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1.
Nat Commun ; 11(1): 4616, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32934229

RESUMO

Para-nematic phases, induced by unwinding chiral helices, spontaneously relax to a chiral ground state through phase ordering dynamics that are of great interest and crucial for applications such as stimuli-responsive and biomimetic engineering. In this work, we characterize the cholesteric phase relaxation behaviors of ß-lactoglobulin amyloid fibrils and cellulose nanocrystals confined into cylindrical capillaries, uncovering two different equilibration pathways. The integration of experimental measurements and theoretical predictions reveals the starkly distinct underlying mechanism behind the relaxation dynamics of ß-lactoglobulin amyloid fibrils, characterized by slow equilibration achieved through consecutive sigmoidal-like steps, and of cellulose nanocrystals, characterized by fast equilibration obtained through smooth relaxation dynamics. Particularly, the specific relaxation behaviors are shown to emerge from the order parameter of the unwound cholesteric medium, which depends on chirality and elasticity. The experimental findings are supported by direct numerical simulations, allowing to establish hard-to-measure viscoelastic properties without applying magnetic or electric fields.


Assuntos
Lactoglobulinas/química , Cristais Líquidos/química , Amiloide/química , Coloides/química , Elasticidade , Cinética , Nanopartículas/química , Transição de Fase , Temperatura
2.
Proc Natl Acad Sci U S A ; 117(31): 18186-18193, 2020 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-32680965

RESUMO

To overcome the reversible nature of low-Reynolds-number flow, a variety of biomimetic microrobotic propulsion schemes and devices capable of rapid transport have been developed. However, these approaches have been typically optimized for a specific function or environment and do not have the flexibility that many real organisms exhibit to thrive in complex microenvironments. Here, inspired by adaptable microbes and using a combination of experiment and simulation, we demonstrate that one-dimensional colloidal chains can fold into geometrically complex morphologies, including helices, plectonemes, lassos, and coils, and translate via multiple mechanisms that can be varied with applied magnetic field. With chains of multiblock asymmetry, the propulsion mode can be switched from bulk to surface-enabled, mimicking the swimming of microorganisms such as flagella-rotating bacteria and tail-whipping sperm and the surface-enabled motion of arching and stretching inchworms and sidewinding snakes. We also demonstrate that reconfigurability enables navigation through three-dimensional and narrow channels simulating capillary blood vessels. Our results show that flexible microdevices based on simple chains can transform both shape and motility under varying magnetic fields, a capability we expect will be particularly beneficial in complex in vivo microenvironments.


Assuntos
Engenharia Química , Coloides/química , Robótica , Magnetismo
3.
J Vis Exp ; (159)2020 05 12.
Artigo em Inglês | MEDLINE | ID: mdl-32478723

RESUMO

In single molecule fluorescence enzymology, background fluorescence from labeled substrates in solution often limits fluorophore concentration to pico- to nanomolar ranges, several orders of magnitude less than many physiological ligand concentrations. Optical nanostructures called zero mode waveguides (ZMWs), which are 100-200 nm in diameter apertures fabricated in a thin conducting metal such as aluminum or gold, allow imaging of individual molecules at micromolar concentrations of fluorophores by confining visible light excitation to zeptoliter effective volumes. However, the need for expensive and specialized nanofabrication equipment has precluded the widespread use of ZMWs. Typically, nanostructures such as ZMWs are obtained by direct writing using electron beam lithography, which is sequential and slow. Here, colloidal, or nanosphere, lithography is used as an alternative strategy to create nanometer-scale masks for waveguide fabrication. This report describes the approach in detail, with practical considerations for each phase. The method allows thousands of aluminum or gold ZMWs to be made in parallel, with final waveguide diameters and depths of 100-200 nm. Only common lab equipment and a thermal evaporator for metal deposition are required. By making ZMWs more accessible to the biochemical community, this method can facilitate the study of molecular processes at cellular concentrations and rates.


