Márta Szekeres - Academia.edu (original) (raw)

Papers by Márta Szekeres

Research paper thumbnail of Bionanocomposites à libération prolongée, leur procédé de fabrication et leur utilisation

L'invention concerne un nanocomposite a liberation prolongee comprenant a) un cœur porteur de... more L'invention concerne un nanocomposite a liberation prolongee comprenant a) un cœur porteur de charges de particules proteiques primaires precipitees de maniere reversible lors d'une procedure ionique a partir de solutions contenant au moins un medicament contenant des cytokines et b) une enveloppe polyelectrolytique composee de 3 a 5 couches alternees de deux polyelectrolytes de charges opposees, l'etat de dissociation d'un des polyelectrolytes variant avec le pH du milieu aqueux tandis que l'autre polyelectrolyte est totalement dissocie, quel que soit le pH du milieu. L'invention concerne aussi un procede pour produire ledit nanocomposite et son utilisation pour produire des formulations medicamenteuses a liberation prolongee.

Research paper thumbnail of Szuperparamágneses vas-oxid nanorészecskék (SPIONs)teranosztikai célú fejlesztése

Magyar Kémiai Folyóirat, 2019

Research paper thumbnail of Multifunctional PEG-carboxylate copolymer coated superparamagnetic iron oxide nanoparticles for biomedical application

Journal of Magnetism and Magnetic Materials, 2018

Highlights • Multicore magnetite nanoparticles (MNPs) were superparamagnetic. • PEG-carboxylate p... more Highlights • Multicore magnetite nanoparticles (MNPs) were superparamagnetic. • PEG-carboxylate polyelectrolytes coat spontaneously MNPs and stabilize them electrosterically. • Biofunction can be attached to MNPs via carboxylated coating layer. • Multifunctional shell prevents MNPs' internalization into cells.

Research paper thumbnail of Polyelectrolyte coating on superparamagnetic iron oxide nanoparticles as interface between magnetic core and biorelevant media

Interface Focus, 2016

Nanoparticles do not exist in thermodynamical equilibrium because of high surface free energy, th... more Nanoparticles do not exist in thermodynamical equilibrium because of high surface free energy, thus they have only kinetic stability. Spontaneous changes can be delayed by designed surface coating. In biomedical applications, superparamagnetic iron oxide nanoparticles (SPIONs) require an optimized coating in order to fulfil the expectation of medicine regulatory agencies and ultimately that of biocompatibility. In this work, we show the high surface reactivity of naked SPIONs due to ≡Fe–OH sites, which can react with H + /OH − to form pH- and ionic strength-dependent charges. We explain the post-coating of naked SPIONs with organic polyacids via multi-site complex bonds formed spontaneously. The excess polyacids can be removed from the medium. The free COOH groups in coating are prone to react with active biomolecules like proteins. Charging and pH- and salt-dependent behaviour of carboxylated SPIONs were characterized quantitatively. The interrelation between the coating quality an...

Research paper thumbnail of Szilícium-oxid alapú szorbensek gázadszorpciós és oldatadszorpciós tulajdonságai

Research paper thumbnail of Hemocompatibility and Biomedical Potential of Poly(Gallic Acid) Coated Iron Oxide Nanoparticles for Theranostic Use

Journal of Nanomedicine & Nanotechnology, 2015

Polyacid covered core-shell iron oxide nanoparticles were designed for potential use in biomedici... more Polyacid covered core-shell iron oxide nanoparticles were designed for potential use in biomedicine with special attention to theranostics-magnetic resonance imaging (MRI), magnetic hyperthermia and magnetic drug targeting. The magnetite nanoparticles coated with a gallic acid shell polymerized in situ on the nanoparticle surface (PGA@MNPs) were tested for hemocompatibility in blood, sedimentation rate, blood smear and blood cell viability experiments and for antioxidant capacity in Jurkat cells in the presence of H 2 O 2 as reactive oxygen species. No signs of interaction of the nanoparticles with whole blood cells were found. In addition, the PGA@MNPs reduced significantly the oxidative stress mediated by H 2 O 2 supporting earlier findings of MTT tests, namely, the improvement of cell viability in their presence. The in vitro tests revealed that PGA@MNPs are not only biocompatible but also bioactive. Preliminary experiments revealed that the nanoparticles are especially efficient MRI and magnetic hyperthermia agents. The r 2 relaxivity was found to be one of the highest among published values (387 mM-1 s-1) and they possess a relatively significant specific absorption rate (SAR) value of 11 W/g magnetite.

