Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 42
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Chem Commun (Camb) ; 56(20): 3015-3018, 2020 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-32048648

RESUMO

The uncapped tripeptide DPhe-Phe-Leu acts as self-assembly template to yield supramolecular hydrogel biomaterials. As an example, self-assembling DPhe-Phe-Leu-Asp-Val contains the LDV bioadhesive motif for ß1 integrin activation. Hydrogels made of the two peptides successfully mimic fibronectin of the extracellular matrix and lead to high cell viability, adhesion, and spreading.


Assuntos
Hidrogéis/química , Imagem Óptica , Peptídeos/química , Adesão Celular , Sobrevivência Celular , Fibroblastos/química , Humanos , Substâncias Macromoleculares/química , Conformação Molecular , Tamanho da Partícula , Propriedades de Superfície
2.
J Phys Chem Lett ; 9(12): 3397-3402, 2018 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-29809009

RESUMO

The transition between the lyotropic liquid crystalline lamellar and the bicontinuous cubic mesophase drives multiple fundamental cellular processes involving changes in cell membrane topology, including endocytosis and membrane budding. While several theoretical models have been proposed to explain this dynamic transformation, experimental validation of these models has been challenging because of the short-lived nature of the intermediates present during the phase transition. Herein, we report the direct observation of a lamellar-to-bicontinuous cubic phase transition in nanoscale dispersions using a combination of cryogenic transmission electron microscopy and static small-angle X-ray scattering. The results represent the first experimental confirmation of a theoretical model which proposed that the bicontinuous cubic phase originates from the center of a lamellar vesicle then propagates outward via the formation of interlamellar attachments and stalks. The observation was possible because of the precise control of the lipid composition to place the dispersion systems at the phase boundary of a lamellar and a cubic phase, allowing for the creation of long-lived structural intermediates. By the surveying of the nanoparticles using cryogenic transmission electron microscopy, a complete phase transition sequence was established.

3.
Sci Rep ; 7: 43947, 2017 03 08.
Artigo em Inglês | MEDLINE | ID: mdl-28272523

RESUMO

Using small angle neutron scattering (SANS), it is shown that the existence of pre-assembled structures at high pH for a capped diphenylalanine hydrogel is controlled by the selection of N-terminal heterocyclic capping group, namely indole or carbazole. At high pH, changing from a somewhat hydrophilic indole capping group to a more hydrophobic carbazole capping group results in a shift from a high proportion of monomers to self-assembled fibers or wormlike micelles. The presence of these different self-assembled structures at high pH is confirmed through NMR and circular dichroism spectroscopy, scanning probe microscopy and cryogenic transmission electron microscopy.


Assuntos
Fenilalanina/análogos & derivados , Dicroísmo Circular , Microscopia Crioeletrônica , Dipeptídeos , Hidrogéis/química , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Espectroscopia de Ressonância Magnética , Microscopia de Força Atômica , Difração de Nêutrons , Fenilalanina/química , Espalhamento a Baixo Ângulo
4.
Colloids Surf B Biointerfaces ; 152: 143-151, 2017 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-28107705

RESUMO

The inverse bicontinuous lipidic cubic phase offers a simple and robust membrane mimetic with the ability to encapsulate peptides, potentially increasing bioavailability, while also offering a platform from which functionalized, targeted nanoparticles can be developed. Herein we have investigated the use of a number of cubic phase nanoparticle systems with encapsulated antimicrobial peptides gramicidin A', melittin, and alamethicin. The optimal peptide loading ranges, over which cubic symmetry was retained, were determined using small angle X-ray scattering. A large variation in peptide loading capability of different cubosome formulations was confirmed using circular dichroism. Observations are supported by particle sizing using dynamic light scattering as well as by direct visualization of nanoparticle morphology using cryogenic transmission electron microscopy. The results are discussed in relation to bilayer properties such as the hydrophobic mismatch between bilayer and peptide, intrinsic surface curvature, and lateral pressure profile of each lipid system. The findings of this study should be of use in the further development of lipid-based peptide encapsulation systems, particularly in the field of drug delivery.


