Microsphere
Encyclopedia
Microsphere are small spherical particles, with diameters in the micrometer
range (typically 1 μm to 1000 μm (1 mm)). 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 widely 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 adsorb
onto polystyrene readily and permanently, which makes polystyrene microspheres suitable for medical research and biological laboratory experiments.
Polyethylene microspheres
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.
In 1953, Stanley Miller
and Harold Urey demonstrated
that many simple biomolecules could be formed spontaneously from inorganic
precursor compounds
under laboratory conditions designed to mimic those found on Earth
before the evolution of life. Of particular interest was the substantial yield of amino acid
s obtained, since amino acids are the building blocks for protein
s.
In 1957, Sidney Fox
demonstrated that dry mixtures of amino acids could be encouraged to polymer
ize upon exposure to moderate heat. When the resulting polypeptides
, or proteinoid
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 cellular
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 genetic
material. However they may have been important in the development of life, providing a 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 osmosis
. 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 photosynthesis
to produce energy.
on a molecular level. According to Wake Oncologists, "SIR-Spheres microspheres are radioactive polymer spheres that emit beta radiation. Physicians insert a catheter
through the groin
into the hepatic artery
and deliver millions of micropheres directly to the tumor site. The SIR-Spheres microspheres target the liver
tumors and spare healthy liver tissue.Cancer microsphere technology is the latest trend in cancer therapy. It helps the pharmacist to formulate the product with maximum therapeutic value and minimum or negligible range side effects. A major disadvantage of anticancer drugs is their lack of selectivity for tumor tissue alone, which causes severe side effects and results in low cure rates. Thus, it is very difficult to target abnormal cells by the conventional method of the drug delivery system. Microsphere technology is probably the only method that can be used for site-specific action, without causing significant side effects on normal cells.
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
range (typically 1 μm to 1000 μm (1 mm)). 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 widely in density and, therefore, are used for different applications. Hollow microspheres are typically used as additives to lower the density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
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 adsorb
Adsorption
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...
onto polystyrene readily and permanently, which makes polystyrene microspheres suitable for medical research and biological laboratory experiments.
Polyethylene microspheres
Polyethylene Microspheres
Polyethylene 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
Troubleshooting
Troubleshooting is a form of problem solving, often applied to repair failed products or processes. It is a logical, systematic search for the source of a problem so that it can be solved, and so the product or process can be made operational again. Troubleshooting is needed to develop and...
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:- AssayAssayAn assay is a procedure in molecular biology for testing 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 - BuoyancyBuoyancyIn physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
- Hollow microspheres are used to decrease material density in plastics (glass and polymerPolymerA polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
) - Ceramics - Used to create porous ceramics used for filters (microspheres melt out during firing, Polyethylene Microspheres)
- CosmeticsCosmeticsCosmetics 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, towelettes, permanent waves, colored contact lenses, hair colors, hair sprays and...
- Opaque microspheres used to hide wrinkles and give color, Clear microspheres provide "smooth ball bearing" texture during application (Polyethylene Microspheres) - Drug deliveryDrug deliveryDrug delivery is the method or process of administering a pharmaceutical compound to achieve a therapeutic effect in humans or animals. Drug delivery technologies modify drug release profile, absorption, distribution and elimination for the benefit of improving product efficacy and safety, as well...
- As miniature time release drug capsule made of, for example, polymers. A similar use is as outer shells of microbubble contrast agents used in contrast-enhanced ultrasound. - Electronic paperElectronic paperElectronic paper, e-paper and electronic ink are a range of display technology which are designed to mimic the appearance of ordinary ink on paper. Unlike conventional backlit flat panel displays, electronic paper displays reflect light like ordinary paper...
- Dual Functional microspheres used in GyriconGyriconGyricon is a type of electronic paper developed at the Xerox PARC . It has many of 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 paperElectronic paper, e-paper and electronic ink are a range of display technology which are designed to mimic the appearance of ordinary ink on paper. Unlike conventional backlit flat panel displays, electronic paper displays reflect light like ordinary paper... - Personal CarePersonal carePersonal care or toiletries is the industry which manufactures 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 Microspheres) - Spacers - Used in LCD screens to provide a precision spacing between glass panels (glass)
- StandardsStandard (metrology)In the science of measurement, a standard is an object, system, or experiment that bears a defined relationship to a unit of measurement of a physical quantity. Standards are the fundamental reference for a system of weights and measures, against which all other measuring devices are compared...
- 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 viscosityViscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
and buoyancyBuoyancyIn physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
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 Miller
Stanley Miller
Stanley 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 demonstrated
Miller-Urey experiment
The Miller and 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 origins of life. Specifically, the experiment tested Alexander Oparin's and J. B. S...
that many simple biomolecules could be formed spontaneously from inorganic
Inorganic chemistry
Inorganic 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 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...
under laboratory conditions designed to mimic those found on Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
before the evolution of life. Of particular interest was the substantial yield of amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s obtained, since amino acids are the building blocks for protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s.
In 1957, Sidney Fox
Sidney W. Fox
Sidney 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 polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
ize upon exposure to moderate heat. When the resulting polypeptides
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
, or proteinoid
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....
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 cellular
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, 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 genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
material. However they may have been important in the development of life, providing a membrane
Biological membrane
A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...
-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 osmosis
Osmosis
Osmosis is the movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides...
. 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 photosynthesis
Photosynthesis
Photosynthesis is a chemical 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. Photosynthetic organisms are called photoautotrophs, since they can...
to produce energy.
Cancer research
One useful discovery made from the research of microspheres is a way to fight cancerCancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
on a molecular level. According to Wake Oncologists, "SIR-Spheres microspheres are radioactive polymer spheres that emit beta radiation. Physicians insert a catheter
Catheter
In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...
through the groin
Groin
In 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. This is also known as the medial compartment of the thigh. A pulled groin muscle usually refers to a painful injury sustained by straining the hip adductor muscles...
into the hepatic artery
Hepatic artery
Hepatic 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 liver
Liver
The 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.Cancer microsphere technology is the latest trend in cancer therapy. It helps the pharmacist to formulate the product with maximum therapeutic value and minimum or negligible range side effects. A major disadvantage of anticancer drugs is their lack of selectivity for tumor tissue alone, which causes severe side effects and results in low cure rates. Thus, it is very difficult to target abnormal cells by the conventional method of the drug delivery system. Microsphere technology is probably the only method that can be used for site-specific action, without causing significant side effects on normal cells.