Biocompatible Magnetic Fluids Research Articles

Biocompatible magnetic core/shell nanoparticles

Biocompatible magnetic fluids composed of modified nano-sized magnetic iron oxide particles have been prepared. The magnetic particles have been obtained (diameter in the order 2–30 nm) by variations of the concentration of reactants, temperature, operation time and pH conditions as well as the electrolyte concentration. Besides one- or two-step coating processes were used successfully. The adsorption process of the modified dextran was checked by determining adsorption isotherms at room temperature. The results are compared with adsorption behaviour of natural acids and surfactants. The characterization of the magnetic particles by various techniques is described.

The comparative study of particle size distribution in magnetic fluids

Water- and physiology-solution-based biocompatible magnetic fluids have been studied in order to determine the size of magnetic particles and their colloidal stability. The results of magnetorheological measurements at room temperature and measurements of the frequency-dependent complex magnetic susceptibility indicate that the fluids have good stability and that the particles are finely dispersed without aggregation. The mean particle diameter for physiology-solution-based magnetic fluid, estimated from measurements of anisttropy of the magnetic susceptibility, was found to be 9.4nm. This value is in good agreement with an estimate of 11.6nm obtained from transmission electron microscopy (TEM) particularly when allowance is made for the thickness of surfactant layer (approx. 2nm).

Biocompatible magnetic fluid precursors based on aspartic and glutamic acid modified maghemite nanostructures

Biocompatible magnetic fluid precursors based on chemically modified maghemite nanostructures (γ-Fe 2O 3) are able to chemisorb aspartic and glutamic acids, as shown by conductometric measurements. The amino acids adsorb onto the maghemite surface following an adsorption isotherm. The modified nanoparticles formed a stable colloidal solution at a pH of 5–8. Raman and FTIR spectroscopy directly showed that the investigated amino acids adsorb on the maghemite surface in the form of their respective salts, glutamate and aspartate.

Magnetic fluids effect upon growth processes in plants

The metabolic processes of plants growth and development take place according to some organic rules which are specific to their genetic potential. These processes may exhibit modifications of intensity, rhythm, sense, under the influence of the environmental conditions of agricultural systems, through certain factors and bioregulators artificially introduced by man. The results of some investigations regarding effects of biocompatible magnetic fluids (LMW 100 G) on the vegetal organism's (growth, development, fructifying, the level and quality of the yield precocity) are presented.

Inter-particle interactions in biocompatible magnetic fluids

Biocompatible magnetic fluids intended for use in protein purification applications have been prepared and characterised. Superparamagnetic iron oxide particles of order 10 nm in diameter were made by co-precipitation of ferric and ferrous chlorides in NaOH solution and were subsequently coated with aminosilane and dispersed in water. The magnetic and structural properties of a series of dispersions were investigated via atomic force microscopy, dynamic light scattering and SQUID magnetometry. These results enabled the interpretation of zero-field cooled and initial magnetisation data in dilute dispersions in terms of superparamagnetic relaxation and inter-particle interactions.

Cellular uptake of magnetic fluid particles and their effects on human adenocarcinoma cells exposed to AC magnetic fields in vitro.

Suspensions of coated superparamagnetic particles (magnetic fluids, MF) in AC magnetic fields have a pronounced specific absorption rate (SAR) per mass compared to multidomain particles. The aim of the present study was to investigate cellular uptake and the biological effects of AC magnetic field excited bio-compatible magnetic fluids on human carcinoma cells in vitro. One of the fluids tested was a dextran magnetite, which has a very low cyto-toxicity with survival fractions (SF) between 0.8 and 0.9 at concentrations of up to 5 mg ferrite per ml. Human carcinoma cells intracellularly accumulate up to 1 pg ferrite/cell which has been demonstrated by electron microscopy (TEM), X-ray spectroscopy and measurements of intracellular iron. It has been shown that the ferrite core is not altered intracellularly, but many of the dextran shells are degraded which yields particle chains and other aggregates observed in TEM. Semi-solid pellets of the tumour cells were treated with AC magnetic fields (520 kHz, 4-12.5 kA/m) or waterbath hyperthermia at 43 and 45 degrees C, in presence of extracellular and/or intracellular magnetic fluid particles. Although MF heating is produced from individual particles, the survival fractions of MF heated and water bath heated cells are equal. In fact, the extracellular MF particle distribution is homogeneous enough to obtain similar inactivation. In contrast to earlier reports intracellular dextran magnetite particles in AC magnetic fields did not induce cell inactivation. Since the amount of intracellular ferrite should be indeed large enough for cell inactivation, the loss of dextran shells is most probably the main cause of limited effectiveness of the intracellular magnetite particles. The present work has demonstrated that: (1) MFH is able to inactivate tumour cells in vitro to at least the same extent as water bath hyperthermia; and (2) that there is a sensitizer effect of ferrofluids at 43 degrees C probably caused by free ferric ions which induce oxidative stress; and (3) that there is no cytotoxic effect of intracellular dextran magnetite particles 30-180 min excited with AC magnetic fields used in this study. For the new method the term 'magnetic fluid hyperthermia (MFH)' is proposed.