In 1955, microcrystalline cellulose (MCC) was first discovered as a potential ingredient for use in solid pharmaceutical dosage forms. A decade later, its first commercial product was made available to the pharmaceutical industry under the brand name Avicel® PH. Fast-forward to today and MCC is one of the most popular pharmaceutical excipients used in tablet manufacturing and is manufactured globally by numerous suppliers.
In this article, we will give you a complete overview of microcrystalline cellulose, from its description to its production process, application in the pharmaceutical industry, and tips for sourcing high-quality MCC for your organization.
So, without further ado, let’s dive right into the article!
What is Microcrystalline Cellulose (MCC)?
Microcrystalline Cellulose (MCC) is a refined form of cellulose, the most abundant natural polymer on Earth. It is derived from alpha cellulose, which is sourced from plant materials such as wood pulp or purified cotton linters. MCC is produced as a highly purified, partially depolymerized cellulose by controlled acid hydrolysis. This process removes the amorphous regions of cellulose, resulting in a crystalline structure with unique physicochemical properties, and is widely used in pharmaceuticals.
Chemical Structure
Cellulose is a linear polymer composed of D-glucose units linked by β(1→4)-glycosidic bonds. In its natural state, cellulose chains form microfibrils, which are aggregates of molecules held together by hydrogen bonds, resulting in a semi-crystalline structure comprising crystalline and amorphous regions. The crystalline regions confer rigidity and strength, while the amorphous regions are more flexible.
During the production of MCC, acid hydrolysis selectively removes these amorphous regions, yielding shorter, crystalline segments. The resulting MCC consists of crystalline cellulose fragments, which contribute to its desirable properties such as high compressibility and binding capacity.
Production Process
Microcrystalline Cellulose is produced through a series of processes briefly discussed below:
Sourcing of Cellulose
In the first step, the primary raw material (cellulose) is sourced from high-quality sources like wood pulp and purified cotton linters. However, wood pulp is the preferred raw material due to its high cellulose content, which ensures that the final MCC product meets the required specifications for pharmaceutical applications.
Pulping Process
In the next step, the raw plant material undergoes a process called pulping to extract cellulose from other components like lignin and hemicellulose. Pulping is performed through chemical treatments such as the Kraft process, which uses a mixture of sodium hydroxide and sodium sulfide to break down lignin and release cellulose fibers. Alternative pulping processes, such as sulfite and organosolv methods, can also be used depending on the desired properties of the final cellulose product.
Alkali Treatment
Once the cellulose fibers are extracted, they are then treated with an alkaline solution at high temperatures. Alkali treatment is used to remove residual hemicelluloses and purify the cellulose even further.
Acid Hydrolysis
The purified cellulose is subjected to acid hydrolysis using mineral acids like hydrochloric acid. Acid hydrolysis is a critical step because it selectively hydrolyzes the amorphous regions of the cellulose fibers, leaving behind only the crystalline regions. The controlled nature of acid hydrolysis allows manufacturers to optimize the degree of depolymerization, influencing the final properties of the MCC, such as its crystallinity and particle size distribution.
Washing and Filtration
After hydrolysis, the crystalline cell...
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