Assuntos
Peptídeos Catiônicos Antimicrobianos/química , Bicamadas Lipídicas/química , Nanoestruturas/química , Dicroísmo Circular , Difusão Dinâmica da Luz , Microscopia Eletrônica de Transmissão , Nanoestruturas/ultraestrutura , Peptídeos/química
5.
Mater Sci Eng C Mater Biol Appl ; 71: 584-593, 2017 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-27987748

RESUMO

Engineered nanoparticles with multiple complementary imaging modalities are of great benefit to the rapid treatment and diagnosis of disease in various organs. Herein, we report the formulation of cubosomes and hexosomes that carry multiple amphiphilic imaging contrast agents in their self-assembled lipid bilayers. This is the first report of the use of both near infrared fluorescent (NIRF) imaging and gadolinium lipid based magnetic resonance (MR) imaging modalities in cubosomes and hexosomes. High-throughput screening was used to rapidly optimize formulations with desirable nano-architectures and low in vitro cytotoxicity. The dual-modal imaging nanoparticles in vivo biodistribution and organ specific contrast enhancement were then studied. The NIRF in vivo imaging results indicated accumulation of both cubosomes and hexosomes in the liver and spleen of mice up to 20h post-injection. Remarkably, the biodistribution of the nanoparticle formulations was affected by the mesophase (i.e. cubic or hexagonal), a finding of significant importance for the future use of these compounds, with hexosomes showing higher accumulation in the spleen than the liver compared to cubosomes. Furthermore, in vivo MRI data of animals injected with either type of lyotropic liquid crystal nanoparticle displayed enhanced contrast in the liver and spleen.


Assuntos
Meios de Contraste , Imageamento por Ressonância Magnética , Nanopartículas/química , Imagem Óptica , Animais , Células CHO , Meios de Contraste/química , Meios de Contraste/farmacocinética , Meios de Contraste/farmacologia , Cricetulus , Humanos , Masculino , Camundongos , Células U937
6.
PLoS One ; 11(3): e0151475, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27002321

RESUMO

BACKGROUND: Apolipoprotein A-II (ApoA-II) is down regulated in the sera of pancreatic ductal adenocarcinoma (PDAC) patients, which may be due to increase utilization of high density lipoprotein (HDL) lipid by pancreatic cancer tissue. This study examined the influence of exogenous ApoA-II on lipid uptake and cell growth in pancreatic cancer (PC) both in vitro and in vivo. METHODS: Cryo transmission electron microscopy (TEM) examined ApoA-II's influence on morphology of SMOFLipid emulsion. The influence of ApoA-II on proliferation of cancer cell lines was determined by incubating them with lipid+/-ApoA-II and anti-SR-B1 antibody. Lipid was labeled with the fluorophore, DiD, to trace lipid uptake by cancer cells in vitro by confocal microscopy and in vivo in PDAC patient derived xenograft tumours (PDXT) by fluorescence imaging. Scavenger receptor class B type-1(SR-B1) expression in PDAC cell lines and in PDAC PDXT was measured by western blotting and immunohistochemistry, respectively. RESULTS: ApoA-II spontaneously converted lipid emulsion into very small unilamellar rHDL like vesicles (rHDL/A-II) and enhanced lipid uptake in PANC-1, CFPAC-1 and primary tumour cells as shown by confocal microscopy. SR-B1 expression was 13.2, 10.6, 3.1 and 2.3 fold higher in PANC-1, MIAPaCa-2, CFPAC-1 and BxPC3 cell lines than the normal pancreatic cell line (HPDE6) and 3.7 fold greater in PDAC tissue than in normal pancreas. ApoA-II plus lipid significantly increased the uptake of labeled lipid and promoted cell growth in PANC-1, MIAPaCa-2, CFPAC-1 and BxPC3 cells which was inhibited by anti SR-B1 antibody. Further, ApoA-II increased the uptake of lipid in xenografts by 3.4 fold. CONCLUSION: Our data suggest that ApoA-II enhance targeting potential of lipid in pancreatic cancer which may have imaging and drug delivery potentialities.