Research paper thumbnail of pH-dependent aggregation state of highly dispersed alumina, titania and silica particles in aqueous medium

Progress in Colloid & Polymer Science

Highly dispersed commercial products (Aluminium oxide C, Titanium dioxide P25 and Aerosil 200) of... more Highly dispersed commercial products (Aluminium oxide C, Titanium dioxide P25 and Aerosil 200) of Degussa were investigated. Their pH-dependent surface charge state was determined from acid-base titrations in the presence of KNO3. The p.z.c. values were measured at pHs 8.0 for Al2O3, 5.9 for TiO2 and ∼4 for SiO2. The calculated intrinsic equilibrium constants for surface charge (σ 0) formation

Research paper thumbnail of Plasmonic structure generation by laser illumination of silica colloid spheres deposited onto prepatterned polymer-bimetal films

Applied Surface Science, 2009

Plasmonic structures are prepared on bimetal films evaporated onto glass substrates applying a mu... more Plasmonic structures are prepared on bimetal films evaporated onto glass substrates applying a multi-step process, and atomic force microscopy is utilized to study the structures after each step. Sub-micrometer gratings are generated on polycarbonate films spin-coated onto silver-gold bimetal layers by interference lithography (IL) applying the fourth harmonics of a Nd:YAG laser. These polymer gratings are used as prepatterned templates

Research paper thumbnail of Photooxidation of dichloroacetic acid controlled by pH-stat technique using TiO2/layer silicate nanocomposites

Applied Catalysis B: Environmental, 2006

Nanocomposites containing anatase nanoparticles were prepared by heterocoagulation, using Na-mont... more Nanocomposites containing anatase nanoparticles were prepared by heterocoagulation, using Na-montmorillonite and titanium dioxide obtained by hydrothermal sol–gel method. Heterocoagulation was carried out at pH 1 and 4. Based on X-ray diffraction measurements, an average particle size of 3.8–4.0nm was calculated by the Scherrer equation for the particles intercalated between the silicate lamellae. Nitrogen adsorption studies revealed that the specific surface

Research paper thumbnail of Kompozit nanofilmek előállítása a komponensek rétegenkénti önrendeződéses adszorpciójával= Preparation of composite nanofilms using layer-by-layer self- …

OTKA Kutatási Jelentések| OTKA Research …, 2007

A projekt eredeti vezető kutatója, Haraszti Tamás (Kutatási Megbízási Szerződés KO-10813/2003.04.... more A projekt eredeti vezető kutatója, Haraszti Tamás (Kutatási Megbízási Szerződés KO-10813/2003.04.02.), külföldi munkavállalása miatt nem tudta végigvinni az eredetileg tervezett munkafolyamatot. 2004-ben, a projekt második évében ezért mint korábbi résztvevő ...

Research paper thumbnail of Preparation and investigation of core-shell nanoparticles containing human interferon-α

International Journal of Pharmaceutics, 2019

Sustained release of active interferon-α (IFN-α) has been achieved from core-shell nanoparticles ... more Sustained release of active interferon-α (IFN-α) has been achieved from core-shell nanoparticles (NPs) prepared by aqueous precipitation of IFN-α-enriched human serum albumin (HSA-IFN-α) and layer-by-layer (L-b-L) by coating of the IFN-α NPs with poly(sodium-4-styrene) sulphonate (PSS) and chitosan (Chit). The concentration and the pH of HSA solution were optimized during the development of this method. Dynamic light scattering (DLS), zeta-potential, thermal analysis (differential scanning calorimetry (DSC) and termogravimetry (TG)), Xray diffraction (XRD), IFN-α activity and morphology (transmission electron microscope (TEM)) studies were used to control the preparation and analyse the products. The dissolution kinetics of NPs was measured in vitro over 7 days in Hanson dissolution tester with Millex membrane. In vivo studies in Pannon white rabbit detected steady IFN-α plasma level for 10 days after subcutaneous injection administration of the HSA-IFN-α NPs. The IFN-α plasma concentration was detected by using the enzyme-linked immunosorbent assay (ELISA) method. In the present paper we discuss the preparation method, the optimization steps and the results of in vitro and in vivo release studies. It was established that 76.13% HSA-IFN-α are encapsulated in the core-shell NPs.

Research paper thumbnail of Chondroitin-Sulfate-A-Coated Magnetite Nanoparticles: Synthesis, Characterization and Testing to Predict Their Colloidal Behavior in Biological Milieu

International Journal of Molecular Sciences, 2019

Biopolymer coated magnetite nanoparticles (MNPs) are suitable to fabricate biocompatible magnetic... more Biopolymer coated magnetite nanoparticles (MNPs) are suitable to fabricate biocompatible magnetic fluid (MF). Their comprehensive characterization, however, is a necessary step to assess whether bioapplications are feasible before expensive in vitro and in vivo tests. The MNPs were prepared by co-precipitation, and after careful purification, they were coated by chondroitin-sulfate-A (CSA). CSA exhibits high affinity adsorption to MNPs (H-type isotherm). We could only make stable MF of CSA coated MNPs (CSA@MNPs) under accurate conditions. The CSA@MNP was characterized by TEM (size ~10 nm) and VSM (saturation magnetization ~57 emu/g). Inner-sphere metal–carboxylate complex formation between CSA and MNP was proved by FTIR-ATR and XPS. Electrophoresis and DLS measurements show that the CSA@MNPs at CSA-loading > 0.2 mmol/g were stable at pH > 4. The salt tolerance of the product improved up to ~0.5 M NaCl at pH~6.3. Under favorable redox conditions, no iron leaching from the magne...

