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Digitally-encoded poly(phosphodiesters) (d-PPDE) with highly complex primary structures are evaluated for layer-by-layer (LbL) assembly. To be easily decoded by mass spectrometry (MS), these digital polymers contain many different monomers: 2 coding units allowing binary encryption, 1 cleavable spacer allowing controlled MS fragmentation, and 3 mass tags allowing fragment identification. These complex heteropolymers are therefore composed of 6 different motifs. Despite this strong sequence heterogeneity, it is found that they enable a highly controlled LbL film formation. For instance, a regular growth is observed when alternating the deposition of negatively-charged d-PPDE and positively-charged poly(allyl amine hydrochloride) (PAH). Yet, in this approach, the interdistance between consecutive coded d-PPDE layers remains relatively small, which may be an issue for data storage applications, especially for the selective decoding of the stored information. Using poly(sodium 4-styrene sulfonate) (PSS) as an intermediate non-coded polyanion, it is shown that a controlled interdistance between d-PPDE layers can be easily achieved, while still maintaining a regular LbL growth. Last but not least, it is found in this work that d-PPDE of relatively small molecular weight (i.e., significantly smaller than those of PAH and PSS) still enables a controlled LbL assembly.
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A library of 16 digitally encoded polyanions was used in a layer-by-layer (LbL) polyelectrolyte assembly to nanofabricate thin films containing digitally coded strata. The polyanions were digital polyphosphodiesters (d-PPDE) prepared via an automated phosphoramidite process. Each component of the library contained 10 bytes of ASCII-encoded text (i.e. 80 coded monomers); thus the entire library allows the writing of a full sentence, which can be stored in a multilayer film as a sequence of sequences. To prepare fully segregated digital domains, non-coded layers composed of poly(allylamine hydrochloride) (PAH)/poly(sodium 4-styrenesulfonate) (PSS) were included between the d-PPDE coded layers as an intermediate barrier. Detailed analysis of the film homogeneity indicated formation of 70â nm-thick films in which digital layers are kept apart from another by non-coded interlayers. As a result, the sequence-coded polymer library could be piled-up in a defined sequence of layers.
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Cellulose-based nanocomposites are highly appealing for the development of next-generation sustainable functional materials. Although many advances have been made in this direction, the true potential of fibrillar nanocomposites has yet to be realized because available fabrication approaches are inadequate for achieving precise structural control at the sub-micrometer scale. Here a spray-assisted alignment methodology of cellulose nanofibrils is combined with the layer-by-layer assembly into an additive manufacturing process in which the alignment direction of each cellulose layer is rationally selected to achieve thin films with a helicoidal arrangement of the nanofibrils. The helicoidal structure of the films is verified by measuring the circular dichroism (CD) of the samples. The sign and position of the structural CD peak show that the handedness and the pitch of the chiral structures can be easily tuned by deliberately selecting simple parameters, such as the number of consecutive cellulose layers sprayed in the same direction, and the angle of rotation between successive stacks of layers. To the authors' knowledge, this approach is unique as it offers the possibility to prepare complex nanocomposite architectures with various nanoscale-controlled sub-structures from different anisometric objects, which is enabling novel designs of composite films with damage-resistant and/or optical filtering functionalities.
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Scientific interest in the self-assembly of collagen composite films has been increasing for their potential application in constructing bioactive materials. Here we report a highly stable and cytocompatible collagen/alginate (COL/ALG) ultrathin film, which was linearly fabricated via a layer-by-layer self-assembled technique. The variation in morphology and thickness of the films in air and in solutions with different pH and ion values were tested by atomic force microscopy. Results showed that the solutions with high pH values or solutions that contained electrolytes would disintegrate the film, while films with that were cross-linked for a long time prevented the dissolution and contributed to stability maintenance of the films. Interestingly, the COL/ALG coating not only improved the adhesion and proliferation of the human periodontal ligament cells, but also modified the morphology and migration of cells on the surface of glass and poly-L-lactic acid (PLA) electrospun scaffolds. In conclusion, the COL/ALG ultrathin films were highly stable and cytocompatible and could be easily fabricated by the cost-effective self-assembled technique presented. The findings of this study have the potential to play an important role in the surface modification of biomaterials.
