Yin-Ting Yeh

Tunable and label-free virus enrichment for ultrasensitive virus detection using carbon nanotube arrays

Aligned carbon nanotube–integrated device can effectively trap and enrich viruses from field samples without using antibodies. Viral infectious diseases can erupt unpredictably, spread rapidly, and ravage mass populations. Although established methods, such as polymerase chain reaction, virus isolation, and next-generation sequencing have been used to detect viruses, field samples with low virus count pose major challenges in virus surveillance and discovery. We report a unique carbon nanotube size-tunable enrichment microdevice (CNT-STEM) that efficiently enriches and concentrates viruses collected from field samples. The channel sidewall in the microdevice was made by growing arrays of vertically aligned nitrogen-doped multiwalled CNTs, where the intertubular distance between CNTs could be engineered in the range of 17 to 325 nm to accurately match the size of different viruses. The CNT-STEM significantly improves detection limits and virus isolation rates by at least 100 times. Using this device, we successfully identified an emerging avian influenza virus strain [A/duck/PA/02099/2012(H11N9)] and a novel virus strain (IBDV/turkey/PA/00924/14). Our unique method demonstrates the early detection of emerging viruses and the discovery of new viruses directly from field samples, thus creating a universal platform for effectively remediating viral infectious diseases.

Point-of-Care Microdevices for Blood Plasma Analysis in Viral Infectious Diseases

Each year, outbreaks of viral infections cause illness, disability, death, and economic loss. As learned from past incidents, the detrimental impact grows exponentially without effective quarantine. Therefore, rapid on-site detection and analysis are highly desired. In addition, for high-risk areas of viral contamination, close monitoring should be provided during the potential disease incubation period. As the epidemic progresses, a response protocol needs tobe rapidly implemented and the virus evolution fully tracked. For these scenarios, point-of-care microdevices can provide sensitive, accurate, rapid and low-cost analysis for a large population, especially in handling complex patient samples, such as blood, urine and saliva. Blood plasma can be considered as a mine of information containing sources and clues of biomarkers, including nucleic acids, immunoglobulin and other proteins, as well as pathogens for clinical diagnosis. However, blood plasma is also the most complicated body fluid. For targeted plasma biomarker detection or untargeted plasma biomarker discovery, the challenges can be as difficult as identifying a needle in a haystack. A useful platform must not only pursue single performance characteristics, but also excel at multiple performance parameters, such as speed, accuracy, sensitivity, selectivity, cost, portability, reliability, and user friendliness. Throughout the decades, tremendous progress has been made in point-of-care microdevices for viral infectious diseases. In this paper, we review fully integrated lab-on-chip systems for blood analysis of viral infectious disease.

A Nanostructured Microfluidic Immunoassay Platform for Highly Sensitive Infectious Pathogen Detection

Rapid and simultaneous detection of multiple potential pathogens by portable devices can facilitate early diagnosis of infectious diseases, and allow for rapid and effective implementation of disease prevention and treatment measures. The development of a ZnO nanorod integrated microdevice as a multiplex immunofluorescence platform for highly sensitive and selective detection of avian influenza virus (AIV) is described. The 3D morphology and unique optical property of the ZnO nanorods boost the detection limit of the H5N2 AIV to as low as 3.6 × 103 EID50 mL−1 (EID50: 50% embryo infectious dose), which is ≈22 times more sensitive than conventional enzyme‐linked immunosorbent assay. The entire virus capture and detection process could be completed within 1.5 h with excellent selectivity. Moreover, this microfluidic biosensor is capable of detecting multiple viruses simultaneously by spatial encoding of capture antibodies. One prominent feature of the device is that the captured H5N2 AIV can be released by simply dissolving ZnO nanorods under slightly acidic environment for subsequent off‐chip analyses. As a whole, this platform provides a powerful tool for rapid detection of multiple pathogens, which may extent to the other fields for low‐cost and convenient biomarker detection.

Microfluidic device with carbon nanotube channel walls for blood plasma extraction

The human plasma biomarker analysis is promised to be a revolution for disease diagnosis and therapeutic monitoring, but it also presents major technical challenges that needs to be addressed [1]. Plasma extract from whole blood is the first step for plasma biomarker analysis. This paper reports a new microfluidic device with channel walls made of nitrogen-doped carbon nanotubes (CNxCNT) as a point-of-care device to continuously extract plasma from human whole blood. The cross flow microfiltration principle is applied in this plasma extraction device. The blood sample is transported within the double spiral channels. The plasma diffuses through the porous CNxCNT wall into the spiral plasma channel while blood cells continue to flow inside the spiral blood sample channel [2].

