Gradient centrifugation of infected Red Blood Cells

Percoll is a tool for efficient density separation in

Cell biology Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and ...

that was first formulated by Pertoft and colleagues. It is used for the isolation of

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...

organelle In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' the ...

s, and/or

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

es by density

centrifugation Centrifugation is a mechanical process which involves the use of the centrifugal force to separate particles from a solution according to their size, shape, density, medium viscosity and rotor speed. The denser components of the mixture migrate ...

. Percoll consists of

colloidal A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

particles of 15–30 nm diameter (23% w/w in water) which have been coated with

polyvinylpyrrolidone Polyvinylpyrrolidone (PVP), also commonly called polyvidone or povidone, is a water-soluble polymer made from the monomer ''N''-vinylpyrrolidone. PVP is available in a range of molecular weights and related viscosities, and can be selected accor ...

(PVP). Percoll is well suited for density gradient experiments because it possesses a low

viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

compared to alternatives, a low

osmolarity Osmotic concentration, formerly known as osmolarity, is the measure of solute concentration, defined as the number of osmoles (Osm) of solute per litre (L) of solution (osmol/L or Osm/L). The osmolarity of a solution is usually expressed as Osm/L ...

, and no toxicity towards cells and their constituents. Percoll is a registered trademark of

GE Healthcare GE HealthCare is a subsidiary of American multinational conglomerate General Electric incorporated in New York and headquartered in Chicago, Illinois. As of 2017, it is a manufacturer and distributor of diagnostic imaging agents and radiopharma ...

Past use in artificial reproduction

Percoll was previously used in

assisted reproductive technology Assisted reproductive technology (ART) includes medical procedures used primarily to address infertility. This subject involves procedures such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), cryopreservation of gametes o ...

(ART) to select

sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...

from

semen Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Semen i ...

by density gradient centrifugation, for use in techniques such as ''in vitro'' fertilization or

intrauterine insemination Artificial insemination is the deliberate introduction of sperm into a female's cervix or uterine cavity for the purpose of achieving a pregnancy through in vivo fertilization by means other than sexual intercourse. It is a fertility treatment ...

. However, in 1996,

Pharmacia Pharmacia was a pharmaceutical and biotechnological company in Sweden that merged with the American pharmaceutical company Upjohn in 1995. History Pharmacia company was founded in 1911 in Stockholm, Sweden by pharmacist Gustav Felix Grönfeldt ...

sent out a letter to laboratories stating that Percoll should be used for research purposes only, not clinical. Pharmacia had not marketed it as a sperm preparation product; it had been repackaged and sold as such by third-party manufacturers. The

FDA Warning Letter An FDA warning letter is an official message from the United States Food and Drug Administration (FDA) to a manufacturer or other organization that has violated some rule in a federally regulated activity. The FDA defines an FDA warning letter as: ...

was due to concerns that PVP might cause damage to sperm (an unknown issue), and also that some batches of Percoll contained high levels of

endotoxin Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer ...

(a known issue). The latter concern also applies to the use of Percoll with any other cells that might be injected back into a patient, since endotoxin can cause severe inflammation and fever. Since then it has been replaced with other

colloids A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

in the ART industry.

References

{{reflist Biochemistry