taken using
confocal microscopy Circulating cells The techniques required to obtain isolated cells vary depending on the cell type required. Circulating cells such as blood cells or some tumour cells can be isolated by taking a blood sample. As blood samples contain a mixture of many different cell types, a method of separating out cells into different types must be used. The most commonly used method for this is
flow cytometry, during which an automated analyser inspects a narrow stream of cells. In one version of this technique, a light is shone on the stream of cells, and the analyser detects the reflected light or fluorescence before using this information to rapidly manoeuvre the cells of interest into a collection chamber.
Solid tissues When dealing with solid tissues, obtaining tissue for cell isolation may be more challenging. Surplus human tissue can sometimes be obtained at the time of planned surgery, for example specimens of
right atrial appendage are often excised and discarded during
open heart surgery such as
coronary artery bypass surgery. Other tissues such as samples of pancreas or bladder may be taken as a biopsy. Alternatively, tissue from animals is frequently obtained by
sacrificing the animal. After a tissue specimen has been obtained, it must be surrounded or perfused by a solution at an appropriate temperature containing the salts and nutrients required to keep the cells alive. This may be performed by simply submerging the tissue in the solution, or may involve more complex arrangements such as
Langendorff perfusion. Proteolytic
enzymes can then be added to the solution. Enzymes that digest
collagen (
collagenases) are often used when isolating cells from the heart or bladder. General-purpose enzymes that digest many sorts of protein (
proteases) may also be used. These enzymes, in addition to digesting the extracellular matrix, can also digest other important proteins essential for the cells of interest to function. If cells are exposed to these enzymes for too long then cell death results, but if they are not exposed to the enzymes for long enough then digestion of the extracellular matrix will not be complete. After the enzymes have been removed from the tissue by perfusing it with a second solution that does not contain enzymes, cells can be mechanically separated or dissociated. A simple technique for dissociating cells involves cutting the tissue into small chunk before agitating the chunks in a solution using a pipette. == Uses ==