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1.
Rev Sci Instrum ; 93(11): 114102, 2022 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-36461462

RESUMO

Neutron reflectivity at the solid/liquid interface offers unique opportunities for resolving the structure-function relationships of interfacial layers in soft matter science. It is a non-destructive technique for detailed analysis of layered structures on molecular length scales, providing thickness, density, roughness, and composition of individual layers or components of adsorbed films. However, there are also some well-known limitations of this method, such as the lack of chemical information, the difficulties in determining large layer thicknesses, and the limited time resolution. We have addressed these shortcomings by designing and implementing a portable sample environment for in situ characterization at neutron reflectometry beamlines, integrating infrared spectroscopy under attenuated total reflection for determination of molecular entities and their conformation, and spectroscopic ellipsometry for rapid and independent measurement of layer thicknesses and refractive indices. The utility of this combined setup is demonstrated by two projects investigating (a) pH-dependent swelling of polyelectrolyte layers and (b) the impact of nanoparticles on lipid membranes to identify potential mechanisms of nanotoxicity.


Assuntos
Nanopartículas , Nêutrons , Espectrofotometria Infravermelho , Síncrotrons , Fatores de Tempo
2.
Langmuir ; 38(45): 14004-14015, 2022 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-36377414

RESUMO

Self-initiated photografting and photopolymerization (SI-PGP) uses UV illumination to graft polymers to surfaces without additional photoinitiators using the monomers as initiators, "inimers". A wider use of this method is obstructed by a lack of understanding of the resulting, presumably heterogeneous, polymer structure and of the parallel degradation under continuous UV illumination. We have used neutron reflectometry to investigate the structure of hydrated SI-PGP-prepared poly(HEMA-co-PEG10MA) (poly(2-hydroxyethyl methacrylate-co-(ethylene glycol)10 methacrylate)) films and compared parabolic, sigmoidal, and Gaussian models for the polymer volume fraction distributions. Results from fitting these models to the data suggest that either model can be used to approximate the volume fraction profile to similar accuracy. In addition, a second layer of deuterated poly(methacrylic acid) (poly(dMAA)) was grafted over the existing poly(HEMA-co-PEG10MA) layer, and the resulting double-grafted films were also studied by neutron reflectometry to shed light on the UV-polymerization process and the inevitable UV-induced degradation which competes with the grafting.


Assuntos
Metacrilatos , Polímeros , Propriedades de Superfície , Metacrilatos/química , Polímeros/química , Polimerização
3.
ACS Appl Mater Interfaces ; 14(37): 41790-41799, 2022 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-36074978

RESUMO

Cells adhering onto surfaces sense and respond to chemical and physical surface features. The control over cell adhesion behavior influences cell migration, proliferation, and differentiation, which are important considerations in biomaterial design for cell culture, tissue engineering, and regenerative medicine. Here, we report on a supramolecular-based approach to prepare reversible self-assembled monolayers (rSAMs) with tunable lateral mobility and dynamic control over surface composition to regulate cell adhesion behavior. These layers were prepared by incubating oxoacid-terminated thiol SAMs on gold in a pH 8 HEPES buffer solution containing different mole fractions of ω-(ethylene glycol)2-4- and ω-(GRGDS)-, α-benzamidino bolaamphiphiles. Cell shape and morphology were influenced by the strength of the interactions between the amidine-functionalized amphiphiles and the oxoacid of the underlying SAMs. Dynamic control over surface composition, achieved by the addition of inert filler amphiphiles to the RGD-functionalized rSAMs, reversed the cell adhesion process. In summary, rSAMs featuring mobile bioactive ligands offer unique capabilities to influence and control cell adhesion behavior, suggesting a broad use in biomaterial design, tissue engineering, and regenerative medicine.


