Microsphere is a term used for small spherical particles, with diameters in the micrometer range (typically 1μm to 1000μm (1mm)). Microspheres are sometimes referred to as microparticles.
Microspheres can be manufactured from various natural and synthetic materials. Glass microspheres, polymer microspheres and ceramic microspheres are commercially available. Solid and hollow microspheres vary a lot in density and, therefore, are used for different applications. Hollow microspheres are typically used as additives to lower the density of a material. Solid microspheres have numerous applications depending on what material they are constructed of and what size they are.
Polyethylene and polystyrene microspheres are two most common types of polymer microspheres.
Polystyrene microspheres are typically used in biomedical applications due to their ability to facilitate procedures such as cell sorting and immunio precipitation. Proteins and ligands absorb onto polystyrene readily and permanently, which makes polystyrene microspheres suitable for medical research and biological laboratory experiments.
Polyethylene MicrospheresPolyethylene microspheres are a group of polymer microspheres, sometimes also referred to as polyethylene spheres, polyethylene beads, polyethylene balls and polyethylene microparticles....
are commonly used as a permanent or temporary filler. Lower melting temperature enables polyethylene microspheres to create porous structures in ceramics and other materials. High sphericity of polyethylene microspheres, as well as availability of colored and fluorescent microspheres, makes them highly desirable for flow visualization and fluid flow analysis, microscopy techniques, health sciences, process troubleshooting and numerous research applications. Charged polyethylene microspheres are also used in electronic paper digital displays.
Glass microspheres are primarily used as a filler and volumizer for weight reduction, retro-reflector for highway safety, additive for cosmetics and adhesives, with limited applications in medical technology.
Ceramic microspheres are used primarily as grinding media.
Microspheres vary widely in quality, sphericity, uniformity, particle size and particle size distribution. The appropriate microsphere needs to be chosen for each unique application.
Applications
New applications for microspheres are discovered every day, below are just a few:
- Assay
An assay is a procedure in molecular biology for testing and/or measuring the activity of a drug or biochemical in an organism or organic sample. A quantitative assay may also measure the amount of a substance in a sample. Bioassays and immunoassays are among the many varieties of specialized...
- Coated microspheres provide measuring tool in biology and drug research
- Buoyancy
In physics, buoyancy is the upward force that keeps things afloat. The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body. This force enables the object to float or at least seem lighter....
- Hollow microspheres are used to decrease material density in plastics (glass and polymerA polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties.Due to the extraordinary...
)
- Ceramics - Used to create porous ceramics used for filters (microspheres melt out during firing, Polyethylene Microspheres
Polyethylene microspheres are a group of polymer microspheres, sometimes also referred to as polyethylene spheres, polyethylene beads, polyethylene balls and polyethylene microparticles....
)
- Cosmetics
Cosmetics are substances used to enhance the appearance or odor of the human body. Cosmetics include skin-care creams, lotions, powders, perfumes, lipsticks, fingernail and toe nail polish, eye and facial makeup, permanent waves, colored contact lenses, hair colors, [hair sprays] and gels,...
- Opaque microspheres used to hide wrinkles and give color, Clear microspheres provide "smooth ball bearing" texture during application (Polyethylene MicrospheresPolyethylene microspheres are a group of polymer microspheres, sometimes also referred to as polyethylene spheres, polyethylene beads, polyethylene balls and polyethylene microparticles....
)
- Drug Delivery
Drug delivery is the method or process of administering a pharmaceutical compound to achieve a therapeutic effect in humans or animals. Drug delivery technologies are patent protected formulation technologies that modify drug release profile, absorption, distribution and elimination for the benefit...
- Miniature time release drug capsule (polymerA polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties.Due to the extraordinary...
)
- Electronic paper
Electronic paper, also called e-paper or electronic ink display is a display technology designed to mimic the appearance of ordinary ink on paper...
- Dual Functional microspheres used in GyriconGyricon is a type of electronic paper developed at the Xerox PARC . It has the same properties as paper: It's flexible, contains an image, and is viewable from a wide angle, but it can be erased and written thousands of times....
electronic paperElectronic paper, also called e-paper or electronic ink display is a display technology designed to mimic the appearance of ordinary ink on paper...
- Personal Care
Personal care or toiletries is the industry which manufacture consumer products used for beautification and in personal hygiene.-Subsectors:Subsectors of personal care include cosmetics and feminine hygiene....
- Added to Scrubs as an exfoliating agent (Polyethylene MicrospheresPolyethylene microspheres are a group of polymer microspheres, sometimes also referred to as polyethylene spheres, polyethylene beads, polyethylene balls and polyethylene microparticles....
)
- Spacers - Used in LCD screens to provide a precision spacing between glass panels (glass)
- Standards - monodispere microspheres are used to calibrate particle sieves, and particle counting apparatus.
- Retroreflective - added on top of paint used on roads and signs to increase night visibility of road stripes and signs (glass)
- Thickening Agent - Added to paints and epoxies to modify viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness." Thus, water is "thin," having a lower viscosity, while honey is "thick," having a higher viscosity...
and buoyancyIn physics, buoyancy is the upward force that keeps things afloat. The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body. This force enables the object to float or at least seem lighter....
Biological Protocells
Some refer to
microspheres or protein
protocells as small spherical units postulated by some scientists as a key stage in the origin of life.
