Biology subjects

Tenje, M.

Publications and source records attributed to Tenje, M..

4 recordsLinked to original sources

bioRxiv2024

Capacity and limitations of microfluidic flow to increase solute transport in three-dimensional cell cultures

Culturing living cells in three-dimensional (3D) environments increases the biological relevance of laboratory experiments, but has the caveat of requiring solutes to overcome a diffusion barrier to reach the center of cellular constructs. We present a theoretical and numerical investigation that brings a mechanistic understanding of how microfluidicculture conditions, including chamber size, inlet fluid velocity, and spatial confinement, affect solute distribution within 3D cellular constructs. Contact with the culture chamber reduces the maximally achievable construct radius by 15%. In practice, finite diffusion and convection kinetics in the microfluidic chamber further lower that limit. The benefits of external convection are greater if transport rates across diffusion-dominated areas are high. Those are omnipresent and include the diffusive boundary layer growing from the fluid-construct interface and regions near corners where fluid is recirculating. Less convection is required to approach an ideal maximally-supplied state when diffusion within the constructs is slow. Our results contribute to defining the conditions where complete solute transport into an avascular 3D cell construct is achievable and demonstrate how flow velocity must evolve with construct radius in order to maintain a given solute penetration depth.

bioengineering↗

bioRxiv2024

A microfluidic platform for in situ studies of bacteria electroporation

Electroporation of dye-labelled bio-molecules has proven to be a valuable alternative to fluorescent protein fusion for single-molecule tracking in living cells. However, control over cell viability, electroporation efficiency and environment conditions before, during and after electroporation is difficult to achieve in bulk experiments. Here, we present a microfluidic platform capable of single-cell electroporation with in situ microscopy and demonstrate delivery of DNA into bacteria. Via real time observation of the electroporation process, we find that the effect of electrophoresis plays an important role when performing electroporation in a miniaturized platform and show that its undesired action can be balanced by using bipolar electrical pulses. We suggest that a low temperature of the sample during electroporation is important for cell viability due to temperature-dependant viscoelastic properties of the cell membrane. We further found that the presence of low conductive liquid between cells and the electrodes leads to a voltage divider effect which strongly influences the success of on-chip electroporation. Finally, we conclude that electroporation is intrinsically a highly stochastic process that is difficult to fully control via external parameters and envision that the microfluidic system presented here, capable of single-cell read-out, can be used for further fundamental studies to increase our understanding of the electroporation process.

bioengineering↗

bioRxiv2023

Variability in single-cell oxygen consumption kinetics

We combined microfabricated devices with multiparameter identification algorithms to probe the variability in size-dependent oxygen consumption parameters of single human hepatic cells. We demonstrate that single cells exhibit an oxygen-dependent metabolic rate, typical of Michaelis-Menten kinetics, and that their maximal oxygen consumption is significantly lower than that of monolayers or 3D hepatic cell aggregates. Notably, we found that clusters of two or more cells competing for a limited oxygen supply reduced their maximal single-cell consumption rate, highlighting their ability to adapt to local resource availability and the presence of nearby cells. Next, we used our high-throughput approach to characterize the covariance of size and oxygen consumption within a cell population. The results show that cooperative behaviour emerges in cell clusters, and that single-cell size and metabolism can be described by a lognormal joint probability density. Our study thus serves as a foundation to connect the metabolic activity of single human hepatocytes to their tissue-or organ-level metabolism as well as describe its size-related variability through scaling laws.

bioengineering↗

bioRxiv2023

Real-time pooled optical screening with single-cell isolation capability.

In a pooled optical screen, a genetically diverse library of living cells is imaged and characterised for phenotypic variations without knowing the genotype of the cells. The genotypes are identified in situ after the cells have been fixed or by physical extraction of interesting phenotypes followed by sequencing. Mother-machine microfluidics devices are efficient tools in pooled optical screens since many strains can be imaged in the same field of view, but the throughput is often limited. In this work, we show a method to extract single bacterial cells from a compact 100,000-trap mother-machine-based fluidic device using an optical tweezer. Unlike previous devices, the fluids in our design are routed in 3D to enable fast loading of cells, increased trap density, and faster imaging. We have also developed software that allows real-time analysis of the phenotyping data.

biophysics↗