Research paper thumbnail of The effect of polycarboxylate shell of magnetite nanoparticles on protein corona formation in blood plasma

Journal of Magnetism and Magnetic Materials, 2017

The development of protein corona around nanoparticles upon administration to the human body is r... more The development of protein corona around nanoparticles upon administration to the human body is responsible in a large part for their biodistribution, cell-internalization and toxicity or biocompatibility. We studied the influence of the chemical composition of polyelectrolyte shells (citric acid (CA) and poly(acrylic-co-maleic acid) (PAM)) of core-shell magnetite nanoparticles (MNPs) on the evolution of protein corona in human plasma (HP). The aggregation state and zeta potential of the particles were measured in the range of HP concentration between 1 and 80 (v/v)% 3 min and 20 h after dispersing the particles in HP diluted with Tris buffered saline. Naked MNPs aggregated in HP solution, but the carboxylated MNPs became stabilized colloidally at higher plasma concentrations. Significant differences were observed at low plasma concentration. CA@MNPs aggregated instantly while the hydrodynamic diameter of PAM@MNP increased only slightly at 1-3 v/v % HP concentrations. The observed differences in protein corona formation can be explained by the differences in the steric effects of the polycarboxylate shells. It is interesting that relatively small but systematic changes in zeta potential alter the aggregation state significantly.

Research paper thumbnail of Clustering of carboxylated magnetite nanoparticles through polyethylenimine: Covalent versus electrostatic approach

Journal of Magnetism and Magnetic Materials, 2017

Carboxylated magnetite nanoparticles (MNPs) are frequently used to develop materials with enhance... more Carboxylated magnetite nanoparticles (MNPs) are frequently used to develop materials with enhanced properties for MRI and hyperthermia. The controlled clustering of MNPs via covalent or electrostatic approaches provides opportunity to prepare high quality materials. MNPs were prepared by co-precipitation and coated by poly(acrylic acid-co-maleic acid) (PAM@MNP). The clusters were synthesized from purified PAM@MNPs and polyethylenimine (PEI) solution via electrostatic interaction and covalent bond formation (ES-cluster and CB-cluster, respectively). The electrostatic adhesion (-NH 3 + and-COO-) and the formed amide bond were confirmed by ATR-FTIR. The averaged area of CB-clusters was about twice as large as that of EScluster, based on TEM. The SAXS results showed that the surface of MNPs was smooth and the nanoparticles were close packed in both clusters. The pH-dependent aggregation state and zeta potential of clusters were characterized by DLS and electrophoresis measurements, the clusters were colloidally stable at pH > 5. In hyperthermia experiments, the values of SAR were about two times larger for the chemically bonded cluster. The MRI studies showed exceptionally high transversion relaxivities, the r 2 values are 457 mM −1 s −1 and 691 mM −1 s −1 for ES-cluster and CB-cluster, respectively. Based on these results, the chemically clustered product shows greater potential for feasible biomedical applications.

Research paper thumbnail of Effects of impurity and solid-phase dissolution on surface charge titration of aluminium oxide

Progress in Colloid and Polymer Science

Potentiometic and calorimetric acid—base titration of aluminium oxide C (Degussa) was performed. ... more Potentiometic and calorimetric acid—base titration of aluminium oxide C (Degussa) was performed. This pyrogenic alumina contains chlorine impurity (about 1 × 10-4 mol/g). Its hydrolysis results in indefinite numbers of H+ and Cl- ions in aqueous suspension, which disturb the surface charge titration. The chlorine impurity could be removed by heat treatment of alumina powder at 1000 °C. The fitting of the titration data for heattreated alumina in indifferent electrolyte (KNO3) solutions between pH∼5 and pH∼9 is good enough assuming only surface charging reactions and any kind of surface complexation model. Outside these material-specific limits the dissolution of the amphoteric solid plays the governing role, especially below pH∼4.5. A partial dissolution of the solid phase and the simultaneous equilibria of mononucleous aluminium-species formation have to be inserted into an appropriate model. Calorimetric data can be assigned to chemical reactions in the absence of impurities and dissolution and if the initial state of titration is fixed to the reference state of oxide suspensions. The partial molar enthalpy of the surface protonation process decreases in absolute value from -34 to -28 kJ/mol and that of deprotonation process increases from 33 to 41 kJ/mol with increasing ionic strength. The standard enthalpy of the surface protolysis reaction on alumina is 34.6 ± 0.6 kJ/mol.

