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Pharmaceutical Excipients Binder Microcrystalline Cellulose

Product Name:Microcrystalline Cellulose,MCC
Alias:Emcocel,crocrystalline-Cellulos
Synonyms: microcrystalline, microcrystalline cellulose powder;microcrystalline cellulose
CAS No.: 9004-34-6
Molecular Formula: (C6H10O5)n,n≈220
MW: about 36000
EINECS: 232-674-9
Content: 99%
Appearance:White crystalline powder
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Description

MCC is a purified, partially depolymerized cellulose prepared by treating alpha cellulose (type Iβ), obtained as a pulp from fibrous plant material, with mineral acids. Cellulose is the most abundant natural polymer on earth with an annual biomass production of 50 billion tons (Carlin, 2008). Cellulose consists of linear chains of β-1,4-D anhydroglucopyranosyl units.


MCC is generally considered as the diluent having the best binding properties and is recognized as one of the preferred direct compression binders . In addition to its dry binding properties, and in comparison to brittle excipients, MCC is self-disintegrating with low lubricant requirement due to its extremely low coefficient of friction and its very low residual die wall pressure .However these properties do not replace the need for true disintegrants and lubricants when MCC is used in a formulation. In fact MCC and superdisintegrants may be complementary to promote fast disintegration. MCC offers other advantages including broad compatibility with APIs, physiological inertness, ease of handling, and security of supply.


During compression MCC plastically deforms and therefore maximizes the area of interparticle bonding. Porous, often spray-dried, agglomerates deform on a macroscale; then due to the presence of slip planes, MCC dislocates on a microscale . This proximity of hydrogen groups on adjacent cellulose molecules enables the formation of numerous hydrogen bonds, which account almost exclusively for the strength and cohesiveness of compacts, even under low compression forces Mechanical interlocking of irregularly shaped and elongated MCC particles has also been suggested to enhance tabletability.


The plasticity of MCC is the main reason of its exceptional binding properties. However, compared to brittle excipients, MCC is more lubricant sensitive. Lubricated MCC particles will deform under pressure and will not fracture to create new and clean (lubricant-free) surfaces .The presence of high levels of hydrophobic lubricants, such as magnesium stearate, the use of long blend times and high blend speeds would then result in softer tablets .For a constant number of revolutions, tabletability may also decrease with increasing blender sizes and decreasing loadings in the blender.Furthermore the transit of the lubricated blend via the hopper and the feed frame of tablet presses may result in additional coverage of lubricant over the MCC particles . The addition of brittle excipients and/or colloidal silicon dioxide to blends containing MCC can successfully prevent lubricants to occupy the MCC surfaces, and would in turn minimize the negative influence of these lubricants on tablet strength .


The viscoelastic behavior of MCC also explains its Strain Rate Sensitivity (SRS), which refers to the greater elastic effects at higher tableting speeds where there is insufficient compaction time for plastic deformation In other words, the tabletability of MCC always decreases when scaled up from slow development tablet presses to high speed production rotary machines. The Strain Rate Sensitivity of viscoelastic excipients has to be taken into account by the formulation scientists in order to design robust formulations. The MCC content should not be minimized based on low speed trials alone. Sufficient overage should be included to compensate for increased elastic effects at higher speeds. Despite the lower tabletability of brittle excipients, which fragment in a time-independent manner, these excipients have been widely combined with plastically deforming binders to minimize the overall Strain Rate Sensitivity of formulations and to facilitate scale-up.


Thanks to its relatively low bulk density and broad particle size distribution, small amounts of MCC are able to efficiently bind other materials, especially poorly tabletable active pharmaceutical ingredients. MCC exhibits a high dilution potential, whereas the broad particle size range provides optimum packing density and coverage of other materials .


Description

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