What is hollow microspheres?
Hollow microspheres (microballoons), loaded with drug in their outer polymer shells, were prepared by a novel emulsion-solvent diffusion method. The gas phase generated in the dispersed polymer droplet by the evaporation of dichloromethane formed an internal cavity in the microsphere of the polymer with the drug.
What are microspheres?
Microspheres are multiparticulate drug delivery systems which are prepared to obtain prolonged or controlled drug delivery to improve bioavailability, stability and to target the drug to specific site at a predetermined rate.
What are microspheres made of?
Microsphere are made from glass, ceramic, carbon or plastic depending on applications. Solid glass microsphere is manufactured by direct burning of glass powders while hollow glass microspheres is produced by adding blowing agent to glass powder.
How do you make glass microspheres?
Glass microspheres. Trace amounts of a sulfur-containing compound, such as sodium sulfate, are then mixed with the glass powder. The particles are run through a high-temperature heat transfer process, during which the viscosity of the glass drops and surface tension causes the particles to form perfect spheres.
What are microspheres used for?
Microspheres in drug delivery are used for targeted as well as prolonged drug release in the diseased area. It also protects the unstable or pH-sensitive drugs before and after the administration. Microspheres are classified into four different types: Table 10.1.
What is hollow glass?
Hollow Glass Microspheres (HGMS) are near perfect engineered spherical bubbles of thin walled glass, that are approximately 50 microns in size, with a really low density of between 0.1-0.4 g/cc. The glass type is amorphous and can come low purity or high purity grades.
Can microspheres reproduce?
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. Microspheres, like cells, can grow and contain a double membrane which undergoes diffusion of materials and osmosis.
How do microspheres work?
In microspheres composed of surface-eroding polymers, drug is released primarily at the surface as the polymer breaks down around it. Erosion of such polymers usually proceeds at a constant velocity [66].
What are microspheres and Coacervates?
Coacervates and microspheres are tiny spherical structures formed by the aggregations of lipids and proteins respectively. They are cell-like structures. But they do not contain all the properties of a living cell. Coacervates have a single membrane like boundary while microspheres have double membranes.
How do microspheres grow and what happens when it reaches an unstable size?
How do microspheres grow and what happens when it reaches an unstable size? They expand by absorbing additional molecules until they reach an unstable size, and then they split into smaller mictosperes.
Which best describes the atmosphere of the early Earth?
For decades, scientists believed that the atmosphere of early Earth was highly reduced, meaning that oxygen was greatly limited. Such oxygen-poor conditions would have resulted in an atmosphere filled with noxious methane, carbon monoxide, hydrogen sulfide, and ammonia.
What did they add to make it like Earth’s early atmosphere?
What did they add to make it like Earth’s early atmosphere? they added methane, ammonia, and hydrogen gases to the water vapor. organic molecules arrived on the early Earth on meteorites and comets from space.
What properties do microspheres and Coacervates share with cells?
Microspheres and coacervates are cell-like structures that can be formed in certain solutions. Both are formed due to chemical reactions spontaneously without any living organisms. These are nonliving things as they do not contain hereditary characteristics, but they have number of cell-like properties.
What were the earliest types of cells?
The first cells were most likely primitive prokaryotic-like cells, even more simplistic than these E. coli bacteria. The first cells were probably no more than organic compounds, such as a simplistic RNA, surrounded by a membrane.
How does the hypothesis of microspheres build off of the RNA world hypothesis?
How do the hypothesis of microspheres and the RNA World hypothesis build off of each other? Replicating RNA molecules transformed into DNA within the microspheres. When microspheres split, the genetic coding in self-replicating RNA would pass to the newly formed microspheres.
What role did the appearance of the ozone layer play in the evolution of early life on Earth?
What role did the appearance of the ozone layer play in the evolution of early life on Earth? Protected Earth from harmful UV rays and allowed organisms to live closer to the surface of the water. Led to use of sunlight for photosynthesis.
What did Earth First Look Like?
The hellish conditions meant Earth resembled Venus for a time, with a hazy, steamy atmosphere. But as the planet cooled, lava became rock and liquid water started to condense, forming Earth’s first ocean. The oldest minerals found on Earth, called zircons, date back to this time and are 4.4 billion years old.
How old is the ozone layer?
600 million years
How big was the ozone hole in 1985?
For several years, the minimum concentrations stayed in the 190s, but then the minimums rapidly grew deeper: 173 DU in 1982, 154 in 1983, 124 in 1985. By 1991, a new threshold was passed, as the ozone concentration fell below 100 DU for the first time.
Which is hotter thermosphere or exosphere?
The thermosphere is directly above the mesosphere and below the exosphere. The thermosphere is typically about 200° C (360° F) hotter in the daytime than at night, and roughly 500° C (900° F) hotter when the Sun is very active than at other times.
Why is exosphere so hot?
The particles in the exosphere are moving very quickly, so the temperature there is quite hot. Since the “air” is so thin in the exosphere – it is almost a vacuum – there are very, very few particles. We feel warmth when particles hit our skin and transfer heat energy to us.
Is the exosphere the thinnest layer?
The air in the exosphere is extremely thin – in many ways it is almost the same as the airless void of outer space. The layer directly below the exosphere is the thermosphere; the boundary between the two is called the thermopause. The bottom of the exosphere is sometimes also referred to as the exobase.
Can you breathe in the exosphere?
The exosphere has gases like hydrogen and helium, but they are very spread out. There is a lot of empty space in between. There is no air to breathe, and it’s very cold.
Is the exosphere the coldest layer?
exosphere—contains few particles that move into and from space. mesopause—the boundary between the mesosphere and the thermosphere; the coldest place on Earth. mesosphere—the layer in which most meteors burn up after entering Earth’s atmosphere and before reaching Earth’s surface.