Shih-Chi Chen

Apoptosis induced by 1,3,6,7-tetrahydroxyxanthone in Hepatocellular carcinoma and proteomic analysis

Gamboge is a traditional Chinese medicine and our previous study showed that gambogic acid and gambogenic acid suppress the proliferation of HCC cells. In the present study, another active component, 1,3,6,7-tetrahydroxyxanthone (TTA), was identified to effectively suppress HCC cell growth. In addition, our Hoechst-PI staining and flow cytometry analyses indicated that TTA induced apoptosis in HCC cells. In order to identify the targets of TTA in HCC cells, a two-dimensional gel electrophoresis was performed, and proteins in different expressions were identified by MALDA-TOF MS and MS/MS analyses. In summary, eighteen proteins with different expressions were identified in which twelve were up-regulated and six were down-regulated. Among them, the four most distinctively expressed proteins were further studied and validated by western blotting. The β-tubulin and translationally controlled tumor protein were decreased while the 14-3-3σ and P16 protein expressions were up-regulated. In addition, TTA suppressed tumorigenesis partially through P16-pRb signaling. 14-3-3σ silence reversed the suppressive effect of cell growth and apoptosis induced by introducing TTA. In conclusion, TTA effectively suppressed cell growth through, at least partially, up-regulation of P16 and 14-3-3σ.

Heat shock protein 27 mediates the effect of 1,3,5-trihydroxy-13,13-dimethyl-2H-pyran [7,6-b] xanthone on mitochondrial apoptosis in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a global public health problem which causes approximately 500,000 deaths annually. Considering that the limited therapeutic options for HCC, novel therapeutic targets and drugs are urgently needed. In this study, we discovered that 1,3,5-trihydroxy-13,13-dimethyl-2H-pyran [7,6-b] xanthone (TDP), isolated from the traditional Chinese medicinal herb, Garcinia oblongifolia, effectively inhibited cell growth and induced the caspase-dependent mitochondrial apoptosis in HCC. A two-dimensional gel electrophoresis and mass spectrometry-based comparative proteomics were performed to find the molecular targets of TDP in HCC cells. Eighteen proteins were identified as differently expressed, with Hsp27 protein being one of the most significantly down-regulated proteins induced by TDP. In addition, the following gain- and loss-of-function studies indicated that Hsp27 mediates mitochondrial apoptosis induced by TDP. Furthermore, a nude mice model also demonstrated the suppressive effect of TDP on HCC. Our study suggests that TDP plays apoptosis-inducing roles by strongly suppressing the Hsp27 expression that is specifically associated with the mitochondrial death of the caspase-dependent pathway. In conclusion, TDP may be a potential anti-cancer drug candidate, especially to cancers with an abnormally high expression of Hsp27.

Design of Contoured Microscale Thermomechanical Actuators

In this paper, we disclose how to contour the beams of microscale thermomechanical actuators (TMAs) in order to enhance the actuators thermal and mechanical performance. In this approach, we vary the cross-section of the heated beams over the length of the beams. Using this approach, the stored strain energy and axial stiffness of the beam may be modified to achieve an optimized force-displacement relationship. Examples are provided to show that in some designs: 1) the maximum achievable thermal strain of a driving beam may be increased by 29%, 2) actuator stroke may be increased by a factor of four, and 3) identical force or displacement characteristics may be achieved with a 90% reduction in power. This paper presents the theory and models used to predict the thermal and mechanical behavior of the actuator. The theory and models were used to create a deterministic link between the actuators design parameters and the actuators performance characteristics. The theory and models were combined within a design tool that is posted at http://pcsl.mit.edu. The tool has been used to generate performance plots that enable designers to: 1) understand the quantitative relationships between design parameters and performance and 2) rapidly converge upon first-pass design parameters.1695

Hollow-Structured Graphene–Silicone-Composite-Based Piezoresistive Sensors: Decoupled Property Tuning and Bending Reliability

A versatile flexible piezoresistive sensor should maintain high sensitivity in a wide linear range, and provide a stable and repeatable pressure reading under bending. These properties are often difficult to achieve simultaneously with conventional filler-matrix composite active materials, as tuning of one material component often results in change of multiple sensor properties. Here, a material strategy is developed to realize a 3D graphene-poly(dimethylsiloxane) hollow structure, where the electrical conductivity and mechanical elasticity of the composite can be tuned separately by varying the graphene layer number and the poly(dimethylsiloxane) composition ratio, respectively. As a result, the sensor sensitivity and linear range can be easily improved through a decoupled tuning process, reaching a sensitivity of 15.9 kPa-1 in a 60 kPa linear region, and the sensor also exhibits fast response (1.2 ms rising time) and high stability. Furthermore, by optimizing the density of the graphene percolation network and thickness of the composite, the stability and repeatability of the sensor output under bending are improved, achieving a measurement error below 6% under bending radius variations from -25 to +25 mm. Finally, the potential applications of these sensors in wearable medical devices and robotic vision are explored.

Design of Contoured Thermomechanical Actuators and Pulsing Actuation to Enhance Dynamic Performance

This paper presents the concepts, models, and experimental validations of the geometric contouring method and a pulsing technique to enhance dynamic performance of micro thermomechanical actuators (μTMAs). For a typical TMA, contouring may improve its stroke, force, and speed performances by a factor of 4, 2.5, and 10, respectively. In the meantime, the required power for achieving the same performance is reduced by 40%. Herein, we show the following: 1) how to obtain marked dynamic and static performance from μTMAs; 2) how to model and optimize these improvements; and 3) how to use transient electrical command signals to augment these improvements. The utility and practical implementation of these techniques are illustrated via a case study on a stage from a three-axis optical scanner for a two-photon endomicroscope.