Assuntos
Materiais Biocompatíveis , Ouro , Amidinas , Materiais Biocompatíveis/farmacologia , Adesão Celular/fisiologia , Etilenoglicol/química , Ouro/farmacologia , HEPES , Cetoácidos , Oligopeptídeos , Compostos de Sulfidrila , Propriedades de Superfície
4.
Langmuir ; 38(5): 1725-1737, 2022 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-35081310

RESUMO

We have prepared a series of ampholytic polymer films, using a self-initiated photografting and photopolymerization (SI-PGP) method to sequentially polymerize first anionic (deuterated methacrylic acid (dMAA)) and thereafter cationic (2-aminoethyl methacrylate (AEMA)) monomers to investigate the SI-PGP grafting process. Dry films were investigated by ellipsometry, X-ray, and neutron reflectometry, and their swelling was followed over a pH range from 4.5 to 10.5 with spectroscopic ellipsometry. The deuterated monomer allows us to separate the distributions of the two components by neutron reflectometry. Growth of both polymers proceeds via grafting of solution-polymerized fragments to the surface, and also the second layer is primarily grafted to the substrate and not as a continuation of the existing chains. The polymer films are stratified, with one layer of near 1:1 composition and the other layer enriched in one component and located either above or below the former layer. The ellipsometry results show swelling transitions at low and high pH but with no systematic variation in the pH values where these transitions occur. The results suggest that grafting density in SI-PGP-prepared homopolymers could be increased via repeated polymerization steps, but that this process does not necessarily increase the average chain length.

5.
Mar Biotechnol (NY) ; 23(5): 724-735, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34528162

RESUMO

Sea stars can adhere to various underwater substrata using an adhesive secretion of which Sfp1 is a major component. Sfp1 is a multimodular protein composed of four subunits (Sfp1 Alpha, Beta, Delta, and Gamma) displaying different functional domains. We recombinantly produced two fragments of Sfp1 comprising most of its functional domains: the C-terminal part of the Beta subunit (rSfp1 Beta C-term) and the Delta subunit (rSfp1 Delta). Surface plasmon resonance analyses of protein adsorption onto different model surfaces showed that rSfp1 Beta C-term exhibits a significantly higher adsorption than the fibrinogen control on hydrophobic, hydrophilic protein-resistant, and charged self-assembled monolayers, while rSfp1 Delta adsorbed more on negatively charged and on protein-resistant surfaces compared to fibrinogen. Truncated recombinant rSfp1 Beta C-term proteins were produced in order to investigate the role of the different functional domains in the adsorption of this protein. The analysis of their adsorption capacities on glass showed that two mechanisms are involved in rSfp1 Beta C-term adsorption: (1) one mediated by the EGF-like domain and involving Ca2+ and Mg2+ ions, and (2) one mediated by the sequence of Sfp1 Beta with no homology with known functional domain in databases, in the presence of Na+, Ca2+ and Mg2+ ions.


Assuntos
Adesivos/química , Proteínas/química , Estrelas-do-Mar/química , Adsorção , Animais , Subunidades Proteicas/química , Proteínas Recombinantes , Ressonância de Plasmônio de Superfície
6.
Int J Mol Sci ; 21(9)2020 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-32365555

RESUMO

O-methyl-serine dodecylamine hydrochloride (MSDH) is a detergent that accumulates selectively in lysosomes, a so-called lysosomotropic detergent, with unexpected chemical properties. At physiological pH, it spontaneously forms vesicles, which disassemble into small aggregates (probably micelles) below pH 6.4. In this study, we characterize the interaction between MSDH and liposomes at different pH and correlate the findings to toxicity in human fibroblasts. We find that the effect of MSDH on lipid membranes is highly pH-dependent. At neutral pH, the partitioning of MSDH into the liposome membrane is immediate and causes the leakage of small fluorophores, unless the ratio between MSDH and lipids is kept low. At pH 5, the partitioning of MSDH into the membrane is kinetically impeded since MSDH is charged and a high ratio between MSDH and the lipids is required to permeabilize the membrane. When transferred to cell culture conditions, the ratio between MSDH and plasma membrane lipids must therefore be low, at physiological pH, to maintain plasma membrane integrity. Transmission electron microscopy suggests that MSDH vesicles are taken up by endocytosis. As the pH of the endosomal compartment progressively drops, MSDH vesicles disassemble, leading to a high concentration of increasingly charged MSDH in small aggregates inside the lysosomes. At sufficiently high MSDH concentrations, the lysosome is permeabilized, the proteolytic content released to the cytosol and apoptotic cell death is induced.


