provide novel insights in understanding the rituximab's clinical efficacies from the nanoscale distribution of CD20 on the tumour cells at single-cell and single-molecule levels.

Imaging and measuring the biophysical properties of Fc gamma receptors on single macrophages using atomic force microscopy

Fc gamma receptors (FcγR), widely expressed on effector cells (e.g., NK cells, macrophages), play an important role in clinical cancer immunotherapy. The binding of FcγRs to the Fc portions of antibodies that are attached to the target cells can activate the antibody-dependent cell-mediated cytotoxicity (ADCC) killing mechanism which leads to the lysis of target cells. In this work, we used atomic force microscopy (AFM) to observe the cellular ultra-structures and measure the biophysical properties (affinity and distribution) of FcγRs on single macrophages in aqueous environments. AFM imaging was used to obtain the topographies of macrophages, revealing the nanoscale cellular fine structures. For molecular interaction recognition, antibody molecules were attached onto AFM tips via a heterobifunctional polyethylene glycol (PEG) crosslinker. With AFM single-molecule force spectroscopy, the binding affinities of FcγRs were quantitatively measured on single macrophages. Adhesion force mapping method was used to localize the FcγRs, revealing the nanoscale distribution of FcγRs on local areas of macrophages. The experimental results can improve our understanding of FcγRs on macrophages; the established approach will facilitate further research on physiological activities involved in antibody-based immunotherapy.

Cellular biophysical dynamics and ion channel activities detected by AFM-based nanorobotic manipulator in insulinoma β-cells

Distinct biochemical, electrochemical and electromechanical coupling processes of pancreatic β-cells may well underlie different response patterns of insulin release from glucose and capsaicin stimulation. Intracellular Ca(2+) levels increased rapidly and dose-dependently upon glucose stimulation, accompanied with about threefold rapid increases in cellular stiffness. Subsequently, cellular stiffness diminished rapidly and settled at a value about twofold of the baseline. Capsaicin caused a similar transient increase in intracellular Ca(2+) changes. However, cellular stiffness increased gradually to about twofold until leveling off. The current study characterizes for the first time the biophysical properties underlying glucose-induced biphasic responses of insulin secretion, distinctive from the slow and single-phased stiffness response to capsaicin despite similar changes in intracellular Ca(2+) levels. The integrated AFM nanorobotics and optical investigation enables the fine dissection of mechano-property from ion channel activities in response to specific and non-specific agonist stimulation, providing novel biomechanical markers for the insulin secretion process.

FROM THE CLINICAL EDITOR

This study characterizes the biophysical properties underlying glucose-induced biphasic responses of insulin secretion. Integrated AFM nanorobotics and optical investigations provided novel biomechanical markers for the insulin secretion process.

Online Sensor Information and Redundancy Resolution Based Obstacle Avoidance for High DOF Mobile Manipulator Teleoperation

Abstract High degrees of freedom (DOF) mobile manipulators provide more flexibility than conventional manipulators. They also provide manipulation operations with a mobility capacity and have potential in many applications. However, due to high redundancy, planning and control become more complicated and difficult, especially when obstacles occur. Most existing obstacle avoidance methods are based on off-line algorithms and most of them mainly focus on planning a new collision-free path, which is not appropriate for some applications, such as teleoperation and uses many system resources as well. Therefore, this paper presents an online planning and control method for obstacle avoidance in mobile manipulators using online sensor information and redundancy resolution. An obstacle contour reconstruction approach employing a mobile manipulator equipped with an active laser scanner system is also introduced in this paper. This method is implemented using a mobile manipulator with a seven-DOF manipulator and a four-wheel drive mobile base. The experimental results demonstrate the effectiveness of this method.

Imaging and measuring the molecular force of lymphoma pathological cells using atomic force microscopy

Atomic force microscopy (AFM) provides a new technology to visualize the cellular topography and quantify the molecular interactions at nanometer spatial resolution. In this work, AFM was used to image the cellular topography and measure the molecular force of pathological cells from B-cell lymphoma patients. After the fluorescence staining, cancer cells were recognized by their special morphological features and then the detailed topography was visualized by AFM imaging. The AFM images showed that cancer cells were much rougher than healthy cells. CD20 is a surface marker of B cells and rituximab is a monoclonal antibody against CD20. To measure the CD20-rituximab interaction forces, the polyethylene glycol (PEG) linker was used to link rituximab onto the AFM tip and the verification experiments of the functionalized probe indicated that rituximab molecules were successfully linked onto the AFM tip. The CD20-rituximab interaction forces were measured on about 20 pathological cells and the force measurement results indicated the CD20-rituximab binding forces were mainly in the range of 110-120 pN and 130-140 pN. These results can improve our understanding of the topography and molecular force of lymphoma pathological cells.

[Study on the removal method of electrogastrogram baseline wander based on wavelet transformation]

This paper presents a removal method of electrogastrogram (EGG) baseline wander based on wavelet transformation. The basic idea of this method is using the low-frequency signal which is obtained through multi-scale decomposition of EGG signals to approximate the baseline wander of EGG, so the component of baseline wander is filtered out from the sampling EGG signals. The method was applied successfully to process the experimental data of dog EGG in our laboratory. The experimental data and analysis of results showed that this method could filter out the baseline wander of EGG, and this method would not affect the gastric spike and slow wave bandwidth signals, which could be shown from the characteristics of bandwidth filter of wavelet transformation.

Design of Robotic Human Assistance Systems Using a Mobile Manipulator

Robotic systems have been widely used in many areas to assist human beings. Mobile manipulators are among the most popular choices. This paper investigates human assistance systems using a mobile manipulator, for example, to guide the blind and to transport objects. Distinct from existing systems, an integrated dynamic model and controller of the mobile manipulator are designed. Singularity, manipulability and safety are all considered in the system design. Furthermore, two human assistance modes – Robot-Human mode and Teleoperator-Robot-Human mode – are designed and analysed. The Teleoperator-Robot-Human mode can integrate human intelligence into the assistance system to further enhance the system efficiency and safety. The experimental results implemented on a mobile manipulator demonstrated the effectiveness of the designed systems.

Gate dependent photo-responses of carbon nanotube field effect phototransistors

Gate dependent photoconductivity of carbon nanotube (CNT) field effect phototransistors (FEPs) was systematically investigated in this study. The photo-response comparisons of CNT FEPs with symmetric and asymmetric metal structures connecting to the same CNT revealed that the gate effect contributed to a sensitivity improvement with a lower dark current, a higher photocurrent, and an enhanced photovoltage. A functionalized asymmetric FEP, fabricated by partially doping the CNT utilizing a polyethylene imine (PEI) polymer, verified that FEPs delivered a better performance by using asymmetric structures. A multi-gate FEP, with three pairs of side-gates that can electrostatically dope different sections of a CNT independently, was fabricated to examine the gate structure dependent photo-responses. Experimental measurements showed an unconventional photocurrent improvement that was weakly dependent on the gate location, which was attributed to the unique charge distribution of one-dimensional semiconductors.