Xiaolin Wang

3D microtumors in vitro supported by perfused vascular networks.

There is a growing interest in developing microphysiological systems that can be used to model both normal and pathological human organs in vitro. This “organs-on-chips” approach aims to capture key structural and physiological characteristics of the target tissue. Here we describe in vitro vascularized microtumors (VMTs). This “tumor-on-a-chip” platform incorporates human tumor and stromal cells that grow in a 3D extracellular matrix and that depend for survival on nutrient delivery through living, perfused microvessels. Both colorectal and breast cancer cells grow vigorously in the platform and respond to standard-of-care therapies, showing reduced growth and/or regression. Vascular-targeting agents with different mechanisms of action can also be distinguished, and we find that drugs targeting only VEGFRs (Apatinib and Vandetanib) are not effective, whereas drugs that target VEGFRs, PDGFR and Tie2 (Linifanib and Cabozantinib) do regress the vasculature. Tumors in the VMT show strong metabolic heterogeneity when imaged using NADH Fluorescent Lifetime Imaging Microscopy and, compared to their surrounding stroma, many show a higher free/bound NADH ratio consistent with their known preference for aerobic glycolysis. The VMT platform provides a unique model for studying vascularized solid tumors in vitro.

Engineering anastomosis between living capillary networks and endothelial cell-lined microfluidic channels

This paper reports a method for generating an intact and perfusable microvascular network that connects to microfluidic channels without appreciable leakage. This platform incorporates different stages of vascular development including vasculogenesis, endothelial cell (EC) lining, sprouting angiogenesis, and anastomosis in sequential order. After formation of a capillary network inside the tissue chamber via vasculogenesis, the adjacent microfluidic channels are lined with a monolayer of ECs, which then serve as the high-pressure input (artery) and low pressure output (vein) conduits. To promote a tight interconnection between the artery/vein and the capillary network, sprouting angiogenesis is induced, which promotes anastomosis of the vasculature inside the tissue chamber with the EC lining along the microfluidic channels. Flow of fluorescent microparticles confirms the perfusability of the lumenized microvascular network, and minimal leakage of 70 kDa FITC-dextran confirms physiologic tightness of the EC junctions and completeness of the interconnections between artery/vein and the capillary network. This versatile device design and its robust construction methodology establish a physiological transport model of interconnected perfused vessels from artery to vascularized tissue to vein. The system has utility in a wide range of organ-on-a-chip applications as it enables the physiological vascular interconnection of multiple on-chip tissue constructs that can serve as disease models for drug screening.

Direct electrodeposition of Graphene enhanced conductive polymer on microelectrode for biosensing application

Engineering of neural interface with nanomaterials for high spatial resolution neural recording and stimulation is still hindered by materials properties and modification methods. Recently, poly(3,4-ethylene-dioxythiophene) (PEDOT) has been widely used as an electrode-tissue interface material for its good electrochemical property. However, cracks and delamination of PEDOT film under pulse stimulation are found which restrict its long-term applications. This paper develops a flexible electrochemical method about the co-deposition of graphene with PEDOT on microelectrode sites to enhance the long-term stability and improve the electrochemical properties of microelectrode. This method is unique and profound because it co-deposits graphene with PEDOT on microelectrode sites directly and avoids the harmful post reduction process. And, most importantly, significantly improved electrochemical performances of the modified microelectrodes (compared to PEDOT-GO) are demonstrated due to the large effective surface area, good conductivity and excellent mechanical property of graphene. Furthermore, the good mechanical stability of the composites is verified by ultrasonication and CV scanning tests. In-vivo acute implantation of the microelectrodes reveals the modified microelectrodes show higher recording performance than the unmodified ones. These findings suggest the composites are excellent candidates for the applications of neural interface.

High performance bimorph piezoelectric MEMS harvester via bulk PZT thick films on thin beryllium-bronze substrate

This letter presents a high performance bimorph piezoelectric MEMS harvester with bulk PZT thick films on both sides of a flexible thin beryllium-bronze substrate via bonding and thinning technologies. The upper and lower PZT layers are thinned down to about 53 μm and 76u2009μm, respectively, and a commercial beryllium bronze with the thickness of about 50u2009μm is used as the substrate. The effective volume of this device is 30.6u2009mm3. The harvester with a tungsten proof mass generated the close-circuit peak-to-peak voltage of 53.1u2009V, the output power of 0.979 mW, and the power density of 31.99 mW/cm3 with the matching load resistance of 360u2009kΩ at the applied acceleration amplitude of 3.5u2009g and the applied frequency of 77.2u2009Hz. Meanwhile, in order to evaluate the stability, the device was measured continuously under applied acceleration amplitudes of 1.0u2009g and 3.5u2009g for one hour and demonstrated a good stability. Then, the harvester was utilized to light up LEDs and about twenty-one serial LEDs were lighted up a...

Cobalt sulfide-reduced graphene oxide nanohybrid as high performance sodium ion battery anode

Recently, sodium-ion batteries (SIBs) have attracted much attention in energy storage field due to their cost-effective, safe and nonpoisonous. However, a huge challenges to find suitable material as anode materials for SIBs due to the relative larger radius of sodium ions. Thus, seeking high specific capacity and low cost anode materials for sodium ion storage is a significant challenge in energy storage field. In our work, cobalt sulfide-reduced graphene oxide (CS–RGO) nanohybrid is prepared and studied as anode materials for SIBs. We found that the CS–RGO nanohybrid exhibits an enhancement of the electrochemical performance for SIBs with reversible capacity and cycling performance as compared to cobalt sulfide. The CS–RGO nanohybrid displays a reversible specific capacity of 426.2xa0mAhxa0g−1 at a current density of 100xa0mAxa0g−1 after 30 cycles, demonstrating that the RGO nanohybrid can effectively improve the sodium ion storage properties of CS–RGO nanohybrid.

Flexible Capacitive Hydrogel Tactile Sensor With Adjustable Measurement Range Using Liquid Crystal and Carbon Nanotubes Composites

In this paper, we present a

Flexible Optoelectric Neural Interface Integrated Wire-Bonding

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capacitive pressure tactile sensor fabricated with new materials, which consists of one dielectric layer and two electrode layers. The dielectric layer is composed of carbon nanotubes dispersed in liquid crystal, which is surrounded by a hydrogel elastomeric membrane. An upper Au parylene film and a lower Au parylene film taped on the kapton tapes are served as the electrode layers. The properties of the devices are well characterized and the capability of adjustable measurement range is successfully realized. Experimental results demonstrate that the capacitance will change with the different driving frequency and voltage accordingly.

LEDs and Microelectrocorticography for Optogenetics

As an advanced brain–computer interface, the flexible surface electrode array has been used for spatiotemporal localization of neural interactions by recording electrocorticography (ECoG) signals over brain cortical areas. Compared with the electrical stimulation, optogenetics provides a potentially ideal way to stimulate the genetically modified brain tissue by light. In this paper, we developed an optoelectric neural interface combining a micro ECoG (<inline-formula> <tex-math notation=LaTeX>

3D Anastomosed Microvascular Network Model with Living Capillary Networks and Endothelial Cell-Lined Microfluidic Channels

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