Assuntos
Microscopia de Fluorescência , Microtecnologia/métodos , Nanoestruturas/química , Imagem Individual de Molécula , Alumínio/química , Coloides/química , Cobre/química , Cristalização , Análise de Elementos Finitos , Transferência Ressonante de Energia de Fluorescência , Corantes Fluorescentes/química , Ouro/química , Microesferas , Poliestirenos/química , Porosidade
4.
Nat Commun ; 11(1): 2495, 2020 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-32427872

RESUMO

Colloidal crystal engineering with nucleic acid-modified nanoparticles is a powerful way for preparing 3D superlattices, which may be useful in many areas, including catalysis, sensing, and photonics. To date, the building blocks studied have been primarily based upon metals, metal oxides, chalcogenide semiconductors, and proteins. Here, we show that metal-organic framework nanoparticles (MOF NPs) densely functionalized with oligonucleotides can be programmed to crystallize into a diverse set of superlattices with well-defined crystal symmetries and compositions. Electron microscopy and small-angle X-ray scattering characterization confirm the formation of single-component MOF superlattices, binary MOF-Au single crystals, and two-dimensional MOF nanorod assemblies. Importantly, DNA-modified porphyrinic MOF nanorods (PCN-222) were assembled into 2D superlattices and found to be catalytically active for the photooxidation of 2-chloroethyl ethyl sulfide (CEES, a chemical warfare simulant of mustard gas). Taken together, these new materials and methods provide access to colloidal crystals that incorporate particles with the well-established designer properties of MOFs and, therefore, increase the scope of possibilities for colloidal crystal engineering with DNA.


Assuntos
Coloides/química , DNA/química , Estruturas Metalorgânicas/química , Nanopartículas/química , Cristalização , DNA/genética , Engenharia/métodos , Microscopia Eletrônica de Transmissão e Varredura/métodos , Nanopartículas/ultraestrutura , Nanotubos/química , Nanotubos/ultraestrutura , Tamanho da Partícula , Espalhamento a Baixo Ângulo , Prata/química , Difração de Raios X
5.
Food Chem ; 326: 127009, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32438230

RESUMO

A rapid Surface Enhanced Raman Spectroscopy (SERS) method to detect SO2 in wine is presented, exploiting the preferential binding of silver nanoparticles (AgNPs) with sulfur-containing species. This interaction promotes the agglomeration of the AgNPs and inducing the formation of SERS "hot spots" responsible for SO2 signals enhancement. For increasing SO2 concentrations from 0 to100 mg/l in wine simulant, SERS intensity showed an increasing trend, following a Langmuir absorption function (R2 = 0.94). Due to the wine matrix variability, a standard additions method was then employed for quantitative analysis in red and white wines. This method does not require the SO2 separation but only a matrix pre-cleaning by solid phase extraction. The limit of detection (LOD) was defined for each wine tested, ranging from 0.6 mg/l to 9.6 mg/l. The results obtained were validated by comparison with the International Organization of Vine and Wine method (OIV-MA-AS323-04A).


Assuntos
Dióxido de Enxofre/análise , Vinho/análise , Coloides/química , Limite de Detecção , Nanopartículas Metálicas/química , Prata/química , Extração em Fase Sólida , Análise Espectral Raman
6.
Nat Commun ; 11(1): 2670, 2020 05 29.
Artigo em Inglês | MEDLINE | ID: mdl-32471993

RESUMO

The assembly of active and self-propelled particles is an emerging strategy to create dynamic materials otherwise impossible. However, control of the complex particle interactions remains challenging. Here, we show that various dynamic interactions of active patchy particles can be orchestrated by tuning the particle size, shape, composition, etc. This capability is manifested in establishing dynamic colloidal bonds that are highly selective and directional, which greatly expands the spectrum of colloidal structures and dynamics by assembly. For example, we demonstrate the formation of colloidal molecules with tunable bond angles and orientations. They exhibit controllable propulsion, steering, reconfiguration as well as other dynamic behaviors that collectively reflect the bond properties. The working principle is further extended to the co-assembly of synthetic particles with biological entities including living cells, giving rise to hybrid colloidal molecules of various types, for example, a colloidal carrousel structure. Our strategy should enable active systems to perform sophisticated tasks in future such as selective cell treatment.