Microfluidic device to perform impedometric detection of Activated Partial Thromboplastin Time of blood

The Activated Partial Thromboplastin Time (APTT) test is performed on a large scale, in laboratories to monitor the functioning of intrinsic and common pathways of blood coagulation cascade and the concentration of anticoagulants such as Heparin among patients. A PDMS based microfluidic device has been fabricated and tested to perform APTT as a point-of-care device using whole blood samples by detecting the change in electrical impedance of blood during coagulation. The two chambered PDMS device integrated with microelectrodes is pre-coated with APTT reagent and heparin respectively for better repeatability. The results indicate a repeatable pattern of change in whole blood impedance during coagulation and confirm the theoretical explanation by Hartert [1]. The devices were also tested for their sensitivity to different concentrations of heparin and found to exhibit a favorable increase in coagulation time for increasing heparin concentration.

A carbon nanotube integrated microfluidic device for blood plasma extraction

Blood is a complex fluid consisting of cells and plasma. Plasma contains key biomarkers essential for disease diagnosis and therapeutic monitoring. Thus, by separating plasma from the blood, it is possible to analyze these biomarkers. Conventional methods for plasma extraction involve bulky equipment, and miniaturization constitutes a key step to develop portable devices for plasma extraction. Here, we integrated nanomaterial synthesis with microfabrication, and built a microfluidic device. In particular, we designed a double-spiral channel able to perform cross-flow filtration. This channel was constructed by growing aligned carbon nanotubes (CNTs) with average inter-tubular distances of ~80 nm, which resulted in porosity values of ~93%. During blood extraction, these aligned CNTs allow smaller molecules (e.g., proteins) to pass through the channel wall, while larger molecules (e.g., cells) get blocked. Our results show that our device effectively separates plasma from blood, by trapping blood cells. We successfully recovered albumin -the most abundant protein inside plasma- with an efficiency of ~80%. This work constitutes the first report on integrating biocompatible nitrogen-doped CNT (CNxCNT) arrays to extract plasma from human blood, thus widening the bio-applications of CNTs.

Zinc oxide nanorod integrated microdevice for multiplex virus detection

Technology development for point-of-care viral pathogen detection is critical for early diagnosis of infectious diseases, and rapid and effective disease intervention. In this paper, we present the development of a zinc oxide nanorod-integrated microdevice for highly sensitive and specific detection of avian influenza virus. This multiplexed immunofluorescence platform takes two advantages of the zinc oxide nanorods. On one hand, the 3D morphology of zinc oxide nanorods efficiently increases the effective surface area for monoclonal antibodies and decreases the diffusion distance between antibody and pathogens. On the other hand, the unique optical property of the translucent randomly ordered zinc oxide nanorod surface enhances fluorescence detection by 30–70%. We demonstrated the detection limit of the H5N2 avian influenza virus could be lowered down to 3.6×103 EID50/mL (EID50: 50% embryo infectious dose), which was about 22 times more sensitive than conventional ELISA assay tested under the same conditions. We further designed the microfluidic biosensor platform to detect multiple viruses simultaneously by spatial encoding of capture antibodies. One prominent feature of the device is that the captured H5N2 avian influenza virus can be released by simply dissolving zinc oxide nanorods under slightly acidic environment for subsequent off-chip analyses. As a whole, this platform provides a powerful tool for rapid detection of multiple pathogens, which may extent to the other fields for low-cost and convenient biomarker detection.

A VACNT integrated handheld device for label-free virus capture, detection and enrichment for genomic analysis

A portable carbon nanotube (CNT) integrated microfluidic device is presented to capture virus by physical size-based isolation. The device contained porous CNT array made of nitrogen-doped CNT on a fused silica substrate. The biocompatible nitrogen-doped CNT was synthesized by aerosol-assist chemical vapor deposition (AACVD). Avian influenza virus (AIV) H5N8 subtype was captured from chicken swab samples and detected by reverse-transcriptase real-time polymerase chain reaction (RT-qPCR).

Nanomaterial integrated microfluidic devices for virus analysis

Outbreaks of viral infectious diseases are often devastating, causing illness, disability, death and massive economic loss. Viral infectious diseases can spread rapid and affecting a large population. The high mutation rate of viruses are especially challenging for disease control and surveillance. Point-of-care technologies using microfluidic principles and integrated with nanomaterials promise to meet these challenges of future analysis of viral infectious diseases by providing cost-effective and sometimes enabling technologies with extraordinary portability, high sensitivity, and fast processing speed.

Temperature-induced nanochannel array synthesis in microchannels

An novel on-chip synthesis technique for nanochannel arrays inside microfluidic channels is reported. The microfluidic channels are constructed with etched silicon trenches and a polydimethylsiloxane (PDMS) slab. These silicon microchannels provide a confined environment for highly oriented nanostructure synthesis. Triblock copolymer (SBA-15) is self-assembled inside the microchannel array as template for silica precursor polymerization under an induced temperature gradient. The temperature gradient is maintained by thermoelectric pads and used to control the direction and rate of organic solvent evaporation. This evaporation-induced self-assembly (EISA) process is confined within the microfluidic channels and guided into formation of highly ordered nanochannels with long range alignment. The fabrication and synthesis process is developed and the resultant nanomaterial is characterized. A fluorescent molecule dye, fluorescein, is used to demonstrate the potentials of the integrated device in nanofluidics applications.