Correction: Fully-automated and field-deployable blood leukocyte separation platform using multi-dimensional double spiral (MDDS) inertial microfluidics.

Correction for 'Fully-automated and field-deployable blood leukocyte separation platform using multi-dimensional double spiral (MDDS) inertial microfluidics' by Hyungkook Jeon et al., Lab Chip, 2020, 20, 3612-3624, https://doi.org/10.1039/D0LC00675K.

Separation of Ultra-High-Density Cell Suspension via Elasto-Inertial Microfluidics.

Separation of high-density suspension particles at high throughput is crucial for many chemical, biomedical, and environmental applications. In this study, elasto-inertial microfluidics is used to manipulate ultra-high-density cells to achieve stable equilibrium positions in microchannels, aided by the inherent viscoelasticity of high-density cell suspension. It is demonstrated that ultra-high-density Chinese hamster ovary cell suspension (>26 packed cell volume% (PCV%), >95 million cells mL-1 ) can be focused at distinct lateral equilibrium positions under high-flow-rate conditions (up to 10 mL min-1 ). The effect of flow rates, channel dimensions, and cell densities on this unique focusing behavior is studied. Cell clarification is further demonstrated using this phenomenon, from 29.7 PCV% (108.1 million cells mL-1 ) to 8.3 PCV% (33.2 million cells mL-1 ) with overall 72.1% reduction efficiency and 10 mL min-1 processing rate. This work explores an extreme case of elasto-inertial particle focusing where ultra-high-density culture suspension is efficiently manipulated at high throughput. This result opens up new opportunities for practical applications of high-particle-density suspension manipulation.

Fully-automated and field-deployable blood leukocyte separation platform using multi-dimensional double spiral (MDDS) inertial microfluidics.

A fully-automated and portable leukocyte separation platform was developed based on a new type of inertial microfluidic device, multi-dimensional double spiral (MDDS) device, as an alternative to centrifugation. By combining key innovations in inertial microfluidic device designs and check-valve-based recirculation processes, highly purified and concentrated WBCs (up to >99.99% RBC removal, ∼80% WBC recovery, >85% WBC purity, and ∼12-fold concentrated WBCs compared to the input sample) were achieved in less than 5 minutes, with high reliability and repeatability (coefficient of variation, CV < 5%). Using this, one can harvest up to 0.4 million of intact WBCs from 50 µL of human peripheral blood (50 µL), without any cell damage or phenotypic changes in a fully-automated operation. Alternatively, hand-powered operation is demonstrated with comparable separation efficiency and speed, which eliminates the need for electricity altogether for truly field-friendly sample preparation. The proposed platform is therefore highly deployable for various point-of-care applications, including bedside assessment of the host immune response and blood sample processing in resource-limited environments.

Diffraction-based acoustic manipulation in microchannels enables continuous particle and bacteria focusing.

Acoustic fields have shown wide utility for micromanipulation, though their implementation in microfluidic devices often requires accurate alignment or highly precise channel dimensions, including in typical standing surface acoustic wave (SSAW) devices and resonant channels. In this work we investigate an approach that permits continuous microscale focusing based on diffractive acoustics, a phenomenon where a time-averaged spatially varying acoustic pressure landscape is produced by bounding a surface acoustic wave (SAW) transducer with a microchannel. By virtue of diffractive effects, this acoustic field is formed with the application of only a single travelling wave. As the field is dictated by the interplay between a propagating substrate-bound wave and a channel geometry, the pressure distribution will be identical for a given channel orientation regardless of its translation on a SAW substrate, and where small variations in channel size have no substantive effect on the pressure field magnitude or overall particle migration. Moreover, in the case of a channel with dimensions on the order of the diffractive fringe pattern spacing, the number of focusing positions will be identical for all channel orientations, with acoustic radiation forces pushing suspended particles to the channel edges. We explore this highly robust particle manipulation technique, determining two distinct sets of streaming and acoustic radiation dominant concentration positions, and show the continuous focusing of polystyrene 1 µm and 0.5 µm diameter particles and fluorescently labeled E. coli bacteria cells at flow rates exceeding those of previous microfluidic implementations for micron and submicron sized particles.

Rapid identification and phylogenetic classification of diverse bacterial pathogens in a multiplexed hybridization assay targeting ribosomal RNA.

Rapid bacterial identification remains a critical challenge in infectious disease diagnostics. We developed a novel molecular approach to detect and identify a wide diversity of bacterial pathogens in a single, simple assay, exploiting the conservation, abundance, and rich phylogenetic content of ribosomal RNA in a rapid fluorescent hybridization assay that requires no amplification or enzymology. Of 117 isolates from 64 species across 4 phyla, this assay identified bacteria with >89% accuracy at the species level and 100% accuracy at the family level, enabling all critical clinical distinctions. In pilot studies on primary clinical specimens, including sputum, blood cultures, and pus, bacteria from 5 different phyla were identified.

Label-free Neutrophil Enrichment from Patient-derived Airway Secretion Using Closed-loop Inertial Microfluidics.

