There are more than 100 prescription drugs in the US market, in which one excipient is commonly used: hydroxypropyl methylcellulose (HPMC). Although water soluble, this polymer provides gelling properties when exposed to an aqueous environment. HPMC with different degrees of substitutions is used in tablet form to control the release of the drug over a longer period. Two features enable the HPMC to function as a controlled delivery system. First, it is very hydrophilic due to its hydroxypropyl contents. Second, the HPMC chains are very compressed in a tablet, preventing them from a fast dissolution in the aqueous environment. These two features provide gelling properties like those in a chemically cross-linked hydrogel. Although there is no chemical cross-linker in the HPMC structure, the applied pressure during tablet preparation supplies enough entanglement and barrier for the retarded polymer dissolution. Interested in understanding the ability of chitosan to promote the healing of cartilage microfractures, Simard et al.91 investigated the recruitment of neutrophils by chitosan implants as the function of the degree of deacylation. While 80% deacylated chitosan attracted neutrophils in a dose-dependent manner, 90% deacylated chitosan was not an attractant.
Nevertheless, both chitosan preparations failed to elicit the release of granule enzymes or the generation of superoxide anions. Polymorphonuclear neutrophils internalized both chitosan preparations. If you are looking for high quality, high purity, and cost-effective Hydroxypropyl methylcellulose, or if you require the latest price of Hydroxypropyl methylcellulose, please feel free to email contact mis-asia.