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Alginatos/química , Colágenos Fibrilares/química , Alicerces Teciduais/química , Adesão Celular , Movimento Celular , Forma Celular , Células Cultivadas , Materiais Revestidos Biocompatíveis/química , Eletrólitos/química , Feminino , Vidro/química , Humanos , Concentração de Íons de Hidrogênio , Ácido Láctico/química , Teste de Materiais , Microscopia de Força Atômica , Ligamento Periodontal/citologia , Poliésteres , Polímeros/química , Estabilidade Proteica , Soluções , Propriedades de Superfície , Adulto JovemRESUMO
Among all methods available for the preparation of multifunctional nanostructured composite materials with remarkable functional properties, Layer-by-Layer (LbL) assembly is currently one of the most widely used techniques due to its environmental friendliness, its ease of use and its versatility in combining a plethora of available colloids and macromolecules into finely tuned multicomponent architectures with nanometer scale control. Despite the importance of these systems in emerging technologies, their nanoscopic 3D structure, and thus the ability to predict and understand the device performance, is still largely unknown. In this article, we use neutron scattering to determine the average conformation of individual deuterated polyelectrolyte chains inside LbL assembled films. In particular, we determine that in LbL-films composed of poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) multilayers prepared from 2 M sodium chloride solutions the PSS chains exhibit a flattened coil conformation with an asymmetry factor of around seven. Albeit this highly non-equilibrium state of the polymer chain, its density profiles follow Gaussian distributions occupying roughly the same volume as in the bulk complex.
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Leydig cells produce hormones required for the development and maintenance of sex characteristics and fertility in males. MEF2 transcription factors are important regulators of Leydig cell gene expression and steroidogenesis. ERK5 is an atypical member of the MAP kinase family that modulates transcription factor activity, either by direct phosphorylation or by acting as a transcriptional coactivator. While MEF2 and ERK5 are known to cooperate transcriptionally, the presence and role of ERK5 in Leydig cells remained unknown. Our goal was to determine whether ERK5 is present in Leydig cells and whether it cooperates with MEF2 to regulate gene expression. We found that ERK5 is present in Leydig cells in testicular tissue and immortalized cell lines. ERK5 knockdown in human chorionic gonadotrophin-treated MA-10 Leydig cells reduced steroidogenesis and decreased Star and Nr4a1 expression. Luciferase assays using a synthetic reporter plasmid containing 3 MEF2 elements revealed that ERK5 enhances MEF2-dependent promoter activation. Although ERK5 did not cooperate with MEF2 on the Star promoter in Leydig cell lines, we found that ERK5 and MEF2C do cooperate on the Nr4a1 promoter, which contains 2 adjacent MEF2 elements. Mutation of each MEF2 element in a short version of the Nr4a1 promoter significantly decreased the ERK5/MEF2C cooperation, indicating that both MEF2 elements need to be intact. The ERK5/MEF2C cooperation did not require phosphorylation of MEF2C on Ser387. Taken together, our data identify ERK5 as a new regulator of MEF2 activity in Leydig cells and provide potential new insights into mechanisms that regulate Leydig cell gene expression and function.