Research paper thumbnail of Interaction between ionic surfactants and soil colloids: adsorption, wetting and structural properties

Progress in Colloid & Polymer Science

The adsorption of ionic surfactants on different soil components such as silica, clay minerals, a... more The adsorption of ionic surfactants on different soil components such as silica, clay minerals, and humic acids was studied. The adsorption processes were controlled by flow microcalorimetry to determine the molar adsorption enthalpies of surfactant accumulation on clay and silicate surfaces. The evaluation of adsorption results for cationic surfactants has shown different mechanisms for solids having permanent (kaolinite, illite, montmorillonite) and pH-dependent surface charges (silica gels and powders). The adsorption mechanism for surfactants on silica surfaces with pH-dependent charges has been explained in terms of the development of charges on the surfaces and their interaction with surfactant cations and micelles. The surface hydrophobicity of clay-organocomplexes was characterized by batch microcalorimetry using pure liquids. The fractal dimensions of clays and their organocomplexes were determined by SAXS. The intercalation of organic compounds in the interlamellar space of layered silicates and humates was measured by x-ray diffraction using powder samples and suspensions. The structural properties of the surfactant coated clay suspension were characterized by rheology.

Research paper thumbnail of Specific Surface Area of Stoeber Silica Determined by Various Experimental Methods

Langmuir, 2002

The specific surface area of amorphous Aerosil 200 and silica particles with 270 nm diameter prep... more The specific surface area of amorphous Aerosil 200 and silica particles with 270 nm diameter prepared by the Stoeber method was investigated by a variety of experimental methods: nitrogen adsorption at 77 and 253 K; adsorption from ethanol/cyclohexane mixture; heats of wetting measurements; small-angle X-ray scattering (SAXS) experiments. The N2 adsorption isotherms at 77 K were analyzed using the BET equation, the modified BET equations of Tóth, and equations of the uniform interpretation method of Tóth. For Aerosil 200, the values of the specific surface varied slightly depending on the applied method. For Stoeber silica, the results from nitrogen adsorption at 77 K ranged between 18 and 24 m 2 /g; these values were 20-30 times smaller than those derived from N2 adsorption at 253 K, binary liquid mixture adsorption, and heats of wetting or SAXS experiments (439-670 m 2 /g). The specific surface area of Stoeber silica estimated from nitrogen adsorption measurement at 77 K could not be applied to adsorption data from liquid medium; the other methods, however, provided reliable surface area and charge density values. According to the pore size distribution curves from thermogravimetry, two mean pore diameter values are distinguished (2 and 16 nm), but larger pores also exist in the structure of the Stoeber silica particles. According to the SAXS results Stoeber silica has a mass fractal structure (Dm) 1.73) on the length scale of 5-25 nm.

Research paper thumbnail of The Effect of Hydroxyl Moieties and Their Oxosubstitution on Bile Acid Association Studied in Floating Monolayers

The Scientific World Journal, 2014

Bile salt aggregates are promising candidates for drug delivery vehicles due to their unique fat-... more Bile salt aggregates are promising candidates for drug delivery vehicles due to their unique fat-solubilizing ability. However, the toxicity of bile salts increases with improving fat-solubilizing capability and so an optimal combination of efficient solubilization and low toxicity is necessary. To improve hydrophilicity (and decrease toxicity), we substituted hydroxyl groups of several natural bile acid (BA) molecules for oxogroups and studied their intrinsic molecular association behavior. Here we present the comparative Langmuir trough study of the two-dimensional (2D) association behavior of eight natural BAs and four oxoderivatives (traditionally called keto-derivatives) floated on an aqueous subphase. The series of BAs and derivatives showed systematic changes in the shape of the compression isotherms. Two types of association could be distinguished: the first transition was assigned to the formation of dimers through H-bonding and the second to the hydrophobic aggregation of ...

Research paper thumbnail of Mechanism of in Situ Surface Polymerization of Gallic Acid in an Environmental-Inspired Preparation of Carboxylated Core–Shell Magnetite Nanoparticles

Langmuir, 2014

Magnetite nanoparticles (MNPs) with biocompatible coatings are good candidates for MRI (magnetic ... more Magnetite nanoparticles (MNPs) with biocompatible coatings are good candidates for MRI (magnetic resonance imaging) contrasting, magnetic hyperthermia treatments and drug delivery systems. The spontaneous surface induced polymerization of dissolved organic matter on environmental mineral particles inspired us to prepare carboxylated core-shell MNPs by using a ubiquitous polyphenolic precursor. Through the adsorption and in-situ surface polymerization of gallic acid (GA), a polygallate (PGA) coating is formed on the nanoparticles (PGA@MNP) with possible antioxidant capacity. The Polygallate on magnetite nanoparticles Humic matter on clays

Research paper thumbnail of Preparation and characterization of chondroitin‐sulfate‐A‐coated magnetite nanoparticles for biomedical applications

Journal of Magnetism and Magnetic Materials, 2015

Highlights * Novel CSA-coated core-shell magnetite nanoparticles were prepared successfully. * Th... more Highlights * Novel CSA-coated core-shell magnetite nanoparticles were prepared successfully. * The aggregation range of MNPs was shifted gradually to the lower pHs by CSA loading. * CSA stabilizes electrosterically the MNPs over wide pH-range relevant to biosystems. * The salt tolerance of CSA@MNP enables them to use under physiological condition.