Assuntos
Apolipoproteína A-II/metabolismo , Proliferação de Células/fisiologia , Lipídeos/fisiologia , Neoplasias Pancreáticas/metabolismo , Receptores Depuradores Classe B/metabolismo , Carcinoma Ductal Pancreático/metabolismo , Linhagem Celular Tumoral , Humanos , Lipoproteínas HDL/metabolismo , Células MCF-7
7.
Chemistry ; 21(40): 13950-60, 2015 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-26376329

RESUMO

Here, a new amphiphilic magnetic resonance imaging (MRI) contrast agent, a Gd(III)-chelated diethylenetriaminepentaacetic acid conjugated to two branched alkyl chains via a dopamine spacer, Gd-DTPA-dopamine-bisphytanyl (Gd-DTPA-Dop-Phy), which is readily capable of self-assembling into liposomal nanoassemblies upon dispersion in an aqueous solution, is reported. In vitro relaxivities of the dispersions were found to be much higher than Magnevist, a commercially available contrast agent, at 0.47 T but comparable at 9.40 T. Analysis of variable temperature (17)O NMR transverse relaxation measurements revealed the water exchange of the nanoassemblies to be faster than that previously reported for paramagnetic liposomes. Molecular reorientation dynamics were probed by (1)H NMRD profiles using a classical inner and outer sphere relaxation model and a Lipari-Szabo "model-free" approach. High payloads of Gd(III) ions in the liposomal nanoassemblies made solely from the Gd-DTPA-Dop-Phy amphiphiles, in combination with slow molecular reorientation and fast water exchange makes this novel amphiphile a suitable candidate to be investigated as an advanced MRI contrast agent.


Assuntos
Meios de Contraste/síntese química , Gadolínio DTPA/química , Gadolínio DTPA/síntese química , Gadolínio/química , Lipossomos/química , Meios de Contraste/química , Dopamina , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética
8.
Langmuir ; 31(39): 10871-80, 2015 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-26362479

RESUMO

Lyotropic liquid crystalline nanoparticle dispersions are of interest as delivery vectors for biomedicine. Aqueous dispersions of liposomes, cubosomes, and hexosomes are commonly stabilized by nonionic amphiphilic block copolymers to prevent flocculation and phase separation. Pluronic stabilizers such as F127 are commonly used; however, there is increasing interest in using chemically reactive stabilizers for enhanced functionalization and specificity in therapeutic delivery applications. This study has explored the ability of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine conjugated with poly(ethylene glycol) (DSPE-PEGMW) (2000 Da ≤ MW ≤ 5000 Da) to engineer and stabilize phytantriol-based lyotropic liquid crystalline dispersions. The poly(ethylene glycol) (PEG) moiety provides a tunable handle to the headgroup hydrophilicity/hydrophobicity to allow access to a range of nanoarchitectures in these systems. Specifically, it was observed that increasing PEG molecular weight promotes greater interfacial curvature of the dispersions, with liposomes (Lα) present at lower PEG molecular weight (MW 2000 Da), and a propensity for cubosomes (QII(P) or QII(D) phase) at MW 3400 Da or 5000 Da. In comparison to Pluronic F127-stabilized cubosomes, those made using DSPE-PEG3400 or DSPE-PEG5000 had enlarged internal water channels. The toxicity of these cubosomes was assessed in vitro using A549 and CHO cell lines, with cubosomes prepared using DSPE-PEG5000 having reduced cytotoxicity relative to their Pluronic F127-stabilized analogues.


