We report an integrated system for rapid sample-to-answer detection of a viral pathogen in a droplet of whole blood comprised of a two-stage microfluidic cartridge for sample processing and nucleic acid amplification, and a clip-on detection instrument that interfaces with the image sensor of a smartphone. The cartridge is designed to release RNA from the Zika virus in whole blood using chemical lysis, followed by mixing with the assay buffer for performing reverse-transcriptase loop-mediated isothermal amplification (RT-LAMP) reactions in six parallel microfluidic compartments. The battery-powered instrument heats the compartments from below, while LEDs illuminate from above. Fluorescence generation in the compartments is dynamically monitored by a smartphone camera. We characterize the assay time and detection limits for detecting Zika RNA and gamma-irradiated Zika virus spiked into buffer and whole blood and compare the performance of the same assay when conducted in conventional PCR tubes. Our approach for kinetic monitoring of the fluorescence-generating process in the microfluidic compartments enables spatial analysis of early fluorescent “bloom” events for positive samples. We show that dynamic image analysis reduces the time required to designate an assay as a positive test to 22 minutes, compared to ~30-45 minutes for conventional analysis of the average fluorescent intensity of the entire compartment. We achieve a total sample-to-answer time in the range of 17-32 minutes, while demonstrating a viral RNA detection as low as 2.70×102 copies/ul, and a gamma-irradiated virus of 103 virus particles in a single 12.5 microliter droplet blood sample.
The COVID pandemic prompted the need for rapid detection of the SARS-CoV-2 virus and potentially other pathogens. In this study, we report a rapid, label-free optical detection method for SARS-CoV-2 that is aimed at detecting the virus in the patient’s breath condensates. We show in the published pre-clinical study that, through phase imaging with computational specificity (PICS), we can detect and classify SARS-CoV-2 versus other viruses (H1N1, HAdV and ZIKV) with 96% accuracy, within a minute after sample collection. PICS combines ultrasensitive quantitative phase imaging (QPI) with advanced deep-learning algorithms to detect and classify viral particles. The second stage of our project, currently under development, involves clinical validation of our proposed testing technique. Breath samples collected from patients in the clinic will be imaged with QPI and a U-Net model trained on the breath samples will identify the SARS-CoV-2 in the sample within a minute.
In this study, we use phase imaging with computational specificity (PICS) to detect single Adenovirus and SARS-CoV2 particles. These viruses are sub-diffraction particles, with maximum diameter of approximately 120nm, which implies that we cannot fully visualize their internal structure. However, due to the very high spatial sensitivity of SLIM (0.3 nm pathlength), we can detect and localize individual viruses and, furthermore, using deep learning, classify them with high accuracy.
Solid-state nanopore sensors are promising devices for single DNA molecule detection and sequencing. This
paper presents a review of our work on solid-state nanopores performed over the last decade. In particular, here
we discuss atomic-layer-deposited (ALD)-based, graphene-based, and functionalized solid state nanopores.
We show that applying the Laplace operator to a speckle-free quantitative phase image reveals an unprecedented level of detail in cell structure, without the gradient artifacts associated with differential interference contrast microscopy, or photobleaching and phototoxicity limitations common in fluorescence microscopy. This method, referred to as Laplace phase microscopy, is an efficient tool for tracking vesicles and organelles in living cells. The principle is demonstrated by tracking organelles in cardiomyocytes and vesicles in neurites of hippocampal neurons, which to our knowledge are the first label-free diffusion measurements of the organelles in such cells.
To produce a large increase in total throughput, a multi-stage microfluidics system (US Patent pending) is being
developed for flow cytometry and closed system cell sorting. The multi-stage system provides for sorting and re-sorting
of cohorts of cells beginning with multiple cells per sorting unit in the initial stages of the microfluidic device and
achieving single cell sorting at subsequent stages. This design theoretically promises increases of 2- or 3-orders of
magnitude in total cell throughput needed for cytomics applications involving gene chip or proteomics analyses of sorted
cell subpopulations.
Briefly, silicon wafers and CAD software were used with SU-8 soft photolithography techniques and used as a mold
to create Y-shaped, multi-stage microfluidic PDMS chips. PDMS microfluidic chips were fabricated and tested using
fluorescent microspheres driven through the chip by a microprocessor-controlled syringe drive and excited on an
inverted Nikon fluorescence microscope. Inter-particle spacings were measured and used as experimental data for
queuing theory models of multi-stage system performance.
A miniaturized electronics system is being developed for a small portable instrument. A variety of LED light sources,
waveguides, and APD detectors are being tested to find optimal combinations for creating an LED-APD configuration at
the entry points of the Y-junctions for the multi-stage optical PDMS microfluidic chips. The LEDs, APDs, and PDMS
chips are being combined into an inexpensive, small portable, closed system sorter suitable for operation inside a
standard biohazard hood for both sterility and closed system cell sorting as an alternative to large, expensive, and
conventional droplet-based cell sorters.
