Cell adhesion manipulation through single cell assembly for characterization of initial cell-to-cell interaction

Directed assembly of genetically engineered eukaryotic cells into living functional materials via ultrahigh-affinity protein interactions

Engineered living materials (ELMs) are gaining traction among synthetic biologists, as their emergent properties and nonequilibrium thermodynamics make them markedly different from traditional materials. However, the aspiration to directly use living cells as building blocks to create higher-order structures or materials, with no need for chemical modification, remains elusive to synthetic biologists. Here, we report a strategy that enables the assembly of engineered Saccharomyces cerevisiae into self-propagating ELMs via ultrahigh-affinity protein/protein interactions. These yeast cells have been genetically engineered to display the protein pairs SpyTag/SpyCatcher or CL7/Im7 on their surfaces, which enable their assembly into multicellular structures capable of further growth and proliferation. The assembly process can be controlled precisely via optical tweezers or microfluidics. Moreover, incorporation of functional motifs such as super uranyl-binding protein and mussel foot proteins via genetic programming rendered these materials suitable for uranium extraction from seawater and bioadhesion, respectively, pointing to their potential in chemical separation and biomedical applications.

A Review of Single-Cell Adhesion Force Kinetics and Applications

Cells exert, sense, and respond to the different physical forces through diverse mechanisms and translating them into biochemical signals. The adhesion of cells is crucial in various developmental functions, such as to maintain tissue morphogenesis and homeostasis and activate critical signaling pathways regulating survival, migration, gene expression, and differentiation. More importantly, any mutations of adhesion receptors can lead to developmental disorders and diseases. Thus, it is essential to understand the regulation of cell adhesion during development and its contribution to various conditions with the help of quantitative methods. The techniques involved in offering different functionalities such as surface imaging to detect forces present at the cell-matrix and deliver quantitative parameters will help characterize the changes for various diseases. Here, we have briefly reviewed single-cell mechanical properties for mechanotransduction studies using standard and recently developed techniques. This is used to functionalize from the measurement of cellular deformability to the quantification of the interaction forces generated by a cell and exerted on its surroundings at single-cell with attachment and detachment events. The adhesive force measurement for single-cell microorganisms and single-molecules is emphasized as well. This focused review should be useful in laying out experiments which would bring the method to a broader range of research in the future.

Red blood cells under varying extracellular tonicity conditions: an optical tweezers combined with micro-Raman study

Extracellular tonicity has a significant influence on human red blood cell deformation capability. Advancements in the area of laser physics and optical trapping have opened up a plethora of applications for understanding cell structure and dynamics. Here, Raman Tweezers technique was employed to investigate the impact of extracellular tonicity by exposing human red blood cells to both hypertonic and hypotonic intravenous fluids. Heme aggregation was observed in hypertonic saline solution, accompanied with damage in membrane protein. Loss of intracellular hemoglobin in hypotonic solution was evident from the decrease in porphyrin breathing mode present at 752 cm^-1. Oxygen binding to the central iron in the red blood cell heme was also affected under both hyper/hypo tonicity conditions. Morphological deviation of discocytes to echinocytes/spherocytes were also evident from quantitative phase imaging. Principal component analysis have showed clear differentiation of samples in order to classify the control erythrocytes and the tonicity stressed erythrocytes. Present study has also demonstrated the application of Raman Tweezers spectroscopy as a potential tool for probing red blood cell under different stress conditions.

Differentiation of single lymphoma primary cells and normal B-cells based on their adhesion to mesenchymal stromal cells in optical tweezers