Assuntos
Coloides/química , Condutividade Elétrica , Interações de Partículas Elementares , Escherichia coli/química , Ciência dos Materiais/métodos , Estrutura Molecular , Nanoestruturas/química , Tamanho da Partícula , Leveduras/química
7.
Soft Matter ; 16(21): 4932-4940, 2020 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-32435786

RESUMO

Experiments on supported lipid bilayers featuring liquid ordered/disordered domains have shown that the spatial arrangement of the lipid domains and their chemical composition are strongly affected by the curvature of the substrate. Furthermore, theoretical predictions suggest that both these effects are intimately related with the closed topology of the bilayer. In this work, we test this hypothesis by fabricating supported membranes consisting of colloidal particles of various shapes lying on a flat substrate. A single lipid bilayer coats both colloids and substrate, allowing local lipid exchange between them, thus rendering the system thermodynamically open, i.e. able to exchange heat and molecules with an external reservoir in the neighborhood of the colloid. By reconstructing the Gibbs phase diagram for this system, we demonstrate that the free-energy landscape is directly influenced by the geometry of the colloid. In addition, we find that local lipid exchange enhances the pinning of the liquid disordered phase in highly curved regions. This allows us to provide estimates of the bending moduli difference of the domains. Finally, by combining experimental and numerical data, we forecast the outcome of possible experiments on catenoidal and conical necks and show that these geometries could greatly improve the precision of the current estimates of the bending moduli.


Assuntos
Bicamadas Lipídicas/química , Coloides/química , Termodinâmica
8.
Nat Biomed Eng ; 4(5): 518-530, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32313101

RESUMO

The detection and quantification of low-abundance molecular biomarkers in biological samples is challenging. Here, we show that a plasmonic nanoscale construct serving as an 'add-on' label for a broad range of bioassays improves their signal-to-noise ratio and dynamic range without altering their workflow and readout devices. The plasmonic construct consists of a bovine serum albumin scaffold with approximately 210 IRDye 800CW fluorophores (with a fluorescence intensity approximately 6,700-fold that of a single 800CW fluorophore), a polymer-coated gold nanorod acting as a plasmonic antenna and biotin as a high-affinity biorecognition element. Its emission wavelength can be tuned over the visible and near-infrared spectral regions by modifying its size, shape and composition. It improves the limit of detection in fluorescence-linked immunosorbent assays by up to 4,750-fold and is compatible with multiplexed bead-based immunoassays, immunomicroarrays, flow cytometry and immunocytochemistry methods, and it shortens overall assay times (to 20 min) and lowers sample volumes, as shown for the detection of a pro-inflammatory cytokine in mouse interstitial fluid and of urinary biomarkers in patient samples.


Assuntos
Bioensaio/métodos , Corantes Fluorescentes/química , Nanopartículas/química , Animais , Células da Medula Óssea/citologia , Linhagem Celular Tumoral , Coloides/química , Células Dendríticas/citologia , Feminino , Citometria de Fluxo , Fluorescência , Humanos , Imunoensaio , Lipopolissacarídeos/farmacologia , Camundongos Endogâmicos C57BL , Microesferas , Proteômica , Padrões de Referência
9.
Food Chem ; 317: 126382, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32114277

RESUMO

Micro-viscosity is an important parameter to describe the microenvironment of the fat crystal network. In this study, we evaluated the micro-viscosity of the liquid oil confined in mixtures of palm kernel stearin (PKS)/soybean oil (SO) and fully hydrogenated rapeseed oil (FHRSO)/SO using molecular rotors. The micro-viscosity was shown to increase with solid fat content (SFC), as well as with high proportion of triglycerides that crystallized and formed stronger linked networks. In addition, the thickness of nanocrystals decreased with the increase of solid fat and denser fat crystal network appeared with larger box-counting fractal dimension. Mathematic fit analysis further indicated that molecular confinement of the oil was strongly dependent on the microstructure with high-space filling colloidal fat crystal networks. Larger box-counting fractal dimension led to higher micro-viscosity. However, the critical box-counting fractal dimension was found to be 1.86 irrespective of the nature of the network.


