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1.
J Am Chem Soc ; 145(49): 26688-26698, 2023 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-38048399

RESUMO

The bicyclic 1,2-substituted, 1,3-diene monomer nopadiene (1R,5S)-2-ethenyl-6,6-dimethylbicyclo[3.1.1]hept-2-ene was successfully polymerized by anionic and catalytic polymerization. Nopadiene is produced either through a facile one-step synthesis from myrtenal via Wittig-olefination or via a scalable two-step reaction from nopol (10-hydroxymethylene-2-pinene). Both terpenoids originate from the renewable ß-pinene. The living anionic polymerization of nopadiene in apolar and polar solvents at 25 °C using organolithium initiators resulted in homopolymers with well-controlled molar masses in the range of 5.6-103.4 kg·mol-1 (SEC, PS calibration) and low dispersities (D) between 1.06 and 1.18. By means of catalytic polymerization with Me4CpSi(Me)2NtBuTiCl2 and (Flu)(Pyr)CH2Lu(CH2TMS)2(THF), the 1,4 and 3,4- microstructures of nopadiene are accessible in excellent selectivity. In pronounced contrast to other 1,3-dienes, the rigid polymers of the sterically demanding nopadiene showed an elevated glass temperature, Tg,∞ = 160 °C (in the limit of very high molar mass, Mn). ABA triblock copolymers with a central polymyrcene block and myrcene content of 60-75 mol %, with molar masses of 100-200 kg/mol were prepared by living anionic polymerization of the pinene-derivable monomers nopadiene and myrcene. This diene copolymerization resulted in thermoplastic elastomers displaying nanophase separation at different molar ratios (DSC, SAXS) and an upper service temperature about 30 K higher than that for traditional petroleum-derived styrenic thermoplastic elastomers due to the high glass temperature of polynopadiene. The materials showed good thermal stability at elevated temperatures under nitrogen (TGA), promising tensile strength and ultimate elongation of up to 1600%.

2.
BMC Pulm Med ; 21(1): 131, 2021 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-33882893

RESUMO

BACKGROUND: The extend of lung disease remains the most important prognostic factor for survival in patients with cystic fibrosis (CF), and lack of adherence is the main reason for treatment failure. Early detection of deterioration in lung function and optimising adherence are therefore crucial in CF care. We implement a randomized controlled trial to evaluate efficacy of telemonitoring of adherence, lung function, and health condition in combination with behavior change interventions using innovative digital technologies. METHODS: This is a multi-centre, randomized, controlled, non-blinded trial aiming to include 402 patients ≥ 12 years-of-age with CF. A standard-of-care arm is compared to an arm receiving objective, continuous monitoring of adherence to inhalation therapies, weekly home spirometry using electronic devices with data transmission to patients and caring physicians combined with video-conferencing, a self-management app and professional telephone coaching. The duration of the intervention phase is 18 months. The primary endpoint is time to the first protocol-defined pulmonary exacerbation. Secondary outcome measures include number of and time between pulmonary exacerbations, adherence to inhalation therapy, changes in forced expiratory volume in 1 s from baseline, number of hospital admissions, and changes in health-related quality of life. CF-associated medical treatment and care, and health care related costs will be assessed by explorative analysis in both arms. DISCUSSION: This study offers the opportunity to evaluate the effect of adherence interventions using telemedicine capable devices on adherence and lung health, possibly paving the way for implementation of telemedicine in routine care for patients with CF. TRIAL REGISTRATION: This study has been registered with the German Clinical Trials Register (Identifier: DRKS00024642, date of registration 01 Mar 2021, URL: https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00024642 ).


Assuntos
Fibrose Cística/terapia , Monitorização Ambulatorial/métodos , Educação de Pacientes como Assunto , Telemedicina , Adolescente , Adulto , Criança , Humanos
3.
Strahlenther Onkol ; 196(1): 48-57, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31418046

RESUMO

PURPOSE: Published results of quality of life (QoL) studies mostly concern whole brain radiotherapy for limited or multiple brain metastases. This prospective multicentre study was designed to compare the QoL of patients with limited (1-3) brain metastases treated with either whole brain (WBRT) or stereotactic radiotherapy (SRT). METHODS: From 01/2007-03/2011, 90 limited brain metastases patients who were previously untreated (n = 77) or had undergone primary surgery (n = 13) were recruited at 14 centres in Germany and Austria. QoL was measured with the EORTC-QLQ-C15-PAL and BN20 brain modules before the start of radiotherapy and after 3 months. RESULTS: Fifty-two patients (58%) received WBRT and 38 (42%) received SRT. At 3 months, 67 patients (74%) were still living, and 92.6% of the 3­month survivors completed the second set of questionnaires. Analysis of the QLQ-C15-PAL and BN20 scales revealed significant deterioration in patients treated with WBRT and SRT in physical function (p < 0.001 and p = 0.007), fatigue (p < 0.001 and p = 0.036), nausea (p = 0.003 and p = 0.002), appetite loss (p < 0.001 and p = 0.025), drowsiness (p < 0.001 and p = 0.011), hair loss (p = 0.019 and p = 0.023) and itchy skin (p = 0.030 and p = 0.018). Motor dysfunction (p < 0.001), communication deficits (p = 0.002) and leg weakness (p < 0.001) declined significantly only in patients treated with WBRT. Comparing the two radiotherapy techniques over time, the results showed significant differences in symptom scores for future uncertainty, fatigue and appetite loss. CONCLUSIONS: QoL data as an outcome of the paper should be considered in decision making on the irradiation technique in patients with small number of brain metastases. Larger studies are required to verify the results according to subgroups.