Assuntos
Álcoois Graxos/química , Álcoois Graxos/toxicidade , Lipídeos/química , Cristais Líquidos/química , Cristais Líquidos/toxicidade , Nanopartículas/química , Nanopartículas/toxicidade , Polietilenoglicóis/química , Animais , Células CHO , Linhagem Celular , Cricetinae , Cricetulus , Meios de Cultura , Humanos , Microscopia Eletrônica de Transmissão
9.
Protein Expr Purif ; 116: 19-29, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26196500

RESUMO

Hendra virus (family Paramyxoviridae) is a negative sense single-stranded RNA virus (NSRV) which has been found to cause disease in humans, horses, and experimentally in other animals, e.g. pigs and cats. Pteropid bats commonly known as flying foxes have been identified as the natural host reservoir. The Hendra virus nucleocapsid protein (HeV N) represents the most abundant viral protein produced by the host cell, and is highly immunogenic with naturally infected humans and horses producing specific antibodies towards this protein. The purpose of this study was to express and purify soluble, functionally active recombinant HeV N, suitable for use as an immunodiagnostic reagent to detect antibodies against HeV. We expressed both full-length HeV N, (HeV NFL), and a C-terminal truncated form, (HeV NCORE), using a bacterial heterologous expression system. Both HeV N constructs were engineered with an N-terminal Hisx6 tag, and purified using a combination of immobilized metal affinity chromatography (IMAC) and size exclusion chromatography (SEC). Purified recombinant HeV N proteins self-assembled into soluble higher order oligomers as determined by SEC and negative-stain transmission electron microscopy. Both HeV N proteins were highly immuno-reactive with sera from animals and humans infected with either HeV or the closely related Nipah virus (NiV), but displayed no immuno-reactivity towards sera from animals infected with a non-pathogenic paramyxovirus (CedPV), or animals receiving Equivac® (HeV G glycoprotein subunit vaccine), using a Luminex-based multiplexed microsphere assay.


Assuntos
Vírus Hendra/química , Vírus Hendra/imunologia , Proteínas do Nucleocapsídeo/química , Proteínas do Nucleocapsídeo/imunologia , Sequência de Aminoácidos , Animais , Anticorpos Antivirais/imunologia , Clonagem Molecular , Escherichia coli/genética , Expressão Gênica , Vírus Hendra/genética , Vírus Hendra/ultraestrutura , Infecções por Henipavirus/imunologia , Infecções por Henipavirus/virologia , Cavalos , Humanos , Dados de Sequência Molecular , Proteínas do Nucleocapsídeo/genética , Proteínas do Nucleocapsídeo/ultraestrutura , Plasmídeos/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Proteínas Recombinantes/ultraestrutura , Suínos
10.
Nano Lett ; 15(6): 4229-33, 2015 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-25984944

RESUMO

We present the first observation of Janus nanoparticles consisting of stable, coexisting ordered mesophases in discrete particles created by lipid self-assembly. Cryo-TEM images provided visual identification of the multicompartment Janus nanoparticles and, combined with SAXS data, confirmed the presence of mixed cubic phases and mixed cubic/hexagonal phases within individual nanoparticles. We further investigated computer visualization models to interpret the potential interface between the interconnected coexisting nanostructured domains within a single nanoparticle.

11.
Biomacromolecules ; 16(3): 790-7, 2015 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-25649901

RESUMO

The use of medical imaging contrast agents may lead to improved patient prognosis by potentially enabling an earlier detection of diseases and therefore an earlier initiation of treatments. In this study, we fabricated superparamagnetic iron oxide (SPIO) nanoparticles within the inner cavity of multiwalled carbon nanotubes (MWCNTs) for the first time; thereby ensuring high mechanical stability of the nanoparticles. A simple, but effective, self-assembled coating with RAFT diblock copolymers ensured the SPIO-MWCNTs have a high dispersion stability under physiological conditions. In vivo acute tolerance testing in mice showed a high tolerance dose up to 100 mg kg(-1). Most importantly, after administration of the material a 55% increase in tumor to liver contrast ratio was observed with in vivo MRI measurements compared to the preinjection image enhancing the detection of the tumor.