Assuntos
Óleo de Palmeira/química , Óleo de Brassica napus/química , Óleo de Soja/química , Compostos Azo , Coloides/química , Cristalização , Fluorescência , Nanopartículas/química , Nanopartículas/ultraestrutura , Viscosidade
10.
Chemosphere ; 252: 126517, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32217407

RESUMO

Estuaries are transitional water systems where the hydrodynamic processes governing water circulation actively influence suspended particle transport and deposition. In the estuarine mixing zone, the strong physico-chemical gradients resulting from the interaction between river freshwater and seawater may affect the distribution, mobility and fate of several potentially toxic compounds, among which trace elements are of major concern. Knowledge regarding the partitioning behaviour of trace elements would provide essential scientific support for the environmental management of estuaries. In this study, trace element occurrence and phase partitioning among suspended particulate matter, colloidal material and the truly dissolved fraction were investigated in the main Italian and Slovenian estuarine environments of the Gulf of Trieste (northern Adriatic Sea). Further information about the water quality at the river mouths was provided and, in addition to the traditional evaluation of single chemical parameters, a multi-way principal component analysis was employed in order to depict disparities among sampling sites, water layers and seasonal conditions with the final aim of evaluating trace element phase partitioning. Results indicated that the suspended particulate matter acts as the main effective vehicle for Cu, Cr, Fe, Ni and Pb, and enhanced adsorption processes resulted in elevated partitioning coefficients, especially for Fe and Pb. Although disparities occurred between sampling sites and seasons, trace elements showing affinity for the solid phase appeared to be partially bound to the colloidal material. Conversely, As and Cs prevailed in the truly dissolved fraction, especially in seawater and showed scarce affinity for both the suspended particles and colloids.


Assuntos
Monitoramento Ambiental , Oligoelementos/análise , Poluentes Químicos da Água/análise , Adsorção , Coloides/química , Poeira/análise , Estuários , Água Doce/química , Material Particulado/análise , Rios/química , Estações do Ano , Água do Mar/química
11.
J Food Sci ; 85(4): 989-997, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32198761

RESUMO

Protein-rich beverages have gained significant attention in recent years. It is a challenge to produce whey protein beverages with high stability, good transparency, and a smooth mouthfeel. The polysaccharide (PS)-protein complex might help the food industry overcome these obstacles. In this study, soybean soluble polysaccharide (SSPS) and high methoxylated pectin (HMP, a traditional PS) are used, at different ratios to the protein, to improve the colloidal stability of the acidified whey protein solution. Both heated and unheated complexes were studied. SSPS-whey protein complexes have shown exceptional stabilities in all ratios while HMP-whey protein complexes revealed coacervation after 72 hr of storage. The prepared complexes exhibited comparable sizes and ζ-potentials. The SSPS-whey protein complexes were less turbid than HMP-whey protein complexes at similar PS to protein ratios. Results also show that greater repulsive interactions occurred in SSPS-whey protein complexes when compared to HMP-whey protein complexes, as examined by free thiol content and intrinsic fluorescence intensity measurements. PRACTICAL APPLICATION: It is a challenge to produce whey protein isolate (WPI) beverages with high stability, good transparency, and smooth mouthfeel. The polysaccharide (PS)-protein complex might help the food industry overcome these obstacles. We have demonstrated that soybean soluble polysaccharide (SSPS), at [SSPS]:[acWPI] ratios of 1:2 to 1:30, can significantly improve the colloidal stability of the acidified whey protein beverages. This SSPS-whey protein system could be used as a stable beverage base for a variety of beverages.


Assuntos
Bebidas/análise , Polissacarídeos/química , Soja/química , Proteínas do Soro do Leite/química , Ácidos/química , Coloides/química , Carboidratos da Dieta/análise , Manipulação de Alimentos , Pectinas/química
12.
Proc Natl Acad Sci U S A ; 117(11): 5617-5623, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32132205

RESUMO

As a strategy for regulating entropy, thermal annealing is a commonly adopted approach for controlling dynamic pathways in colloid assembly. By coupling DNA strand-displacement circuits with DNA-functionalized colloid assembly, we developed an enthalpy-mediated strategy for achieving the same goal while working at a constant temperature. Using this tractable approach allows colloidal bonding to be programmed for synchronization with colloid assembly, thereby realizing the optimal programmability of DNA-functionalized colloids. We applied this strategy to conditionally activate colloid assembly and dynamically switch colloid identities by reconfiguring DNA molecular architectures, thereby achieving orderly structural transformations; leveraging the advantage of room-temperature assembly, we used this method to prepare a lattice of temperature-sensitive proteins and gold nanoparticles. This approach bridges two subfields: dynamic DNA nanotechnology and DNA-functionalized colloid programming.


