The moisture content of MCC influences compaction properties, tensile strength, and Viscoelastic properties. Moisture within the pores of MCC may act as an internal lubricant, Reduce frictional forces, and facilitate slippage and plastic flow within the individual Microcrystals. The lubricating properties of water may also reduce tablet density variation by Providing a better transmission of the compression force through the compact and by Decreasing the adhesion of the tablet to the die wall. Compressibility of MCC depends on Moisture content, which means that when MCC having different moisture content is Compressed with the same pressure, it may not result in the same compact porosity. It is very Well known that compaction pressure required to produce certain porosity (or solid fraction) Decreases with increasing moisture content, at below 3% water content the compaction Properties of MCC were insensitive to variation of moisture.
However up to an optimum level, An increase of moisture will increase the tablet strength of most excipients. This can be Explained by the fact that molecular binding in water vapor layers reduces inter-particular Surface distances, hence increasing intermolecular attraction forces. The storage conditions of the MCC compacts also play an important role, As an increase in relative humidity will negatively impact tablet strength.
Particle size has a very little effect on the tabletability of neat MCC, i.e., not lubricated nor Blended with other excipients or active pharmaceutical ingredients (APIs). MCC particle size And moisture content are often considered as the most important CMAs for tableting Performance. Considering that the brittle ductile transition diameter (Dcrit) of MCC is 1949 Mm, standard MCC grades, having particle sizes below Dcrit, should all deform plastically When compression pressure exceeds yield pressure. Coarser grades of MCC, characterized by A smaller envelope surface area, have been reported to be more lubricant sensitive than finer MCC. In complete formulations finer MCCs would therefore promote tablet (compact) Strength. Reducing the particle size of MCC will increase cohesiveness and hence as a Consequence surely affect its flowability, different particle sizes of excipient may impact tablet Characteristics including hardness, friability, disintegration, and content uniformity. Improved Flowability will be obtained when MCCs are employed as well as reduction in tablet weight Variation.The particle size may also impact wetting properties, dissolution of the API, and Stability of drug products.
The MCC morphology, described by the length of particles Length (L) and their Width (D), was one of the most important factors influencing tabletability. Rod-shaped particles which are fibrous and having higher L/D ratios resulted in higher tablet strengths than round-shaped particles. Other physico- chemical properties of MCC including moisture content, bulk density, and specific surface area did not correlate well with tensile strength of obtained tablet. The reduction of bulk density and flow ability and the increase of specific surface area when the L/D ratio increased. This may be due to the property of the particles which is more fibrous. MCC morphology was found to be affecting the drug dissolution which may due to porosity.
Modifying the hydrolysis conditions, including temperature, time, and acid concentration, Also has a very little impact on the degree of crystallinity, i.e., the regularity of the Arrangement of the cellulose polymer chains. This observation indicates that crystallinity Cannot be controlled at the hydrolysis stage. Crystallinity appears to be more dependent on Pulp source rather than on processing conditions, which is consistent with the method of MCC manufacture where the acid preferentially attacks the (pulp dependent) amorphous Regions. The total amount of sorbed water in MCC is proportional to the fraction of Amorphous material. Therefore MCC powders with a lower degree of crystallinity may contain More water than their counterparts with a higher degree. If low-crystallinity MCC Preferentially binds more water, moisture-sensitive APIs may exhibit lower rates of Degradation. Despite the controversial impact of crystallinity, it may influence the adsorption Of water on cellulose microfibrils, which may in turn influence flowability, tabletability, and Stability of the drug product.
Mostly, direct compression excipients are dried; therefore porous structure was produced as a Result. This property is characterized by a relatively low bulk density. Increase in porosity (lower density) facilitates higher compressibility, i.e., the densification of a powder bed due to The application of a stress. The improved compressibility of plastically deforming materials, Such as MCC, might then result in improved tabletability as a result of the increased bonding Surface area. The higher roughness of low density MCC particles may also contribute to Particle interlocking. Low bulk density MCC will provide higher dilution potential and hence Better counteract the poor tableting properties of APIs. Granulation or Drying as preprocesses Of tablet formulation will densify MCC hence less tabletable than the original porous MCC. It Can therefore be generalized that a decrease in bulk density improves tabletability; however, It will often hinder flowability.
Degree of Polymerization
The Degree of Polymerization (DoP) expresses the number of Glucose units (C6H10O5) in the Cellulose chain. It decreases exponentially as a function of hydrolysis conditions, including Temperature, acid concentration, and time of reaction. The rate of hydrolysis slows down to a Certain value which is stated as level-off degree of polymerization (LoDP). The LoDP value is Specific for a particular pulp, and it is usually between the range of 200 and 300, e.g., 180–210 Range for hardwood pulps and 210–250 for softwood pulps. Theoretically, to obtain a certain Degree of polymerization which is higher than the LoDP value, hydrolysis process could be Terminated at any time. However, due to the exponential decay of DoP, this termination is Neither a robust nor a reproducible approach. The degree of polymerization is used as an Identity test, as Pharmacopoeial MCC is defined by a DoP below 350 glucose units, compared To DoPs in the order of 10,000 units for the original native cellulose. The correlation between the degree of polymerization (DoP) of MCC and its tabletability has Not been explored yet. Therefore, it is merely an identity test to distinguish the tabletability of MCC (DoP 440). The origin of the raw Materials and the production method of MCC more decisively influence the physical Characteristics than DoP.