Assuntos
Meios de Contraste , Neoplasias Hepáticas Experimentais/diagnóstico , Nanopartículas de Magnetita , Nanotubos de Carbono , Animais , Linhagem Celular Tumoral , Coloides , Feminino , Humanos , Imageamento por Ressonância Magnética , Camundongos Endogâmicos BALB C , Nanocompostos
12.
Langmuir ; 31(4): 1556-63, 2015 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-25580808

RESUMO

Supramolecular self-assembling amphiphiles have been widely used in drug delivery and diagnostic imaging. In this report, we present the self-assembly of Gd (III) chelated DTPA-monophytanyl (Gd-DTPA-MP) amphiphiles incorporated within phytantriol (PT), an inverse bicontinuous cubic phase forming matrix at various compositions. The dispersed colloidal nanoassemblies were evaluated as potential MRI contrast agents at various magnetic field strengths. The homogeneous incorporation of Gd-DTPA-MP in PT was confirmed by polarized optical microscopy (POM) and synchrotron small-angle X-ray scattering (SAXS) of the bulk phases of the mixtures. The liquid crystalline nanostructures, morphology, and the size distribution of the nanoassemblies were studied by SAXS, cryogenic transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS). The dispersions with up to 2 mol % of Gd-DTPA-MP in PT retained inverse cubosomal nanoassemblies, whereas the rest of the dispersions transformed to liposomal nanoassemblies. In vitro relaxivity studies were performed on all the dispersions at 0.54, 9.40, and 11.74 T and compared to Magnevist, a commercially available contrast agent. All the dispersions showed much higher relaxivities compared to Magnevist at both low and high magnetic field strengths. Image contrast of the nanoassemblies was also found to be much better than Magnevist at the same Gd concentration at 11.74 T. Moreover, the Gd-DTPA-MP/PT dispersions showed improved relaxivities over the pure Gd-DTPA-MP dispersion at high magnetic fields. These stable colloidal nanoassemblies have high potential to be used as combined delivery matrices for diagnostics and therapeutics.


Assuntos
Meios de Contraste , Álcoois Graxos/química , Gadolínio DTPA/administração & dosagem , Imageamento por Ressonância Magnética , Microscopia Crioeletrônica , Gadolínio DTPA/química , Microscopia Eletrônica de Transmissão , Espalhamento a Baixo Ângulo , Difração de Raios X
13.
Nanoscale ; 7(7): 2905-13, 2015 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-25516406

RESUMO

Next generation drug delivery utilising nanoparticles incorporates active targeting to specific sites. In this work, we combined targeting with the inherent advantages of self-assembled lipid nanoparticles containing internal nano-structures. Epidermal growth factor receptor (EGFR)-targeting, PEGylated lipid nanoparticles using phytantriol and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-PEG-maleimide amphiphiles were created. The self-assembled lipid nanoparticles presented here have internal lyotropic liquid crystalline nano-structures, verified by synchrotron small angle X-ray scattering and cryo-transmission electron microscopy, that offer the potential of high drug loading and enhanced cell penetration. Anti-EGFR Fab' fragments were conjugated to the surface of nanoparticles via a maleimide-thiol reaction at a high conjugation efficiency and retained specificity following conjugation to the nanoparticles. The conjugated nanoparticles were demonstrated to have high affinity for an EGFR target in a ligand binding assay.


Assuntos
Receptores ErbB/química , Lipídeos/química , Nanopartículas/química , Microscopia Crioeletrônica , Portadores de Fármacos/química , Álcoois Graxos/química , Humanos , Fragmentos Fab das Imunoglobulinas/química , Ligantes , Lipossomos/química , Cristais Líquidos , Maleimidas/química , Nanotecnologia , Tamanho da Partícula , Fosfatidiletanolaminas/química , Proteínas Recombinantes/química , Espalhamento de Radiação , Compostos de Sulfidrila/química , Raios X
14.
Phys Chem Chem Phys ; 17(3): 1705-15, 2015 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-25459998

