Purification of mononuclear cells, monocytes and polymorphonuclear leukocytes

In the early nineteen-sixties Arne Bøyum, who was working in Oslo on the fractionation of blood leukocytes, recognized that the derivatives of triiodobenzoic acid that were being synthesized as X-ray imaging agents (for human intravenous injection) would also make ideal density gradient media for mammalian cell fractionation. 

The modern version of the medium that he devised for the purification of human peripheral blood mononuclear cells (PBMCs), which is marketed by Axis-Shield under the trade-name Lymphoprep™, is almost identical to that described in Boyum’s seminal paper published in 1968 [1]. 

It contains the ionic compound sodium diatrizoate (also known as Hypaque™); its molecular structure is shown in Figure 1. Later non-ionic derivatives, which are better tolerated by cells, were produced as X-ray imaging agents. These included iohexol (known under the commercial name Nycodenz®) in the early nineteen-eighties and about ten years later iodixanol, which is more or less a dimer of Nycodenz® (see Figure 1). Iodixanol is available commercially as a sterile 60% (w/v) solution called OptiPrep™. 

All of Axis-Shield’s density gradient media are produced in facilities that operate under strict FDA and EU cGMP compliance and to the European Pharmacological Standard of <1.0 endotoxin unit/ml. 

The actual measured levels of endotoxin are regularly <0.13 units/ml. This information, together with density and osmolality data, is available on the Certificate of Analysis that accompanies each batch of medium.

Because of their use as X-ray imaging agents, these compounds have been clinically tested; no other density gradient media conform to this high standard. More information about the industrial production of these compounds is available in the Axis-Shield Density Gradient Media catalogue.