Rapid nanomolding of nanotopography on flexible substrates to control muscle cell growth with enhanced maturation.

In vivo, multiple biophysical cues provided by highly ordered connective tissues of the extracellular matrix regulate skeletal muscle cells to align in parallel with one another. However, in routine in vitro cell culture environments, these key factors are often missing, which leads to changes in cell behavior. Here, we present a simple strategy for using optical media discs with nanogrooves and other polymer-based substrates nanomolded from the discs to directly culture muscle cells to study their response to the effect of biophysical cues such as nanotopography and substrate stiffness. We extend the range of study of biophysical cues for myoblasts by showing that they can sense ripple sizes as small as a 100 nm width and a 20 nm depth for myotube alignment, which has not been reported previously. The results revealed that nanotopography and substrate stiffness regulated myoblast proliferation and morphology independently, with nanotopographical cues showing a higher effect. These biophysical cues also worked synergistically, and their individual effects on cells were additive; i.e., by comparing cells grown on different polymer-based substrates (with and without nanogrooves), the cell proliferation rate could be reduced by as much as ~29%, and the elongation rate could be increased as much as ~116%. Moreover, during myogenesis, muscle cells actively responded to nanotopography and consistently showed increases in fusion and maturation indices of ~28% and ~21%, respectively. Finally, under electrical stimulation, the contraction amplitude of well-aligned myotubes was found to be almost 3 times greater than that for the cells on a smooth surface, regardless of the substrate stiffness.

Fluctuation in red cell distribution width predicts disseminated intravascular coagulation morbidity and mortality in sepsis: a retrospective single-center study.

BACKGROUND: Red cell distribution width (RDW) values increase in many diseases and conditions, including sepsis. However, the relationship between RDW fluctuation and prognosis in patients with sepsis or the likely morbidity associated with sepsis-induced disseminated intravascular coagulation (DIC) has not been previously investigated. This study examined the association between dynamic changes to RDW and DIC occurrence in sepsis, as well as the prognostic significance of changes to RDW during hospital stay in patients with sepsis. METHODS: We collected baseline emergency department admissions' data. All RDW values recorded during hospitalization of patients with sepsis were combined to calculate RDW standard deviation (RDW-SD) and the increase rate of RDW; we also collected data on coagulation indicators. The endpoints were 28-day mortality and sepsis-related DIC morbidity. RESULTS: Of 232 patients included in our analysis, 66 were diagnosed with DIC (28.4%), and 86 (37.1%) died within 28 days. The RDW-SD and the increase rate of RDW were independent risk factors for 28-day mortality and sepsis-associated DIC morbidity, respectively. The DIC occurrence and mortality rate increased continually with an increasing rate of RDW of at least 6%. CONCLUSIONS: The RDW-SD and RDW increase rate shown in the study as the indicators of RDW fluctuation can help predict sepsis-related DIC morbidity and prognosis in patients with sepsis.

A Review on Microscopic Visual Servoing for Micromanipulation Systems: Applications in Micromanufacturing, Biological Injection, and Nanosensor Assembly.

Micromanipulation is an interdisciplinary technology that integrates advanced knowledge of microscale/nanoscale science, mechanical engineering, electronic engineering, and control engineering. Over the past two decades, it has been widely applied in the fields of MEMS (microelectromechanical systems), bioengineering, and microdevice integration and manufacturing. Microvision servoing is the basic tool for enabling the automatic and precise micromanipulation of microscale/nanoscale entities. However, there are still many problems surrounding microvision servoing in theory and the application of this technology's micromanipulation processes. This paper summarizes the research, development status, and practical applications of critical components of microvision servoing for micromanipulation, including geometric calibration, autofocus techniques, depth information, and visual servoing control. Suggestions for guiding future innovation and development in this field are also provided in this review.

A Review of Automated Microinjection of Zebrafish Embryos.

Cell microinjection is a technique of precise delivery of substances into cells and is widely used for studying cell transfection, signaling pathways, and organelle functions. Microinjection of the embryos of zebrafish, the third most important animal model, has become a very useful technique in bioscience. However, factors such as the small cell size, high cell deformation tendency, and transparent zebrafish embryo membrane make the microinjection process difficult. Furthermore, this process has strict, specific requirements, such as chorion softening, avoiding contacting the first polar body, and high-precision detection. Therefore, highly accurate control and detection platforms are critical for achieving the automated microinjection of zebrafish embryos. This article reviews the latest technologies and methods used in the automated microinjection of zebrafish embryos and provides a detailed description of the current developments and applications of robotic microinjection systems. The review covers key areas related to automated embryo injection, including cell searching and location, cell position and posture adjustment, microscopic visual servoing control, sensors, actuators, puncturing mechanisms, and microinjection.

Fabrication of all-transparent polymer-based and encapsulated nanofluidic devices using nano-indentation lithography.