Assuntos
DNA/química , Nanopartículas Metálicas/química , Polímeros Responsivos a Estímulos/química , Pareamento de Bases , Coloides/química , Ouro/química , Simulação de Dinâmica Molecular , Pressão , Conformação Proteica , Temperatura , Termodinâmica
13.
J Chem Phys ; 152(8): 084901, 2020 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-32113348

RESUMO

Recent experiments have shown how nematically ordered tactoid shaped actin droplets can be reorganized and divided by the action of myosin molecular motors. In this paper, we consider how similar morphological changes can potentially be achieved under equilibrium conditions. Using simulations, both atomistic and continuum, and a simple macroscopic model, we explore how the nucleation dynamics, shape changes, and the final steady state of a nematic tactoid droplet can be modified by interactions with model adhesive colloids that mimic a myosin motor cluster. We show how tactoid reorganization may occur in an equilibrium colloidal-nematic setting. We then suggest based on the simple macroscopic model how the simulation models may be extended to potentially stabilize divided tactoids.


Assuntos
Simulação de Dinâmica Molecular , Miosinas/química , Adesivos , Coloides/química , Tamanho da Partícula , Propriedades de Superfície
14.
Chemosphere ; 250: 126216, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32087384

RESUMO

Photodegradation of dissolved organic matter (DOM) is highly important in humic waters of peatland regions, yet the coupling between organic and organo-mineral colloids, trace metals and bioavailability of photodegraded products is poorly known. Here we studied photo-destruction of organo-mineral colloids induced by UV-irradiation of sterile-filtered mire water. We revealed two simultaneously occurring processes of transformation of DOM and trace elements speciation: (i) disintegration of high molecular weight organo-mineral colloids into lower molecular weight (<1 kDa) DOM and metal complexes and (ii) formation of particulate (>0.22 µm) aggregates of metals and organic matter. Over 26 days of UV-irradiation, up to 20% of dissolved organic carbon from peat waters was transformed into CO2. In addition to transformation of organic compounds, sizeable change in speciation and size fractionation of many trace metals such as Fe, Pb, Cd, Co, Zn, Cu, V, La, Ni and Cr occurred. Although short-term (1 day) UV-irradiation of mire water stimulated growth of cultivable Pseudomonas sp. bacterium, the long-term exposure (26 days) of organic substrate had a negative effect on bacterial development. Therefore, while sizeable transformation of the organic and metal colloidal load of peat water may occur over first 10 days of UV-irradiation, the enhanced bioavailability of UV-treated substrate is achieved after first day of exposure. The present study demonstrates the importance of even short-term UV-irradiation on colloidal transformation and potential bioavailability of humic waters from temperate mires and highlights the need for more detailed study of coupled metal-organic matter transformation induced by sunlight exposure of mire waters.


Assuntos
Coloides/química , Modelos Químicos , Rios/química , Complexos de Coordenação , Água Doce/química , Substâncias Húmicas/análise , Metais/análise , Minerais , Peso Molecular , Fotólise , Solo , Oligoelementos/análise , Raios Ultravioleta
15.
Chemosphere ; 248: 125992, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32006832

RESUMO

Natural colloids can influence the binding mechanisms between nano-hydroxyapatite (nHAP) and Cd(II). In this study, the effects of organic and inorganic natural colloids on Cd(II) sorption onto nHAP were compared. Different experimental approaches combined with the additivity model and the Extended-Derjaguin-Landau-Verwey-Overbeek model were used to quantify the distribution of Cd(II) in the systems of nHAP and natural colloid, and the interaction energy between particles. The results showed that both fulvic acid (FA) and montmorillonite colloid (MONT) had the promotion and inhibition effects on Cd(II) sorption onto nHAP. Coexistence of FA or MONT could stabilize nHAP particles. FA could adsorb onto nHAP particle surface via carboxylic and phenolic groups, which increased nHAP electronegativity and formed steric resistance effect. Coexistence of MONT mainly increased nHAP electronegativity. These effects prevented the reduction of the specific surface area of nHAP particles and increased the Cd(II) sorption onto nHAP. However, the inhibition effect on Cd(II) sorption was enhanced with increasing concentration of FA or MONT because more soluble FA-Cd or suspended MONT-Cd complexes formed in the system. In nHAP-FA-Cd systems, the Cd(II) sorption onto FA was well predicted but that onto solid phase was underestimated by the additivity model. In nHAP-MONT-Cd systems, Cd(II) sorbed onto mixtures of nHAP and MONT was well described by the additive model. The findings of this study can help to understand the fate of Cd(II) in natural water and soil.


