Adsorption of Organic Dyes on Magnetic Iron Oxide Nanoparticles. Part II: Field-Induced Nanoparticle Agglomeration and Magnetic Separation.

This paper (part II) is devoted to the effect of molecular adsorption on the surface of magnetic iron oxide nanoparticles (IONP) on the enhancement of their (secondary) field-induced agglomeration and magnetic separation. Experimentally, we use Methylene Blue (MB) cationic dye adsorption on citrate-coated maghemite nanoparticles to provoke primary agglomeration of IONP in the absence of the field. The secondary agglomeration is manifested through the appearance of needlelike micron-sized agglomerates in the presence of an applied magnetic field. With the increasing amount of adsorbed MB molecules, the size of the field-induced agglomerates increases and the magnetic separation on a magnetized micropillar becomes more efficient. These effects are mainly governed by the ratio of magnetic-to-thermal energy α, suspension supersaturation Δ0, and Brownian diffusivity Deff of primary agglomerates. The three parameters (α, Δ0, and Deff) are implicitly related to the surface coverage θ of IONP by MB molecules through the hydrodynamic size of primary agglomerates exponentially increasing with θ. Experiments and developed theoretical models allow quantitative evaluation of the θ effect on the efficiency of the secondary agglomeration and magnetic separation.

Design of magnetic molecularly imprinted polymer nanoparticles for controlled release of doxorubicin under an alternative magnetic field in athermal conditions.

An innovative magnetic delivery nanomaterial for triggered cancer therapy showing active control over drug release by using an alternative magnetic field is proposed. In vitro and In vivo release of doxorubicin (DOX) were investigated and showed a massive DOX release under an alternative magnetic field without temperature elevation of the medium.

Poly(acrylic acid)-coated iron oxide nanoparticles: quantitative evaluation of the coating properties and applications for the removal of a pollutant dye.

In this work, 6-12 nm iron oxide nanoparticles were synthesized and coated with poly(acrylic acid) chains of molecular weight 2100 g mol(-1). Based on a quantitative evaluation of the dispersions, the bare and coated particles were thoroughly characterized. The number densities of polymers adsorbed at the particle surface and of available chargeable groups were found to be 1.9±0.3 nm(-2) and 26±4 nm(-2), respectively. Occurring via a multi-site binding mechanism, the electrostatic coupling leads to a solid and resilient anchoring of the chains. To assess the efficacy of the particles for pollutant remediation, the adsorption isotherm of methylene blue molecules, a model of pollutant, was determined. The excellent agreement between the predicted and the measured amounts of adsorbed dyes suggests that most carboxylates participate to the complexation and adsorption mechanisms. An adsorption of 830 mg g(-1) was obtained. This quantity compares well with the highest values available for this dye.

Splice variant PRKC-ζ(-PrC) is a novel biomarker of human prostate cancer.

BACKGROUND: Previously, using gene-knockdown techniques together with genome expression array analysis, we showed the gene protein Kinase C (PKC)-zeta (PRKCZ) to mediate the malignant phenotype of human prostate cancer. However, according to NCBI, the gene has undergone several major iterations. Therefore, to understand the relationship between its structure and biological activities, we have analysed its expressed sequence in prostate cancer cell lines and tissues. METHODS: Transcriptome-walking and targeted PCR were used to sequence the mRNA transcribed from PRKCZ. Hydropathy analysis was employed to analyse the hypothetical protein sequence subsequently translated and to identify an appropriate epitope to generate a specific monoclonal antibody. RESULTS: A novel sequence was identified within the 3'-terminal domain of human PRKCZ that, in prostate cancer cell lines and tissues, is expressed during transcription and thereafter translated into protein (designated PKC-ζ(-PrC)) independent of conventional PKC-ζ(-a). The monoclonal antibody detected expression of this 96 kD protein only within malignant prostatic epithelium. INTERPRETATION: Transcription and translation of this gene sequence, including previous intronic sequences, generates a novel specific biomarker of human prostate cancer. The presence of catalytic domains characteristic of classic PKC-ß and atypical PKC-ι within PKC-ζ(-PrC) provides a potential mechanism for this PRKCZ variant to modulate the malignant prostatic phenotype out-with normal cell-regulatory control.

Magneto-orientational properties of ionically stabilized aqueous dispersions of Ni(OH)2 nanoplatelets.

Magnetic and orientational behavior of nickel hydroxide nanoplatelets ionically stabilized in a liquid matrix is studied. Under an applied field the platelets orient their faces normal to its direction. For characterization of the individual behavior of dispersed and non-interacting particles three techniques are used: SAXS, SQUID and magneto-optics. Analysis reveals that nickel hydroxide in a platelet phase is paramagnetic with a pronounced anisotropy of the intrinsic susceptibility, the major component of which (in the direction normal to platelet face) exceeds the minor one by about 25%.

Synthesis and dispersion of Ni(OH)2 platelet-like nanoparticles in water.

Synthesis of nanometric platelet-like Ni(OH)2 particles is described. The role of several experimental parameters on the particle size is investigated. A colloidal dispersion of particles is produced by adsorbing ionizable organic ligands (trisodium citrate) on the particle surface. The stability of this colloidal dispersion and the particle charge density are determined for different citrate ions concentrations.

