Computational cytometer based on magnetically modulated coherent imaging and deep learning.

Detecting rare cells within blood has numerous applications in disease diagnostics. Existing rare cell detection techniques are typically hindered by their high cost and low throughput. Here, we present a computational cytometer based on magnetically modulated lensless speckle imaging, which introduces oscillatory motion to the magnetic-bead-conjugated rare cells of interest through a periodic magnetic force and uses lensless time-resolved holographic speckle imaging to rapidly detect the target cells in three dimensions (3D). In addition to using cell-specific antibodies to magnetically label target cells, detection specificity is further enhanced through a deep-learning-based classifier that is based on a densely connected pseudo-3D convolutional neural network (P3D CNN), which automatically detects rare cells of interest based on their spatio-temporal features under a controlled magnetic force. To demonstrate the performance of this technique, we built a high-throughput, compact and cost-effective prototype for detecting MCF7 cancer cells spiked in whole blood samples. Through serial dilution experiments, we quantified the limit of detection (LoD) as 10 cells per millilitre of whole blood, which could be further improved through multiplexing parallel imaging channels within the same instrument. This compact, cost-effective and high-throughput computational cytometer can potentially be used for rare cell detection and quantification in bodily fluids for a variety of biomedical applications

Microscale Symmetrical Electroporator Array as a Versatile Molecular Delivery System

Successful developments of new therapeutic strategies often rely on the ability to deliver exogenous molecules into cytosol. We have developed a versatile on-chip vortex-assisted electroporation system, engineered to conduct sequential intracellular delivery of multiple molecules into various cell types at low voltage in a dosage-controlled manner. Micro-patterned planar electrodes permit substantial reduction in operational voltages and seamless integration with an existing microfluidic technology. Equipped with real-time process visualization functionality, the system enables on-chip optimization of electroporation parameters for cells with varying properties. Moreover, the system’s dosage control and multi-molecular delivery capabilities facilitate intracellular delivery of various molecules as a single agent or in combination and its utility in biological research has been demonstrated by conducting RNA interference assays. We envision the system to be a powerful tool, aiding a wide range of applications, requiring single-cell level co-administrations of multiple molecules with controlled dosages

Comparison of dynamic response of functionalized and bare multi-walled carbon nanotube sensors

A resistive sensing device based on functionalized multi-walled carbon nanotubes (f-MWNTs) utilizing chemical oxidation method was fabricated successfully and proved sensitive to ethanol vapor. Dielectrophoresis (DEP) manipulation was used to achieve CNTs alignment between pairs of gold microelectrodes in fabricating the CNT sensing elements. I-V characteristics were tested to ensure that the sensors operate within the linear range, i.e., no over-heat ratio was induced onto the sensing elements during operation. Upon exposure to ethanol vapor, an increase of resistance was observed in both bare MWNTs and f-MWNTs sensors. However, compared to bare MWNTs, the f-MWNTs sensors proved to have lower power consumption (i.e., as low as nano-watt level), larger responsivity and faster time response. In addition, cycling responses of the sensors were evaluated and demonstrated to have good repeatability. Moreover, resistance of both sensors would drop under applied compressed air flow, which has been utilized to clear the residual ethanol and reset the sensors to their initial condition after each cycle of measurement. © 2008 IEEE

Investigation of electrical properties of DNA-attached carbon nano-particles for biological applications

Carbon nano-particles are nano-sized crystalline with predominantly graphitic structure. Our recent work showed that DNA-attached Carbon Nano-Particles (DAC) can be positioned between microelectrodes in a microfluidic system to investigate its electrical properties. Dielectrophoretic based "deposition" led to a robust adhesion of various DACs with the chip substrate even after repeatedly DI water flushing. The IV characteristics and stability of three types of DACs under different conditions (i.e., towards open environment, sealed in dry microchannel, or immerged in DI water) were compared and analyzed. In addition, experiments were conducted to determine the temperature and humidity dependency of the DACs. © 2012 IEEE

Fabrication and manipulation of fluorescent carbon nanoparticles for biosensing applications

