Interaction of Chitosan with Cell Membrane Models at the Air−Water Interface

In this paper we employed phospholipid Langmuir monolayers as membrane models to probe interactions with chitosan. Using a combination of surface pressure--area and surface potential--area isotherms and rheological measurements with the pendent drop technique, we observed that chitosan interacts with phospholipid molecules at the air-water interface. We propose a model in which chitosan interacts with the phospholipids mainly through electrostatic interactions, but also including H-bonding and hydrophobic forces, depending on the phospholipid packing density. At large areas per molecule, chitosan in the subphase adsorbs onto the monolayer, expanding it. At small areas per molecule, chitosan is located in the subsurface. Indeed, a mixed chitosan-phospholipid monolayer can be transferred onto solid supports, even at high surface pressures. The effects of chitosan on the viscoelastic properties of phospholipid monolayers may be taken as evidence for the ability of chitosan to disrupt cell membranes.

Applications of photosynthetic bacteria for medical fields

The medical applications of photosynthetic bacteria are summarized. Photosynthetic bacteria can produce various types of physiological active substance such as vitamin B(12), ubiquinone (coenzyme Q10), 5-aminolevulinic acid (ALA), porphyrins and RNA. In particular, photosynthetic bacterial ALA was commercially applied to cancer diagnosis and treatment. Recently, ALA has been applied to the treatment of acne vulgaris and the suppression of the inflammatory response to coronary and iliac injuries. In addition, the recent applications of RNA from a marine photosynthetic bacterium as a medical supplement for immune improvement and suppression of infection are described. Furthermore, the feasible application of a biopolymer consisting of RNA from a photosynthetic bacterium as a drug delivery system (DDS) to cancer treatment is described.

In vitro evaluation of a chitosan membrane cross-linked with genipin

The study was to evaluate the characteristics of a chitosan membrane cross-linked with a naturally-occurring cross-linking reagent, genipin. This newly-developed genipin-cross-linked chitosan membrane may be used as an implantable drug-delivery system. The chitosan membrane without cross-linking (fresh) and the glutaraldehyde-cross-linked chitosan membrane were used as controls. The characteristics of test chitosan membranes evaluated were their cross-linking degree, swelling ratio, mechanical properties. antimicrobial activity, cytotoxicity, and degradability. It was found that cross-linking of chitosan membrane using genipin increased its ultimate tensile strength but significantly reduced its strain-at-fracture and swelling ratio. There was no significant difference in antimicrobial activity between the genipin-cross-linked chitosan membrane and its fresh counterpart. Additionally, the results showed that the genipin-cross-linked chitosan membrane had a significantly less cytotoxicity and a slower degradation rate compared to the glutaraldehyde-cross-linked membrane. These results suggested that the genipin-cross-linked chitosan membrane may be a promising carrier for fabricating an implantable drug-delivery system. The drug-release characteristics of the genipin-cross-linked chitosan membrane are currently under investigation.

In vivo biocompatibility and degradability of a novel injectable-chitosan-based implant

A novel injectable-chitosan-based delivery system with low cytotoxicity was fabricated in the study. The chitosan microspheres with small particle size, low crystallinity and good sphericity were prepared by a spray-drying method followed by treating with a crosslinker. In the study, a naturally occurring crosslinking reagent (genipin), which has been used in herbal medicine and in the production of food dyes, was used to crosslink the chitosan microspheres. The glutaraldehyde-crosslinked counterparts were used as a control. Histological study of the genipin-crosslinked chitosan microspheres injected intramuscularly into the skeletal muscle of a rat model showed a less inflammatory reaction than its glutaraldehyde-crosslinked counterparts. The results of the scanning electron microscopic examination indicated that the glutaraldehyde-crosslinked chitosan microspheres retrieved at 12-week postoperatively were already degraded into a loose and porous structure. However, the degradation of the genipin-crosslinked chitosan microspheres was not significant after 20 weeks of implantation. The results of the study demonstrated that the genipin-crosslinked chitosan microspheres have a superior biocompatibility and a slower degradation rate than the glutaraldehyde-crosslinked chitosan microspheres. Accordingly, the genipin-crosslinked chitosan microspheres may be a suitable polymeric carrier for long-acting injectable drug delivery.

Sustained release of 5-fluorouracil from polymeric nanoparticles

The use of biodegradable nanoparticles loaded with 5-fluorouracil was investigated as a potential means to sustain the release of this drug. Nanoparticles prepared from four biodegradable polymers were loaded with 5-fluorouracil using three loading concentrations of drug and three different concentrations of added polymer. Washing particles using a centrifugation/re-suspension with ultrasound protocol was found to dislodge the majority of drug, resulting in an over-estimation of incorporation efficiency and low levels of strongly entrapped drug. Increasing the initial 5-fluorouracil concentration before polymer/monomer addition increased the drug loading in both washed and unwashed particles. Increasing the amount of polymer used to make nanoparticles did not increase loadings, but did produce increased amounts of unusable polymer waste. Drug release from nanoparticles was evaluated using a Franz cell diffusion apparatus, which showed an initial burst effect followed by a slower release phase over 24 h. Indeed, nanoparticles prepared from poly(lactide-co-glycolide) released 66% of their 5-fluorouracil payload over this period. It was concluded that 5-fluorouracil-loaded nanoparticles could be readily included into a hydrogel-based delivery system to provide sustained drug release for trans-epithelial drug-delivery applications.

Sustained-release of oxytetracycline from chitosan microspheres prepared by interfacial acylation and spray hardening methods

Chitosan microspheres containing oxytetracycline (OTC), an antibiotic agent, were prepared by spray hardening and interfacial acylation methods. The object of this study was to prepare oxytetracycline-containing microspheres for oral administration and injection using different molecular weight (Mw 70,000 approximately 2,000,000) of chitosan. By the spray hardening method, microspheres with particle sizes between 5 and 30 microns could be obtained and might be suitable for intramuscular injection. On the other hand, chitosan microspheres with the ability to extend the dissolution period of oxytetracycline in low pH medium were also prepared by the interfacial acylation method. The result indicated that the releasing of oxytetracycline from various acylated chitosan microspheres was decreased with increasing the molecular weight of chitosan and would show well sustained-release property. Besides, the morphology of various microspheres and crystalline form transition of oxytetracycline were also studied using electron scanning microscope and X-ray analysis.

Bioactive polymers 53: synthesis of poly(vinyl alcohol) and nalidixic acid based pro-drugs

The present paper studies the process of esterification of nalidixic acid on poly(vinyl alcohol). The influence of time, dilution and concentration of the reactants on the efficiency of esterification with dicyclohexylcarbodiimide has been followed. By experiment scheduling according to a centered, rotatory, compound, second order program, optimum conditions for the system under study have been found. On the other hand, the evolution of reaction of esterification of the nalidixic acid on poly(vinyl alcohol) was followed by using the activator-catalyst (4-pirolidinopyridine) system. An increase of the esterification yield up to 37% has been observed.