Magnetoliposomes based on nickel/silica core/shell nanoparticles : synthesis and characterization

"Available online 18 September 2014"In the present work, nickel magnetic nanoparticles with diameters lower than 100nm, with and without silica shell, were synthesized by microheterogeneous templating. The magnetic properties of the nanoparticles show a typical ferromagnetic behavior with a coercive field of 80Oe. Dry magnetoliposomes (DMLs) with diameter between 58nm and 76nm were obtained from the synthesis of nanoparticles in the presence of a lipid or surfactant layer, and aqueous magnetoliposomes (AMLs) were obtained by encapsulation of the nanoparticles in liposomes. FRET (Förster resonance energy transfer) experiments were performed to study the non-specific interactions between aqueous magnetoliposomes and giant unilamellar vesicles (GUVs), as models of cell membranes. It was possible to detect membrane fusion between GUVs and AMLs containing both NBD-C6-HPC (donor) and the dye Nile Red (acceptor).This work was supported by FEDER through the COMPETE/QREN/EU Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project of CFUM [PEst-C/FIS/UI0607/2013 (F-COMP-01-0124-FEDER-022711)] and through the research project PTDC/QUI/81238/2006 (FCOMP-01-0124-FEDER-007467). FCT, POPH-QREN and FSE are acknowledged for the PhD grant of A.R.O. Rodrigues (SFRH/BD/90949/2012) and for financial support to MAP-Fis PhD Programme

Magnetic liposomes based on nickel ferrite nanoparticles as nanocarriers for new potential antitumor compounds

Guided transport of biologically active molecules (most of them toxic and with systemic side effects) to target specific sites in human body has been a focus of research in therapeutics in the past years. Magnetoliposomes (liposomes entrapping magnetic nanoparticles) are of large importance, as they can overcome many pharmacokinetics problems and can be guided and localized to the therapeutic site of interest by external magnetic field gradients [1,2]. In this work, nickel ferrite nanoparticles (NPs) with size distribution of 11±5 nm were obtained. Synthesized NPs show superparamagnetic behaviour at room temperature (magnetic squareness of 7.2×10-5 and coercivity field of 12 Oe), being suitable for biological applications. These NPs were either entrapped in liposomes, originating aqueous magnetoliposomes (AMLs), or covered with a lipid bilayer, forming dry magnetoliposomes (DMLs), the last ones prepared by a new promising route. Recently, AMLs and DMLs containing nickel-based nanoparticles were successfully prepared and characterized [3]. A potential antitumor compound [4] was successfully incorporated into the lipid bilayer of magnetoliposomes. DMLs structure was evaluated by FRET (Förster Resonance Energy Transfer) measurements between the fluorescent-labeled lipids NBD-C12-HPC (donor) included in the second lipid layer and rhodamine B DOPE (acceptor) in the first lipid layer. A FRET efficiency of 23% was calculated, with a corresponding donor-acceptor distance (r) of 3.11 nm, confirming DMLs structure. Preliminary assays of the non-specific interactions of both types of magnetoliposomes with biological membranes (modeled by giant unilamellar vesicles, GUVs) were performed, keeping in mind future applications of drug delivery using this type of magnetic systems. Membrane fusion between magnetoliposomes and GUVs was confirmed by FRET.FCT - Fundação para a Ciência e a Tecnologia, PEst-C/FIS/UI0607/2013 (F-COMP-01-0124-FEDER-022711

Magnetic liposomes based on nickel ferrite and manganese ferrite nanoparticles for biomedical applications

In this work, nickel ferrite and manganese ferrite nanoparticles were synthesized and characterized. These nanoparticles were incorporated in liposomes for biomedical applications.Fundação para a Ciência e a Tecnologia (FCT

Magnetoliposomes based on manganese ferrite nanoparticles as nanocarriers for antitumor drugs

Publicado em "NanoPT2016 book of abstracts"In this work, manganese ferrite (MnFe2O4) nanoparticles with superparamagnetic behaviour at room temperature and size distribution of 26 ± 5 nm, were obtained by coprecipitation method. Structural and magnetic properties of the nanoparticles (NPs) were evaluated by XRD, HR-TEM and SQUID. The synthesized NPs were either entrapped in liposomes, originating aqueous magnetoliposomes (AMLs), or covered with a lipid bilayer, forming solid magnetoliposomes (SMLs).This work was supported by FEDER through the COMPETE/QREN/EU Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Projects of CFUM [PEst-C/FIS/UI0607/2013 (F-COMP-01-0124-FEDER-022711)] and CQ/UM [PEst-C/QUI/UI0686/2013 (FCOMP-01-0124-FEDER -022716)]. FCT, POPH-QREN and FSE are acknowledged for the PhD grant of A.R.O. Rodrigues (SFRH/BD/90949/2012) and for financial support to MAP-Fis PhD Programme