In 1953,
Stanley MillerStanley Lloyd Miller was an American chemist and biologist who is known for his studies into the origin of life, particularly the Miller-Urey experiment which demonstrated that organic compounds can be created by fairly simple physical processes from inorganic substances...
and Harold Urey
demonstratedThe Miller–Urey experiment was an experiment that simulated hypothetical conditions thought at the time to be present on the early Earth, and tested for the occurrence of chemical evolution. Specifically, the experiment tested Soviet scientist Alexander Oparin's and J. B. S...
that many simple biomolecules could be formed spontaneously from
inorganicInorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compounds. This field covers all chemical compounds except the myriad organic compounds , which are the subjects of organic chemistry...
precursor
compoundsA 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...
under laboratory conditions designed to mimic those found on
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
before the evolution of life. Of particular interest was the substantial yield of
amino acidAmino acids are molecules containing an amine group, a carboxylic acid group and one of the twenty R-groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H
2NCHRCOOH, where R is an organic substituent...
s obtained, since amino acids are the building blocks for
proteinProteins are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues...
s.
In 1957,
Sidney FoxSidney Walter Fox was a Los Angeles-born biochemist responsible for unique discoveries in the autosynthesis of protocells.-Professor:In 1943 Fox was granted his first academic position at Iowa State College....
demonstrated that dry mixtures of amino acids could be encouraged to
polymerA polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties.Due to the extraordinary...
ize upon exposure to moderate heat. When the resulting
polypeptidesPeptides are short polymers formed from the linking, in a defined order, of α-amino acids. The link between one amino acid residue and the next is called an amide bond or a peptide bond....
, or
proteinoidProteinoids, or thermal proteins, are protein-like molecules formed inorganically from amino acids. Some theories of abiogenesis propose that proteinoids were a precursor to the first living cells....
s, were dissolved in hot water and the solution allowed to cool, they formed small spherical shells about 2 μm in diameter—microspheres. Under appropriate conditions, microspheres will bud new spheres at their surfaces.
Although roughly
cellularThe cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...
in appearance, microspheres in and of themselves are not alive. Although they do reproduce asexually by budding, they do not pass on any type of
geneticGenetics, , a discipline of biology, is the science of heredity and variation in living organisms. The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding...
material. However they may have been important in the development of life, providing a
membraneA biological membrane or biomembrane is an enclosing or separating amphipathic layer that acts as a barrier within or around a cell. It is almost invariably a lipid bilayer, composed of a double layer of lipid molecules and proteins that may constitute close to 50% of membrane...
-enclosed volume which is similar to that of a cell. Microspheres, like cells, can grow and contain a double membrane which undergoes diffusion of materials and
osmosisOsmosis is the diffusion of water through a semi-permeable membrane. More specifically, it is the movement of water across a semi-permeable membrane from an area of high water potential to an area of low water potential...
. Sidney Fox postulated that as these microspheres became more complex, they would carry on more lifelike functions. They would become heterotrophs, organisms with the ability to absorb nutrients from the environment for energy and growth. As the amount of nutrients in the environment decreased, competition for those precious resources increased. Heterotrophs with more complex biochemical reactions would have an advantage in this competition. Over time, organisms would evolve that used
photosynthesisPhotosynthesis is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of Bacteria, but not in Archaea...
to produce energy.
Cancer research
One useful discovery made from the research of microspheres is a way to fight
cancerCancer is a class of diseases in which a group of cells display uncontrolled growth , invasion , and sometimes metastasis...
on a molecular level. According to Wake Oncologists, "SIR-Spheres microspheres are radioactive polymer spheres that emit beta radiation. Physicians insert a
catheterIn medicine a catheter is a tube that can be inserted into a body cavity, duct or vessel. Catheters thereby allow drainage, injection of fluids or access by surgical instruments. The process of inserting a catheter is catheterization. In most uses a catheter is a thin, flexible tube , although...
through the
groinIn human anatomy, the groin areas are the two creases at the junction of the torso with the legs, on either side of the pubic area. A pulled groin muscle usually refers to a painful injury sustained by straining the hip adduction muscle....
into the
hepatic arteryHepatic artery can refer to:* Common hepatic artery * Hepatic artery proper...
and deliver millions of micropheres directly to the tumor site. The SIR-Spheres microspheres target the
liverThe liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
tumors and spare healthy liver tissue. Approximately 55 physicians in the United States use Sirtex’s SIR-Spheres microspheres in more than 60 medical centers."
See also
- Coacervate
A coacervate is a tiny spherical droplet of assorted organic molecules which is held together by hydrophobic forces from a surrounding liquid....
- Luminescent
- Proteinoid
Proteinoids, or thermal proteins, are protein-like molecules formed inorganically from amino acids. Some theories of abiogenesis propose that proteinoids were a precursor to the first living cells....
- Glass microspheres
- Microparticles
Microparticles are particles between 0.1 and 100 m in size. Commercially available microparticles include those made of glass, latex, polystyrene, various metals , and various magnetic materials...
- Polyethylene Microspheres
Polyethylene microspheres are a group of polymer microspheres, sometimes also referred to as polyethylene spheres, polyethylene beads, polyethylene balls and polyethylene microparticles....
External links