Flexure-based Roll-to-roll Platform: A Practical Solution for Realizing Large-area Microcontact Printing

A continuous roll-to-roll microcontact printing (MCP) platform promises large-area nanoscale patterning with significantly improved throughput and a great variety of applications, e.g. precision patterning of metals, bio-molecules, colloidal nanocrystals, etc. Compared with nanoimprint lithography, MCP does not require a thermal imprinting step (which limits the speed and material choices), but instead, extreme precision with multi-axis positioning and misalignment correction capabilities for large area adaptation. In this work, we exploit a flexure-based mechanism that enables continuous MCP with 500 nm precision and 0.05 N force control. The fully automated roll-to-roll platform is coupled with a new backfilling MCP chemistry optimized for high-speed patterning of gold and silver. Gratings of 300, 400, 600 nm line-width at various locations on a 4-inch plastic substrate are fabricated at a speed of 60 cm/min. Our work represents the first example of roll-to-roll MCP with high reproducibility, wafer scale production capability at nanometer resolution. The precision roll-to-roll platform can be readily applied to other material systems.

Soft mold-based hot embossing process for precision imprinting of optical components on non-planar surfaces.

Patterning micro- and nano-scale optical elements on nonplanar substrates has been technically challenging and prohibitively expensive via conventional processes. A low-cost, high-precision fabrication process is thus highly desired and can have significant impact on manufacturing that leads to wider applications. In this paper, we present a new hot embossing process that enables high-resolution patterning of micro- and nano-structures on non-planar substrates. In this process, a flexible elastomer stamp, i.e., PDMS, was used as a mold to perform hot-embossing on substrates of arbitrary curvatures. The new process was optimized through the development of an automated vacuum thermal imprinting system that allows non-clean room operation as well as precise control of all process parameters, e.g., pressure, temperature and time. Surface profiles and optical properties of the fabricated components, including micro-lens array and optical gratings, were characterized quantitatively, e.g., RMS ~λ/30 for a micro-lens, and proved to be comparable with high cost conventional precision processes such as laser lithographic fabrication.

Fast 3-D temporal focusing microscopy using an electrically tunable lens

In this paper, we present a 3-D temporal focusing microscope based on an electrically tunable lens (ETL) and a femtosecond regenerative laser amplifier. The focus-tunable lens provides a fast and compact way to perform non-mechanical z-scanning and resolves the blurry image issue compared with GVD-based z-scanning methods. The optical performance of the temporal focusing system, including z-scanning characteristics, the associated the magnification variation, and the lateral and axial resolution, has been studied and characterized using calibrated Rhodamine-6G thin film sample, fluorescent beads, and pollen samples. Lastly, we demonstrate the optical cross-sectioning and z-scanning capability with an in vivo experiment, where Ca(2+) imaging of neurons in GaCamp6 labeled zebrafish was performed.

Design of an Ultra Precision Diaphragm Flexure Stage for Out-of-Plane Motion Guidance

An ultra-precision diaphragm flexure stage was designed and optimized for pure out-of-plane Z-motion guidance with an effort to minimize parasitic lateral and tilt motions. The diaphragm flexure stage will be used to guide an objective lens along the optical axis in a high performance microscope. A concept with cross-linked radial spoke geometry akin to a bicycle wheel was designed to maximize its in-plane to out-of-plane stiffness ratio. The geometry was then optimized using finite element analysis. Several prototypes were manufactured using an abrasive water jet machining center and tested with a reconfigurable test fixture. Sets of two and four diaphragms were tested. Negligible improvement in parasitic motion was observed between the two and four-diaphragm configurations. The experimental results for out-of-plane stiffness matched the finite element result within 0.3%. Negligible hysteresis in vertical motion was observed. Maximum lateral parasitic motion on the order 2 μm was measured over a Z-motion range of 140 μm. The lateral displacement was linear (R2 =0.998) and repeatable, and could be an artifact of misalignment of the diaphragms in the test fixture.Copyright

Functional characterization of a PEI-CyD-FA-coated adenovirus as delivery vector for gene therapy

The recombinant adenovirus is evolving as a promising gene delivery vector for gene therapy due to its efficiency in transducing different genes into most types of cells. However, the host-immune response elicited by primary inoculation of an adenovirus can cause rapid clearance of the vector, impairing the efficacy of the adenovirus and hence obstructing its clinical application. We have previously synthesized a biodegradable co-polymer consisting of a low molecular weight PEI (MW 600 Da), cross-linked with β-cyclodextrin, and conjugated with folic acid (PEI-CyD-FA, named H1). Here we report that coating the adenovirus vector (Adv) with H1 (H1/rAdv) could significantly improve both the efficacy and biosafety of Adv. Enhanced transfection efficiency as well as prolonged duration of gene expression were clearly demonstrated either by intratumoral or systemic injection of a single dose of H1/rAdv in immunocompetent mice. Importantly, repeated injections of H1/rAdv did not reduce the transfection efficiency in immunocompetent mice. Furthermore, H1 transformed the surface charge of the adenovirus capsomers from negative to positive in physiological solution, suggesting that H1 coated the capsid protein of the adenovirus. This could shelter the epitopes of capsid proteins of the adenovirus, resulting in a reduced host-immune response and enhanced transfection efficiency. Taken together, these findings suggest that H1/rAdv is an effective gene delivery system superior to the adenovirus alone and that it could be considered as a preferred vehicle for gene therapy.