Characterization of the flow and compression properties of chitosan
MetadataShow full item record
The most useful dosage form taken from a patient's point of view is tablets because of its simplicity and portability (Takeuchi et al., 2004:132). Manufacturing of tablets can be done by wet granulation or direct compression of powders. For direct compression it is important that the powder has good particle flow ability and compactability. Various methods to investigate these properties of the powder have been developed, which provide comparative indices to assist in the process and formulation design (Li et al., 2004:77). Chitin is the second most abundant naturally occurring biopolymer after cellulose (Asada et al., 2004: 169). Chitosan is produced by the partial alkaline N-deacetylation of chitin (Berger et al., 2004:36). The structure of chitosan is similar to that of cellulose, an excipient with acceptable compression properties. According to Olsson and Nystrom (2001 :204) hydrogen bonds are considered to be one of the dominating bonding mechanisms for most pharmaceutical powders. The extent of the effect will depend on the particle shape and surface characteristics (Hiestand, 1997:237-241). Considering the structure of chitosan it predicts the ability to form H-bonds, and produce tablets with acceptable mechanical strength. The two major problems identified in terms of the use of chitosan as directly compressible filler in tablet formulations is its poor flow and compressibility properties (Aucamp, 2004; Buys, 2006; De Kock, 2005). During the characterization of chitosan raw material the aim was to determine to which extend its physical properties affects the flow of the material and to compare its flow properties to that of other commonly used tablet fillers. Two batches chitosan were compared to each other to determine the effect of morphology on their physical properties. When ranking the composite index of the powders it was clear that in regards to the other materials used, chitosan was ranked the lowest. These results confirmed the poor flow of chitosan. The characterization of the two chitosan batches used in this study revealed significant differences in the morphology of the particles of the different batches. Because of these large inter-batch variations with respect to the physical properties of the different batches even when manufactured by the same company via the same method, these variations also affected the flow characteristics of the two batches. From the particle characterization in chitosan it could be concluded that the previously observed poor compression characteristics (De Kock, 2005; Aucamp, 2004) could be attributed to the low density and high porosity of the material. Only one of the batches studied could be compressed on a standard eccentric press, which could be attributed to the differences between the physical properties of two batches. Chitosan showed promising compression characteristics at specific machine settings (limited range of upper punch settings), with good crushing strength and low friabifity. The drawbacks of the compression properties for chitosan on the standard press was the relative low tablet weights that could be compressed for a specific die size and the narrow range for the upper punch setting to achieve an acceptable mechanical tablet strength and friability. The results of Buys (2006) showed promising results for chitosan when changing the compression cycle from a single fill to a double die fill for each compression cycle. The advantage of the modified eccentric tablet press in terms of improvement of the compactibility of low density materials was clearly demonstrated by the results from the compression studies of both chitosan batches. With the double fill cycle on the modified press it was possible to fill the die with a sufficient amount of powder to produce acceptable tablets with sufficient crushing strength and low friability. The modified tablet press made it possible to compress the batch (021010) chitosan which couldn't be compressed on the standard tablet press. Batch (030912), which was compressed on the standard as well as the modified press, showed improved results in the crushing strength and friability with increase of the percentage compression setting at a constant upper punch setting. Batch 030912 showed better results than that of batch 021010 and this could be attributed to the physical differences between the two batches.
- Health Sciences