In this paper, we describe a novel and simple process for the fabrication of all-transparent and encapsulated polymeric nanofluidic devices using nano-indentation lithography. First, a nanomechanical probe is used to 'scratch' nanoscale channels on polymethylmethacrylate (PMMA) substrates with sufficiently high hardness. Next, polydimethylsiloxane (PDMS) is used twice to duplicate the nanochannels onto PDMS substrates from the 'nano-scratched' PMMA substrates. A number of experiments are conducted to explore the relationships between the nano-indentation parameters and the nanochannel dimensions and to control the aspect ratio of the fabricated nanochannels. In addition, traditional photolithography combined with soft lithography is employed to fabricate microchannels on another PDMS 'cap' substrate. After manually aligning the substrates, all uncovered channels on two separate PDMS substrates are bonded to achieve a sealed and transparent nanofluidic device, which makes the dimensional transition from microscale to nanoscale feasible. The smallest dimensions of the achievable nanochannels that we have demonstrated thus far are of ~20 nm depth and ~800 nm width, with lengths extendable beyond 100 µm. Fluid flow experiments are performed to verify the reliability of the device. Two types of colloidal solution are used to visualize the fluid flow through the nanochannels, that is, ethanol is mixed with gold colloid or fluorescent dye (fluorescein isothiocyanate), and the flow rate and filling time of liquid in the nanochannels are estimated based on time-lapsed image data. The simplicity of the fabrication process, bio-compatibility of the polymer substrates, and optical transparency of the nanochannels for flow visualization are key characteristics of this approach that will be very useful for nanofluidic and biomolecular research applications in the future.

Rapidly patterning micro/nano devices by directly assembling ions and nanomaterials.

The synthesis and assembly of components are key steps in micro/nano device manufacturing. In this article, we report an optically controlled assembly method that can rapidly pattern micro/nano devices by directly assembling ions and nanomaterials without expensive physical masks and complex etching processes. Utilizing this controllable process, different types of device components (e.g., metallic and semiconductor) can be fabricated and assembled in 10-30 seconds, which is far more rapid and cost-effective than any other micro/nano fabrication method.

Graphene-Based Glucose Sensors: A Brief Review.

Since the existence of graphene, a material only a single atomic layer thick, was demonstrated about a decade ago, it has caught the attention of researchers worldwide. This paper begins with a historical overview of graphene since its discovery, in 2004, and focuses on a citation-weighted review of graphene-based sensors developed for the detection of biological targets. Based on this statistical analysis, we categorize recent developments in graphene-based biosensors (GBBs) as optimized for detecting 1) proteins, 2) nucleic acids, 3) carbohydrates, or 4) compounds generated by metabolic processes. Existing detection methods employed by these sensors include electrical, electrochemical, and photonic approaches with respect to detecting labeled (or enzyme-assisted) and label-free (or enzyme-free) probe structures. Herein, we focus on graphene-based glucose sensors because glucose-monitoring technology is extremely important in the management of diabetes and many practical examples of these carbohydrate sensors have been developed using the aforementioned detection methods.

Hand-writing motion tracking with vision-inertial sensor fusion: calibration and error correction.

The purpose of this study was to improve the accuracy of real-time ego-motion tracking through inertial sensor and vision sensor fusion. Due to low sampling rates supported by web-based vision sensor and accumulation of errors in inertial sensors, ego-motion tracking with vision sensors is commonly afflicted by slow updating rates, while motion tracking with inertial sensor suffers from rapid deterioration in accuracy with time. This paper starts with a discussion of developed algorithms for calibrating two relative rotations of the system using only one reference image. Next, stochastic noises associated with the inertial sensor are identified using Allan Variance analysis, and modeled according to their characteristics. Finally, the proposed models are incorporated into an extended Kalman filter for inertial sensor and vision sensor fusion. Compared with results from conventional sensor fusion models, we have shown that ego-motion tracking can be greatly enhanced using the proposed error correction model.

Extracellular-controlled breast cancer cell formation and growth using non-UV patterned hydrogels via optically-induced electrokinetics.

