Microtiter plate
Encyclopedia
A Microtiter plate or microplate or microwell plate, is a flat plate with multiple "wells" used as small test tubes. The microplate has become a standard tool in analytical research and clinical diagnostic testing laboratories. A very common usage is in the enzyme-linked immunosorbent assay (ELISA
), the basis of most modern medical diagnostic testing in humans and animals.
A microplate typically has 6, 12, 24, 48, 96, 384 or even 1536 sample wells arranged in a 2:3 rectangular
matrix
. Some microplates have even been manufactured with 3456 or even 9600 wells, and an "array tape" product has been developed that provides a continuous strip of microplates embossed on a flexible plastic tape.
Each well of a microplate typically holds somewhere between tens of nanolitres to several millilitres of liquid. They can also be used to store dry powder or as racks to support glass tube inserts. Wells can be either circular or square. For compound storage applications, square wells with close fitting silicone cap-mats are preferred. Microplates can be stored at low temperatures for long periods, may be heated to increase the rate of solvent evaporation from their wells and can even be heat-sealed with foil or clear film. Microplates with an embedded layer of filter material were developed in the early 1990s by several companies, and in 1992, the world's first Solid Phase Extraction
(SPE) microplate was launched by Porvair Sciences. This allowed simple column chromatography
to be carried out in a microplate footprint for the first time. Today there are microplates for just about every application in life Science research which involves filtration, separation, optical detection, storage, reaction mixing or cell culture.
The enormous growth in studies of whole live cells has led to an entirely new range of microplate products which are "tissue culture
treated" especially for this work. The surfaces of these products are modified using a plasma
discharge to make them easier for adherent cells to grow on.
A number of companies have developed robot
s to specifically handle SBS microplates. These robots may be liquid handlers which aspirate or dispense liquid samples from and to these plates, or "plate movers" which transport them between instruments, plate stackers which store microplates during these processes, plate hotels for longer term storage or microplate incubators to ensure constant temperature during testing.
Instrument companies have designed plate reader
s which can detect specific biological, chemical or physical events in samples stored in these plates.
, used for most optical detection microplates. It can be coloured white by the addition of titanium dioxide
for optical absorbance or luminescence
detection or black by the addition of carbon
for fluorescent biological assays. Polypropylene
is used for the construction of plates subject to wide changes in temperature, such as storage at -80C and thermal cycling. It has excellent properties for the long-term storage of novel chemical compounds
. Polycarbonate
is cheap and easy to mould and has been used for disposable microplates for the polymerase chain reaction
(PCR
) method of DNA amplification. Cyclo-olefins are now being used to provide microplates which transmit ultraviolet
light for use in newly developed assays.
The most common manufacturing process is injection moulding
, used for polystyrene, polypropylene and cyclo-olefin. Vacuum forming can be used with softer plastics such as polycarbonate. Composite microplates, such as filter plates and SPE
plates and even some advanced PCR
plate designs use multiple components which are moulded separately and later assembled into a finished product. ELISA
plates may now be assembled from twelve separate strips of eight wells, making it easier to only partially use a plate. This saves cost for the scientist.
, who machined 6 rows of 12 "wells" in Lucite
. However, common usage of the microplate began in the late 1950s when John Liner in USA had introduced a molded version. By 1990 there were more than 15 companies producing a wide range of microplates with different features. It was estimated that 125 million microplates were used in 2000 alone. The word "Microtiter" is a registered trademark of Cooke Engineering Company, and Thermo Electron OY is the last listed owner of the trademark (.) It is now more usual to use the generic term "microplate".
In 1996, the Society for Biomolecular Sciences (SBS) began an initiative to create a standard definition of a microtiter plate. A series of standards was proposed in 2003 and published by the American National Standards Institute
(ANSI) on behalf of the SBS. The standards govern various characteristics of a microplate including well dimensions (e.g. diameter
, spacing and depth
) as well as plate properties (e.g. dimensions and rigidity) (typical dimension ~5"x3.33").
ELISA
Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...
), the basis of most modern medical diagnostic testing in humans and animals.
A microplate typically has 6, 12, 24, 48, 96, 384 or even 1536 sample wells arranged in a 2:3 rectangular
Rectangle
In Euclidean plane geometry, a rectangle is any quadrilateral with four right angles. The term "oblong" is occasionally used to refer to a non-square rectangle...
matrix
Matrix (mathematics)
In mathematics, a matrix is a rectangular array of numbers, symbols, or expressions. The individual items in a matrix are called its elements or entries. An example of a matrix with six elements isMatrices of the same size can be added or subtracted element by element...
. Some microplates have even been manufactured with 3456 or even 9600 wells, and an "array tape" product has been developed that provides a continuous strip of microplates embossed on a flexible plastic tape.
Each well of a microplate typically holds somewhere between tens of nanolitres to several millilitres of liquid. They can also be used to store dry powder or as racks to support glass tube inserts. Wells can be either circular or square. For compound storage applications, square wells with close fitting silicone cap-mats are preferred. Microplates can be stored at low temperatures for long periods, may be heated to increase the rate of solvent evaporation from their wells and can even be heat-sealed with foil or clear film. Microplates with an embedded layer of filter material were developed in the early 1990s by several companies, and in 1992, the world's first Solid Phase Extraction
Solid phase extraction
Solid-phase extraction is a separation process by which compounds that are dissolved or suspended in a liquid mixture are separated from other compounds in the mixture according to their physical and chemical properties. Analytical laboratories use solid phase extraction to concentrate and purify...
