Quantifying the volume of single cells continuously using a microfluidic pressure-driven trap with media exchange

Deep Learning-Enabled Technologies for Bioimage Analysis

Deep learning (DL) is a subfield of machine learning (ML), which has recently demonstrated its potency to significantly improve the quantification and classification workflows in biomedical and clinical applications. Among the end applications profoundly benefitting from DL, cellular morphology quantification is one of the pioneers. Here, we first briefly explain fundamental concepts in DL and then we review some of the emerging DL-enabled applications in cell morphology quantification in the fields of embryology, point-of-care ovulation testing, as a predictive tool for fetal heart pregnancy, cancer diagnostics via classification of cancer histology images, autosomal polycystic kidney disease, and chronic kidney diseases.

Measuring Single-Cell Phenotypic Growth Heterogeneity Using a Microfluidic Cell Volume Sensor

An imaging-integrated microfluidic cell volume sensor was used to evaluate the volumetric growth rate of single cells from a Saccharomyces cerevisiae population exhibiting two phenotypic expression states of the PDR5 gene. This gene grants multidrug resistance by transcribing a membrane transporter capable of pumping out cytotoxic compounds from the cell. Utilizing fluorescent markers, single cells were isolated and trapped, then their growth rates were measured in two on-chip environments: rich media and media dosed with the antibiotic cycloheximide. Approximating growth rates to first-order, we assessed the fitness of individual cells and found that those with low PDR5 expression had higher fitness in rich media whereas cells with high PDR5 expression had higher fitness in the presence of the drug. Moreover, the drug dramatically reduced the fitness of cells with low PDR5 expression but had comparatively minimal impact on the fitness of cells with high PDR5 expression. Our experiments show the utility of this imaging-integrated microfluidic cell volume sensor for high-resolution, single-cell analysis, as well as its potential application for studies that characterize and compare the fitness and morphology of individual cells from heterogeneous populations under different growth conditions.

Recent advances in the use of microfluidic technologies for single cell analysis

The inherent heterogeneity in cell populations has become of great interest and importance as analytical techniques have improved over the past decades. With the advent of personalized medicine, understanding the impact of this heterogeneity has become an important challenge for the research community. Many different microfluidic approaches with varying levels of throughput and resolution exist to study single cell activity. In this review, we take a broad view of the recent microfluidic developments in single cell analysis based on microwell, microchamber, and droplet platforms. We cover physical, chemical, and molecular biology approaches for cellular and molecular analysis including newly emerging genome-wide analysis.

Beyond the bulk: disclosing the life of single microbial cells

Microbial single cell analysis has led to discoveries that are beyond what can be resolved with population-based studies. It provides a pristine view of the mechanisms that organize cellular physiology, unbiased by population heterogeneity or uncontrollable environmental impacts. A holistic description of cellular functions at the single cell level requires analytical concepts beyond the miniaturization of existing technologies, defined but uncontrolled by the biological system itself. This review provides an overview of the latest advances in single cell technologies and demonstrates their potential. Opportunities and limitations of single cell microbiology are discussed using selected application-related examples.

Manipulating Electrical and Fluidic Access in Integrated Nanopore-Microfluidic Arrays Using Microvalves

On-chip microvalves regulate electrical and fluidic access to an array of nanopores integrated within microfluidic networks. This configuration allows for on-chip sequestration of biomolecular samples in various flow channels and analysis by independent nanopores.

3D nano- and micro-patterning of biomaterials for controlled drug delivery

Recently, there has been an emerging interest in controlling 3D structures and designing novel 3D shapes for drug carriers at nano- and micro-scales. Certain 3D shapes and structures of drug particles enable transportation of the drugs to desired areas of the body, allow drugs to target specific cells and tissues, and influence release kinetics. Advanced nano- and micro-manufacturing methods including 3D printing, photolithography-based processes, microfluidics and DNA origami have been developed to generate defined 3D shapes and structures for drug carriers. This paper reviews the importance of 3D structures and shapes on controlled drug delivery, and the current state-of-the-art technologies that allow the creation of novel 3D drug carriers at nano- and micro-scales.

Passive flow regulator for precise high-throughput flow rate control in microfluidic environments

In this paper, we propose a passive flow regulator with a five-layer structure for high-throughput flow-rate control in microfluidic environments.

Microfluidics platform for measurement of volume changes in immobilized intestinal enteroids

Intestinal enteroids are ex vivo primary cultured single-layer epithelial cell spheroids of average diameter ∼150 μm with luminal surface facing inward. Measurement of enteroid swelling in response to secretagogues has been applied to genetic testing in cystic fibrosis and evaluation of drug candidates for cystic fibrosis and secretory diarrheas. The current measurement method involves manual addition of drugs and solutions to enteroids embedded in a Matrigel matrix and estimation of volume changes from confocal images of fluorescently stained enteroids. We developed a microfluidics platform for efficient trapping and immobilization of enteroids for quantitative measurement of volume changes. Multiple enteroids are trapped in a "pinball machine-like" array of polydimethylsiloxane posts for measurement of volume changes in unlabeled enteroids by imaging of an extracellular, high-molecular weight fluorescent dye. Measurement accuracy was validated using slowly expanding air bubbles. The method was applied to measure swelling of mouse jejunal enteroids in response to an osmotic challenge and cholera toxin-induced chloride secretion. The microfluidics platform allows for parallel measurement of volume changes on multiple enteroids during continuous superfusion, without an immobilizing matrix, and for quantitative volume determination without chemical labeling or assumptions about enteroid shape changes during swelling.

Quantifying the volume of single cells continuously using a microfluidic pressure-driven trap with media exchange

We demonstrate a microfluidic device capable of tracking the volume of individual cells by integrating an on-chip volume sensor with pressure-activated cell trapping capabilities. The device creates a dynamic trap by operating in feedback; a cell is periodically redirected back and forth through a microfluidic volume sensor (Coulter principle). Sieve valves are positioned on both ends of the sensing channel, creating a physical barrier which enables media to be quickly exchanged while keeping a cell firmly in place. The volume of individual Saccharomyces cerevisiae cells was tracked over entire growth cycles, and the ability to quickly exchange media was demonstrated.