Microsphere: An Overview

About Author:
Rajesh Mujoriya
Sardar patel college of technology,
Balaghat, dis. Balaghat,
MP–481001,INDIA

Abstract
Microspheres offer an excellent solution to creating precise pore sizes in ceramics at reasonable prices.  Polyethylene microspheres offer the added benefit of minimal residue after firing, and the availability in wide size ranges from a few micron up to 1000um (1mm).    Highly spherical microspheres have the added benefit of creating strong pores without any stress risers. Biodegradable microspheres are used to control drug release rates thereby decreasing toxic side effects, and eliminating the inconvenience of repeated injections. Microparticulate carrier system can be administered through different routes such as i.v,ocular,i.m,oral,intra arterial.etc.Each routes has it’s own biological significance, limitation & pharmaceutical feasibility.

WHAT IS A MICROSPHERE?
“Microspheres are defined as solid spherical particles containing dispersed drug in either solution or micro-crystalline form”.
“A plastic compound used in some dermal fillers for the correction of wrinkles that are filled with a substance and released as the shell disintegrates”
“Small, hollow glass spheres used as fillers n epoxy and polyester compounds to reduce density”

Reference Id: PHARMATUTOR-ART-1157

ADVANTAGE OF MICROSPHERE
1. Controlled release delivery Biodegradable microspheres are used to control drug  release rates thereby decreasing toxic side effects, and eliminating the inconvenience of repeated injections.
2. Biodegradable microspheres have the advantage over large polymer implants in that they do not require surgical procedures for implantation and removal.
3. PLGA copolymer is one of the synthetic biodegradable and biocompatible  polymers that have reproducible and slow-release characteristics in vivo.

1) Type Of Microspheres :
1.1)  Fluorescent Microspheres

Fluorescent Microspheres are round
spherical particles that emit bright colors when illuminated by UV light. Ability to emit intense color under UV (black light) illumination provides contrast and visibility of Microspheres relative to background materials. For example, fluorescent micro beads are often used as traces to simulate spread of viruses in medical research.

Fig. 1 FLUORESCENT MICROSPHERES

Fluorescent spheres have a unique ability to appear translucent (clear) and practically invisible under ordinary light, and emit intense visible color when energized by ultraviolet (UV) light. This effect allows scientists and engineers to design blind tests and controlled experiments (e.g. simulate spread of viruses) This unique feature of fluorescent       
Microspheres has numerous applications in biomedical research and process troubleshooting.

1.2) Glass Microsphere
Glass Microspheres are microscopic spheres of glass manufactured for a wide variety of uses in research,   medicine, consumer goods and various industries. Glass Microspheres are usually between 1 to 1000 micrometers in diameter, although the sizes can range from 100 nanometers to 5 millimeters in diameter..
Hollow spheres are used as a light weight filler in composite materials such as syntactic foam and concrete. Hollow spheres also have uses ranging from storage and slow release of pharmaceuticals and radioactive tracers to research in controlled storage and release of hydrogen.
Fig. 2.  GLASS MICROSPHERE

1.3) Paramagnetic Microsphere
They have the ability to increase in magnetization with an applied magnetic field and lose their magnetism when the field is removed. Neither hysteretic nor   . This property allows efficient washing steps, low background and good       reproducibility.
One use of paramagnetic Microspheres as large as 1mm in diameter to simulate salmon eggs, Scientists are able to place them in a natural habitat, observe how they move with the water currents and then use their magnetic properties to clean them up.
Fig. 3.  PARAMAGNETIC MICROSPHERE

2)    Different Form Of Polymeric Microspheres
2.1)  Albumin Microspheres:-    
The albumin is a widely distributed natural protein. The particulate or the colloidal form of albumin is considered as the potential carrier of drug for either there sites specific localization or their local application into anatomical discrete sites. Albumin microspheres loaded with anticancer drug such as misogynic-C were found to be more effective than the drug alone. Burger et al., 1985 observed that cisplatin- loaded microspheres are 10 times more potent in targeting the drug to the patient with hyper vascular liver carcinoma.
 2.2)  Gelatin Microspheres:-    
It is a biodegradable polymer obtained from the partial hydrolysis of the collagen derived from the skin, connective tissue & bones of animals. The acid treated collagen is called type-A & the alkali treated is referred as type   B.Gelatin microspheres.
The gelatin microspheres being susceptible for the macrophages recognition can be used as carrier for the antigens. The antigens from microspheres are released within the macrophages upon their degradation leading to enhanced production of antigen specific antibody

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