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pH-responsive polymer shell chitosan/poly (methacrylic acid) (CS-PMAA) was coated on mesoporous silica nanoparticles (MSN) through the facile in situ polymerization method. The resultant composite microspheres showed a flexible control over shell thickness, surface charges and hydrodynamic size by adjusting the feeding amount of MSN and the molar ratio of [-NH(2)]/MAA. The MSN/CS-PMAA composite microspheres were stable in the pH range of 5-8 as well as in the physiological saline (0.15M NaCl). Doxorubicin hydrochloride (DOX) was applied as a model drug to investigate the drug storage and release behavior. The results demonstrated that DOX could be effectively loaded into the composite microspheres. The cumulative release of DOX-loaded composite microspheres was pH dependent and the release rate was much faster at low pH (5.5) than that of pH 7.4. The cytotoxicity test by MTT assay showed that the blank carrier MSN/CS-PMAA microspheres were suitable as drug carriers. The cellular uptake of composite microspheres was investigated by confocal laser scanning microscopy (CLSM), which indicated that MSN/CS-PMAA could deliver the drugs into HeLa cell. The above results imply that the composite microspheres are a promising drug delivery system for cancer therapy., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A series of multiradiate calcium phosphate patterns have been observed by a gradating chitosan-polyaspartatic acid (PAsp) system, and their morphology evolution reveals the effect of chitosan and PAsp on the interfacial biomineralization.

New nonstoichiometric polyelectrolyte complex nanoparticles were prepared based on chitosan (CS) and polyaspartic acid sodium salt (PAsp). The physicochemical properties of the complexes were investigated by means of turbidity, dynamic light scattering, transmission electron microscopy and zeta potential. The results indicated that the slow dropwise addition of chitosan into PAsp allowed to elaborate either anionic or cationic particles in the size range of 85-300 nm with proper CS and PAsp unit molar ratios. Investigation of structural changes during the addition of CS revealed that the microstructure of the nanoparticles depended strongly on the unit molar ratio of CS to PAsp. Nanoparticles containing a hydrophilic drug, 5-fluorouracil (5FU), were prepared by mixing and absorption method. In vitro and in vivo experiment indicated that the drug-loaded CS-PAsp nanoparticles presented a sustained release of 5FU compared to the 5FU solution and the areas under curve (AUC) were increased by about four times.

A suitable carrier chitosan (CS) was used to prepare CS-Glycyrrhetic acid (GLA) nanoparticles under very mild conditions by polyelectrolyte complexation. These nanoparticles were well dispersed and stable in aqueous solution, and the physicochemical properties of which were investigated by FT-IR, dynamic light scattering, transmission electron microscope, fluorescence spectra and zeta potential. It was found that only when the weight ratio of CS to GLA was lower than 16.7, could the nanoparticles be formed. The prepared nanoparticles carried a positive charge and had the dried TEM-assessed size in the range from 20 to 30 nm. The mean hydrated diameter, size distribution and zeta potential of the nanoparticles could be controlled by some factors including the weight ratio of CS to GLA, the average molecular weight of CS and the pH value of the medium. It was also found that GLA encapsulation efficiency into the nanoparticles increased with the increase of the weight ratio of CS to GLA. The experiment of GLA release in vitro showed that the effect of CS encapsulation on GLA release was obvious and the CS-GLA nanoparticles system might be used to provide a continuous release.

The ammonium glycyrrhizinate-loaded chitosan nanoparticles were prepared by ionic gelation of chitosan with tripolyphosphate anions (TPP). The particle size and zeta potential of nanoparticles were determined, respectively, by dynamic light scattering (DLS) and a zeta potential analyzer. The effects, including chitosan molecular weight, chitosan concentration, ammonium glycyrrhizinate concentration and polyethylene glycol (PEG) on the physicochemical properties of the nanoparticles were studied. These nanoparticles have ammonium glycyrrhizinate loading efficiency. The encapsulation efficiency decreased with the increase of ammonium glycyrrhizinate concentration and chitosan concentration. The introduction of PEG can decrease significantly the positive charge of particle surface. These studies showed that chitosan can complex TPP to form stable cationic nanoparticles for subsequent ammonium glycyrrhizinate loading.

Abstract: In this paper, a simple approach was presented to prepare functional inorganic/organic composite microspheres in which the inorganic nanoparticles were encapsulated into the polyelectrolyte complexes between chitosan (CS) and poly(aspartic acid) sodium salt (PAsp). The magnetic microspheres were prepared via electrostatic interaction between the citrate groups stabilizing Fe3O4 nanoparticles and the amino groups of CS. Being taken as a kind of special polyelectrolyte with high molecular weight, the inorganic nanoparticles presented strong interaction with polyelectrolyte. By tuning the unit molar ratio of the opposite charged polyelectrolytes and the amount of Fe3O4 nanoparticles, the structure of the composite microspheres could be controlled and the dimension of microspheres ranged from 110 nm to 320 nm. Then the approach was extended to prepare luminescent-magnetic CS–PAsp microspheres by encapsulated Fe3O4 nanoparticles and CdTe quantum dots synchronously, which exhibited superior pH stability and remained strong photoluminescence properties after crosslinking. The CdTe–Fe3O4/CS–PAsp composite microspheres are potentially useful for further application in biolabeling and imaging. [Copyright &y& Elsevier]

Abstract: A modified method to prepare chitosan–poly(acrylic acid)(CS–PAA) polymer magnetic microspheres was reported in this paper. First, via self-assembly of positively charged CS and negatively charged Fe3O4 nanoparticles, magnetic CS cores with a large amount of Fe3O4 nanoparticles were successfully prepared. Subsequently, the AA monomers were polymerized on the magetic CS cores based on the reaction system of water-soluble polymer–monomer pairs. These polymer magnetic microspheres had a high Fe3O4 loading content, and showed unique pH-dependent behaviors on the size and zeta potential. From the magnetometer measurements data, the CS–PAA polymer magnetic microspheres also had superparamagnetic property as well as fast magnetic response. A continuous release of the entrapped ammonium glycyrrhizinate in such polymer magnetic microspheres occurred, which confirmed the potential applications of these microspheres for the targeted delivery of drugs. [Copyright &y& Elsevier]

Abstract: Water soluble chitosan (CS) derivatives containing polylactide unit were synthesized by reacting dl-lactide (DLLA) with chitosan in dimethyl sulfoxide solution in the presence of triethylamine. The chemical structure and physical properties of chitosan derivatives were characterized by FTIR, 1HNMR, TGA and XRD. Formation and characteristics of polymeric micelles of graft copolymers were studied by fluorescence spectroscopy and dynamic light scattering (DLS) method. The critical micelles concentration (cmc) of polymeric amphiphiles was determined by measuring the fluorescence intensity of pyrene as a fluorescent probe. The cmc value of DLLA/CS (11:1) (dl-lactide/aminoglucoside units molar ratio=11:1) in water was 6.49×10-2mg/ml. The size of micelles and their size distribution in water were measured by DLS. Mean diameter of the polymeric amphiphiles micelles of DLLA/CS (11:1) in water was 154nm with an unimodal size distribution (polydispersity=μ/Γ2=0.03). The spherical micelles were observed by transmission electron microscopy (TEM). [Copyright &y& Elsevier]