RESUMO

Self-assembled amphiphile nanostructures of colloidal dimensions such as cubosomes and hexosomes are of interest as delivery vectors in pharmaceutical and nanomedicine applications. Translation would be assisted through a better of understanding of the effects of drug loading on the internal nanostructure, and the relationship between this nanostructure and drug release profile. Positron annihilation lifetime spectroscopy (PALS) is sensitive to local microviscosity and is used as an in situ molecular probe to examine the Q2 (cubosome) → H2 (hexosome) → L2 phase transitions of the pharmaceutically relevant phytantriol-water system in the presence of a model hydrophobic drug, vitamin E acetate (VitEA). It is shown that the ortho-positronium lifetime (τ) is sensitive to molecular packing and mobility and this has been correlated with the rheological properties of individual lyotropic liquid crystalline mesophases. Characteristic PALS lifetimes for L2 (τ4∼ 4 ns) ∼ H2 (τ4∼ 4 ns) > Q(2 Pn3m) (τ4∼ 2.2 ns) are observed for the phytantriol-water system, with the addition of VitEA yielding a gradual increase in τ from τ∼ 2.2 ns for cubosomes to τ∼ 3.5 ns for hexosomes. The dynamic chain packing at higher temperatures and in the L2 and H2 phases is qualitatively less "viscous", consistent with rheological measurements. This information offers increased understanding of the relationship between internal nanostructure and species permeability.


Assuntos
Álcoois Graxos/química , Nanoestruturas/química , Análise Espectral , Química Farmacêutica , Coloides , Microscopia Eletrônica de Transmissão , Modelos Biológicos , Estrutura Molecular , Tamanho da Partícula
15.
Phys Chem Chem Phys ; 17(1): 276-86, 2015 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-25412405

RESUMO

Lipid lamellar mesophases and their colloidal dispersions (liposomes) are increasingly being deployed in vivo as drug delivery vehicles, and also as models of biological membranes in fundamental biophysics studies. The permeability and diffusion of small molecules such as drugs is accommodated by a change in local curvature and molecular packing (mesophase behaviour) of the bilayer membrane molecules. Positron annihilation lifetime spectroscopy (PALS) is capable of providing in situ molecular level information on changes in free volume and void space arising from such changes in a non-perturbative manner. In this work PALS was used to systematically characterise the temperature-induced melting transitions (Tm) of saturated and unsaturated phospholipid-water systems while systematically varying lipid chain length, as both bulk lamellar mesophase and as aqueous colloidal dispersions (liposomes). A four-component fit of the data was used that provides separate PALS lifetimes for the aqueous (τ3) and organic domains (τ4). The oPs lifetime (τ4), for the lamellar phases of DSPC (C18:0), DPPC (C16:0), DMPC (C14:0) and DLPC (C12:0) was found to be independent of chain length, with characteristic lifetime value τ4 ∼ 3.4 ns. τ4 is consistently larger in the dispersed liposomes compared to the bulk mesophases, suggesting that the hydrocarbon chains are more mobile. The use of contemporary and consistent analytical approaches as described in this study is the key to future deployment of PALS to interrogate the in situ influence of drugs on membrane and cellular microenvironments.


Assuntos
Lipossomos/química , Cristais Líquidos/química , Fosfolipídeos/química , Elétrons , Hidrocarbonetos/química , Bicamadas Lipídicas/química , Permeabilidade , Transição de Fase , Análise Espectral , Temperatura de Transição
16.
Phys Chem Chem Phys ; 16(45): 24936-53, 2014 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-25325902

RESUMO

Lipid-based liquid crystalline systems are showing potential as stimuli-responsive nanomaterials, and NIR-responsive gold nanoparticles have been demonstrated to provide control of transitions in non-lamellar phases. In this study, we focus on a deeper understanding of the photothermal response of both lamellar and non-lamellar phases, and new systems formed by alternative lipid systems not previously reported, by linking the photothermal heating to the bulk thermal properties of the materials. Dynamic photothermal studies were performed using NIR laser irradiation and monitoring the structural response using time resolved small angle X-ray scattering for the bulk phases and hexosomes. In addition, cryoFESEM and cryoTEM were used to visualise and assess the effect of GNR incorporation into hexagonal phase nanostructures. The ability of the systems to respond to photothermal heating was correlated with the thermal phase behaviour and heat capacities of the different structures. Access to alternative phase transitions in these systems and understanding the likely photothermal response will facilitate different modes of application of these hybrid nanomaterials for on-demand drug delivery applications.


