The preparation of maghemite (gama-Fe2O3) micro- and nanoparticles coated with chitosan, used as carriers for immobilized enzymes, was investigated. Fe2O3 nanoparticles were synthesized by coprecipitation of Fe2+ and Fe3+ ions in the presence of ammonium. They were coated with chitosan by the microemulsion process, suspension cross-linking technique, and covalent binding of chitosan on the Fe2O3 surface. The methods distinguished the concentration of chitosan, concentration of acetic acid solution, concentration of a cross-linking agent, temperature of synthesis, pH of the medium, and time of synthesis. Fe2O3 micro- and nanoparticles coated with chitosan prepared after three preparation methods were evaluated by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy analysis, energy dispersive spectrometry, thermogravimetric analysis, differential scanning calorimetry analysis, vibrating sample magnetometry, dynamic light scattering, laser diffraction granulometry, and X-ray diffractometry. These positive attributes demonstrated that these magnetic micro- and nanoparticles coated with chitosan may be used as a promising carrier for further diverse biomedical applications.
COBISS.SI-ID: 16941078
A new concept of nicotinamide adenine dinucleotide hydrate (NADH) oxidation which combines advantages of the microreactor technology with the advantages of magnetic nanoparticles (MNPs) application is developed. Acetaldehyde was used as a substrate for the NADH regeneration process while the reaction was performed in a batch reactor and in a microreactor using alcohol dehydrogenase(ADH)-loaded MNPs. Three different microreactor systems with MNPswere studied, two with stationary MNPs trapped on the inner surface of microchannel by permanent magnetic field and one where the MNPs actively move across the channel (movement inside microchannel allowed by oscillating magnetic field). In reactor system with oscillating magnetic field and actively moving ADH-loaded MNPs 100% NADH conversion was achieved for residence time of just 2 min.
COBISS.SI-ID: 17312022
Nanoparticles of inorganic magnetic core surrounded by layers of functional coatings are potential representatives of nanostructures for immobilization of bio-substances. Magnetic nanoparticles (MNPs) are often bound in aggregates due to a strong magnetic dipole, which has a lot of advantages, such as large surface area for binding biologically active substances. Chitosan is a polysaccharide polymer that is non-toxic, hydrophilic, biocompatible and has hydroxy and amino groups in its structure. Because of these chemical and biological properties it is a desirable bio-product for immobilization of enzymes and for binding of other biologically active substances. Magnetic micro and nanoparticles were synthesized with chitosan by three different methods; microemulsion process, suspension cross-linking technique and covalent binding of chitosan. Toxic effect of the prepared magnetic particles was determined as well and was examined on five different bacterial cultures; Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis and Klebsiella pneumoniae. At concentrations of 10-30 mg of magnetic particles per 0.5 McFarland Standard solution of E. coli and per 400 CFU of S. aureus, P. aeruginosa, E. faecalis in K. pneumonia, no inhibition on the chosen bacterial cultures was detected.