Preparation and characterization of superparamagnetic chitosan microspheres: Application as a support for the immobilization of tyrosinase

Abstract

Superparamagnetic chitosan microspheres were prepared by a water-in-oil suspension-crosslinking technique. To this end, magnetite particles were dispersed in a chitosan solution in acetic acid. The dispersion was added to toluene containing Span 20 as a surfactant with stirring. Chitosan solution droplets were hardened with glutaraldehyde. The magnetic chitosan microspheres obtained were characterized with scanning electron microscopy, differential thermal analysis, and vibrational magnetometry. The microspheres had a wide size distribution, ranging from 43 Ϯ 25 to 255 Ϯ 55 m, that depended on the reaction conditions. The mean particle size decreased with an increase in the concentration of Span 20 or the amount of glutaraldehyde and with the addition of NaCl. However, a major size reduction was achieved by an increase in the stirring rate. Tyrosinase was immobilized on the microspheres. The immobilized enzyme retained 70% of its activity, as determined by the capacity to degrade phenolic compounds. The immobilized tyrosinase resulted in greater stability than the free enzyme. In addition, the enzyme maintained 65% of its phenol oxidation activity after 10 cycles of reuse. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: [651][652][653][654][655][656][657] 2005

Influence of iron oxide nanoparticles on the rheological properties of hybrid chitosan ferrogels

“…The iron oxide content was calculated assuming that the ratio between the weight of the residue at 950°C and the weight loss in the interval of 200-575°C for pure chitosan is the same for chitosan in the ferrogels [34]. Therefore, the weight percentage of magnetite, M, in the ferrogels can be calculated as follows:…”

Characterization of chitosan magnetic nanoparticles for in situ delivery of tissue plasminogen activator

“…Taken together, this indicates the interactions between Fe 3 O 4 MNP and chitosan is stronger in C500, C1000, and C2000 than in C125 or C250, which also raised the decomposition temperature of the coated chitosan. The weight percentage of chitosan in chitosan-MNP can be calculated according to the following formula (Peniche, Osorio, Acosta, de la Campa, & Peniche, 2005),…”

Wytwarzanie homo- i heterogenicznych mikrokapsułek oraz ich zastosowanie

“…What is more, hipocholesterolemic, hipolipidemic [32], antimicrobial [33] and antitumor activity [34] of chitosan have been reported. It is very often used for encapsulating enzymes [35], in dentistry [36], but also to manufacture matrices for drug delivery [37].…”