Preparation and release properties of biodegradable chitin microcapsules: II. Sustained release of 6-mercaptopurine from chitin microcapsules

Abstract

Chitin microcapsules are prepared using a simple desolvation or nonsolvent addition phase separation method with 6-mercaptopurine (6-MP) as a reference core. Chitin with a molecular weight about 400,000 is used to prepare different core loaded microcapsules. The drug release rates of chitin microcapsules prepared by simple desolvation or nonsolvent addition method have different release profiles which are related to the rate of phase separation. With respect to the solubility parameter difference (delta delta) value between solvent and nonsolvent, the release rate of 6-MP from microcapsules decreases with increasing delta delta of the preparative system. The chitin beads show poor swelling properties and their release rates are pH-dependent. Sustained release of 6-MP from chitin microcapsules in low pH and neutral medium can be accomplished. To determine if the drug release from the polymer matrix is via a diffusion controlled or by an erosion controlled process, 6-MP release profiles of various chitin microcapsules degraded by lysozyme are investigated. The drug-release patterns of the chitin microcapsules prepared by nonsolvent addition (acetone, n-propanol, n-butanol) and simple desolvation in acetone are not only diffusion but also lysozyme digestion influenced. Whereas, by using water or ethanol as nonsolvent or desolvating agent, release profiles of the microcapsules prepared by nonsolvent addition and the simple desolvation method seem to be little affected by enzyme degradation. These results indicate that chitin might prove useful as a polymer carrier for the sustained release of drugs.

Synthesis, Structure, and Antitumor Activity of a Novel Tetranuclear Titanium Complex

“…They are composed of one or several lipid bilayers enclosing aqueous compartments. When phospholipids are hydrated, they spontaneously form lipid spheres enclosing the aqueous mediun and the solute . The particular nature of liposomes causes them to be distributed within the body in a pattern significantly different from that of free drugs .…”

“…When phospholipids are hydrated, they spontaneously form lipid spheres enclosing the aqueous mediun and the solute. 9 The particular nature of liposomes causes them to be distributed within the body in a pattern significantly different from that of free drugs. 10 Temperature-sensitive release can be engineered by the selection of pure lipids that undergo sharp transition temperatures to adjust the transition temperature of the liposomecomplex adduct to the desired point.…”

Development and Evaluation of In-Situ Gel Containing Ornidazole Loaded Microspheres for Treatment of Periodontitis

“…The water absorption capacity of chitosan microspheres was determined using the earlier reported method (Mi et al, 1997). One hundred milligrams of the microsphere sample was placed in 25 ml water for 2.5 h. The microspheres were filtered, blotted with filter paper to remove excess water on the surface and weighed immediately on an electronic balance (Adventurer TM Ohaus, NJ, USA).…”