Biomedical or Biological Micro-Electro-Mechanical- Systems (BioMEMS) have in recent years become increasingly prevalent and have found widespread use in a wide variety of applications such as diagnostics, therapeutics and tissue engineering. This paper reviews the interdisciplinary work performed in our group in recent years to develop micro-integrated devices to characterize biological entities. We present the use of electrical and mechanically based phenomena to perform characterization and various functions needed for integrated biochips. One sub-system takes advantage of the dielectrophoretic effect to sort and concentrate bacterial cells and viruses within a micro-fluidic biochip. Another sub-system measures impedance changes produced by the metabolic activity of bacterial cells to determine their viability. A third sub-system is used to detect the mass of viruses as they bind to micro-mechanical sensors. The last sub-system described has been used to detect the charge on DNA molecules as it translocates through nanopore channels. These devices with an electronic or mechanical signal output can be very useful in producing practical systems for rapid detection and characterization of cells for a wide variety of applications in the food safety and health diagnostics industries. The paper will also briefly discuss future prospects of BioMEMS and its possible impact and on bionanotechnology.
This paper describes a surface micromachined cantilever beam based oscillator detector for biological applications. This study used a novel microfabrication technique of merged epitaxial lateral overgrowth (MELO) and chemical mechanical polishing (CMP) to fabricate thin, low stress, single-crystal silicon cantilever beams. Vibration spectra of the cantilever beams, excited by thermal and ambient noise, was measured in air using a Digital Instrument Dimension 3100 Series scanning probe microscope (SPM). The cantilever beams were calibrated by obtaining the spring constant using the added-mass method. The sensors were used to detect the presence of Listeria innocua bacteria by applying increasing concentration of bacteria suspension on the same cantilever beam and measuring the resonant frequency changes in air. Cantilever beams were also used to detect the mass of the adsorbed antibodies and used to show selective capture of bacterial cells. The results indicate that the developed biosensor is capable of rapid and ultra-sensitive detection of bacteria and promises significant potential for enhancement of microbiological research and diagnostics.
Listeria monocytogenes is a deadly foodbome human pathogen. Its ubiquitous nature and its ability to grow at refrigeration temperatures makes this organism a difficult one to control. High-volume processing of food products and poor sanitary conditions of the processing plants often allow this organism to be present in processed, ready-to-eat (RTE) foods. Improved processing along with real-time detection could reduce the incidence of this pathogen. Conventional methods can detect this pathogen accurately, but take several days (2-7d) to complete, which is not practical considering the short shelf-life and cost of storage of RTE foods. Biosensor based approaches were adopted for sensitive detection of Listeria. Antibody-coupled fiber optic and microelectrical-mechanical system (MEMS) biochips were designed and examined for direct detection of L. monocytogenes from liquid samples. Also, interdigitated microsensor electrode (IME) chip and spectrofluorometer were used to measure L. monocytogenes interaction with mammalian cells (cytopathogenic activities) for indirect detection. Preliminary data generated using laboratory cultures of Listeria species indicated that L. monocytogenes could be detected in 30 mm to 1 h 30 mm depending on the techniques used.
We have developed novel techniques for the preparation of micropatterned structures from thin films prepared by the block copolymerization of monomers using UV free-radial polymerizations. The process involves polymerizing the first monomer layer in the presence of an iniferter (initator-transfer agent-terminator) with a dithiocarbamate group to make a photosensitive polymer. Upon application of the second monomer layer on the first polymer layer and irradiation, a copolymer is formed between the two layers. Patterns are created on the films by applying a mask and selectively irradiating the surface. We have successfully polymerized poy (ethylene glycol) (PEG) onto a highly crosslinked material of poly(ethylene glycol) dimethacrylate. Various patterns have been created to determine the precision that can be achieved with this method. Preliminary results show that the patterns in the second monomer layer can be from 5 micrometers to 100 micrometers thick, with feature size as small as 5 micrometers , allowing the use of this material to high aspect ratio structures for micro-fluidics. In addition, applications of this type of material are also in bioMEMS, biomaterials, and biosensors for the selective adhesion of cells and proteins.
Kevin Brown, Chris Bracken, Rashid Bashir, Kulwant Egan, Joe DeSantis, Abul Kabir, Wipawan Yindeepol, Joel McGregor, S. Prasad, Reda Razouk, Victor Boksha, Juan Rey
A trench isolation architecture for a low voltage (< 15 V), high frequency, complementary bipolar process technology has been developed. This technology features shallow and deep trench isolation with a minimum design rule of 1.0 (mu) , along with a zero encroachment deposited field oxide. Trench etch process results suggest a mechanism whereby, depending on the amount of exposed silicon, the plasma can either be considered `silicon deficient' or `oxygen deficient.' Black silicon formation during trench etching has been eliminated with an in-situ removal of the photoresist after the hardmask oxide has been defined. Terrain isolation process simulation results are shown to be more accurate in depicting actual wafer processing structures than Tsuprem-4. Initial bipolar device characteristics are reported that illustrate the integration of the introduced PlaTOx device isolation architecture. Realized ft/fmax are 6.3/9.5 GHz for NPN, and 3.8/8.2 GHz for PNP transistors.
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