Assuntos
Portadores de Fármacos/química , Desenho de Fármacos , Temperatura Alta , Raios Infravermelhos , Lipídeos/química , Cristais Líquidos/química , Álcoois Graxos/química , Glicerídeos/química , Ouro/química , Lasers , Nanotubos/química , Transição de Fase , Fosforilcolina/química
17.
Langmuir ; 30(29): 8898-906, 2014 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-24979524

RESUMO

The purpose of this work was to synthesize and screen, for their effectiveness to act as T1-enhancing magnetic resonance imaging (MRI) contrast agents, a small library of nitroxide lipids incorporated into cubic-phase lipid nanoparticles (cubosomes). The most effective nitroxide lipid was then formulated into lower-toxicity lipid nanoparticles (hexosomes), and effective MR contrast was observed in the aorta and spleen of live rats in vivo. This new class of lower-toxicity lipid nanoparticles allowed for higher relaxivities on the order of those of clinically used gadolinium complexes. The new hexosome formulation presented herein was significantly lower in toxicity and higher in relaxivity than cubosome formulations previously reported by us.


Assuntos
Meios de Contraste/síntese química , Imageamento por Ressonância Magnética/métodos , Miristatos/química , Nanopartículas/química , Óxidos de Nitrogênio/química , Animais , Aorta/anatomia & histologia , Células CHO , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Cricetulus , Eritrócitos/efeitos dos fármacos , Álcoois Graxos/química , Feminino , Glicerídeos/química , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Nanopartículas/ultraestrutura , Ratos , Ratos Sprague-Dawley , Baço/anatomia & histologia
18.
Soft Matter ; 10(35): 6666-76, 2014 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-25058647

RESUMO

Copolymers, particularly Pluronics®, are typically used to sterically stabilise colloidal nanostructured particles composed of a lyotropic liquid crystalline bicontinuous cubic phase (cubosomes). There is a need to design and assess new functionalisable stabilisers for these colloidal drug delivery systems. Six amphiphilic brush copolymers, poly(octadecyl acrylate)-block-poly(polyethylene glycol methyl ether acrylate) (P(ODA)-b-P(PEGA-OMe)), synthesised by reversible addition-fragmentation chain transfer (RAFT), were assessed as novel steric stabilisers for cubosomes. It was found that increasing the density of PEG on the nanostructured particle surface by incorporating a PEG brush design (i.e., brush copolymer), provided comparable and/or increased stabilisation effectiveness compared to a linear PEG structure, Pluronic® F127, which is extensively used for steric stabilisation of cubosomes. Assessment was conducted both prior to and following the removal of the dodecyl trithiocarbonate end-group, by free radical-induced reduction. The reduced (P(ODA)-b-P(PEGA-OMe) copolymers were more effective steric stabilisers for phytantriol and monoolein colloidal particle dispersions than their non-reduced analogues. High throughput characterisation methodologies, including an accelerated stability assay (ASA) and synchrotron small angle X-ray scattering (SAXS), were implemented in this study for the rapid assessment of steric stabiliser effectiveness and lyotropic liquid crystalline phase identification. Phytantriol cubosomes stabilised with P(ODA)-b-P(PEGA-OMe) copolymers exhibited a double diamond cubic phase (Q(2)(D)), whilst monoolein cubosomes exhibited a primitive cubic phase (Q(2)(P)), analogous to those formed using Pluronic® F127.