Carbon Nano-Particles (CNPs) were fabricated by our team which showed green fluorescence under blue excitation, and is promising for future biosensing applications. The possibility of using dielectrophoresis (DEP) manipulation to assemble these CNPs between Au micro-electrodes has been investigated. Preliminary experiments showed that DEP manipulation could accelerate the evaporation of CNPs solution, control the position of resulted structure, and significantly improve the successful rate of the CNPs assembly. In addition, series of experiments have been carried out to determine the optimal DEP parameters. Moreover, in order to improve the electrical stability of the assembled and aligned CNPs based sensing elements, different geometries of micro-electrodes were compared. Experimental results showed that samples prepared by using interdigitated micro-electrodes proved to have better electrical stability than those using a simple pair of micro-electrodes. © 2011 IEEE

Ultra-low-powered CNTs-based aqueous shear stress sensors integrated in microfluidic channels

We have developed carbon nanotubes (CNTs) based aqueous shear stress sensors integrated in microfluidic channels. The sensors utilized electronics-grade carbon nanotubes (EG-CNTs) as sensing elements, and were built by combining MEMS-compatible fabrication technology with AC dielectrophoretic (DEP) technique. The assembled sensing element has a room-temperature resistance of similar to 100 to 200 Omega by using the original concentration of 1:1 EG-CNTs in DI-water. The I-V measurements of EG-CNTs show the heating effects of the sensors, and the current required to induce the nonlinearity of EG-CNTs is in the order of 100 mu A, which implies the operation power of the sensor is in the range of mu W. Upon exposure to DI-water flow, the characteristics of the sensor have been investigated at room temperature under constant current (CC) activation mode. It was found that the electrical resistance of the CNT sensors increased linearly with the introduction of constant fluidic shear stress. We have tested the response of the sensors with flow velocity from 0.3 to 3.4m/s. The experimental results show that there is a linear relation between the output resistance change and the flow velocity to the one-third power. This result proved that the CNT sensors work with the same principle as conventional MEMS thermal shear stress sensors but only require ultra-low activation power (similar to 1 mu W), which is similar to 1000 times lower than that of conventional MEMS thermal shear stress sensor

Direct Drug Cocktail Analyses Using Microscale Vortex-Assisted Electroporation

Combination therapy has become one of the leading approaches for treating complex diseases because it coadministers clinically proven drugs to concurrently target multiple signaling pathways of diseased cells. Identification of synergic drug combinations at their respective effective doses without unwanted accumulative side effects is the key to success for such therapy. In this work, we demonstrate the feasibility of the vortex-assisted microfluidic electroporation system for direct drug cocktail analyses where drug substances were individually delivered into cytosols in a sequential and dosage-controlled manner. Through quantitative analyses, the synergic combinational dosage ratios of the chemotherapeutic drug and the anticancer flavonoid were identified. When integrated with high-throughput label-free rare cell purification techniques, the presented system has the potential for development of personalized medicines as the system would be capable of comprehensively assessing drug combinations directly on patients’ cellular samples

Inducing self-rotation of cells with natural and artificial melanin in a linearly polarized alternating current electric field

The phenomenon of self-rotation observed in naturally and artificially pigmented cells under an applied linearly polarized alternating current (non-rotating) electrical field has been investigated. The repeatable and controllable rotation speeds of the cells were quantified and their dependence on dielectrophoretic parameters such as frequency, voltage, and waveform was studied. Moreover, the rotation behavior of the pigmented cells with different melanin content was compared to quantify the correlation between self-rotation and the presence of melanin. Most importantly, macrophages, which did not originally rotate in the applied non-rotating electric field, began to exhibit self-rotation that was very similar to that of the pigmented cells, after ingesting foreign particles (e.g., synthetic melanin or latex beads). We envision the discovery presented in this paper will enable the development of a rapid, non-intrusive, and automated process to obtain the electrical conductivities and permittivities of cellular membrane and cytoplasm in the near future. (C) 2013 AIP Publishing LLC

Monodisperse drops templated by 3D-structured microparticles.

The ability to create uniform subnanoliter compartments using microfluidic control has enabled new approaches for analysis of single cells and molecules. However, specialized instruments or expertise has been required, slowing the adoption of these cutting-edge applications. Here, we show that three dimensional-structured microparticles with sculpted surface chemistries template uniformly sized aqueous drops when simply mixed with two immiscible fluid phases. In contrast to traditional emulsions, particle-templated drops of a controlled volume occupy a minimum in the interfacial energy of the system, such that a stable monodisperse state results with simple and reproducible formation conditions. We describe techniques to manufacture microscale drop-carrier particles and show that emulsions created with these particles prevent molecular exchange, concentrating reactions within the drops, laying a foundation for sensitive compartmentalized molecular and cell-based assays with minimal instrumentation