(SPE) microplate was launched by Porvair Sciences. This allowed simple column chromatography
Column chromatography
Column chromatography in chemistry is a method used to purify individual chemical compounds from mixtures of compounds. It is often used for preparative applications on scales from micrograms up to kilograms.The main advantage of column chromatography is the relatively low cost and disposability...
to be carried out in a microplate footprint for the first time. Today there are microplates for just about every application in life Science research which involves filtration, separation, optical detection, storage, reaction mixing or cell culture.
The enormous growth in studies of whole live cells has led to an entirely new range of microplate products which are "tissue culture
Tissue culture
Tissue culture is the growth of tissues or cells separate from the organism. This is typically facilitated via use of a liquid, semi-solid, or solid growth medium, such as broth or agar...
treated" especially for this work. The surfaces of these products are modified using a plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
discharge to make them easier for adherent cells to grow on.
A number of companies have developed robot
Robot
A robot is a mechanical or virtual intelligent agent that can perform tasks automatically or with guidance, typically by remote control. In practice a robot is usually an electro-mechanical machine that is guided by computer and electronic programming. Robots can be autonomous, semi-autonomous or...
s to specifically handle SBS microplates. These robots may be liquid handlers which aspirate or dispense liquid samples from and to these plates, or "plate movers" which transport them between instruments, plate stackers which store microplates during these processes, plate hotels for longer term storage or microplate incubators to ensure constant temperature during testing.
Instrument companies have designed plate reader
Plate reader
Microplate Readers are laboratory instruments designed to detect biological, chemical or physical events of samples in microtiter plates. They are widely used in research, drug discovery, bioassay validation, quality control and manufacturing processes in the pharmaceutical and biotechnological...
s which can detect specific biological, chemical or physical events in samples stored in these plates.
Manufacture and composition
Microplates are manufactured in a variety of materials. The most common is polystyrenePolystyrene
Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry...
, used for most optical detection microplates. It can be coloured white by the addition of titanium dioxide
Titanium dioxide
Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...
for optical absorbance or luminescence
Luminescence
Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a...
detection or black by the addition of carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
for fluorescent biological assays. Polypropylene
Polypropylene
Polypropylene , also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes...
is used for the construction of plates subject to wide changes in temperature, such as storage at -80C and thermal cycling. It has excellent properties for the long-term storage of novel chemical compounds
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
. Polycarbonate
Polycarbonate
PolycarbonatePhysical PropertiesDensity 1.20–1.22 g/cm3Abbe number 34.0Refractive index 1.584–1.586FlammabilityV0-V2Limiting oxygen index25–27%Water absorption – Equilibrium0.16–0.35%Water absorption – over 24 hours0.1%...
is cheap and easy to mould and has been used for disposable microplates for the polymerase chain reaction
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
(PCR
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
) method of DNA amplification. Cyclo-olefins are now being used to provide microplates which transmit ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light for use in newly developed assays.
The most common manufacturing process is injection moulding
Injection moulding
Injection molding is a manufacturing process for producing parts from both thermoplastic and thermosetting plastic materials. Material is fed into a heated barrel, mixed, and forced into a mold cavity where it cools and hardens to the configuration of the cavity...
, used for polystyrene, polypropylene and cyclo-olefin. Vacuum forming can be used with softer plastics such as polycarbonate. Composite microplates, such as filter plates and SPE
Solid phase extraction
Solid-phase extraction is a separation process by which compounds that are dissolved or suspended in a liquid mixture are separated from other compounds in the mixture according to their physical and chemical properties. Analytical laboratories use solid phase extraction to concentrate and purify...
plates and even some advanced PCR
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
plate designs use multiple components which are moulded separately and later assembled into a finished product. ELISA
ELISA
Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...
plates may now be assembled from twelve separate strips of eight wells, making it easier to only partially use a plate. This saves cost for the scientist.
History
The earliest microplate was created in 1951 by a Hungarian, Dr. Gyula TakátsyGyula Takátsy
Gyula Takátsy , was a Hungarian medical doctor, microbiologist and inventor.In 1938 he graduated from the University of Medicine in Pécs, Hungary; , and joined the staff at the Institute of Public Health, where he worked until his early death in 1980.An influenza epidemic in Hungary in the early...
, who machined 6 rows of 12 "wells" in Lucite
Acrylic glass
Poly is a transparent thermoplastic, often used as a light or shatter-resistant alternative to glass. It is sometimes called acrylic glass. Chemically, it is the synthetic polymer of methyl methacrylate...
. However, common usage of the microplate began in the late 1950s when John Liner in USA had introduced a molded version. By 1990 there were more than 15 companies producing a wide range of microplates with different features. It was estimated that 125 million microplates were used in 2000 alone. The word "Microtiter" is a registered trademark of Cooke Engineering Company, and Thermo Electron OY is the last listed owner of the trademark (.) It is now more usual to use the generic term "microplate".
In 1996, the Society for Biomolecular Sciences (SBS) began an initiative to create a standard definition of a microtiter plate. A series of standards was proposed in 2003 and published by the American National Standards Institute
American National Standards Institute
The American National Standards Institute is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international...
(ANSI) on behalf of the SBS. The standards govern various characteristics of a microplate including well dimensions (e.g. diameter
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
, spacing and depth
Thickness
Thickness may refer to:Thickness may refer to:* Thickness in graph theory* Thickness of layers in Geology* Thickness The difference in height between two atmospheric pressure levels* Thickness planer a woodworking machine...
) as well as plate properties (e.g. dimensions and rigidity) (typical dimension ~5"x3.33").
External links
- http://www.biotek.com/resources/docs/Necessity_is_the_mother_of_invention_GIT-Verlag.pdf An article about the invention of the microplate, published in G.I.T. Laboratory Journal (accessed 06/10/10)
- http://www.oek.hu/oek.web?nid=499&pid=1 Dr. Gyula Takátsy, at the Hungarian National Center of Epidemiology website (accessed 06/10/10)