Cell Isolation

Short definition:
Cell Isolation techniques are methods to identify, to separate and to transfer certain cells from a complex mixture of cells. The aim is to obtain single cells or to sort the cells according to a property of choice and thus to generate a homogenous cell population.

What is Cell Isolation?

Cell Isolation techniques are methods to separate and to transfer certain cells from a complex mixture of cells to obtain single cells or to sort the cells according to a property of choice and thus to generate a homogenous cell population.

What are the different Cell Isolation techniques and how do they work?

There are several very different cell isolation methods available depending on the starting material, and varying on throughput as well as on sample requirements as well as downstream technologies. The starting material can be tissue, cell suspensions and cell culture. The main categories of cell isolation techniques are flow cytometry and selective single cell isolation.

Cell isolation techniques based on flow cytometry such as fluorescence activated cell sorting (FACS) or magnetic activated cell sorting (MACS) distinguish cells according to their fluorescence or magnetic labeling. Fluorescent dyes and magnetic microbeads can be coupled to cell-type specific antibodies which then allow to uniquely identify target cells from unwanted cells. The cells are then automatically sorted into distinct vials to generate a homogenous cell population for further analyses. These cell isolation techniques offer high throughput cell sorting with little hands-on time.

To be able to apply FACS or MACS cell isolation techniques, the cells need to be available as cell suspension. This is already the case for cells from blood or bone marrow. Most other cell types are embedded in tissue and surrounded by other cell types and extracellular matrix. Thus, tissue blocks need to be subjected to mechanical and enzymatic treatment to form a single cell suspension. Collagenases and DNases are applied to enzymatically digest extracellular matrix proteins and cell-free DNA to ensure that cells are adequately suspended. Cells grown in cell culture can typically be suspended by pipetting or using gentle dissociation buffers.

Flow cytometry methods such as FACS or MACS are popular cell isolation techniques as they offer high throughput with little hands-on time. Therefore, these cell isolation techniques are the methods of choice for sorting thousands of cells at a time. Developed already in the late 60ies of the last century, flow cytometry is an established technique with applications in research and in diagnostics.

Cell isolation techniques based on microfluidics, especially droplet-based methods, have been developed in the last decade and enable sorting of cells and combining cell isolation with video documentation of each single cell or with PCR methods for single cell analysis. Several companies have been founded to develop and optimize cell isolation techniques using microfluidics and droplet-based technologies. Droplets are typically formed from aqueous solutions containing cells (dispersed phase) and oil (continuous phase). In addition to single cells, the droplets can also contain reagents for PCR and thus allow for a combined workflow of single cell isolation and single cell analysis.

In contrast to flow cytometry and microfluidics, single cell isolation technologies such as laser microdissection or manual cell picking allow for highly selective single cell isolation as these systems are based on microscopes and thus enable visual control throughout the whole process of single cell isolation. Manual micromanipulators have been developed already beginning of last century, whereas laser microdissection was available in the early 2000s. Recent advances focus on automatization of workflows, as well as on image recognition for target cell identification.Thus, identification of target cells can nowadays be supported by software algorithms, but target cell selection can also be performed by the users upon visual inspection through the microscope. These cell isolation techniques therefore provide highly specific single cell isolation, however, the throughput is limited compared to flow cytometry based cell isolation techniques such as FACS. In contrast, as devices for specific single cell isolation do not lose any void volume and the whole sample can be scanned for target cells, cell picking instruments are also suitable to isolate rare cells.

How do the products and solutions of MMI help me when it comes to Cell Isolation?

With the MMI CellCut and MMI CellEctor systems, MMI offers two instruments for selective single cell isolation from tissue, suspension and cell culture. Both cell isolation techniques are based on research microscopes to enable visual inspection and identification of target cells before, during and after the isolation procedure.

The MMI CellCut is a laser microdissection system to cut single cells and larger areas of interest from tissue sections. In addition, living target cells can be selectively isolated from cell culture dishes both for re-cultivation as well as for molecular biology analyses. The MMI CellTools software package enables fully automated workflows to reduce hands-on time and to ensure specific single cell isolation at the same time.

The MMI CellEctor is able to pick single cells from suspension or from cell culture. The instrument consists of a dedicated 3D robot and a capillary holder, as well as a patented nanoliter pump. Microcapillaries are available in different sizes to be able to pick a variety of diverse cell types. The 3D robot is precisely controlled by the MMI CellTools software platform to isolate the cell of interest with a one-click routine. The pump sucks in the target cell and releases it in pre-defined deposition vials.

In contrast to manual cell picking devices, the MMI CellEctor cell isolation technique offers fully automated workflows, including cell recognition of target cells using the MMI CellExplorer module, video-supported acquisition and deposition of single cells, as well as capillary rinsing. The MMI CellEctor is therefore a unique instrument with cell isolation techniques supporting automated and selective single cell isolation.