Assuntos
Amidas/química , Amidas/farmacologia , Detergentes/química , Detergentes/farmacologia , Bicamadas Lipídicas/efeitos adversos , Lisossomos/efeitos dos fármacos , Serina/análogos & derivados , Permeabilidade da Membrana Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Endocitose/efeitos dos fármacos , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Membranas Intracelulares/efeitos dos fármacos , Membranas Intracelulares/ultraestrutura , Bicamadas Lipídicas/química , Lipídeos/química , Serina/química , Serina/farmacologia
7.
Nat Commun ; 11(1): 1424, 2020 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-32188853

RESUMO

The rapid growth of wearables has created a demand for lightweight, elastic and conformal energy harvesting and storage devices. The conducting polymer poly(3,4-ethylenedioxythiophene) has shown great promise for thermoelectric generators, however, the thick layers of pristine poly(3,4-ethylenedioxythiophene) required for effective energy harvesting are too hard and brittle for seamless integration into wearables. Poly(3,4-ethylenedioxythiophene)-elastomer composites have been developed to improve its mechanical properties, although so far without simultaneously achieving softness, high electrical conductivity, and stretchability. Here we report an aqueously processed poly(3,4-ethylenedioxythiophene)-polyurethane-ionic liquid composite, which combines high conductivity (>140 S cm-1) with superior stretchability (>600%), elasticity, and low Young's modulus (<7 MPa). The outstanding performance of this organic nanocomposite is the result of favorable percolation networks on the nano- and micro-scale and the plasticizing effect of the ionic liquid. The elastic thermoelectric material is implemented in the first reported intrinsically stretchable organic thermoelectric module.

8.
Philos Trans R Soc Lond B Biol Sci ; 374(1784): 20190205, 2019 10 28.
Artigo em Inglês | MEDLINE | ID: mdl-31495308

RESUMO

Adhesive proteins of barnacle cement have potential as environmentally friendly adhesives owing to their ability to adhere to various substrates in aqueous environments. By understanding the taxonomic breath of barnacles with different lifestyles, we may uncover commonalities in adhesives produced by these specialized organisms. The 19 kDa cement protein (cp19k) of the stalked barnacle Pollicipes pollicipes was expressed in Escherichia coli BL21 to investigate its adhesive properties. Initial expression of hexahistidine-tagged protein (rPpolcp19k-his) yielded low levels of insoluble protein. Co-overproduction of E. coli molecular chaperones GroEL-GroES and trigger factor (TF) increased soluble protein yields, although TF co-purified with the target protein (TF-rPpolcp19k-his). Surface coat analysis revealed high levels of adsorption of the TF-rPpolcp19k-his complex and of purified E. coli TF on both hydrophobic and hydrophilic surfaces, while low levels of adsorption were observed for rPpolcp19k-his. Tag-free rPpolcp19k protein also exhibited low adsorption compared to fibrinogen and Cell-Tak controls on hydrophobic, neutral hydrophilic and charged self-assembled monolayers under surface plasmon resonance assay conditions designed to mimic the barnacle cement gland or seawater. Because rPpolcp19k protein displays low adhesive capability, this protein is suggested to confer the ability to self-assemble into a plaque within the barnacle cement complex. This article is part of the theme issue 'Transdisciplinary approaches to the study of adhesion and adhesives in biological systems'.


Assuntos
Proteínas de Artrópodes/genética , Expressão Gênica , Thoracica/genética , Animais , Proteínas de Artrópodes/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Thoracica/metabolismo
9.
Philos Trans R Soc Lond B Biol Sci ; 374(1784): 20190197, 2019 10 28.
Artigo em Inglês | MEDLINE | ID: mdl-31495315

RESUMO

Tunicates populate a great variety of marine underwater substrates worldwide and represent a significant concern in marine shipping and aquaculture. Adhesives are secreted from the anterior papillae of their swimming larvae, which attach and metamorphose into permanently adhering, filter-feeding adults. We recently described the cellular composition of the sensory adhesive organ of the model tunicate Ciona intestinalis in great detail. Notably, the adhesive secretions of collocytes accumulate at the tip of the organ and contain glycoproteins. Here, we further explore the components of adhesive secretions and have screened for additional specificities that may influence adhesion or cohesion of the Ciona glue, including other carbohydrate moieties, catechols and substrate properties. We found a distinct set of sugar residues in the glue recognized by specific lectins with little overlap to other known marine adhesives. Surprisingly, we also detect catechol residues that likely originate from an adjacent cellular reservoir, the test cells. Furthermore, we provide information on substrate preferences where hydrophobicity outperforms charge in the attachment. Finally, we can influence the settlement process by the addition of hydrophilic heparin. The further analysis of tunicate adhesive strategies should provide a valuable knowledge source in designing physiological adhesives or green antifoulants. This article is part of the theme issue 'Transdisciplinary approaches to the study of adhesion and adhesives in biological systems'.