Assuntos
Bentonita/química , Benzopiranos/química , Cádmio/química , Modelos Químicos , Poluentes do Solo/química , Adsorção , Cádmio/metabolismo , Coloides/química , Durapatita/química , Solo/química , Poluentes do Solo/análise , Água
16.
Proc Natl Acad Sci U S A ; 117(7): 3375-3381, 2020 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-32019883

RESUMO

When a colloidal suspension is dried, capillary pressure may overwhelm repulsive electrostatic forces, assembling aggregates that are out of thermal equilibrium. This poorly understood process confers cohesive strength to many geological and industrial materials. Here we observe evaporation-driven aggregation of natural and synthesized particulates, probe their stability under rewetting, and measure bonding strength using an atomic force microscope. Cohesion arises at a common length scale (∼5 µm), where interparticle attractive forces exceed particle weight. In polydisperse mixtures, smaller particles condense within shrinking capillary bridges to build stabilizing "solid bridges" among larger grains. This dynamic repeats across scales, forming remarkably strong, hierarchical clusters, whose cohesion derives from grain size rather than mineralogy. These results may help toward understanding the strength and erodibility of natural soils, and other polydisperse particulates that experience transient hydrodynamic forces.


Assuntos
Coloides/química , Solo/química , Hidrodinâmica , Tamanho da Partícula , Eletricidade Estática
17.
Macromol Rapid Commun ; 41(5): e1900555, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32003532

RESUMO

Structured color in nature is controlled by nano- and micro-structured interfaces giving rise to a photonic bandgap. This study presents a biomimetic optical material based on polymeric inverse opals that respond to enzyme activity. Polymer colloids provide a template in which acryloyl-functionalized poly(ethylene glycol) is integrated; dissolution of the colloids leads to a hydrogel inverse opal that can be lithographically patterned using transfer printing. Incorporating enzyme substrates within the voids provides a material that responds to the presence of proteases through a shift in the optical properties.


Assuntos
Materiais Biocompatíveis/química , Hidrogéis/química , Nanoestruturas/química , Peptídeo Hidrolases/metabolismo , Polímeros/química , Materiais Biomiméticos/química , Coloides/química , Cor , Iridescência , Microscopia Eletrônica de Varredura , Nanoestruturas/ultraestrutura , Fótons , Polietilenoglicóis/química , Polimetil Metacrilato/química , Impressão
18.
Food Chem ; 315: 126240, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-31991255

RESUMO

Water migration was used to depict the effect of hydrocolloids on the structural and textural properties of lotus seed starch (LS) during long-term retrogradation. The results showed that chitosan (CS) increased water migration and starch retrogradation of LS gel, causing the water molecules to easily diffuse as higher mobility free water (T24), which was strongly related to the higher short-range ordered and greater hardness of LS-CS gels. The addition of guar gum (GG) and xanthan (XN) interfered with water exudation, and thus increased the tightly bound water fraction (A21) of LS-GG blends and decreased the higher mobility free water fraction (A24) of LS-XN blends. This retarded the formation of ordered structures of LS gels, consequently, softening LS gel. GG performed better than XN in the above-mentioned effects due to their different molecular characteristics. Water migration can thus effectively depict the effect of hydrocolloids on the properties of LS.