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Regulação da Expressão Gênica , Células Intersticiais do Testículo , Humanos , Masculino , Linhagem Celular , Células Intersticiais do Testículo/metabolismo , Fatores de Transcrição MEF2/genética , Fatores de Transcrição MEF2/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismoRESUMO
The adsorption of molecular films made of small molecules with a large intrinsic electrical dipole has been explored. The data indicate that such dipolar molecules may be used for altering the interface dipole screening at the metal electrode interface in organic electronics. More specifically, we have investigated the surface electronic spectroscopic properties of zwitterionic molecules containing 12π electrons of the p-benzoquinonemonoimine type, C(6)H(2)(···NHR)(2)(···O)(2)(R = H (1), n-C(4)H(9) (2), C(3)H(6)-S-CH(3) (3), C(3)H(6)-O-CH(3) (4), CH(2)-C(6)H(5) (5)), adsorbed on Au. These molecules are stable zwitterions by virtue of the meta positions occupied by the nitrogen and oxygen substituents on the central ring, respectively. The structures of 2-4 have been determined by single crystal X-ray diffraction and indicate that in these molecules, two chemically connected but electronically not conjugated 6π electron subunits are present, which explains their strong dipolar character. We systematically observed that homogeneous molecular films with thickness as small as 1 nm were formed on Au, which fully cover the surface, even for a variety of R substituents. Preferential adsorption toward the patterned gold areas on SiO(2) substrates was found with 4. Optimum self-assembling of 2 and 5 results in ordered close packed films, which exhibit n-type character, based on the position of the Fermi level close to the conduction band minimum, suggesting high conductivity properties. This new type of self-assembled molecular films offers interesting possibilities for engineering metal-organic interfaces, of critical importance for organic electronics.
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The development of nanoscale composites with hierarchical architecture and complex anisotropies enables the fabrication of new classes of devices. Stretchable strain sensors have been developed in the past for applications in various fields such as wearable electronics and soft robotics, yet the sensing capacities of most of these sensors are independent of the direction of deformation. In the present work, we report on the preparation of a direction-sensitive strain sensor using the anisotropic optical properties of a monolayer of oriented plasmonic 1D nano-objects. Grazing incidence spraying (GIS) is used for depositing a monolayer of in-plane aligned silver nanowires with a controlled density on a deformable and transparent substrate. Using the selective excitation of transverse and longitudinal localized plasmon resonance modes of silver nanowires by polarized UV-visible-NIR spectroscopy, we show that the macroscopic anisotropic properties of the monolayer upon stretching are highly dependent on the stretching direction and light polarization. Measuring the polarized optical properties of the anisotropic thin films upon stretching thus allow for retrieving both the local strain and the direction of the deformation using a simple model.
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Virtually transparent films of Aeroxide TiO(2) P25 were fabricated via layer-by-layer assembly with sodium poly(styrene sulfonate). Nanoscale films are formed on model surfaces for characterization or inside of cylindrical reactors for investigating the catalytic properties. Films are fairly homogeneous and smooth over large areas and show different optical interference colors depending on film thickness. The application-relevant photocatalytic performance of such films toward on-flow degradation of hydrogen sulfide under UV-A irradiation was investigated. Scanning electron microscopy reveals a nanoporous structure allowing for the permeation of gas. Consequently, the catalytic efficiency of the films increases with increasing film thickness retaining a considerable activity of the corresponding nanoparticle powder. Scheme 1 depicts in a general way the functionalized reactor and the principle of the measurement.
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Poluentes Atmosféricos/química , Eletrólitos/química , Sulfeto de Hidrogênio/química , Nanopartículas/química , Dióxido de Enxofre/química , Catálise , Processos Fotoquímicos , Raios UltravioletaRESUMO
Natural structural materials frequently consist of multimaterial nanocomposites with complex superstructure giving rise to exceptional mechanical properties, but also commonly preventing access to their synthetic reproduction. Here we present the spin-assisted layer-by-layer assembly of anisotropic wood-inspired films composed of anionic cellulose nanofibrils and cationic poly(vinyl amine) possessing a tensile strength that exceeds that of the wood from which the fibers originate. The degree of orientation of the nanofibrils was studied by atomic force microscopy and depends strongly on the distance from the center of the spun surface. The nanofibrils are preferentially aligned in the direction of the shear flow, and consequently, the mechanical properties of such films differ substantially when measured parallel and perpendicular to the fibril orientation direction. For enabling a diversity of bioinspired applications including sensing, packaging, electronics, or optics, the preparation of nanocomposite materials and devices with anisotropic physical properties requires an extreme level of control over the positioning and alignment of nanoscale objects within the matrix material.