Research paper thumbnail of Bionanocomposites à libération prolongée, leur procédé de fabrication et leur utilisation

L'invention concerne un nanocomposite a liberation prolongee comprenant a) un cœur porteur de... more L'invention concerne un nanocomposite a liberation prolongee comprenant a) un cœur porteur de charges de particules proteiques primaires precipitees de maniere reversible lors d'une procedure ionique a partir de solutions contenant au moins un medicament contenant des cytokines et b) une enveloppe polyelectrolytique composee de 3 a 5 couches alternees de deux polyelectrolytes de charges opposees, l'etat de dissociation d'un des polyelectrolytes variant avec le pH du milieu aqueux tandis que l'autre polyelectrolyte est totalement dissocie, quel que soit le pH du milieu. L'invention concerne aussi un procede pour produire ledit nanocomposite et son utilisation pour produire des formulations medicamenteuses a liberation prolongee.

Research paper thumbnail of Szuperparamágneses vas-oxid nanorészecskék (SPIONs)teranosztikai célú fejlesztése

Magyar Kémiai Folyóirat, 2019

Research paper thumbnail of Multifunctional PEG-carboxylate copolymer coated superparamagnetic iron oxide nanoparticles for biomedical application

Journal of Magnetism and Magnetic Materials, 2018

Highlights • Multicore magnetite nanoparticles (MNPs) were superparamagnetic. • PEG-carboxylate p... more Highlights • Multicore magnetite nanoparticles (MNPs) were superparamagnetic. • PEG-carboxylate polyelectrolytes coat spontaneously MNPs and stabilize them electrosterically. • Biofunction can be attached to MNPs via carboxylated coating layer. • Multifunctional shell prevents MNPs' internalization into cells.

Research paper thumbnail of Polyelectrolyte coating on superparamagnetic iron oxide nanoparticles as interface between magnetic core and biorelevant media

Interface Focus, 2016

Nanoparticles do not exist in thermodynamical equilibrium because of high surface free energy, th... more Nanoparticles do not exist in thermodynamical equilibrium because of high surface free energy, thus they have only kinetic stability. Spontaneous changes can be delayed by designed surface coating. In biomedical applications, superparamagnetic iron oxide nanoparticles (SPIONs) require an optimized coating in order to fulfil the expectation of medicine regulatory agencies and ultimately that of biocompatibility. In this work, we show the high surface reactivity of naked SPIONs due to ≡Fe–OH sites, which can react with H + /OH − to form pH- and ionic strength-dependent charges. We explain the post-coating of naked SPIONs with organic polyacids via multi-site complex bonds formed spontaneously. The excess polyacids can be removed from the medium. The free COOH groups in coating are prone to react with active biomolecules like proteins. Charging and pH- and salt-dependent behaviour of carboxylated SPIONs were characterized quantitatively. The interrelation between the coating quality an...

Research paper thumbnail of Szilícium-oxid alapú szorbensek gázadszorpciós és oldatadszorpciós tulajdonságai

Research paper thumbnail of Hemocompatibility and Biomedical Potential of Poly(Gallic Acid) Coated Iron Oxide Nanoparticles for Theranostic Use

Journal of Nanomedicine & Nanotechnology, 2015

Polyacid covered core-shell iron oxide nanoparticles were designed for potential use in biomedici... more Polyacid covered core-shell iron oxide nanoparticles were designed for potential use in biomedicine with special attention to theranostics-magnetic resonance imaging (MRI), magnetic hyperthermia and magnetic drug targeting. The magnetite nanoparticles coated with a gallic acid shell polymerized in situ on the nanoparticle surface (PGA@MNPs) were tested for hemocompatibility in blood, sedimentation rate, blood smear and blood cell viability experiments and for antioxidant capacity in Jurkat cells in the presence of H 2 O 2 as reactive oxygen species. No signs of interaction of the nanoparticles with whole blood cells were found. In addition, the PGA@MNPs reduced significantly the oxidative stress mediated by H 2 O 2 supporting earlier findings of MTT tests, namely, the improvement of cell viability in their presence. The in vitro tests revealed that PGA@MNPs are not only biocompatible but also bioactive. Preliminary experiments revealed that the nanoparticles are especially efficient MRI and magnetic hyperthermia agents. The r 2 relaxivity was found to be one of the highest among published values (387 mM-1 s-1) and they possess a relatively significant specific absorption rate (SAR) value of 11 W/g magnetite.

