Microcrystalline cellulose crystallinity

Although its two domains could function independently, removal of the substrate-binding domain of ngCenA reduced enzymatic activity against microcrystalline cellulose but not against CMC or amorphous cellulose (12). This suggested that the substrate-binding domain played a critical role in the hydrolysis of crystalline cellulose. 

Nakai, Y., Fukuoka, E., Nakajima, S., and Yamamoto, K. 1977. Effects of grinding on physical and chemical properties of crystalline medicinals with microcrystalline cellulose. I. Some physical properties of crystalline medicinals in ground mixturd hem. Pharm. Bull., 25 3340-3346. 

Rowe, R. C., McKillop, A. G., Bray, D. The effect of batch and source variation on the crystallinity of microcrystalline cellulose. Intemat J Pharm 101 169-172 (1994). 

Microcrystalline Cellulose. Microcrystalline cellulose is a purified, partially depolymerized cellulose that occurs as a white, odorless, tasteless, crystalline powder composed of porous particles. It is widely used in pharmaceutical dosage forms, primarily as a filler-binder in oral tablets and capsules with both wet granulation and direct compression processes. Microcrystalline cellulose was marketed first in 1964 by the FMC Corporation under name Avicel PH in four different particle size grades, each with different properties.37 Addition of Avicel into a spray-dried lactose-based formulation overcame compressibility problems. At the same time, the lactose enhanced the flowability of the Avicel products available at that time. The direct compression tableting process became a reality, rather than a concept, partially because of the availability of Avicel. As of 2007, Avicel PH is commercially available in 10 types with different particle size, density, and moisture grades that have different properties and applications (Table 7.6).38 Other brands of microcrystalline cellulose are also available on the pharmaceutical market, including Pharmacel 101 and 102 from DMV International and Emcocel 50 M and 90 M from JRS Pharma. 

Apart from the sorbents already mentioned in connection with HPTLC pre-coated layers, a micro-crystalline cellulose has also been produced in an average particle size and a narrow particle size distribution suitable for HPTLC (9.). HPTLC pre-coated plates cellulose P 254 s (E. Merck, Darmstadt), composed of this microcrystalline cellulose, were used to separate Trevespan 6058. This is a mixture of the substances ioxynil (3,5-diiodo-4-hydroxy-benzo-nitrile), flurenol (9-hydroxyfluorenecarboxylic acid) and MCPA (2-methyl-4-chlorophenoxyacetic acid). For comparison purposes Trevespan 6038 was also separated on HPTLC pre-coated plates silica gel 60 F 254 (E. Merck, Darmstadt). 

Microcrystalline cellulose (Avicel) is purified partially depolymerized cellulose, prepared by treating a-cellulose with mineral acids. In addition to being used as a filler, it is also used as dry binder and disintegrant in tablet formulations. Depending on the preparation conditions, it can be produced with a variety of technical specifications depending on particle size and crystallinity. It is often used as an excipient in direct compression formulations but can also be incorporated as a diluent for tablets prepared by wet granulation, as a filler for capsules and for the production of spheres. 

Zeronian et al. [261] hypothesized that if microcrystalline cellulose is prepared that is a facsimile of the crystalline regions present in the fiber then the fraction of amorphous material F) of the fiber can be obtained from the relation... 

Different localized levels of molecular order can coexist in some pharmaceutical materials, giving rise to the occurrence of partially crystalline (and partially amorphous ) systems. In most cases, the properties of such materials (e.g., density) are intermediate to those of the 100% amorphous and 100% crystalline samples. By deliberately varying the level of crystallinity in such systems, their properties can be customized for a particular purpose. An example of this is with the tableting excipients microcrystalline cellulose and spray-dried lactose, which have had their compression characteristics optimized by manipulating their amorphous content. The properties of partially crystalline materials may be approximated in many instances by making physical mixtures of the totally amorphous and crystalline samples. This is known as the two-state model for partially crystalline systems.However, such experiments should be undertaken with caution as the mixed two-state material can sometimes have significantly different properties from the partially crystalline material that is manufactured directly (the real one-state system). ... 

Zografi and Kontny corrected the experimentally determined monolayer capacities of microcrystalline cellulose for degree of crystallinity and found reasonably consistent values. This result supported the conclusion that water in microcrystalline cellulose is confined to the non-crystalline regions. ... 

Microcrystalline cellulose is a purified, partially depolymerized cellulose that occurs as a white, odorless, tasteless, crystalline powder composed of porous particles. It is commercially available in different particle sizes and moisture grades that have different properties and applications. 

Kothari SH, Kumar V, Banker GS. Comparative evaluations of powder and mechanical properties of low crystallinity celluloses, microcrystalline celluloses, and powdered celluloses. Int J Pharm 2002 232 69-80. 

Suzuki T, Nakagami H. Effect of crystallinity of microcrystalline cellulose on the compactability and dissolution of tablets. Eur ] Pharm Biopharm 1999 47 225—230. 

One of the barriers to cellulose hydrolysis by cellulases is the high crystallinity of cellulose in its native form. The regeneration of cellulose after dissolution in ionic liquids results in cellulose of amorphous form. Microcrystalline cellulose was found to be hydrolysed 50-90 times faster by cellulases following regeneration after dissolution in [C,mim][Cl] or [Amim][Cl] [182], which indicates that dissolution of cellulose in an ionic liquid may be useful as a pretreatment method. 

The hydrolysis rate of the microcrystalline cellulose can be increased by treatment with ionic liquids (ILs) (see also Chapter 13). The essentially amorphous or a mixture of amorphous and partially crystalline cellulose were recovered with an antisolvent. With appropriate selection of IL treatment conditions and enzymes, the initial hydrolysis rates for IL-treated cellulose were up to 90 times greater than those of untreated cellulose [185]. 

Cellulase is a complex of enzymes showing various types of activities. Cellulose substrates include highly resistant crystalline forms such as cotton, various types of microcrystalline cellulose such as Avicel and hydrocellulose, sulfite pulps such as Solka Floe, as well as filter paper and cotton fabrics. More susceptible substrates include swollen or reprecipitated cellulose, cellophane, and ball-milled cellulose. Most susceptible are the soluble derivatives (of low D.S.) such as carboxymethylcellulose and cellulose sulfate. It is not surprising that there are many assay methods to detect or measure cellulase (9). These methods differ markedly in sensitivity, and in cellulase components detected, depending on the substrate used, the effect measured, and the duration and conditions of... 

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