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BACKGROUND: Recent technologies, such as the iPod, are often equipped with an accelerometer and magnetometer, which, through software applications, can perform various inclinometric functions. These applications have the potential to measure and quantify range of motion (ROM). OBJECTIVE: The purpose of this study was to estimate the iPod "Gyroscope" application intra- and inter-rater reliability as well as its criterion validity in healthy participants lumbar ROM assessment. METHODS: The sample consisted of 29 healthy participants. For the estimation of intra- and inter-reliability, two examiners measured the lumbar ROM of each participant twice using the iPod. To estimate the criterion validity, the measures were compared to those obtained with the Back Range of Motion Device (BROM; lateral flexion) and the double inclinometer (flexion and extension). Reliability and validity were then established using the intraclass correlation coefficient (ICC). RESULTS: We observed a moderate to high intra-rater reliability (ICCs = 0.67-0.91) and a moderate to high inter-rater reliability for each movement (ICCs = 0.72-0.89). For the criterion validity, the ICCs were all high (ICCs = 0.65-0.89). CONCLUSION: Our results provide evidence that the iPod "Gyroscope" application can be used to assess lumbar ROM for all movements.
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Movimento/fisiologia , Amplitude de Movimento Articular/fisiologia , Adulto , Feminino , Voluntários Saudáveis , Humanos , Dor Lombar/diagnóstico , Dor Lombar/fisiopatologia , MP3-Player , Masculino , Variações Dependentes do Observador , Reprodutibilidade dos Testes , Software , Adulto JovemRESUMO
Metal nanoparticle coatings are widely employed as fluorescence-enhanced platforms for high-throughput biological detection; however, complex manufacturing technologies and stringent fabrication procedures hinder their development for use in bioassays. Here, we present the preparation of fluorescence-based bioassay platforms using spray-assisted step-by-step assembly of silver nanoparticles (Ag NPs) and poly(diallyldimethylammonium chloride) (PDDA). This approach allowed us to control the density and the degree of aggregation of Ag NPs on large surfaces which are prerequisites for the development of bioassay platforms with a substantial fluorescence enhancement. After one assembly cycle (1-Ag platform) the adsorbed particles are not forming aggregates or ones composed of very few particles which, as expected, led to poor fluorescence enhancement (1.1) for cyanine 5. Further assembly steps induce the clustering of Ag NPs by multiple electrostatic interactions between PDDA and Ag NPs and thus increase the number of nanoparticles per aggregate in a controlled way. We observed that the nanoparticle island growth takes place first mainly in the plane (2D) and then in the plane and in the third dimension and that the aggregate morphology (2D versus 3D) strongly affects the plasmonic fluorescence enhancement of the fluorescent dye. A substantial fluorescence enhancement (12.3) was measured for a Ag NP platform obtained after twelve assembly cycles. This result is within the ballpark of values reported in the literature for bioassay platforms using metal nanoparticles and opens the route towards the preparation of fluorescence-based bioassay platforms on the large scale.
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Corantes Fluorescentes , Nanopartículas Metálicas , Prata , Bioensaio , Análise por Conglomerados , Polietilenos , Compostos de Amônio QuaternárioRESUMO
We present a simple yet efficient method for orienting cellulose nanofibrils in layer-by-layer assembled films through spray-assisted alignment. While spraying at 90° against a receiving surface produces films with homogeneous in-plane orientation, spraying at smaller angles causes a macroscopic directional surface flow of liquid on the receiving surface and leads to films with substantial in-plane anisotropy when nanoscale objects with anisotropic shapes are used as components. First results with cellulose nanofibrils demonstrate that such fibrils are easily aligned by grazing incidence spraying to yield optically birefringent films over large surface areas. We show that the cellulosic nanofibrils are oriented parallel to the spraying direction and that the orientational order depends for example on the distance of the receiving surface from the spray nozzle. The alignment of the nanofibrils and the in-plane anisotropy of the films were independently confirmed by atomic force microscopy, optical microscopy between crossed polarizers, and the ellipsometric determination of the apparent refractive index of the film as a function of the in-plane rotation of the sample with respect to the plane of incidence of the ellipsometer.