Airway secretions contain a large number of immune-related cells, e.g., neutrophils, macrophages, and lymphocytes, which can be used as a major resource to evaluate a variety of pulmonary diseases, both for research and clinical purposes. However, due to the heterogeneous and viscous nature of patient mucus, there is currently no reliable dissociation method that does not damage the host immune cells in the patient airway secretion. In this research, we introduce a sample preparation method that uses inertial microfluidics for the patient's immune assessment. Regardless of the heterogeneous fluidic properties of the clinical samples, the proposed method recovers more than 95% of neutrophils from airway secretion samples that are diluted 1,000-fold with milliliters of clean saline. By recirculating the concentrated output stream to the initial sample reservoir, a high concentration, recovery, and purity of the immune cells are provided; recirculation is considered a trade-off to the single-run syringe-based operation of inertial microfluidics. The closed-loop operation of spiral microfluidics provides leukocytes without physical or chemical disturbance, as demonstrated by the phorbol 12-myristate 13-acetate (PMA)-induced elastase release of sorted neutrophils.

Negative Selection by Spiral Inertial Microfluidics Improves Viral Recovery and Sequencing from Blood.

In blood samples from patients with viral infection, it is often important to separate viral particles from human cells, for example, to minimize background in performing viral whole genome sequencing. Here, we present a microfluidic device that uses spiral inertial microfluidics with continuous circulation to separate host cells from viral particles and free nucleic acid. We demonstrate that this device effectively reduces white blood cells, red blood cells, and platelets from both whole blood and plasma samples with excellent recovery of viral nucleic acid. Furthermore, microfluidic separation leads to greater viral genome coverage and depth, highlighting an important application of this device in processing clinical samples for viral genome sequencing.

Patient-Derived Airway Secretion Dissociation Technique To Isolate and Concentrate Immune Cells Using Closed-Loop Inertial Microfluidics.

Assessment of airway secretion cells, both for research and clinical purposes, is a highly desired goal in patients with acute and chronic pulmonary diseases. However, lack of proper cell isolation and enrichment techniques hinder downstream evaluation and characterization of cells found in airway secretions. Here, we demonstrate a novel enrichment method to capture immune-related cells from clinical airway secretions using closed-loop separation of spiral inertial microfluidics (C-sep). By recirculating the output focusing stream back to the input reservoir and running continuously with a high flow processing rate, one can achieve optimal concentration, recovery and purity of airway immune cells from a large volume of diluent, which was not readily possible in the single-pass operation. Our method reproducibly recovers 94.0% of polymorphonuclear leukocytes (PMNs), with up to 105 PMNs in clear diluted buffer from 50 µL of airway secretions obtained from mechanically ventilated patients. We show that C-sep isolated PMNs show higher neutrophil elastase (NE) release following activation by phorbol 12-myristate 13-acetate (PMA) than cells isolated by conventional mucolytic method. By capturing cells without chemically disrupting their potential function, our method is expected to expand the possibility of clinical in vitro cell based biological assays for various pulmonary diseases such as acute respiratory distress syndrome, pneumonia, cystic fibrosis, and bronchiectasis.

Surface engineering for enhancement of sensitivity in an underlap-FET biosensor by control of wettability.

The present work aims to improve the sensitivity of an electrical biosensor by simply changing a surface property of the passivation layer, which covers the background region except for the sensing site for electrical isolation among adjacent interconnection lines. The hydrophobic passivation layer dramatically enhances the sensitivity of the biosensor when compared with a hydrophilic passivation layer. A revamped metal oxide semiconductor field-effect transistor (MOSFET), which has a designed underlap region between a gate and a drain, is used as the electrical biosensor. A thin film of CYTOP(TM) and silicon nitride is used as the hydrophobic and hydrophilic passivation layers, respectively. The surface antigen and its specific antibody of the avian influenza virus were employed as the probe and target biomolecule, respectively, to confirm the enhanced sensitivity of the proposed biosensor. By using hydrophobic passivation, the limit of detection of the biosensor was improved up to 100-fold compared with that resulting from hydrophilic passivation. Therefore, a simple surface engineering to control surface wettability can notably improve the sensitivity of a biosensor without additional efforts, such as modifying the sensor structure, optimizing the bio-treatment protocol, or increasing the binding yield between a probe and its target, among other efforts.

Integration of field effect transistor-based biosensors with a digital microfluidic device for a lab-on-a-chip application.

A new platform for lab-on-a-chip system is suggested that utilizes a biosensor array embedded in a digital microfluidic device. With field effect transistor (FET)-based biosensors embedded in the middle of droplet-driving electrodes, the proposed digital microfluidic device can electrically detect avian influenza antibody (anti-AI) in real time by tracing the drain current of the FET-based biosensor without a labeling process. Digitized transport of a target droplet enclosing anti-AI from an inlet to the embedded sensor is enabled by the actuation of electrowetting-on-dielectrics (EWOD). A reduction of the drain current is observed when the target droplet is merged with a pre-existing droplet on the embedded sensor. This reduction of the drain current is attributed to the specific binding of the antigen and the antibody of the AI. The proposed hybrid device consisting of the FET-based sensor and an EWOD device, built on a coplanar substrate by monolithic integration, is fully compatible with current fabrication technology for control and read-out circuitry. Such a completely electrical manner of inducing the transport of bio-molecules, the detection of bio-molecules, the recording of signals, signal processing, and the data transmission process does not require a pump, a fluidic channel, or a bulky transducer. Thus, the proposed platform can contribute to the construction of an all-in-one chip.