We have adapted a non-invasive method based on optical tweezers technology to differentiate between the normal B-cells and the B-cell non-Hodgkin lymphoma (B-NHL) cells derived from clinical samples. Our approach bases on the nascent adhesion between an individual B-cell and a mesenchymal stromal cell. In this study, a single B-cell was trapped and optically seeded on a mesenchymal stromal cell and kept in a direct contact with it until a stable connection between the cells was formed in time scale. This approach allowed us to avoid the introduction of any exogenous beads or chemicals into the experimental setup which would have affected the cell-to-cell adhesion. Here, we have provided new evidence that aberrant adhesive properties found in transformed B-cells are related to malignant neoplasia. We have demonstrated that the mean time required for establishing adhesive interactions between an individual normal B-cell and a mesenchymal stromal cell was 26.7 ± 16.6 s, while for lymphoma cell it was 208.8 ± 102.3 s, p < 0.001. The contact time for adhesion to occur ranged from 5 to 90 s and from 60 to 480 s for normal B-cells and lymphoma cells, respectively. This method for optically controlled cell-to-cell adhesion in time scale is beneficial to the successful differentiation of pathological cells from normal B-cells within the fine needle aspiration biopsy of a clinical sample. Additionally, variations in time-dependent adhesion among subtypes of B-NHL, established here by the optical trapping, confirm earlier results pertaining to cell heterogeneity.

Microfluidic device performing on flow study of serial cell–cell interactions of two cell populations

In this study we present a novel microfluidic hydrodynamic trapping device to probe the cell–cell interaction between all cell samples of two distinct populations. We have exploited an hydrodynamic trapping method using microfluidics to immobilize a batch of cells from the first population at specific locations, then relied on hydrodynamic filtering principles, the flowing cells from the second cell population are placed in contact with the trapped ones, through a roll-over mechanism. The rolling cells interact with the serially trapped cells one after the other. The proposed microfluidic phenomenon was characterized with beads. We have shown the validity of our method by detecting the capacity of olfactory receptors to induce adhesion of cell doublets overexpressing these receptors. We report here the first controlled on-flow single cell resolution cell–cell interaction assay in a microfluidic device for future application in cell–cell interactions-based cell library screenings.

In this study we present a novel microfluidic hydrodynamic trapping device to probe the cell–cell interaction between all cell samples of two distinct populations.

Automatic and Selective Single Cell Manipulation in a Pressure-Driven Microfluidic Lab-On-Chip Device

A microfluidic lab-on-chip device was developed to automatically and selectively manipulate target cells at the single cell level. The device is composed of a microfluidic chip, mini solenoid valves with negative-pressurized soft tubes, and a LabView^®-based data acquisition device. Once a target cell passes the resistive pulse sensing gate of the microfluidic chip, the solenoid valves are automatically actuated and open the negative-pressurized tubes placed at the ends of the collecting channels. As a result, the cell is transported to that collecting well. Numerical simulation shows that a 0.14 mm³ volume change of the soft tube can result in a 1.58 mm/s moving velocity of the sample solution. Experiments with single polystyrene particles and cancer cells samples were carried out to demonstrate the effectiveness of this method. Selectively manipulating a certain size of particles from a mixture solution was also achieved. Due to the very high pressure-driven flow switching, as many as 300 target cells per minute can be isolated from the sample solution and thus is particularly suitable for manipulating very rare target cells. The device is simple, automatic, and label-free and particularly suitable for isolating single cells off the chip one by one for downstream analysis.

Nanomechanical measurement of adhesion and migration of leukemia cells with phorbol 12-myristate 13-acetate treatment

The adhesion and traction behavior of leukemia cells in their microenvironment is directly linked to their migration, which is a prime issue affecting the release of cancer cells from the bone marrow and hence metastasis. In assessing the effectiveness of phorbol 12-myristate 13-acetate (PMA) treatment, the conventional batch-cell transwell-migration assay may not indicate the intrinsic effect of the treatment on migration, since the treatment may also affect other cellular behavior, such as proliferation or death. In this study, the pN-level adhesion and traction forces between single leukemia cells and their microenvironment were directly measured using optical tweezers and traction-force microscopy. The effects of PMA on K562 and THP1 leukemia cells were studied, and the results showed that PMA treatment significantly increased cell adhesion with extracellular matrix proteins, bone marrow stromal cells, and human fibroblasts. PMA treatment also significantly increased the traction of THP1 cells on bovine serum albumin proteins, although the effect on K562 cells was insignificant. Western blots showed an increased expression of E-cadherin and vimentin proteins after the leukemia cells were treated with PMA. The study suggests that PMA upregulates adhesion and thus suppresses the migration of both K562 and THP1 cells in their microenvironment. The ability of optical tweezers and traction-force microscopy to measure directly pN-level cell–protein or cell–cell contact was also demonstrated.