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Layer-by-Layer (LbL) assemblies of heparin (Hep) and chitosan (Chi) were prepared for use as reservoirs for acidic and basic fibroblast growth factors (aFGFs and bFGFs, respectively). The effects of the architecture and composition of the reservoirs on the viability and proliferation of NIH-3T3 fibroblast cells were studied under starvation conditions. The reservoir stability was monitored by ellipsometry. The aFGF and bFGF loadings were determined using a dissipation-enhanced quartz crystal microbalance (QCM-D). Stability and release assays were performed in a phosphate buffer at physiological conditions. The results demonstrated that the amount of aFGF and bFGF loaded into and released from LbL reservoirs composed of 3 and 6 layer pairs could be controlled. Cell culture assays in low serum culture medium (LSCM) demonstrated that incorporating very small amounts of aFGF and bFGF into the (Hep/Chi)n multilayers significantly improved the proliferation of the NIH-3T3 fibroblasts. The cells did not proliferate on (Hep/Chi)n assemblies prepared in the absence of FGF under identical conditions. The LbL reservoirs were highly effective for the long-term storage (up to 9 months) of aFGF and bFGF. This work demonstrates the potential of LbL reservoirs for use as biomaterial coatings.
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Quitosana/química , Preparações de Ação Retardada/farmacologia , Fator 1 de Crescimento de Fibroblastos/farmacologia , Fator 2 de Crescimento de Fibroblastos/farmacologia , Heparina/química , Animais , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Preparações de Ação Retardada/síntese química , Preparações de Ação Retardada/metabolismo , Composição de Medicamentos , Liberação Controlada de Fármacos , Fator 1 de Crescimento de Fibroblastos/metabolismo , Fator 2 de Crescimento de Fibroblastos/metabolismo , Cinética , Camundongos , Células NIH 3T3 , Polietilenoimina/químicaRESUMO
Layer-by-layer (LbL) assembled multicomponent films offer the opportunity to control and to fine-tune cell attachment and behavior on solid surfaces [Layer-by-Layer Films for Biomedical Applications, edited by Picart et al. (Wiley, Weinheim, 2014) and El-Khouri et al., "Multifunctional layer-by-layer architectures for biological applications," in Functional Polymeric Ultrathin Films, edited by Advincula and Knoll (Wiley, Weinheim, 2011), Vol. 1]. At the same time, these films allow for quite detailed physicochemical characterization of static and dynamic surface properties that are typically not available in classic cell culture. In this report, the authors investigate cell adhesion and cytocompatibility of compositionally and morphologically similar thin films composed of oppositely charged synthetic or natural polyelectrolytes in which different physical parameters such as surface charge or water content are varied through chemical composition and deposition conditions. Human adult dermal fibroblasts were chosen as a model because of the need for chemically defined matrix in the field of primary cell amplification. The growth and the stability of the multilayer films in the incubation media were studied dissipation-enhanced quartz crystal micobalance (QCM-D) and ellipsometry. The QCM-D signals observed during the film deposition were analyzed qualitatively to estimate the viscoelastic properties of the films. The authors used contact angle measurements with water to study the contribution of the chemical functionalities to wetting behavior of the films. Most importantly, they also studied the interaction of the films with serum components. Our results underline that cell adhesion is a highly complex process which is not only governed by the functionality of a surface but also by its morphology, its affinity for serum components, and also by changes of surface properties brought about by adsorbing molecules. Of the many LbL-films tested, poly(4-styrenesulfonate)/poly(allyl amine) multilayers were best suited for our fibroblast cultures, which opens a way to avoid gelatin based and similar substrates whose exact chemical composition is unknown.