Assuntos
Ciona intestinalis/fisiologia , Animais , Adesão Celular , Polímeros/metabolismo
10.
ACS Omega ; 4(3): 5670-5681, 2019 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-31459721

RESUMO

Rational design and informed development of nontoxic antifouling coatings requires a thorough understanding of the interactions between surfaces and fouling species. With more complex antifouling materials, such as composites or zwitterionic polymers, there follows also a need for better characterization of the materials as such. To further the understanding of the antifouling properties of charge-balanced polymers, we explore the properties of layered polyelectrolytes and their interactions with charged surfaces. These polymers were prepared via self-initiated photografting and photopolymerization (SIPGP); on top of a uniform bottom layer of anionic poly(methacrylic acid) (PMAA), a cationic poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) thickness gradient was formed. Infrared microscopy and imaging spectroscopic ellipsometry were used to characterize chemical composition and swelling of the combined layer. Direct force measurements by colloidal probe atomic force microscopy were performed to investigate the forces between the polymer gradients and charged probes. The swelling of PMAA and PDMAEMA are very different, with steric and electrostatic forces varying in a nontrivial manner along the gradient. The gradients can be tuned to form a protein-resistant charge-neutral region, and we demonstrate that this region, where both electrostatic and steric forces are small, is highly compressed and the origin of the protein resistance of this region is most likely an effect of strong hydration of charged residues at the surface, rather than swelling or bulk hydration of the polymer. In the highly swollen regions far from charge-neutrality, steric forces dominate the interactions between the probe and the polymer. In these regions, the SIPGP polymer has qualitative similarities with brushes, but we were unable to quantitatively describe the polymer as a brush, supporting previous data suggesting that these polymers are cross-linked.

11.
Chem Mater ; 31(9): 3395-3406, 2019 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-31296974

RESUMO

We investigated the influence of backbone regiochemistry on the conductivity, charge density, and polaron structure in the widely studied n-doped donor-acceptor polymer poly[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenediimide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene) [P(NDI2OD-T2)]. In contrast to classic semicrystalline polymers such as poly(3-hexylthiophene) (P3HT), the regioirregular (RI) structure of the naphthalenediimide (NDI)-bithiophene (T2) backbone does not alter the intramolecular steric demand of the chain versus the regioregular (RR) polymer, yielding RI-P(NDI2OD-T2) with similar energetics and optical features as its RR counterpart. By combining the electrical, UV-vis/infrared, X-ray diffraction, and electron paramagnetic resonance data and density functional theory calculations, we quantitatively characterized the conductivity, aggregation, crystallinity, and charge density, and simulated the polaron structures, molecular vibrations, and spin density distribution of RR-/RI-P(NDI2OD-T2). Importantly, we observed that RI-P(NDI2OD-T2) can be doped to a greater extent compared to its RR counterpart. This finding is remarkable and contrasts benchmark P3HT, allowing us to uniquely study the role of regiochemistry on the charge-transport properties of n-doped donor-acceptor polymers.

