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1.
ACS Omega ; 2(6): 2630-2638, 2017 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-31457604

RESUMO

Solution processing-based fabrication techniques such as liquid phase exfoliation may enable economically feasible utilization of graphene and related nanomaterials in real-world devices in the near future. However, measurement of the thickness of the thin film structures fabricated by these approaches remains a significant challenge. By using surface plasmon resonance (SPR), a simple, accurate, and quick measurement of the deposited thickness for inkjet-printed graphene thin films is reported here. We show that the SPR technique is convenient and well-suited for the measurement of thin films formulated from nanomaterial inks, even at sub-10 nm thickness. We also demonstrate that the analysis required to obtain results from the SPR measurements is significantly reduced compared to that required for atomic force microscopy (AFM) or stylus profilometer, and much less open to interpretation. The gathered data implies that the film thickness increases linearly with increasing number of printing repetitions. In addition, SPR also reveals the complex refractive index of the printed thin films composed of exfoliated graphene flakes, providing a more rigorous explanation of the optical absorption than that provided by a combination of AFM/profilometer and the extinction coefficient of mechanically exfoliated graphene flakes. Our results suggest that the SPR method may provide a new pathway for the thickness measurement of thin films fabricated from any nanomaterial containing inks.

2.
Int J Pharm ; 494(1): 531-6, 2015 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-26319634

RESUMO

The aim of the present study is to monitor the release of perphenazine (PPZ) from thin polymer films in real-time by the multi-parametric surface plasmon resonance method (MP-SPR). The MP-SPR method is capable of measuring changes in polymer films that are significantly thicker than the apparent scanning depth of the SPR field. The in vitro reference measurements confirm that the MP-SPR results can be correlated to the in vitro release of PPZ. However, information gained by MP-SPR can be used to identify three different modes of change in the films with different kinetic timescales, which are not visible in the in vitro testing. The EUDRAGIT(®) RL PO-PVP-PPZ-film shows significantly faster changes than the film without polyvinylpyrroline (PVP). This information can be used to optimize the drug-release profile of different film formulations for different pharmaceutical purposes.


Assuntos
Liberação Controlada de Fármacos , Perfenazina/química , Polímeros/química , Ressonância de Plasmônio de Superfície , Cinética , Ácidos Polimetacrílicos/química , Povidona/química
3.
Langmuir ; 30(10): 2799-809, 2014 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-24564782

RESUMO

In this study, surface coatings were used to control the morphology of the deposited lipid layers during vesicle spreading, i.e., to control if liposomes self-assemble on a surface into a supported lipid bilayer or a supported vesicular layer. The influence of the properties of the surface coating on formation of the deposited lipid layer was studied with quartz crystal microbalance and two-wavelength multiparametric surface plasmon resonance techniques. Control of lipid self-assembly on the surface was achieved by two different types of soft substrate materials, i.e., dextran and thiolated polyethylene glycol, functionalized with hydrophobic linkers for capturing the lipid layer. The low-molecular-weight dextran-based surface promoted formation of supported lipid bilayers, while the thiolated polyethylene glycol-based surface promoted supported vesicular layer formation. A silicon dioxide surface was used as a reference surface in both measurement techniques. In addition to promoting supported lipid bilayer formation of known lipid mixtures, the dextran surface also promoted supported lipid bilayer formation of vesicles containing the cell membrane extract of human hepatoblastoma cells. The new dextran-based surface was also capable of protecting the supported lipid bilayer against dehydration when exposed to a constant flow of air. The well-established quartz crystal microbalance technique was effective in determining the morphology of the formed lipid layer, while the two-wavelength surface plasmon resonance analysis enabled further complementary characterization of the adsorbed supported lipid bilayers and supported vesicular layers.


Assuntos
Bicamadas Lipídicas/química , Linhagem Celular Tumoral , Humanos , Propriedades de Superfície
4.
Sensors (Basel) ; 13(11): 15348-63, 2013 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-24217357

RESUMO

Surface plasmon resonance (SPR) is a well-established optical biosensor technology with many proven applications in the study of molecular interactions as well as in surface and material science. SPR is usually applied in the label-free mode which may be advantageous in cases where the presence of a label may potentially interfere with the studied interactions per se. However, the fundamental challenges of label-free SPR in terms of limited sensitivity and specificity are well known. Here we present a new concept called label-enhanced SPR, which is based on utilizing strongly absorbing dye molecules in combination with the evaluation of the full shape of the SPR curve, whereby the sensitivity as well as the specificity of SPR is significantly improved. The performance of the new label-enhanced SPR method was demonstrated by two simple model assays: a small molecule assay and a DNA hybridization assay. The small molecule assay was used to demonstrate the sensitivity enhancement of the method, and how competitive assays can be used for relative affinity determination. The DNA assay was used to demonstrate the selectivity of the assay, and the capabilities in eliminating noise from bulk liquid composition variations.


