We describe a single microfluidic device and two methods for the passive storage of aqueous drops... more We describe a single microfluidic device and two methods for the passive storage of aqueous drops in a continuous stream of oil without any external control but hydrodynamic flow. Advantages of this device are that it is simple to manufacture, robust under operation, and drops never come into contact with each other, making it unnecessary to stabilize drops against coalescence. In one method the device can be used to store drops that are created upstream from the storage zone. In the second method the same device can be used to simultaneously create and store drops from a single large continuous fluid stream without resorting to the usual flow focusing or T-junction drop generation processes. Additionally, this device stores all the fluid introduced, including the first amount, with zero waste. Transport of drops in this device depends, however, on whether or not the aqueous drops wet the device walls. Analysis of drop transport in these two cases is presented. Finally, a method for extraction of the drops from the device is also presented, which works best when drops do not wet the walls of the chip.
Abstract DNA hybridization kinetics has been playing a critical role in molecular diagnostics for... more Abstract DNA hybridization kinetics has been playing a critical role in molecular diagnostics for binding discrimination, but its study on digital microfluidic (DMF) systems is ultimately restrained by the laminar flow condition. The kinetic mixing technique is widely employed to ensure a fast reaction rate, but poses intrinsic risk in cross contamination and exhibits instable fluorescence intensity during the droplet transportation. While the electrothermal technique can provide stationary droplet mixing through the established thermal gradient within the hybridization solution, the significant increase in the droplet temperature will inevitably undermine the hybridization equilibrium and jeopardize the binding discrimination. To enhance the hybridization efficiency while ensuring a stable droplet temperature (within ±0.1℃), this paper presents a DMF platform that can perform isothermal hydrodynamic-flow-enhanced droplet mixing. Specifically, with a single electrode, droplet-boundary oscillation under a slow AC actuation is studied for improving the reaction rate. The dependencies between the mixing efficiency and the actuation voltage, actuation frequency and the spacer thickness are also systematically studied. Reliable mixing efficiency improvement is further validated over a wide range of solute concentrations. The results from real-time on-chip DNA hybridization kinetics with stationary droplets using the complete sandwiched DMF system shows that the proposed rapid mixer can achieve the same hybridization equilibrium with >13 times faster reaction rate when compared to the reference one through pure diffusion, while preventing biased hybridization kinetics as demonstrated in the electrothermal technique.
The emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a zoonot... more The emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a zoonotic pathogen, has led to the outbreak of coronavirus disease 2019 (COVID-19) pandemic and brought serious threats to public health worldwide. The gold standard method for SARS-CoV-2 detection requires both reverse transcription (RT) of the virus RNA to cDNA and then polymerase chain reaction (PCR) for the cDNA amplification, which involves multiple enzymes, multiple reactions and a complicated assay optimization process. Here, we developed a duplex-specific nuclease (DSN)-based signal amplification method for SARS-CoV-2 detection directly from the virus RNA utilizing two specific DNA probes. These specific DNA probes can hybridize to the target RNA at different locations in the nucleocapsid protein gene (N gene) of SARS-CoV-2 to form a DNA/RNA heteroduplex. DSN cleaves the DNA probe to release fluorescence, while leaving the RNA strand intact to be bound to another available probe molecul...
Convenient electric control and electrode design allow flexible sample delivery on-chip in a wide... more Convenient electric control and electrode design allow flexible sample delivery on-chip in a wide range on microfluidics.
A proposed DNA amplification enhancer with a “clip-to-release on amplification” mechanism reduces... more A proposed DNA amplification enhancer with a “clip-to-release on amplification” mechanism reduces dye-mediated inhibition to amplification, increases fluorescence signal up to 10-fold, and eliminates false-negative results for on-chip PCR.
We reported two Au clusters with precisely controlled molecular size (AuPeptide and AuPeptide) sh... more We reported two Au clusters with precisely controlled molecular size (AuPeptide and AuPeptide) showing different antitumor effects. In vitro, both AuPeptide and AuPeptide were well taken up by human nasopharyngeal cancer cells (CNE1 cells). However, only AuPeptide significantly induced CNE1 cell apoptosis. Further studies showed that CNE1 cells took up AuPeptide (1.98 × 10 mol/cell), and 9% of them entered mitochondria (0.186 × 10 mol/cell). As a comparison, the uptake of AuPeptide was only half the amount of AuPeptide (1.11 × 10 mol/cell), and only 1% of them entered mitochondria (0.016 × 10 mol/cell). That gave 11.6-fold more AuPeptide in mitochondria of CNE1 cells than AuPeptide. Further cell studies revealed that the antitumor effect may be due to the enrichment of AuPeptide in mitochondria. AuPeptide slightly decreased the Mcl-1 (antiapoptotic protein of mitochondria) and significantly increased the Puma (pro-apoptotic protein of mitochondria) expression level in CNE1 cells, wh...