Research paper thumbnail of pH-dependent aggregation state of highly dispersed alumina, titania and silica particles in aqueous medium

Progress in Colloid & Polymer Science

Highly dispersed commercial products (Aluminium oxide C, Titanium dioxide P25 and Aerosil 200) of... more Highly dispersed commercial products (Aluminium oxide C, Titanium dioxide P25 and Aerosil 200) of Degussa were investigated. Their pH-dependent surface charge state was determined from acid-base titrations in the presence of KNO3. The p.z.c. values were measured at pHs 8.0 for Al2O3, 5.9 for TiO2 and ∼4 for SiO2. The calculated intrinsic equilibrium constants for surface charge (σ 0) formation

Research paper thumbnail of Plasmonic structure generation by laser illumination of silica colloid spheres deposited onto prepatterned polymer-bimetal films

Applied Surface Science, 2009

Plasmonic structures are prepared on bimetal films evaporated onto glass substrates applying a mu... more Plasmonic structures are prepared on bimetal films evaporated onto glass substrates applying a multi-step process, and atomic force microscopy is utilized to study the structures after each step. Sub-micrometer gratings are generated on polycarbonate films spin-coated onto silver-gold bimetal layers by interference lithography (IL) applying the fourth harmonics of a Nd:YAG laser. These polymer gratings are used as prepatterned templates

Research paper thumbnail of Photooxidation of dichloroacetic acid controlled by pH-stat technique using TiO2/layer silicate nanocomposites

Applied Catalysis B: Environmental, 2006

Nanocomposites containing anatase nanoparticles were prepared by heterocoagulation, using Na-mont... more Nanocomposites containing anatase nanoparticles were prepared by heterocoagulation, using Na-montmorillonite and titanium dioxide obtained by hydrothermal sol–gel method. Heterocoagulation was carried out at pH 1 and 4. Based on X-ray diffraction measurements, an average particle size of 3.8–4.0nm was calculated by the Scherrer equation for the particles intercalated between the silicate lamellae. Nitrogen adsorption studies revealed that the specific surface

Research paper thumbnail of Kompozit nanofilmek előállítása a komponensek rétegenkénti önrendeződéses adszorpciójával= Preparation of composite nanofilms using layer-by-layer self- …

OTKA Kutatási Jelentések| OTKA Research …, 2007

A projekt eredeti vezető kutatója, Haraszti Tamás (Kutatási Megbízási Szerződés KO-10813/2003.04.... more A projekt eredeti vezető kutatója, Haraszti Tamás (Kutatási Megbízási Szerződés KO-10813/2003.04.02.), külföldi munkavállalása miatt nem tudta végigvinni az eredetileg tervezett munkafolyamatot. 2004-ben, a projekt második évében ezért mint korábbi résztvevő ...

Research paper thumbnail of Preparation and investigation of core-shell nanoparticles containing human interferon-α

International Journal of Pharmaceutics, 2019

Sustained release of active interferon-α (IFN-α) has been achieved from core-shell nanoparticles ... more Sustained release of active interferon-α (IFN-α) has been achieved from core-shell nanoparticles (NPs) prepared by aqueous precipitation of IFN-α-enriched human serum albumin (HSA-IFN-α) and layer-by-layer (L-b-L) by coating of the IFN-α NPs with poly(sodium-4-styrene) sulphonate (PSS) and chitosan (Chit). The concentration and the pH of HSA solution were optimized during the development of this method. Dynamic light scattering (DLS), zeta-potential, thermal analysis (differential scanning calorimetry (DSC) and termogravimetry (TG)), Xray diffraction (XRD), IFN-α activity and morphology (transmission electron microscope (TEM)) studies were used to control the preparation and analyse the products. The dissolution kinetics of NPs was measured in vitro over 7 days in Hanson dissolution tester with Millex membrane. In vivo studies in Pannon white rabbit detected steady IFN-α plasma level for 10 days after subcutaneous injection administration of the HSA-IFN-α NPs. The IFN-α plasma concentration was detected by using the enzyme-linked immunosorbent assay (ELISA) method. In the present paper we discuss the preparation method, the optimization steps and the results of in vitro and in vivo release studies. It was established that 76.13% HSA-IFN-α are encapsulated in the core-shell NPs.

Research paper thumbnail of Chondroitin-Sulfate-A-Coated Magnetite Nanoparticles: Synthesis, Characterization and Testing to Predict Their Colloidal Behavior in Biological Milieu

International Journal of Molecular Sciences, 2019

Biopolymer coated magnetite nanoparticles (MNPs) are suitable to fabricate biocompatible magnetic... more Biopolymer coated magnetite nanoparticles (MNPs) are suitable to fabricate biocompatible magnetic fluid (MF). Their comprehensive characterization, however, is a necessary step to assess whether bioapplications are feasible before expensive in vitro and in vivo tests. The MNPs were prepared by co-precipitation, and after careful purification, they were coated by chondroitin-sulfate-A (CSA). CSA exhibits high affinity adsorption to MNPs (H-type isotherm). We could only make stable MF of CSA coated MNPs (CSA@MNPs) under accurate conditions. The CSA@MNP was characterized by TEM (size ~10 nm) and VSM (saturation magnetization ~57 emu/g). Inner-sphere metal–carboxylate complex formation between CSA and MNP was proved by FTIR-ATR and XPS. Electrophoresis and DLS measurements show that the CSA@MNPs at CSA-loading > 0.2 mmol/g were stable at pH > 4. The salt tolerance of the product improved up to ~0.5 M NaCl at pH~6.3. Under favorable redox conditions, no iron leaching from the magne...