Assuntos
Técnicas Biossensoriais/métodos , Ressonância de Plasmônio de Superfície/métodos , Bioensaio/métodos , DNA/análise
5.
PLoS One ; 8(8): e72192, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24015218

RESUMO

In vitro cell-based assays are widely used during the drug discovery and development process to test the biological activity of new drugs. Most of the commonly used cell-based assays, however, lack the ability to measure in real-time or under dynamic conditions (e.g. constant flow). In this study a multi-parameter surface plasmon resonance approach in combination with living cell sensing has been utilized for monitoring drug-cell interactions in real-time, under constant flow and without labels. The multi-parameter surface plasmon resonance approach, i.e. surface plasmon resonance angle versus intensity plots, provided fully specific signal patterns for various cell behaviors when stimulating cells with drugs that use para- and transcellular absorption routes. Simulated full surface plasmon resonance angular spectra of cell monolayers were compared with actual surface plasmon resonance measurements performed with MDCKII cell monolayers in order to better understand the origin of the surface plasmon resonance signal responses during drug stimulation of cells. The comparison of the simulated and measured surface plasmon resonance responses allowed to better understand and provide plausible explanations for the type of cellular changes, e.g. morphological or mass redistribution in cells, that were induced in the MDCKII cell monolayers during drug stimulation, and consequently to differentiate between the type and modes of drug actions. The multi-parameter surface plasmon resonance approach presented in this study lays the foundation for developing new types of cell-based tools for life science research, which should contribute to an improved mechanistic understanding of the type and contribution of different drug transport routes on drug absorption.


Assuntos
Avaliação Pré-Clínica de Medicamentos/métodos , Ressonância de Plasmônio de Superfície , Animais , Adesão Celular , Cães , Células Madin Darby de Rim Canino , Manitol/farmacologia , Modelos Biológicos , Propranolol/farmacologia
6.
Langmuir ; 29(27): 8561-71, 2013 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-23758623

RESUMO

A three-wavelength angular-scanning surface plasmon resonance based analysis has been utilized for characterizing optical properties of organic nanometer-thick layers with a wide range of thicknesses. The thickness and refractive index were determined for sample layers with thicknesses ranging from subnanometer to hundreds of nanometers. The analysis approach allows for simultaneous determination of both the refractive index and thickness without prior knowledge of either the refractive index or the thickness of the sample layers and without the help of other instruments, as opposed to current methods and approaches for characterizing optical properties of organic nanometer-thick layers. The applicability of the three-wavelength angular-scanning surface plasmon resonance approach for characterizing thin and thick organic layers was demonstrated by ex situ deposited mono- and multilayers of stearic acid and hydrogenated soy phosphatidylcholine and in situ layer-by-layer deposition of two different polyelectrolyte multilayer systems. In addition to the three-wavelength angular-scanning surface plasmon resonance approach, another surface plasmon resonance optical phenomenon, i.e., the surface plasmon resonance waveguide mode, was utilized to characterize organic sample layers whose thicknesses border the micrometer scale. This was demonstrated by characterizing both in situ layer-by-layer deposited polyelectrolyte multilayer systems and an ex situ deposited spin-coated polymer layer.


Assuntos
Polímeros/química , Ressonância de Plasmônio de Superfície , Tamanho da Partícula , Propriedades de Superfície
7.
PLoS One ; 7(4): e35630, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22536418

RESUMO

Dysregulation of PKCε is involved in several serious diseases such as cancer, type II diabetes and Alzheimer's disease. Therefore, specific activators and inhibitors of PKCε hold promise as future therapeutics, in addition to being useful in research into PKCε regulated pathways. We have previously described llama single chain antibodies (VHHs) that specifically activate (A10, C1 and D1) or inhibit (E6 and G8) human recombinant PKCε. Here we report a thorough kinetic analysis of these VHHs. The inhibiting VHHs act as non-competitive inhibitors of PKCε activity, whereas the activating VHHs have several different modes of action, either increasing V(max) and/or decreasing K(m) values. We also show that the binding of the VHHs to PKCε is conformation-dependent, rendering the determination of affinities difficult. Apparent affinities are in the micromolar range based on surface plasmon resonance studies. Furthermore, the VHHs have no effect on the activity of rat PKCε nor can they bind the rat form of the protein in immunoprecipitation studies despite the 98% identity between the human and rat PKCε proteins. Finally, we show for the first time that the VHHs can influence PKCε function also in cells, since an activating VHH increases the rate of PKCε translocation in response to PMA in HeLa cells, whereas an inhibiting VHH slows down the translocation. These results give insight into the mechanisms of PKCε activity modulation and highlight the importance of protein conformation on VHH binding.


Assuntos
Ativadores de Enzimas/farmacologia , Proteína Quinase C-épsilon/metabolismo , Anticorpos de Cadeia Única/farmacologia , Animais , Encéfalo/enzimologia , Ativação Enzimática , Proteínas de Fluorescência Verde/metabolismo , Células HeLa , Humanos , Cinética , Ligação Proteica , Proteína Quinase C-épsilon/antagonistas & inibidores , Proteína Quinase C-épsilon/química , Transporte Proteico , Ratos , Proteínas Recombinantes de Fusão/metabolismo , Anticorpos de Cadeia Única/biossíntese , Anticorpos de Cadeia Única/química , Especificidade da Espécie , Ressonância de Plasmônio de Superfície , Acetato de Tetradecanoilforbol/farmacologia
8.
Macromol Rapid Commun ; 31(22): 1977-80, 2010 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-21567621

RESUMO

By using an advanced polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS) device it is possible to study the photopolymerization of an ultrathin layer of a porphyrin monomer in real time. The method can be compared with the indirect UV/Vis method previously introduced by our group. With PM-IRRAS it is possible to analyze polymerization kinetics of photopolymerization at various temperatures to determine the activation energy of the reaction.

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