Size-selective chemical synthesis of tartrate stabilized cobalt ferrite ionic magnetic fluid.

Ionic magnetic fluid (ferrofluid) is a stable suspension of magnetic nanoparticles in water. Cobalt ferrite nanoparticles are interesting in view of high-density recording storage. The size of the magnetic particles strongly influences the physical properties of the ferrofluids. In this study, we describe the synthesis of ionic magnetic fluid in the presence of tartrate ions. By varying the amount of organic ligands, nanoparticles in a large range of size are obtained: the mean diameter varies from 3 to 10 nm. The effect of tartrate ions on the stability of the ionic magnetic fluid is also studied in relation with the size of the magnetic particles and the amount of adsorbed ligand.

Transformation of Leishmania mexicana metacyclic promastigotes to amastigote-like forms mediated by binding of human C-reactive protein.

Infective metacyclic promastigote forms of Leishmania mexicana are introduced by the bite of sandfly vectors into their human hosts where they transform into the amastigote form. The kinetics of this process was examined in vitro in response to different combinations of temperature (26 degrees C or 32 degrees C), pH (7.2 or 5.5), and exposure to human serum. Little transformation occurred at 26 degrees C/pH 7.2, intermediate levels at 26 degrees C/pH 5.5 and 32 degrees C/pH 7.2, and the greatest response at 32 degrees C/pH 5.5. Transformation was stimulated by exposure to normal human serum, but was markedly reduced when serum previously incubated at 56 degrees C for 1 h was used (complement heat-inactivated). This stimulatory effect was reproduced by exposure to a single purified component of human serum, C-reactive protein (CRP). Binding of CRP to the whole surface of L. mexicana metacyclic promastigotes, including the flagella, was demonstrated by an indirect fluorescent antibody test. The effect of purified CRP was dose dependent and occurred using normal serum concentrations. The stimulatory effect of whole serum was oblated by CRP depletion and restored by addition of purified CRP. The effects of cAMP analogues indicated that transformation could be mediated via an adenylate cyclase cascade.

Novel in vitro assays for assessing the haemorrhagic activity of snake venoms and for demonstration of venom metalloproteinase inhibitors.

Standard methods used for assessing the haemorrhagic toxicity of snake venoms and the effectiveness of antivenoms are laborious, expensive and involve the use of large numbers of laboratory animals. This paper examined the feasibility of using a gelatin degradation ELISA for preliminary screening of snake venom metalloproteinases (MPs). Potent gelatinolytic activity was observed in venoms from snakes of the family Viperidae and, as expected, little or no activity was evident in the venoms of snakes that induce neurotoxic pathology (most elapids). A reverse gelatin zymography assay was used on a variety of venoms to demonstrate a number of inhibitors of MP activity, the first such demonstration of its kind.

Adsorption Isotherms of Cetylpyridinium Chloride with Iron III Salts at Air/Water and Silica/Water Interfaces.

The interaction of iron III salts and cetylpyridinium chloride (CPC) has been studied at the air/water and silica/water interfaces. The surface tension of cetylpyridinium chloride has been determined in aqueous solutions in the presence of iron III chloride and iron III nitrate at two constant pH values, namely, 3.5 and 1.2. It is shown that the surface tension of the cationic surfactant depends upon the ionic strength of the solution through the pH adjustment in the presence of the former salt but not in the presence of the latter. The effect of iron III nitrate on the surface tension of CPC is similar to that of potassium nitrate, indicating that the iron III various-hydrolyzed species do not interfere with the composition of the air/water interface. The competitive adsorption of iron III nitrate salt and the cationic surfactant at a silica/water interface was next investigated. The adsorption isotherms were determined at pH 3.5. It is shown that although the iron III ions, which were added to the silica dispersion in the presence of the cetylpyridinium ions, were strongly bound to the anionic surface sites, the surfactant ions are not salted out in the solution but remain in close vicinity of the silica surface. Conversely as the cationic surfactant is added first to the silica dispersion in the presence of the adsorbed iron III ions, the metal ions and the surfactant ions are both coadsorbed onto the silica surface. It is suggested that iron III hydrolyzed or free cations and the cationic surfactant molecules may not compete for the same adsorption sites onto the silica surface. Copyright 2000 Academic Press.

Canine TIMP-2: purification, characterization and molecular detection.

Matrix metalloproteinases (MMPs), which degrade tissues in health and disease are under the control of the tissue inhibitors of MMPs, the TIMPs. TIMP-2 is particularly important for control of MMP-2 and both have been implicated in many pathological processes from arthritis to tumour invasion. This study characterized and detected TIMP-2 from canine cells; including synovial fibroblasts and three tumour-derived canine cell lines, K1, K6 and DH82. Gelatin zymography demonstrated that pro-MMP-2 is produced by synovial fibroblasts and the three cells lines. Reverse zymograms showed that all the cell sources tested secrete both TIMP-1 and TIMP-2. The 22 kDa band was purified and n-terminal amino acid sequencing showed it to be highly homologous to equine and human TIMP-2. Analysis of purified canine MMP-2 and MMP-9 showed that TIMP-2 is associated, and co-purifies with MMP-2. Polymerase chain reaction, using consensus primers, was used to detect TIMP-2 mRNA from the cell sources and proved positive in all cases. This work highlights the importance of TIMP-2 as the main inhibitor for MMP-2 and, therefore, opens the possibilities of targeting TIMP-2 for therapeutic intervention against connective amino acid tissue degradation in a range of diseases.