Assuntos
Coloides/química , Lotus/química , Amido/química , Água/química , Quitosana/química , Galactanos/química , Géis/química , Mananas/química , Gomas Vegetais/química , Polissacarídeos Bacterianos/química , Sementes/química , Espectroscopia de Infravermelho com Transformada de Fourier , Análise Espectral Raman , Difração de Raios X
19.
IET Nanobiotechnol ; 14(1): 33-39, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31935675

RESUMO

Magnetic manotheranostics can be a fascinating charm to diagnose a tumour with MRI, and treatment through hyperthermia. This study aims to synthesise and characterise magnetically responsive polymer colloids (MRPCs). Healthy tissue damage done by chemotherapy session could be minimised by MRPCs. For the colloidal formulation of MRPCs, the oil in water emulsion technique was employed with the aid of sonication and stirring. The organic phase of emulsion contained methotrexate (MTX) drug, Eudragit E100 and CoFe2O4 (synthesised by co-precipitation) in ethanol, and the aqueous phase contained tween 80 in deionised water. The emulsion was optimised by studying/adjusting two different parameters, i.e. the concentration of constituents and sonication cycles. Multiple formulations were produced at sonication amplitude of 60% at 20 kHz, followed by centrifugation and lyophilisation. Characterisation of MRPCs was done for morphology, size measurement (23-25 nm), surface charge (∼15.12), coercivity (∼1549.6 G), magnetisation (2.6 emu) and retentivity (1.34 emu). Drug release in simulating physiological environment (pH = 7.4), was observed for up to 48 h, and, to determine the best release kinetic mechanism results were compared with kinetic models. Magnetic hyperthermia studies showed that MRPCs achieved an acceptable temperature of 42°C, for hyperthermia treatments in cancer patients.


Assuntos
Cobalto/química , Coloides/química , Composição de Medicamentos/métodos , Compostos Férricos/química , Metotrexato/química , Acrilatos/química , Hipertermia Induzida , Nanopartículas de Magnetita/química , Metotrexato/farmacocinética , Tamanho da Partícula , Polímeros/química
20.
J Fluoresc ; 30(1): 193-204, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31925653

RESUMO

Binding strength of the anti-diabetic drugs chlorpropamide (CPM) and tolbutamide (TBM) with model protein bovine serum albumin (BSA) shows strong modulation in presence of colloidal gold nanoparticles (AuNP). Intrinsic tryptophan fluorescence of both the native BSA and BSA-AuNP conjugate quenched in presence of the drugs. Stern-Volmer quenching constant (KSV) of CPM binding to BSA-AuNP conjugate at different temperatures is almost twice (6.76~14.76 × 103 M-1) than the corresponding values in native BSA (3.21~5.72 × 103 M-1). However, the calculated KSV values with TBM show certain degree of reduction in presence of AuNP (6.46× 103 M-1), while comparing with native BSA (8.83 × 103 M-1). The binding mode of CPM towards BSA-AuNP conjugate is mainly through hydrophobic forces; whereas, TBM binding is identified to be Van der Waal's and hydrogen bonding type of interaction. Fluorescence lifetime analysis confirms static type of quenching for the intrinsic tryptophan fluorescence of BSA as well as BSA-AuNP conjugate with addition of CPM and TBM at different concentrations. The α-helical content in the secondary structure of BSA is decreased to 48.32% and 45. 28% in presence of AuNP, when the concentration of CPM is 0.08 mM and 0.16 mM in comparison with that of native protein (50.13%). On the other hand, the intensity of sugar induced advanced glycated end (AGE) product fluorescence is decreased by 55% and 80% at 0.13 nM and 0.68 nM AuNP, respectively. Change in the binding strength of the drugs with transport protein and reduced AGE product formation in presence of AuNP could lead to a major development in the field of nanomedicine and associated drug delivery techniques. Graphical Abstract Modulated drug binding ability and AGE product formation of serum proteins in presence of AuNP.


Assuntos
Clorpropamida/farmacologia , Produtos Finais de Glicação Avançada/antagonistas & inibidores , Hipoglicemiantes/farmacologia , Soroalbumina Bovina/química , Tolbutamida/farmacologia , Adsorção , Animais , Sítios de Ligação/efeitos dos fármacos , Bovinos , Clorpropamida/química , Coloides/química , Produtos Finais de Glicação Avançada/metabolismo , Ouro/química , Ouro/farmacologia , Interações Hidrofóbicas e Hidrofílicas , Hipoglicemiantes/química , Nanopartículas Metálicas/química , Tamanho da Partícula , Soroalbumina Bovina/antagonistas & inibidores , Soroalbumina Bovina/metabolismo , Espectrometria de Fluorescência , Propriedades de Superfície , Temperatura , Tolbutamida/química
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