12.
Mater Sci Eng C Mater Biol Appl ; 102: 492-501, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31147020

RESUMO

The technology of an immunoassay detection platform is critical to clinical disease diagnoses, especially for developing a medical diagnostic system. A polymer-based immunoassay platform was fabricated on nonwoven fabric polypropylene (PP) using a photografting reaction to graft 2-hydroxyethyl methacrylate (HEMA) and sulfobetaine (SBMA). The antifouling properties of PP-g-P(HEMA-co-SBMA) were investigated by fibrinogen adsorption and platelet adhesion. Carbonyldiimidazole was employed to activate the pendant hydroxyl groups in HEMA moieties and covalently coupled antibody molecules. The detection of the limit of the immunoassay platform was as low as 10 pg/mL. Antibody amount and bioactivity affected the availability of antibody and the sensitivity of immunoassay. The immune efficiency was dependent on the strategies of antibody immobilization. The immune efficiency of Au-g-P(SBMA-co-HEMA) and Au-SH surfaces measured by QCM-D was 165% and 35.7%, respectively. The covalently binding antibody via hydrophilic polymer chains as spacers could retain fragment antigen-binding up orientation, maintain the bioactivity of antibody, and mainly improve the accessibility of antibody molecules via adjusting the conformations of polymer chains when the antibodies recognized the antigens. Therefore, grafting hydrophilic polymers, such as zwitterionic PSBMA and reactive PHEMA onto nonwoven fabric PP, and binding antibody by covalent strategy had the potential to be developed as a commercial immunoassay platform.


Assuntos
Imunoensaio/métodos , Processos Fotoquímicos , Polipropilenos/química , Adsorção , Animais , Anticorpos/metabolismo , Antígenos/metabolismo , Fibrinogênio/metabolismo , Fluorescência , Proteínas Imobilizadas/metabolismo , Limite de Detecção , Teste de Materiais , Coelhos , Razão Sinal-Ruído , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície
13.
Proc Natl Acad Sci U S A ; 116(10): 4297-4306, 2019 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-30782790

RESUMO

The flatworm Macrostomum lignano features a duo-gland adhesive system that allows it to repeatedly attach to and release from substrates in seawater within a minute. However, little is known about the molecules involved in this temporary adhesion. In this study, we show that the attachment of M. lignano relies on the secretion of two large adhesive proteins, M. lignano adhesion protein 1 (Mlig-ap1) and Mlig-ap2. We revealed that both proteins are expressed in the adhesive gland cells and that their distribution within the adhesive footprints was spatially restricted. RNA interference knockdown experiments demonstrated the essential function of these two proteins in flatworm adhesion. Negatively charged modified sugars in the surrounding water inhibited flatworm attachment, while positively charged molecules impeded detachment. In addition, we found that M. lignano could not adhere to strongly hydrated surfaces. We propose an attachment-release model where Mlig-ap2 attaches to the substrate and Mlig-ap1 exhibits a cohesive function. A small negatively charged molecule is secreted that interferes with Mlig-ap1, inducing detachment. These findings are of relevance for fundamental adhesion science and efforts to mitigate biofouling. Further, this model of flatworm temporary adhesion may serve as the starting point for the development of synthetic reversible adhesion systems for medicinal and industrial applications.


Assuntos
Adesão Celular/fisiologia , Gônadas/metabolismo , Proteínas de Helminto/metabolismo , Platelmintos/fisiologia , Adesivos , Animais , Feminino , Técnicas de Silenciamento de Genes , Gônadas/citologia , Proteínas de Helminto/genética , Peptídeos e Proteínas de Sinalização Intracelular , Masculino , Platelmintos/citologia , Platelmintos/metabolismo , Interferência de RNA , Transdução de Sinais
14.
Langmuir ; 35(5): 1818-1827, 2019 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-30103609

RESUMO

Self-assembled monolayers (SAMs) are widely used in science and engineering, and recent progress has demonstrated the utility of zwitterionic peptides with alternating lysine (K) and glutamic acid (E) residues for antifouling purposes. Aiming at developing a peptide-based fouling-resistant SAM suitable for presentation of surface-attached pheromones for barnacle larvae, we have investigated five different peptide SAMs, where four are based on the EK motif, and the fifth was designed based on general principles for fouling resistance. The SAMs were formed by self-assembly onto gold substrates via cysteine residues on the peptides, and formation of SAMs was verified via ellipsometry, wettability, infrared reflection-absorption spectroscopy and cyclic voltammetry. Settlement of cypris larvae of the barnacle Balanus (=Amphibalanus) amphitrite, the target of pheromone studies, was tested. SAMs were also subjected to fouling assays using protein solutions, blood serum, and the bacterium Mycobacterium marinum. The results confirm the favorable antifouling properties of EK-containing peptides in most of the assays, although this did not apply to the barnacle larvae settlement test, where settlement was low on only one of the peptide SAMs. The one peptide that had antifouling properties for barnacles did not contain a pheromone motif, and would not be susceptible to degredation by common serine proteases. We conclude that the otherwise broadly effective antifouling properties of EK-containing peptide SAMs is not directly applicable to barnacles, and that great care must be exercised in the design of peptide-based SAMs for presentation of barnacle-specific ligands.