Immunological and inflammatory characterisation of three canine cell lines: K1, K6 and DH82.

Three canine cell lines, K1, K6 and DH82, derived from canine malignant neoplasms, were characterised. They were examined for expression of surface antigens, cytokines, neuropeptide receptors, matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). The growth characteristics of the cell lines were established and bioassays used to detect production of TNF-alpha, IL-1 and IL-6. In the DH82 cell line, production of TNF-alpha and IL-6 was readily detected. Neither K1 or K6 cell lines produced any measurable amounts of TNF-alpha, IL-1 or IL-6. At a molecular level, using reverse transcription-polymerase chain reaction (RT-PCR) to detect specific mRNA, the DH82 cell line expressed TNF-alpha, IL-1 and IL-6, whereas the K1 and K6 cell lines expressed TNF-alpha. Canine IL-5, IL-8 and IL-10 mRNA were detected in the DH82 cell line but only IL-5 and IL-8 mRNA were detected in the K1 and K6 cell lines. Gelatin zymography was used for the detection of MMP-2 and MMP-9 and all three cell lines produced MMP-2 but only the DH82 cell line produced MMP-9. Reverse zymography was used to detect TIMP-1 and TIMP-2 and all three cell lines produced both proteins. The presence of these MMPs and TIMPs was confirmed at a molecular level using RT-PCR. Canine MMP-14 mRNA was detected in all three cell lines. For this investigation several genes for canine inflammatory molecules were cloned and sequenced for molecular detection; these included IL-1, IL-6, IL-8, TNF-alpha, MMP-9, MMP-14, TIMP-1, TIMP-2 and beta-actin. Of all the cell surface antigens tested, only CD14 was expressed on the DH82 cell line although CD5 and CD45 was partially expressed. The K1 and K6 cell lines were negative for all of the CD markers tested. K1 and K6 were negative for Neurokinin 1 receptor (NK1-R) but positive for Calcitonin gene related peptide receptor type 1 (CGRP-1R) and Calcitonin gene related peptide receptor component protein (CGRP-RCP). The DH82 cell line expressed neither NK1-R or CGRP-1R; however, it did express CGRP-RCP. Generally the DH82 cell line exhibited considerable similarity to canine monocytes, but all three cell lines will be useful as standards and for the purification of various immunological and inflammatory mediators in the dog.

Adsorption Isotherm of Sodium Octylbenzenesulfonate on Iron Oxide Particles in Aqueous Solutions.

The adsorption isotherm of sodium octylbenzene sulfonate has been determined at two pH values on dispersed maghemite particles in water. The isotherms present an adsorption maximum in the region of the surfactant critical micelle concentration. Additional adsorption experiments at the alumina/water interface as well as at the air/water interface in the presence of ferric ions suggest that the adsorption maximum in the case of the iron oxide particles is due to the presence of very small concentrations of ferric ions in the aqueous solution. These ions form surface active complexes with sodium octylbenzenesulfonate. These complexes are adsolubilized in the surfactant layers on the particles below the critical micelle concentration. They are desorbed from the surface and transferred into free micelles above the critical micelle concentration. These two phenomena are shown to be responsible for the adsorption maximum observed. The presence of ferric ions induces a surface tension minimum of the anionic surfactant at the air/water interface. This effect is discussed in relation to the adsorption maximum at the solid/water interface. Copyright 1998 Academic Press.

Thiolation of Maghemite Nanoparticles by Dimercaptosuccinic Acid

Magnetic particle-effector conjugates are widely used in vitro for cell sorting in various pathologies. The coupling between the particles and the effectors being realized through S-S bridges, the particles must first be thiolated before the coupling. In this work, the synthesis, in aqueous medium, of nanoparticles of maghemite thiolated by dimercaptosuccinic acid is described. The superficial complexation by a thiol-containing ligand induces a reductive dissolution of the oxide and leads to the adsorption of polydisulfide species coming from the oxidation of the ligand. Adsorption and redox reactions being strongly correlated to the composition of the medium, the amount of adsorbed ligand and the quantity of iron(II) released into the medium have been simultaneously determined, at various pH, for different concentrations of ligand added. The charge of the particles is drastically modified in the presence of a chelating agent; as a consequence, the colloidal stability is greatly affected and so the flocculation ranges of the complexed particles have been established for different pH. When the quantity of ligand added is sufficient (0.05 mol/mol of iron), the ferrofluid based on thiolated maghemite particles is stable between pH 3 and 11 and can be used for biomedical applications. Copyright 1997 Academic Press. Copyright 1997Academic Press