Magnetoliposomes based on manganese ferrite nanoparticles for guided transport of antitumor drugs

Publicado em "RICI6 abstract book"In this work, manganese ferrite nanoparticles with size distribution of 46 ± 17 nm and superparamagnetic behavior were synthesized by coprecipitation method. These magnetic nanoparticles were either entrapped in liposomes, originating aqueous magnetoliposomes (AMLs), or covered with a lipid bilayer, forming solid magnetoliposomes (SMLs).MAP-Fis PhD Programme, FEDER, COMPETE/QREN/EU for financial support to CFUM (PEst-C/FIS/UI0607/2013) and FCT and POPH/QREN for PhD grant (SFRH/BD/90949/2012)

Manganite thin films deposited on piezoelectric substrates

Tese de doutoramento Programa Doutoral em Física (MAP-FIS)O interesse crescente em conseguir controlar a magnetização de materiais magnéticos através de campos eléctricos, para aplicações em spintrónica, levou ao desenvolvimento de compósitos magnetoeléctricos com diversas geometrias e composiçoes. Entre estas estruturas compósitas encontram-se os lmes nos de manganites com magnetorresistência colossal depositados sobre substratos piezoeléctricos. Estas estruturas permitem, por um lado, tirar partido do facto de as manganites com magnetorresistência colossal serem particularmente sensíveis aos efeitos de deformação e, por outro, da possibilidade de controlar de maneira reversível a deformação imposta aos lmes e, consequentemente, a sua magnetização, por meio da utilização de substratos piezoeléctricos. Neste trabalho, lmes nos da manganite ferromagnética e metálica La0:67Sr0:33MnO3 (LSMO), com alta largura de banda, e da manganite com ordenamento de carga e baixa largura de banda Pr0:50Ca0:50MnO3 (PCMO) foram depositados em substratos cristalinos piezoeléctricos de LiNbO3 e 0.68Pb(Mg1=3Nb2=3)O3 0.32PbTiO3 (PMN-PT). Foi feita uma caracterização detalhada das suas propriedades estruturais, magnéticas e de transporte eléctrico. Os lmes de LSMO depositados sobre LiNbO3 eram fortemente orientados, com uma direcção preferencial de crescimento (111) pseudocúbica. Veri cou-se, nos lmes, uma transição paramagnética-ferromagnética, com temperaturas de Curie entre 265 K e 360 K, e resistividades eléctricas de baixa temperatura na gama 0:15 0 4:5 .cm. Nestas amostras veri cou-se que a temperatura de deposição afectou as propriedades dos lmes produzidos, no sentido em que um aumento da temperatura de deposição de 600 C para 690 C aumentou a temperatura de Curie de 265 K para 330 K e originou um comportamento metálico. O comportamento da magnetorresistência variou com o aumento da temperatura de deposição, tendo-se observado a supressão da acentuada magnetorresistência de baixo campo. Esta tinha um valor aproximado de -15%, e tinha surgido no lme depositado a 600 C devido ao efeito túnel através das fronteiras de grão, que é dependente do spin. Isto foi também observado nas medidas de magnetorresistência anisotrópica. Nos lmes nos de LSMO sobre substratos ferroeléctricos de PMN-PT do tipo relaxor , foi observado um crescimento com orientação pseudocúbica (001). Foram também observados pequenos incrementos na magnetização abaixo da temperatura de Curie TC = 340 K. Veri cou-se uma correlação entre estas variações na magnetização dos lmes e variações na constante dieléctrica dos substratos, o que sugere um acoplamento magnetoeléctrico. A resistência eléctrica dos lmes foi medida em função do campo eléctrico aplicado ao substrato, o que mais uma vez mostrou um acoplamento através da deformação piezoeléctrica. A maior taxa de variação da resistência obtida foi de 10 /V. Este valor foi medido na zona de baixo campo eléctrico, i.e., onde a deformação é reversível. Os lmes nos de PCMO depositados sobre LiNbO3, orientados segundo c, possuíam também uma orientação (111) pseudocúbica. O seu parâmetro de rede variou sistematicamente com a sua espessura. A fase com ordenamento de carga foi estabilizada nestes lmes e a temperatura TCO a qual ela ocorreu encontrava-se na gama 210 TCO 240 K. Para além disso, TCO aumentou com o decréscimo da espessura dos lmes, devido a deformação epitaxial induzida pelo seu crescimento. A magnetorresistência do PCMO depositado num substrato de LiNbO3 orientado segundo c foi medida numa unidade de campos magnéticos pulsados. Foi observada uma transição de uma fase metálica com cargas desordenadas, para uma fase isoladora com ordenamento de carga. Esta transição ocorreu a um campo crítico H c = 2:3 T a temperatura de 200 K, numa medida efectuada em campo magnético decrescente. Finalmente, os lmes nos de PCMO depositados em PMN-PT eram orientados, com uma orientação preferencial de crescimento (001) pseudocúbica. Foi observado o controlo piezoeléctrico da resistência eléctrica. A taxa de variação da resistência eléctrica dos lmes foi de 11 /V na região reversível da curva de deformação em função