Assuntos
Incrustação Biológica/prevenção & controle , Membranas Artificiais , Peptídeos/química , Adsorção/efeitos dos fármacos , Sequência de Aminoácidos , Animais , Sangue , Ouro/química , Humanos , Mycobacterium marinum/metabolismo , Proteínas/química , Propriedades de Superfície , Thoracica/metabolismo
15.
Langmuir ; 34(19): 5517-5526, 2018 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-29672068

RESUMO

Hydrogels are widely used in biomedicine and for bioanalytical purposes, normally under wet conditions. For certain applications, processing steps, or process monitoring, hydrogel films are used or treated under ambient conditions, and because they are hygroscopic, it is of interest to investigate how they respond to changes in atmospheric humidity. We have used neutron reflectometry to follow the swelling of thin UV-polymerized hydrogel films in air under different relative humidities (RHs). These polymers were prepared to similar thicknesses on silica and gold substrates, and the chemical similarity between them was verified by infrared spectroscopy. The swelling in response to variations in RH was different for the layers on the two substrate types, reflecting structural changes induced by differences in the UV exposure required to achieve a given polymer thickness, as demonstrated also by differences in the Flory-Huggins interaction parameter, obtained by fitting a Flory-Huggins-type sorption model to the swelling data. Wetting studies show small changes in contact angles with surrounding humidity variations, indicating that structural reorganization at the interface in response to humidity changes is limited.

16.
Langmuir ; 34(13): 4107-4115, 2018 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-29553755

RESUMO

Lipid bilayers, forming the outer barrier of cells, display a wide array of proteins and carbohydrates for modulating interfacial biological interactions. Formed by the spontaneous self-assembly of lipid molecules, these bilayers feature liquid crystalline order, while retaining a high degree of lateral mobility. Studies of these dynamic phenomena have been hampered by the fragility and instability of corresponding biomimetic cell membrane models. Here, we present the construct of a series of oligoethylene glycol-terminated reversible self-assembled monolayers (rSAMs) featuring lipid-bilayer-like fluidity, while retaining air and protein stability and resistance. These robust and ordered layers were prepared by simply immersing a carboxylic acid-terminated self-assembled monolayer into 5-50 µM aqueous ω-(4-ethylene glycol-phenoxy)-α-(4-amidinophenoxy)decane solutions. It is anticipated that this new class of robust and fluidic two-dimensional biomimetic surfaces will impact the design of rugged cell surface mimics and high-performance biosensors.


Assuntos
Biomimética , Técnicas Biossensoriais , Bicamadas Lipídicas/química , Etilenoglicol/química , Água/química
17.
Biofouling ; 33(2): 169-183, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-28151007

RESUMO

Marine biofouling has detrimental effects on the environment and economy, and current antifouling coatings research is aimed at environmentally benign, non-toxic materials. The possibility of using contact-active coatings is explored, by considering the antialgal activity of cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. The antialgal activity was investigated via zoospore settlement and sporeling growth assays of the marine algae Ulva linza and U. lactuca. The assay results for PDMAEMA brushes were compared to those for anionic and neutral surfaces. It was found that only PDMAEMA could disrupt zoospores that come into contact with it, and that it also inhibits the subsequent growth of normally settled spores. Based on the spore membrane properties, and characterization of the PDMAEMA brushes over a wide pH range, it is hypothesized that the algicidal mechanisms are similar to the bactericidal mechanisms of cationic polymers, and that further development could lead to successful contact-active antialgal coatings.