Multi-modal imaging agents are desirable for tumor diagnosis because they can provide more inform... more Multi-modal imaging agents are desirable for tumor diagnosis because they can provide more information on the tumor than single-modal imaging agents. However, most reported multi-modal imaging agents are dual-modal agents rather than tri-modal agents; therefore, detailed information on the tumor may still be insufficient when such imaging agents are used. To ameliorate this issue, we synthesized a tri-modal imaging agent, composed of gold cluster and gadolinium oxide integrated nanoparticles (denoted as AuGds) using bovine serum albumin (BSA) as the template via a bio-mineralization method. The AuGds exhibit red fluorescence at ∼660 nm for optical imaging, strong X-ray absorption (around 700 HU) for CT imaging, and a high r1 value (∼12.39 mM(-1) s(-1)) for MR imaging. After being chemically modified with folic acid (FA), the AuGds can specifically target folate receptors on KB tumor cells, and permit in vivo optical, MR, and CT imaging of xenografted tumors. By comparing these three...
A new criterion based on surface and volume diffusion kinetics was established to predict protein... more A new criterion based on surface and volume diffusion kinetics was established to predict protein crystallization. Similar to the layer-by-layer crystal growth process of protein, the kinetics of the two-dimensional selfassembly of protein at the aqueous solution surface provides a convenient and reliable way to estimate the surface integration and the volume transport during protein crystallization. Both the surface and diffusion kinetics were estimated based on the protein self-assembly at the air/solution interface, which can be obtained by measuring the surface tension. A crystallization coefficient is found to provide an effective and reliable criterion to predict protein crystallization conditions. This criterion has been applied to lysozyme, concanavalin A and BSA crystallization, and it turns out to be very successful and more reliable than the second virial coefficient criterion.
A silane-based adhesion promoter suitable for a multi-dielectric-layer coating on a digital micro... more A silane-based adhesion promoter suitable for a multi-dielectric-layer coating on a digital microfluidic chip is reported.
We employ the PhaseChip, a (poly)dimethylsiloxane (PDMS) microfluidic device, for statistical stu... more We employ the PhaseChip, a (poly)dimethylsiloxane (PDMS) microfluidic device, for statistical studies of protein crystal nucleation. The PhaseChip is designed to decouple nucleation and growth of protein crystals and to improve their yield and quality. Two layers of fluidic channels containing salt reservoirs and nanoliter-sized wells for protein drops in oil are separated by a thin PDMS membrane, which is permeable to water, but not to salt or macromolecules such as protein. We reversibly vary the supersaturation of protein inside the stored droplets by controlling the chemical potential of the reservoir. Lysozyme in the presence of sodium chloride is used as a model system. We determine the crystal nucleation rate as a function of protein supersaturation by counting the number of crystal nuclei per droplet, as demonstrated by Galkin and Vekilov (J.
We describe a single microfluidic device and two methods for the passive storage of aqueous drops... more We describe a single microfluidic device and two methods for the passive storage of aqueous drops in a continuous stream of oil without any external control but hydrodynamic flow. Advantages of this device are that it is simple to manufacture, robust under operation, and drops never come into contact with each other, making it unnecessary to stabilize drops against coalescence. In one method the device can be used to store drops that are created upstream from the storage zone. In the second method the same device can be used to simultaneously create and store drops from a single large continuous fluid stream without resorting to the usual flow focusing or T-junction drop generation processes. Additionally, this device stores all the fluid introduced, including the first amount, with zero waste. Transport of drops in this device depends, however, on whether or not the aqueous drops wet the device walls. Analysis of drop transport in these two cases is presented. Finally, a method for extraction of the drops from the device is also presented, which works best when drops do not wet the walls of the chip.
Abstract DNA hybridization kinetics has been playing a critical role in molecular diagnostics for... more Abstract DNA hybridization kinetics has been playing a critical role in molecular diagnostics for binding discrimination, but its study on digital microfluidic (DMF) systems is ultimately restrained by the laminar flow condition. The kinetic mixing technique is widely employed to ensure a fast reaction rate, but poses intrinsic risk in cross contamination and exhibits instable fluorescence intensity during the droplet transportation. While the electrothermal technique can provide stationary droplet mixing through the established thermal gradient within the hybridization solution, the significant increase in the droplet temperature will inevitably undermine the hybridization equilibrium and jeopardize the binding discrimination. To enhance the hybridization efficiency while ensuring a stable droplet temperature (within ±0.1℃), this paper presents a DMF platform that can perform isothermal hydrodynamic-flow-enhanced droplet mixing. Specifically, with a single electrode, droplet-boundary oscillation under a slow AC actuation is studied for improving the reaction rate. The dependencies between the mixing efficiency and the actuation voltage, actuation frequency and the spacer thickness are also systematically studied. Reliable mixing efficiency improvement is further validated over a wide range of solute concentrations. The results from real-time on-chip DNA hybridization kinetics with stationary droplets using the complete sandwiched DMF system shows that the proposed rapid mixer can achieve the same hybridization equilibrium with >13 times faster reaction rate when compared to the reference one through pure diffusion, while preventing biased hybridization kinetics as demonstrated in the electrothermal technique.
The emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a zoonot... more The emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a zoonotic pathogen, has led to the outbreak of coronavirus disease 2019 (COVID-19) pandemic and brought serious threats to public health worldwide. The gold standard method for SARS-CoV-2 detection requires both reverse transcription (RT) of the virus RNA to cDNA and then polymerase chain reaction (PCR) for the cDNA amplification, which involves multiple enzymes, multiple reactions and a complicated assay optimization process. Here, we developed a duplex-specific nuclease (DSN)-based signal amplification method for SARS-CoV-2 detection directly from the virus RNA utilizing two specific DNA probes. These specific DNA probes can hybridize to the target RNA at different locations in the nucleocapsid protein gene (N gene) of SARS-CoV-2 to form a DNA/RNA heteroduplex. DSN cleaves the DNA probe to release fluorescence, while leaving the RNA strand intact to be bound to another available probe molecul...
Convenient electric control and electrode design allow flexible sample delivery on-chip in a wide... more Convenient electric control and electrode design allow flexible sample delivery on-chip in a wide range on microfluidics.
A proposed DNA amplification enhancer with a “clip-to-release on amplification” mechanism reduces... more A proposed DNA amplification enhancer with a “clip-to-release on amplification” mechanism reduces dye-mediated inhibition to amplification, increases fluorescence signal up to 10-fold, and eliminates false-negative results for on-chip PCR.
We reported two Au clusters with precisely controlled molecular size (AuPeptide and AuPeptide) sh... more We reported two Au clusters with precisely controlled molecular size (AuPeptide and AuPeptide) showing different antitumor effects. In vitro, both AuPeptide and AuPeptide were well taken up by human nasopharyngeal cancer cells (CNE1 cells). However, only AuPeptide significantly induced CNE1 cell apoptosis. Further studies showed that CNE1 cells took up AuPeptide (1.98 × 10 mol/cell), and 9% of them entered mitochondria (0.186 × 10 mol/cell). As a comparison, the uptake of AuPeptide was only half the amount of AuPeptide (1.11 × 10 mol/cell), and only 1% of them entered mitochondria (0.016 × 10 mol/cell). That gave 11.6-fold more AuPeptide in mitochondria of CNE1 cells than AuPeptide. Further cell studies revealed that the antitumor effect may be due to the enrichment of AuPeptide in mitochondria. AuPeptide slightly decreased the Mcl-1 (antiapoptotic protein of mitochondria) and significantly increased the Puma (pro-apoptotic protein of mitochondria) expression level in CNE1 cells, wh...
Multi-modal imaging agents are desirable for tumor diagnosis because they can provide more inform... more Multi-modal imaging agents are desirable for tumor diagnosis because they can provide more information on the tumor than single-modal imaging agents. However, most reported multi-modal imaging agents are dual-modal agents rather than tri-modal agents; therefore, detailed information on the tumor may still be insufficient when such imaging agents are used. To ameliorate this issue, we synthesized a tri-modal imaging agent, composed of gold cluster and gadolinium oxide integrated nanoparticles (denoted as AuGds) using bovine serum albumin (BSA) as the template via a bio-mineralization method. The AuGds exhibit red fluorescence at ∼660 nm for optical imaging, strong X-ray absorption (around 700 HU) for CT imaging, and a high r1 value (∼12.39 mM(-1) s(-1)) for MR imaging. After being chemically modified with folic acid (FA), the AuGds can specifically target folate receptors on KB tumor cells, and permit in vivo optical, MR, and CT imaging of xenografted tumors. By comparing these three...
A new criterion based on surface and volume diffusion kinetics was established to predict protein... more A new criterion based on surface and volume diffusion kinetics was established to predict protein crystallization. Similar to the layer-by-layer crystal growth process of protein, the kinetics of the two-dimensional selfassembly of protein at the aqueous solution surface provides a convenient and reliable way to estimate the surface integration and the volume transport during protein crystallization. Both the surface and diffusion kinetics were estimated based on the protein self-assembly at the air/solution interface, which can be obtained by measuring the surface tension. A crystallization coefficient is found to provide an effective and reliable criterion to predict protein crystallization conditions. This criterion has been applied to lysozyme, concanavalin A and BSA crystallization, and it turns out to be very successful and more reliable than the second virial coefficient criterion.
A silane-based adhesion promoter suitable for a multi-dielectric-layer coating on a digital micro... more A silane-based adhesion promoter suitable for a multi-dielectric-layer coating on a digital microfluidic chip is reported.
We employ the PhaseChip, a (poly)dimethylsiloxane (PDMS) microfluidic device, for statistical stu... more We employ the PhaseChip, a (poly)dimethylsiloxane (PDMS) microfluidic device, for statistical studies of protein crystal nucleation. The PhaseChip is designed to decouple nucleation and growth of protein crystals and to improve their yield and quality. Two layers of fluidic channels containing salt reservoirs and nanoliter-sized wells for protein drops in oil are separated by a thin PDMS membrane, which is permeable to water, but not to salt or macromolecules such as protein. We reversibly vary the supersaturation of protein inside the stored droplets by controlling the chemical potential of the reservoir. Lysozyme in the presence of sodium chloride is used as a model system. We determine the crystal nucleation rate as a function of protein supersaturation by counting the number of crystal nuclei per droplet, as demonstrated by Galkin and Vekilov (J.
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Papers by Yanwei Jia