A novel synthesis of chitosan nanoparticles in reverse emulsion.

BioMerieux, Chemin de l'orme, Marcy l'Etoile 69280, France.
Langmuir (Impact Factor: 4.38). 10/2008; 24(20):11370-7. DOI: 10.1021/la801917a
Source: PubMed

ABSTRACT Physical hydrogels of chitosan in the colloidal domain were obtained in the absence of both cross-linker and toxic organic solvent. The approach was based on a reverse emulsion of a chitosan solution in a Miglyol/Span 80 mixture, generally regarded as safe. Temperature and surfactant concentration were optimized, and the impact of the degree of acetylation (DA) and the molar mass of chitosan was investigated. When chitosan had a DA above 30%, only macroscopic gels were obtained, because of the predominance of attractive Van der Waals forces. The lower the molar mass of chitosan, the better the control over particle size and size distribution, probably as a result of either a reduction in the viscosity of the internal aqueous phase or an increase in the disentanglement of the polymer chain during the process. After extraction and redispersion of the colloid in an ammonium acetate buffer, the composition of the particles was around 80% of pure chitosan corresponding to a recovery of 60% of the original input. These new and safe colloids offer wide perspectives of development in further applications.

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    ABSTRACT: Pure chitosan nanogels were produced, used to adsorb copper(II), and their antimicrobial activities were assessed. The complexation of copper(II) with chitosan solutions and dispersions was studied using UV-vis spectrometry. The adsorption capacity of chitosan nanogels was comparable to that of chitosan solutions, but copper(II)-loaded nanogels were more stable (i.e. no flocculation was observed while chitosan solutions showed macroscopic gelation at high copper concentration) and were easier to handle (i.e. no increase in viscosity). Adsorption isotherms of copper(II) onto chitosan were established and the impact of the pH on copper(II) release was investigated. The formation of a copper(II)-chitosan complex strongly depended on pH. Hence, release of copper(II) can be triggered by a decrease in pH (i.e. the protonation of chitosan amino groups). Furthermore, chitosan nanohydrogels were shown to be a suitable substrate for chitosan hydrolytic enzymes. Finally, a strong synergistic effect between chitosan and copper in inhibiting Fusarium graminearum growth was observed. The suitability of these copper(II)-chitosan colloids as a new generation of copper-based bio-pesticides, i.e. as a bio-compatible, bio-active and pH-sensitive delivery system, is discussed.
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May 27, 2014