Thermo-Sensitive Release Behavior of 5-Fluorouracil from Chitosan-Gel Microspheres Coated with Lipid Multilayers

Abstract

In order to provide a device that would release anticancer drugs in response to temperature, chitosan microspheres with immobilized 1-[N-(5- aminopentyl)urea]-5-fluorouracil (Ap-5FU) and coated with dipalmitoyl phosphatidyl choline (DPPC) multilayers were prepared. The chitosan-DPPC- chitosan microspheres were prepared by coating chitosan-DPPC microspheres with polyelectrolyte complex membrane of chitosan. Good distributive stability of microspheres in aqueous solution was achieved with the DPPC multilayers coating. When chitosan was crosslinked with glutaraldehyde, Ap-5FU was si multaneously immobilized to the microspheres by means of Schiffs base forma tion. In physiological saline media, free 5FU released from the microspheres was detected, but the 5FU derivative was not. The release rate of 5 FU from the microspheres was decreased by coating with DPPC multilayers, and further depressed by the formation of polyelectrolyte complex membrane. The thermo- sensitive release behavior of 5FU from chitosan-DPPC microspheres and chitosan-DPPC-chitosan microspheres was observed in vitro across the phase transition temperature ( T m) of the DPPC multilayer (41.4 ° C).

Fourth 3D Structure of the Chitosan Molecule: Conformation of Chitosan in Its Salts with Medical Organic Acids Having a Phenyl Group

“…The signals of carbon atoms comprising glucosamine residue of both acids are shown in Table 3. It has been demonstrated that the conformation-dependent 13 C chemical shifts of the C-1 and C-4 carbon atoms of chitosan and its acid salts, which are next to the glycosidic linkage, varied appreciably (up to 8 ppm) with the two torsion angles at the glycosidic linkages, C-1-Ogly (q) and Ogly-C-4 (c), respectively. 21) Clearly, the chemical shifts of both C-1 and C-4 carbon atoms of the gentisic acid and aspirin salts were diŠerent from those of tendon chitosan.…”

“…Figure 3 shows 13 C CP-MAS NMR spectra of tendon chitosan and its salts of gentisic acid and aspirin; all sample specimens were the same as those served for the x-ray diŠraction measurements. According to Saito et al, 21) the 13 C-NMR signals of tendon chitosan are assigned as shown in Fig. 3 and Table 2.…”

“…This observation has also been found with type II salts and is an indication that the acid ions are not arranged in regular positions in the crystals. A comparison of solid-state 13 C-NMR spectra of the gentisic acid salt and the aspirin salt, which could not be crystallized, suggests that, in the latter salt, the chitosan molecules also formed a 5 W 3 helix.…”

“…12) Chitosan and partially N-acetylated chitosan are expected to be applied as drug carriers in drug delivery system (DDS). 13,14) The ascorbic acid salt of chitosan has recently received strong attention, since ascorbic acid is known to enhance such chitosan functions as the adsorption of transition metals, inhibition of fat digestion, and prevention of dental periodontitis. An x-ray study of chitosan salt with L-ascorbic acid (vitamin C) 15) has revealed that it was a type I salt in which the chitosan extended two-fold helix was retained.…”

Synthesis and characterization of a novel chitosan-based network prepared using naturally occurring crosslinker

“…Chitosans are commercially available and could be reshaped into different forms of films, fibers, hydrogel beads, and microspheres. Due to its excellent biocompatibility and biodegradability, chitosan and its derivatives were widely applied to not only the field of heavy metal ions adsorption and chromatographic separation but also the fabrication of biomedical materials, enzyme and cell immobilization, especially for drug delivery 1–6. Over the last 30 years, chitosan microspheres have become important vehicles for its use as potential drug delivery systems 7–10.…”