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This study reports on the synthesis and characterization of interpenetrating polymeric network (IPN) and polyelectrolyte complexes (PEC) produced by ion-complex formation between natural and synthetic polymer bearing opposed charge. PEC of sodium alginate (NaAlg) and poly(acryloxyethyl-trimethylammonium chloride- co-2-hydroxyethyl methacrylate) (poly(Q- co-H)) were formed by addition of 2.0 wt % sodium alginate solution to 1.5 wt % poly(Q- co-H) solution, and by adding the poly(Q- co-H) solution to the NaAlg solution under magnetic agitation. The IPN were prepared using the sequential method with three different compositions, in which Q and H monomers were mixed in the 95/5 proportions in presence of NaAlg. The mixture was polymerized at 60°C using potassium persulfate as initiator. The characterizations of scaffolds were investigated by Fourier-transform infrared spectroscopy and thermogravimetric analysis. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Chitosan nanogels functionalized with folic acid and crosslinked with PEG diacid or tartaric acid have been prepared by inverse microemulsion method for targeted delivery into cancer cells. Nanogels with varying degrees of crosslinking (4.5–10 mol% of crosslinker) have been obtained. The particle sizes determined by TEM are below 50 nm with narrow size distributions. Nanogels show a clear improvement in solubility compared with pure chitosan. Their swelling ability is pH sensitive, due to the protonation of the free amino groups when the pH is varied from 10 to 4. The nanogels have been loaded with 5-fluorouracil, which is retained at pHs greater than 7.4 and released at pH = 5.5. These nanoparticles are degraded by lysozyme at physiological pH in a period of 20 days and are easily labeled with fluorescein isothiocyanate. All these features make them promising materials for the controlled release of anticancer drugs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Folate-chitosan nanogels were crosslinked with genipin in microemulsion medium. [•] Nanogels are water soluble at neutral and basic pHs. [•] Degradation rate was slightly higher at endosomic pH 5.5 than at physiological 7.4. [•] Nanogels displayed a pH-responsive release of 5-fluorouracil. [ABSTRACT FROM AUTHOR]

Abstract: Chitosan nanoparticles crosslinked with genipin were prepared by reverse microemulsion that allowed to obtain highly monodisperse (3–20nm by TEM) nanogels. The incorporation of genipin into chitosan was confirmed and quantitatively evaluated by UV–vis and 1H NMR. Loosely crosslinked chitosan networks showed higher water solubility at neutral pHs than pure chitosan. The hydrodynamic diameter of the genipin–chitosan nanogels ranged from 270 to 390nm and no remarkable differences were found when the crosslinking degree was varied. The hydrodynamic diameters of the nanoparticles increased slightly at acidic pH and the protonation of ionizable amino groups with the pH was confirmed by the zeta potential measurements. The biocompatible and biodegradable nature, as well as the colloidal and monodisperse particle size of the prepared nanogels, make them attractive candidates for a large variety of biomedical applications. [Copyright &y& Elsevier]

Abstract: Chitosan nanoparticles were obtained by crosslinking with two biocompatible dicarboxylic acids: polyethylene glycol dicarboxylic acid and tartaric acid. The water-in-oil (W/O) microemulsion method yielded particle sizes around 10–15 nm in the dried state (TEM) and 200–700 nm in the swollen state (QELS) from commercial chitosan. All the synthesized nanogels showed improved water solubility and most of them were stable at physiological pH. QELS studies revealed the influence of the hydrophilic character and flexibility of the crosslinker on the swelling behaviour of the nanogels. The nanoparticles showed a pH-sensitive volume transition that was consistent with the pKa of chitosan. The collected zeta potential data corroborated the electrostatic repulsion mechanism responsible for the pH-responsive behaviour. [Copyright &y& Elsevier]