Surfactant double layer stabilized magnetic nanofluids for biomedical application

Abstract

Magnetite nanoparticles were coated with surfactant double layers in order to prepare water based magnetic fluids (MFs). The effects of head group (sulfonate, carboxylate) and alkyl chain length (11-17 C atoms) and the combination of surfactants were studied. Adsorption, dynamic light scattering (DLS) and electrophoretic mobility measurements were performed. The quantity of surfactant varied between 0.3 and 0.5 g, i.e. their specific amount ranges over 1.5-2 mmol g(-1) magnetite in MFs. The adsorption isotherm of Na oleate on magnetite proved the double layer formation with 2 mmol g(-1) saturation value in good harmony with the empirical doses. The effect of diluting MFs, pH and salt concentration was studied. The pH-dependent stability and the salt tolerance of MFs were different owing to the dissociation of the outermost hydrophilic groups and the hydrophobic interactions scaling with the alkyl chain length of surfactant. The hydrophobic interactions are favored only for oleic and myristic acid double layers. In these MFs, aggregation cannot be observed even in fairly dilute systems up to the physiological salt concentration around neutral pH 6-8 favored in biomedical application. The stable oleic and myristic acid double layers can hinder effectively the aggregation of magnetite particles due to the combined steric and electrostatic stabilization.

PEGylation of surfacted magnetite core–shell nanoparticles for biomedical application

“…4a) displays a distinct IEP (isoelectric point) at pH ~8 [14,15,35]. When the bare purified nanomagnets become coated with an oleate double layer (red symbols), the pH-dependence of the electrokinetic potential resembles that of carboxylic acids due to the carboxylic groups linked to the outer surface of MNPs.…”

“…This coating of MNPs prevents the aggregation and can hinder chemical and biological degradation of the particles. Adsorption of small molecules, such as citric acid, fatty acids (especially the oleic acid), amino acids, various natural molecules (e.g., lecithin) and their combination have been applied to cover magnetic nanoparticles [1,[11][12][13][14][15][16][17][18][19][20][21][22]. Biocompatible SPION coating can be also achieved by using macromolecules, e.g., homopolymers (PVA, PVP, PAA, PEG (polyethylene-glycol)) [10,16,18,19,[23][24][25][26][27][28], copolymers (PEO-PPO(polypropylene oxide)-PEO (also known as Pluronics)) [4,29] or natural polymers (gelatine, polysaccharides, dextran) [11,21].…”

“…As surface modified MNPs can be prepared in several different ways [14,19,22], it has a great importance to compare the physico-chemical properties, bio-applicability and biocompatibility of the products prepared according to different methodologies. We have chosen two radically different approaches for the aims of comparison: "one-pot" synthesis with addition of reactants into the reaction mixture of MNP preparation and the more complicated synthesis process with separating and purifying steps and finally coating the MNPs.…”

Preparation and Magnetic Characteristics of Co1-δZnδFe2O4 Ferrite Nanopowders

“…One can mention their high catalytic activity and applications in drug delivery systems or in MRI technology as contrasts agents [1][2][3][4]. Especially interesting are magnetic oxide nanoparticles with a spinel type structure and chemical composition of the form MFe 2 O 4 where M denotes Co, Zn, Mn, Cu etc.…”

A Polarized Fourier Transform Infrared Spectrometry Attenuated Total Reflection Study of Bentonite Settled onto Magnetite

“…There are investigations suggesting that the point of zero charge of the edge surfaces is close to pH ≈ 5, 3,4 whereas the magnetite particles are positively charged up to pH ) 7.9. 5 At pH values lower than 6, so-called card-house structures may form due to electrostatic attraction between positive and negative charges, implying that the edges of the bentonite platelets may adhere to the 001 surfaces of other platelets. 2 If these card-house structures are formed, they will certainly affect the dichroic ratio of the Si-O vibrations with transition moments perpendicular and parallel to the surface normal of the platelets and, consequently, the average orientation of bentonite particles on the particulate magnetite substrate.…”