do campo eléctrico aplicado.The growing interest in controlling the magnetization by electric elds for spintronics applications has led to the development of magnetoelectric composites with diverse geometries and compositions. Among these composite structures are colossal magnetoresistive manganite thin lms deposited on piezoelectric substrates. Colossal magnetoresistive manganites, on the one hand, are particularly sensitive to the e ects of strain, making them good candidates for incorporation in magnetoelectric composites. On the other hand, piezoelectric substrates allow for a reversible control of the strain applied to the lms, and therefore of the magnetization. In this work, high-bandwidth ferromagnetic metallic manganite La0:67Sr0:33MnO3 (LSMO) and low-bandwidth charge-ordered Pr0:50Ca0:50MnO3 (PCMO) were deposited on LiNbO3 and 0.68Pb(Mg1=3Nb2=3)O3 0.32PbTiO3 (PMN-PT) single crystal piezoelectric substrates. A detailed characterization of the structural, magnetic and transport properties of the produced samples has been performed. The LSMO thin lms on LiNbO3 were highly oriented, with a pseudocubic (111) preferred growth direction. The lms were ferromagnetic with Curie temperatures between 265 K and 360 K and low temperature resistivity values in the range 0:15 0 4:5 .cm. In these samples the deposition temperature was seen to a ect the properties of the deposited lms, in the sense that an increase in the deposition temperature from 600 C to 690 C strongly enhances the ferromagnetic Curie temperature from 265 K to 330 K and increases metallic conduction. The magnetoresistance behaviour is also modi ed as the deposition temperature is increased, with the suppression of the low eld magnetoresistance due to spin polarized tunnelling across grain boundaries. This is con rmed by the measurements of anisotropic magnetoresistance. In the LSMO thin lms deposited on the relaxor ferroelectric PMN PT a pseudocubic (001)-oriented growth was observed. Slight increases in the magnetization, below the Curie temperature TC = 340 K, were observed in the lms. These variations were found to correlate with variations in the dielectric constant of the substrate, suggesting a magnetoelectric coupling. The electrical In the LSMO thin lms deposited on the relaxor ferroelectric PMN PT a pseudocubic (001)-oriented growth was observed. Slight increases in the magnetization, below the Curie temperature TC = 340 K, were observed in the lms. These variations were found to correlate with variations in the dielectric constant of the substrate, suggesting a magnetoelectric coupling. The electrical In the LSMO thin lms deposited on the relaxor ferroelectric PMN PT a pseudocubic (001)-oriented growth was observed. Slight increases in the magnetization, below the Curie temperature TC = 340 K, were observed in the lms. These variations were found to correlate with variations in the dielectric constant of the substrate, suggesting a magnetoelectric coupling. The electrical In the LSMO thin lms deposited on the relaxor ferroelectric PMN PT a pseudocubic (001)-oriented growth was observed. Slight increases in the magnetization, below the Curie temperature TC = 340 K, were observed in the lms. These variations were found to correlate with variations in the dielectric constant of the substrate, suggesting a magnetoelectric coupling. The electrical resistance of the lms was measured as a function of the electric eld applied to the substrate, once again showing a coupling via piezoelectric strain. The resistance varied up to 10 /V in the low electric eld region, i.e., where the strain is reversible. The PCMO thin lms deposited on z-cut LiNbO3 were also pseudocubic (111)-oriented. Their pseudocubic lattice parameter varied systematically with lm thickness. The charge-ordered phase was stabilized in the lms and the temperature TCO at which it occurs was in the range 210 TCO 240 K. Moreover, TCO increased with decreasing lm thickness due to thickness-induced strain in the lms. The magnetoresistance of a PCMO lm on z-cut LiNbO3 was measured with pulsed magnetic elds. The critical magnetic eld at which the crossover from the charge-disordered, metallic phase to the charge-ordered phase was measured in decreasing eld, and the obtained value was H c = 2:3T at 200 K, much smaller than in previous studies of lms on SrTiO3 or LaAlO3. If this corresponds to a lower value for the charge ordering melting eld, it can make the PCMO thin lms on LiNbO3 more suitable for applications. Finally, the thin lms of PCMO deposited on PMN-PT were oriented, with a preferred pseudocubic (001) growth direction. A piezoelectric control of the electrical resistance of the lms was observed. The variation of the electrical resistance with the applied electric eld was around 11 /V in the reversible region of the strainelectric eld curve