Assuntos
Acrilatos/química , Metacrilatos/química , Polietilenoglicóis/química , Coloides/química , Microscopia Crioeletrônica , Sistemas de Liberação de Medicamentos , Radicais Livres , Luz , Lipídeos/química , Cristais Líquidos , Teste de Materiais , Microscopia Eletrônica de Transmissão , Nanoestruturas/química , Tamanho da Partícula , Poloxâmero/química , Espalhamento de Radiação , Espalhamento a Baixo Ângulo , Temperatura , Raios X
19.
Biomaterials ; 35(1): 378-86, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24120046

RESUMO

An efficient MRI T2-weighted contrast agent incorporating a potential liver targeting functionality was synthesized via the combination of superparamagnetic iron oxide (SPIO) nanoparticles with multiwalled carbon nanotubes (MWCNTs). Poly(diallyldimethylammonium chloride) (PDDA) was coated on the surface of acid treated MWCNTs via electrostatic interactions and SPIO nanoparticles modified with a potential targeting agent, lactose-glycine adduct (Lac-Gly), were subsequently immobilized on the surface of the PDDA-MWCNTs. A narrow magnetic hysteresis loop indicated that the product displayed superparamagnetism at room temperature which was further confirmed by ZFC (zero field cooling)/FC (field cooling) curves measured by SQUID. The multifunctional MWCNT-based magnetic nanocomposites showed low cytotoxicity in vitro to HEK293 and Huh7 cell lines. Enhanced T2 relaxivities were observed for the hybrid material (186 mM(-1) s(-1)) in comparison with the pure magnetic nanoparticles (92 mM(-1) s(-1)) due to the capacity of the MWCNTs to "carry" more nanoparticles as clusters. More importantly, after administration of the composite material to an in vivo liver cancer model in mice, a significant increase in tumor to liver contrast ratio (277%) was observed in T2 weighted magnetic resonance images.


Assuntos
Meios de Contraste , Imageamento por Ressonância Magnética/métodos , Magnetismo , Nanotubos de Carbono , Água , Linhagem Celular , Humanos , Microscopia Eletrônica de Transmissão , Espectroscopia Fotoeletrônica
20.
J Mater Chem B ; 2(9): 1225-1233, 2014 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-32261359

RESUMO

Self-assembly of lipid-based amphiphiles into various supramolecular nanostructured particles has been used in creating novel nanomaterials with diverse applications in drug delivery and diagnostic imaging. Here we report on Gd(iii) chelated DTPA amphiphiles with an oleyl chain (Gd-DTPA-MO) incorporated within the self-assembly matrix of glycerol monooleate (GMO), an inverse cubic phase forming system, at varying compositions. The dispersed colloidal nanoassemblies were explored for their potential as magnetic resonance imaging (MRI) contrast agents. We investigated the homogeneity of the mixed amphiphiles in bulk phases by differential scanning calorimetry (DSC) and their lyotropic phase behaviour by synchrotron small angle X-ray scattering (SAXS). The liquid crystalline nanostructures, morphology and the size distribution of the nanoassemblies were studied by synchrotron SAXS, cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS). SAXS and cryo-TEM results revealed the formation of inverse cubosomes in dispersions with ≤1 mol% of Gd-DTPA-MO, and liposomal and rod-shaped micellar aggregates with >1 mol%. The stability of cubosomal nanoassemblies was assessed in the presence of fetal bovine serum, showing minimal effect on their nanostructures. In vitro relaxivity studies were performed at four different magnetic field strengths (0.54, 7.05, 9.40 and 11.74 T). All the colloidal dispersions displayed enhanced longitudinal relaxivities per Gd over Magnevist, a commercially available contrast agent, at both low and high magnetic field strengths. In addition, cubosomes with 3D-periodic interior nanostructures, extensive water channels and high interfacial surface area, showed promise as high field contrast agents. These stable colloidal particles also have potential to be used as combined delivery matrices for diagnostics and therapeutics (theranostics).

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...