The culturing of cancer cells on micropatterned substrates can provide insight into the factors of the extracellular environment that enable the control of cell growth. We report here a novel non-UV-based technique to quickly micropattern a poly-(ethylene) glycol diacrylate (PEGDA)-based hydrogel on top of modified glass substrates, which were then used to control the growth patterns of breast cancer cells. Previously, the fabrication of micropatterned substrates required relatively complicated steps, which made it impractical for researchers to rapidly and systematically investigate the effects of different cell growth patterns. The technique presented herein operates on the principle of optically-induced electrokinetics (OEKs) and uses computer-generated projection light patterns to dynamically pattern the hydrogel on a hydrogenated amorphous silicon (a-Si:H) thin-film, atop an indium tin oxide (ITO) glass substrate. This technique allows us to pattern lines, circles, pentagons, and more complex shapes in the hydrogel with line widths below 3 µm and thicknesses of up to 6 µm within 8 s by simply controlling the projected illumination pattern and applying an appropriate AC voltage between the two ITO glass substrates. After separating the glass substrates to expose the patterned hydrogel, we experimentally demonstrate that MCF-7 breast cancer cells will adhere to the bare a-Si:H surface, but not to the hydrogel patterned in various geometric shapes and sizes. Theoretical analysis and finite-element model simulations reveal that the dominant OEK forces in our technique are the dielectrophoresis (DEP) force and the electro-osmosis force, which enhance the photo-initiated cross-linking reaction in the hydrogel. Our preliminary cultures of breast cancer cells demonstrate that this reported technique could be applied to effectively confine the growth of cancer cells on a-Si:H surfaces and affect individual cell geometry during their growth.

Fabrication of Schottky barrier carbon nanotube field effect transistors using dielectrophoretic-based manipulation.

Nanoscale electronic devices made from carbon nanotubes (CNTs) such as transistors and sensors are much smaller and potentially more versatile than those built using conventional IC technology. In this paper, we present a method that uses dielectrophoretic (DEP) manipulation process for the fabrication of single-channel and multi-channel carbon nanotube field effect transistors (CNT-FETs). For a typical fabrication process, single-walled carbon nanotubes (SWCNTs) are first pre-aligned to micron-precision range between two microelectrodes using DEP technique. The typically applied alternating current (AC) voltage to generate the DEP force for manipulation has a frequency of 1 MHz and amplitude of 10 V. We first demonstrated single-channel or multi-channel structures of CNT-FETs. An AFM is then used to "clean" or "sweep away" unwanted particles or CNTs around the electrodes. Lastly, the fabricated FETs were covered in a polymethylmethacrylate (PMMA) thin film and treated with an annealing process. The PMMA covered devices show improved performances over the non-covered devices.

Carbon nanotube-sensor-integrated microfluidic platform for real-time chemical concentration detection.

This paper presents the development of a chemical sensor employing electronic-grade carbon nanotubes (EG-CNTs) as the active sensing element for sodium hypochlorite detection. The sensor, integrated in a PDMS-glass microfluidic chamber, was fabricated by bulk aligning of EG-CNTs between gold microelectrode pairs using dielectrophoretic technique. Upon exposure to sodium hypochlorite solution, the characteristics of the carbon nanotube chemical sensor were investigated at room temperature under constant current mode. The sensor exhibited responsivity, which fits a linear logarithmic dependence on concentration in the range of 1/32 to 8 ppm, a detection limit lower than 5 ppb, while saturating at 16 ppm. The typical response time of the sensor at room temperature is on the order of minutes and the recovery time is a few hours. In particular, the sensor showed an obvious sensitivity to the volume of detected solution. It was found that the activation power of the sensor was extremely low, i.e. in the range of nanowatts. These results indicate great potential of EG-CNT for advanced nanosensors with superior sensitivity, ultra-low power consumption, and less fabrication complexity.

A vortex pump-based optically-transparent microfluidic platform for biotech and medical applications.

This paper reports an automated polymer based microfluidic analysis system integrated with a surface plasmon resonance (SPR) biosensor that demonstrates the detection of specific binding of biomolecules and that qualitatively monitors cell adhesion on the sensor surface. Micropumps, microchannels, and an SPR biosensor were integrated into a single polymer (PMMA) based microfluidic system. The integrated system has been studied for its potential applications in bio-molecules detection and drugs discovery. Two experiments, (1) monitoring the reaction between the BSA-BSA antibody, and (2) monitoring the activities of living cells in the presence or absence of trypsin in a RPMI-1640 medium, were conducted to show the biomedical application capability. Because SPR based bio-detection requires optically transparent substrates, PMMA is a potential replacement for glass and silicon-glass in microfluidic systems, if bio-compatibility and low-cost are desired. Hence, our work has shown the feasibility of commercializing an SPR based bio-medical/chemical analysis system in the near future.

Novel micro gripping, probing, and sensing devices for single-cell surgery.

Several novel devices under development in our laboratories to ultimately realize a micro robotic system for single cell nanoscale probing, injection, imaging and surgery is described in this paper. Thus far, we have 1) developed MEMS polymer grippers that can be actuated under water with very large deflection and are capable of gripping 500mum embryonic cells in water with approximately 2 V input; 2) developed a probe-etching technique to controllably shape fiber probes into various tip geometries, i.e., fibers with initial diameter of 125 mum were sharpened into tips with angles ranging from <2.7-9.7 degrees and with nanoscale tip diameters of <1mum; 3) developed a novel PVDF force sensing system with resolution in the sub-muN range for applications in bio-manipulation, bio-injection, and potentially single cell surgery. Details of these technologies are discussed in this paper.