Research paper thumbnail of The effect of polycarboxylate shell of magnetite nanoparticles on protein corona formation in blood plasma

Journal of Magnetism and Magnetic Materials, 2017

The development of protein corona around nanoparticles upon administration to the human body is r... more The development of protein corona around nanoparticles upon administration to the human body is responsible in a large part for their biodistribution, cell-internalization and toxicity or biocompatibility. We studied the influence of the chemical composition of polyelectrolyte shells (citric acid (CA) and poly(acrylic-co-maleic acid) (PAM)) of core-shell magnetite nanoparticles (MNPs) on the evolution of protein corona in human plasma (HP). The aggregation state and zeta potential of the particles were measured in the range of HP concentration between 1 and 80 (v/v)% 3 min and 20 h after dispersing the particles in HP diluted with Tris buffered saline. Naked MNPs aggregated in HP solution, but the carboxylated MNPs became stabilized colloidally at higher plasma concentrations. Significant differences were observed at low plasma concentration. CA@MNPs aggregated instantly while the hydrodynamic diameter of PAM@MNP increased only slightly at 1-3 v/v % HP concentrations. The observed differences in protein corona formation can be explained by the differences in the steric effects of the polycarboxylate shells. It is interesting that relatively small but systematic changes in zeta potential alter the aggregation state significantly.

Research paper thumbnail of Clustering of carboxylated magnetite nanoparticles through polyethylenimine: Covalent versus electrostatic approach

Journal of Magnetism and Magnetic Materials, 2017

Carboxylated magnetite nanoparticles (MNPs) are frequently used to develop materials with enhance... more Carboxylated magnetite nanoparticles (MNPs) are frequently used to develop materials with enhanced properties for MRI and hyperthermia. The controlled clustering of MNPs via covalent or electrostatic approaches provides opportunity to prepare high quality materials. MNPs were prepared by co-precipitation and coated by poly(acrylic acid-co-maleic acid) (PAM@MNP). The clusters were synthesized from purified PAM@MNPs and polyethylenimine (PEI) solution via electrostatic interaction and covalent bond formation (ES-cluster and CB-cluster, respectively). The electrostatic adhesion (-NH 3 + and-COO-) and the formed amide bond were confirmed by ATR-FTIR. The averaged area of CB-clusters was about twice as large as that of EScluster, based on TEM. The SAXS results showed that the surface of MNPs was smooth and the nanoparticles were close packed in both clusters. The pH-dependent aggregation state and zeta potential of clusters were characterized by DLS and electrophoresis measurements, the clusters were colloidally stable at pH > 5. In hyperthermia experiments, the values of SAR were about two times larger for the chemically bonded cluster. The MRI studies showed exceptionally high transversion relaxivities, the r 2 values are 457 mM −1 s −1 and 691 mM −1 s −1 for ES-cluster and CB-cluster, respectively. Based on these results, the chemically clustered product shows greater potential for feasible biomedical applications.

Research paper thumbnail of Effects of impurity and solid-phase dissolution on surface charge titration of aluminium oxide

Progress in Colloid and Polymer Science

Potentiometic and calorimetric acid—base titration of aluminium oxide C (Degussa) was performed. ... more Potentiometic and calorimetric acid—base titration of aluminium oxide C (Degussa) was performed. This pyrogenic alumina contains chlorine impurity (about 1 × 10-4 mol/g). Its hydrolysis results in indefinite numbers of H+ and Cl- ions in aqueous suspension, which disturb the surface charge titration. The chlorine impurity could be removed by heat treatment of alumina powder at 1000 °C. The fitting of the titration data for heattreated alumina in indifferent electrolyte (KNO3) solutions between pH∼5 and pH∼9 is good enough assuming only surface charging reactions and any kind of surface complexation model. Outside these material-specific limits the dissolution of the amphoteric solid plays the governing role, especially below pH∼4.5. A partial dissolution of the solid phase and the simultaneous equilibria of mononucleous aluminium-species formation have to be inserted into an appropriate model. Calorimetric data can be assigned to chemical reactions in the absence of impurities and dissolution and if the initial state of titration is fixed to the reference state of oxide suspensions. The partial molar enthalpy of the surface protonation process decreases in absolute value from -34 to -28 kJ/mol and that of deprotonation process increases from 33 to 41 kJ/mol with increasing ionic strength. The standard enthalpy of the surface protolysis reaction on alumina is 34.6 ± 0.6 kJ/mol.