Assuntos
Incrustação Biológica/prevenção & controle , Desinfetantes/farmacologia , Metacrilatos/farmacologia , Nylons/farmacologia , Ulva/efeitos dos fármacos , Cátions , Concentração de Íons de Hidrogênio , Esporos , Propriedades de Superfície , Ulva/crescimento & desenvolvimento , Ulva/fisiologia
18.
ACS Appl Mater Interfaces ; 9(3): 2747-2757, 2017 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-28032741

RESUMO

An understanding of the doping and ion distributions in light-emitting electrochemical cells (LECs) is required to approach a realistic conduction model which can precisely explain the electrochemical reactions, p-n junction formation, and ion dynamics in the active layer and to provide relevant information about LECs for systematic improvement of function and manufacture. Here, Fourier-transform infrared (FTIR) microscopy is used to monitor anion density profile and polymer structure in situ and for time-resolved mapping of electrochemical doping in an LEC under bias. The results are in very good agreement with the electrochemical doping model with respect to ion redistribution and formation of a dynamic p-n junction in the active layer. We also physically slow ions by decreasing the working temperature and study frozen-junction formation and immobilization of ions in a fixed-junction LEC device by FTIR imaging. The obtained results show irreversibility of the ion redistribution and polymer doping in a fixed-junction device. In addition, we demonstrate that infrared microscopy is a useful tool for in situ characterization of electroactive organic materials.

19.
Langmuir ; 32(50): 13566-13575, 2016 12 20.
Artigo em Inglês | MEDLINE | ID: mdl-27936755

RESUMO

Lysosomotropic detergents (LDs) selectively rupture lysosomal membranes through mechanisms that have yet to be characterized. A consensus view, currently, holds that LDs, which are weakly basic, diffuse across cellular membranes as monomers in an uncharged state, and via protonation in the acidic lysosomal compartment, they become trapped, accumulate, and subsequently solubilize the membrane and induce lysosomal membrane permeabilization. Here we demonstrate that the lysosomotropic detergent O-methyl-serine dodecylamide hydrochloride (MSDH) spontaneously assembles into vesicles at, and above, cytosolic pH, and that the vesicles disassemble as the pH reaches 6.4 or lower. The aggregation commences at concentrations below the range of those used in cell studies. Assembly and disassembly of the vesicles was studied via dynamic light scattering, zeta potential measurements, cryo-TEM, and fluorescence correlation spectroscopy and was found to be reversible via control of the pH. Aggregation of MSDH into closed vesicles under cytosolic conditions is at variance with the commonly held view of LD behavior, and we propose that endocytotic pathways should be considered as possible routes of LD entry into lysosomes. We further demonstrate that MSDH vesicles can be loaded with fluorophores via a solution transition from low to high pH, for subsequent release when the pH is lowered again. The ability to encapsulate molecular cargo into MSDH vesicles together with its ability to disaggregate at low pH and to permeabilize the lysosomal membrane presents an intriguing possibility to use MSDH as a delivery system.


Assuntos
Amidas/química , Detergentes/química , Membranas Intracelulares/química , Lisossomos/química , Serina/análogos & derivados , Apoptose , Serina/química
20.
Biofouling ; 32(6): 609-25, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27125564

RESUMO

The resistance of charged polymers to biofouling was investigated by subjecting cationic (PDMAEMA), anionic (PSPMA), neutral (PHEMA-co-PEG10MA), and zwitterionic (PSBMA) brushes to assays testing protein adsorption; attachment of the marine bacterium Cobetia marina; settlement and adhesion strength of zoospores of the green alga Ulva linza; settlement of barnacle (Balanus amphitrite and B. improvisus) cypris larvae; and field immersion tests. Several results go beyond the expected dependence on direct electrostatic attraction; PSPMA showed good resistance towards attachment of C. marina, low settlement and adhesion of U. linza zoospores, and significantly lower biofouling than on PHEMA-co-PEG10MA or PSBMA after a field test for one week. PDMAEMA showed potential as a contact-active anti-algal coating due to its capacity to damage attached spores. However, after field testing for eight weeks, there were no significant differences in biofouling coverage among the surfaces. While charged polymers are unsuitable as antifouling coatings in the natural environment, they provide valuable insights into fouling processes, and are relevant for studies due to charging of nominally neutral surfaces.


Assuntos
Incrustação Biológica/prevenção & controle , Gammaproteobacteria/fisiologia , Metacrilatos/química , Nylons/química , Poli-Hidroxietil Metacrilato/química , Thoracica/fisiologia , Ulva/fisiologia , Adsorção , Animais , Aderência Bacteriana , Cátions , Interações Hidrofóbicas e Hidrofílicas , Esporos Bacterianos/fisiologia , Propriedades de Superfície
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