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Materiais Biocompatíveis/química , Adesão Celular , Fenômenos Químicos , Fibroblastos/fisiologia , Propriedades de Superfície , Células Cultivadas , Humanos , Soro/metabolismoRESUMO
Heparin and different chitosan derivatives were applied to produce stable electrostatic layer-by-layer assemblies and further used as coating technique to inhibit natural inflammatory response to implants. Heparin was assembled with chitosan and N-methylated chitosan derivatives, namely N,N-dimethyl chitosan (DMC) and N,N,N-trimethyl chitosan (TMC), by dipping method. DMC and TMC (chitosan derivatives) were synthesized and characterized before LbL assembly. Ellipsometry, quartz crystal microbalance (QCM-D), and contact angle were used to demonstrate the deposition of polyelectrolyte multilayers onto silicon wafers using polyelectrolyte solutions with different ionic strength. The biological properties of these films were evaluated by cell culture assays using NIH/3T3 fibroblast cells. LbL assemblies of Heparin and chitosan derivatives showed to be biocompatible, and at the same time they strongly hinder the proliferation speed of fibroblasts up to 40-fold factors. Therefore, the multilayers prepared from heparin and chitosan derivatives have good features to be used as an alternative coating treatment for biomedical implants with reduced body rejection properties.
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Materiais Biocompatíveis/farmacologia , Quitosana/análogos & derivados , Quitosana/farmacologia , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Heparina/análogos & derivados , Heparina/farmacologia , Eletricidade Estática , Animais , Materiais Biocompatíveis/síntese química , Materiais Biocompatíveis/química , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Quitosana/síntese química , Quitosana/química , Heparina/síntese química , Heparina/química , Camundongos , Células NIH 3T3 , Tamanho da Partícula , Cloreto de Sódio/farmacologia , Propriedades de SuperfícieRESUMO
Nanocomposite films possessing multiple interesting properties (mechanical strength, optical transparency, self-healing, and partial biodegradability) are discussed. We used Layer-by-Layer assembly to prepare micron thick wood-inspired films from anionic nanofibrillated cellulose and cationic poly(vinyl amine). The film growth was carried out at different pH values to obtain films of different chemical composition, whereby, and as expected, higher pH values led to a higher polycation content and also to 6 times higher film growth increments (from 9 to 55 nm per layer pair). In the pH range from 8 to 11, micron thick and optically transparent LbL films are obtained by automated dipping when dried regularly in a stream of air. Films with a size of 10 cm(2) or more can be peeled from flat surfaces; they show tensile strengths up to about 250 MPa and Young's moduli up to about 18 GPa as controlled by the polycation/polyanion ratio of the film. Experiments at different humidities revealed the plasticizing effect of water in the films and allowed reversible switching of their mechanical properties. Whereas dry films are strong and brittle (Young's modulus: 16 GPa, strain at break: 1.7%), wet films are soft and ductile (Young's modulus: 0.1 GPa, strain at break: 49%). Wet film surfaces even amalgamate upon contact to yield mechanically stable junctions. We attribute the switchability of the mechanical properties and the propensity for self-repair to changes in the polycation mobility that are brought about by the plastifying effect of water.
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Materiais Biomiméticos/química , Celulose/química , Fenômenos Mecânicos , Nanocompostos/química , Fenômenos Ópticos , Madeira , Concentração de Íons de Hidrogênio , Plastificantes/química , Propriedades de Superfície , Água/químicaRESUMO
Neutral hybrid 2-D networks have been generated using a bis-amidinium capable of chelating M(CN)6(3-) anions via hydrogen bonds: the packing of the achiral 2-D networks leads to channels which are occupied by water molecules forming polymeric H-bonded chains; furthermore, owing to the dihapto mode of H-bonding, the presence of supramolecular chirality of the delta' and lambda' types taking place within the second coordination sphere of the metallic centre has been demonstrated.