Research paper thumbnail of Interaction between ionic surfactants and soil colloids: adsorption, wetting and structural properties

Progress in Colloid & Polymer Science

The adsorption of ionic surfactants on different soil components such as silica, clay minerals, a... more The adsorption of ionic surfactants on different soil components such as silica, clay minerals, and humic acids was studied. The adsorption processes were controlled by flow microcalorimetry to determine the molar adsorption enthalpies of surfactant accumulation on clay and silicate surfaces. The evaluation of adsorption results for cationic surfactants has shown different mechanisms for solids having permanent (kaolinite, illite, montmorillonite) and pH-dependent surface charges (silica gels and powders). The adsorption mechanism for surfactants on silica surfaces with pH-dependent charges has been explained in terms of the development of charges on the surfaces and their interaction with surfactant cations and micelles. The surface hydrophobicity of clay-organocomplexes was characterized by batch microcalorimetry using pure liquids. The fractal dimensions of clays and their organocomplexes were determined by SAXS. The intercalation of organic compounds in the interlamellar space of layered silicates and humates was measured by x-ray diffraction using powder samples and suspensions. The structural properties of the surfactant coated clay suspension were characterized by rheology.

Research paper thumbnail of Specific Surface Area of Stoeber Silica Determined by Various Experimental Methods

Langmuir, 2002

The specific surface area of amorphous Aerosil 200 and silica particles with 270 nm diameter prep... more The specific surface area of amorphous Aerosil 200 and silica particles with 270 nm diameter prepared by the Stoeber method was investigated by a variety of experimental methods: nitrogen adsorption at 77 and 253 K; adsorption from ethanol/cyclohexane mixture; heats of wetting measurements; small-angle X-ray scattering (SAXS) experiments. The N2 adsorption isotherms at 77 K were analyzed using the BET equation, the modified BET equations of Tóth, and equations of the uniform interpretation method of Tóth. For Aerosil 200, the values of the specific surface varied slightly depending on the applied method. For Stoeber silica, the results from nitrogen adsorption at 77 K ranged between 18 and 24 m 2 /g; these values were 20-30 times smaller than those derived from N2 adsorption at 253 K, binary liquid mixture adsorption, and heats of wetting or SAXS experiments (439-670 m 2 /g). The specific surface area of Stoeber silica estimated from nitrogen adsorption measurement at 77 K could not be applied to adsorption data from liquid medium; the other methods, however, provided reliable surface area and charge density values. According to the pore size distribution curves from thermogravimetry, two mean pore diameter values are distinguished (2 and 16 nm), but larger pores also exist in the structure of the Stoeber silica particles. According to the SAXS results Stoeber silica has a mass fractal structure (Dm) 1.73) on the length scale of 5-25 nm.

Research paper thumbnail of The Effect of Hydroxyl Moieties and Their Oxosubstitution on Bile Acid Association Studied in Floating Monolayers

The Scientific World Journal, 2014

Bile salt aggregates are promising candidates for drug delivery vehicles due to their unique fat-... more Bile salt aggregates are promising candidates for drug delivery vehicles due to their unique fat-solubilizing ability. However, the toxicity of bile salts increases with improving fat-solubilizing capability and so an optimal combination of efficient solubilization and low toxicity is necessary. To improve hydrophilicity (and decrease toxicity), we substituted hydroxyl groups of several natural bile acid (BA) molecules for oxogroups and studied their intrinsic molecular association behavior. Here we present the comparative Langmuir trough study of the two-dimensional (2D) association behavior of eight natural BAs and four oxoderivatives (traditionally called keto-derivatives) floated on an aqueous subphase. The series of BAs and derivatives showed systematic changes in the shape of the compression isotherms. Two types of association could be distinguished: the first transition was assigned to the formation of dimers through H-bonding and the second to the hydrophobic aggregation of ...

Research paper thumbnail of Mechanism of in Situ Surface Polymerization of Gallic Acid in an Environmental-Inspired Preparation of Carboxylated Core–Shell Magnetite Nanoparticles

Langmuir, 2014

Magnetite nanoparticles (MNPs) with biocompatible coatings are good candidates for MRI (magnetic ... more Magnetite nanoparticles (MNPs) with biocompatible coatings are good candidates for MRI (magnetic resonance imaging) contrasting, magnetic hyperthermia treatments and drug delivery systems. The spontaneous surface induced polymerization of dissolved organic matter on environmental mineral particles inspired us to prepare carboxylated core-shell MNPs by using a ubiquitous polyphenolic precursor. Through the adsorption and in-situ surface polymerization of gallic acid (GA), a polygallate (PGA) coating is formed on the nanoparticles (PGA@MNP) with possible antioxidant capacity. The Polygallate on magnetite nanoparticles Humic matter on clays

Research paper thumbnail of Preparation and characterization of chondroitin‐sulfate‐A‐coated magnetite nanoparticles for biomedical applications

Journal of Magnetism and Magnetic Materials, 2015

Highlights * Novel CSA-coated core-shell magnetite nanoparticles were prepared successfully. * Th... more Highlights * Novel CSA-coated core-shell magnetite nanoparticles were prepared successfully. * The aggregation range of MNPs was shifted gradually to the lower pHs by CSA loading. * CSA stabilizes electrosterically the MNPs over wide pH-range relevant to biosystems. * The salt tolerance of CSA@MNP enables them to use under physiological condition.