Assuntos
Neoplasias Encefálicas/radioterapia , Neoplasias Encefálicas/secundário , Irradiação Craniana/efeitos adversos , Qualidade de Vida/psicologia , Lesões por Radiação/etiologia , Radiocirurgia/efeitos adversos , Atividades Cotidianas/classificação , Alopecia/etiologia , Áustria , Neoplasias Encefálicas/psicologia , Transtornos da Comunicação/etiologia , Fadiga/etiologia , Transtornos da Alimentação e da Ingestão de Alimentos/etiologia , Seguimentos , Alemanha , Humanos , Debilidade Muscular/etiologia , Estudos Prospectivos
4.
J Biol Chem ; 293(13): 4913-4927, 2018 03 30.
Artigo em Inglês | MEDLINE | ID: mdl-29378850

RESUMO

The heterologous expression of integral membrane proteins (IMPs) remains a major bottleneck in the characterization of this important protein class. IMP expression levels are currently unpredictable, which renders the pursuit of IMPs for structural and biophysical characterization challenging and inefficient. Experimental evidence demonstrates that changes within the nucleotide or amino acid sequence for a given IMP can dramatically affect expression levels, yet these observations have not resulted in generalizable approaches to improve expression levels. Here, we develop a data-driven statistical predictor named IMProve that, using only sequence information, increases the likelihood of selecting an IMP that expresses in Escherichia coli The IMProve model, trained on experimental data, combines a set of sequence-derived features resulting in an IMProve score, where higher values have a higher probability of success. The model is rigorously validated against a variety of independent data sets that contain a wide range of experimental outcomes from various IMP expression trials. The results demonstrate that use of the model can more than double the number of successfully expressed targets at any experimental scale. IMProve can immediately be used to identify favorable targets for characterization. Most notably, IMProve demonstrates for the first time that IMP expression levels can be predicted directly from sequence.


Assuntos
Escherichia coli , Expressão Gênica , Modelos Genéticos , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/genética
5.
Nature ; 503(7475): 247-51, 2013 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-24185010

RESUMO

The concept of hierarchical bottom-up structuring commonly encountered in natural materials provides inspiration for the design of complex artificial materials with advanced functionalities. Natural processes have achieved the orchestration of multicomponent systems across many length scales with very high precision, but man-made self-assemblies still face obstacles in realizing well-defined hierarchical structures. In particle-based self-assembly, the challenge is to program symmetries and periodicities of superstructures by providing monodisperse building blocks with suitable shape anisotropy or anisotropic interaction patterns ('patches'). Irregularities in particle architecture are intolerable because they generate defects that amplify throughout the hierarchical levels. For patchy microscopic hard colloids, this challenge has been approached by using top-down methods (such as metal shading or microcontact printing), enabling molecule-like directionality during aggregation. However, both top-down procedures and particulate systems based on molecular assembly struggle to fabricate patchy particles controllably in the desired size regime (10-100 nm). Here we introduce the co-assembly of dynamic patchy nanoparticles--that is, soft patchy nanoparticles that are intrinsically self-assembled and monodisperse--as a modular approach for producing well-ordered binary and ternary supracolloidal hierarchical assemblies. We bridge up to three hierarchical levels by guiding triblock terpolymers (length scale ∼10 nm) to form soft patchy nanoparticles (20-50 nm) of different symmetries that, in combination, co-assemble into substructured, compartmentalized materials (>10 µm) with predictable and tunable nanoscale periodicities. We establish how molecular control over polymer composition programs the building block symmetries and regulates particle positioning, offering a route to well-ordered mixed mesostructures of high complexity.

6.
J Bacteriol ; 200(15)2018 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-29555694

RESUMO

Many bacteria use extracellular signaling molecules to coordinate group behavior, a process referred to as quorum sensing (QS). However, some QS molecules are hydrophobic in character and are probably unable to diffuse across the bacterial cell envelope. How these molecules are disseminated between bacterial cells within a population is not yet fully understood. Here, we show that the marine pathogen Vibrio harveyi packages the hydrophobic QS molecule CAI-1, a long-chain amino ketone, into outer membrane vesicles. Electron micrographs indicate that outer membrane vesicles of variable size are predominantly produced and released into the surroundings during the stationary phase of V. harveyi, which correlates with the timing of CAI-1-dependent signaling. The large vesicles (diameter, <55 nm) can trigger a QS phenotype in CAI-1-nonproducing V. harveyi and Vibrio cholerae cells. Packaging of CAI-1 into outer membrane vesicles might stabilize the molecule in aqueous environments and facilitate its distribution over distances.IMPORTANCE Formation of membrane vesicles is ubiquitous among bacteria. These vesicles are involved in protein and DNA transfer and offer new approaches for vaccination. Gram-negative bacteria use hydrophobic signaling molecules, among others, for cell-cell communication; however, due to their hydrophobic character, it is unclear how these molecules are disseminated between bacterial cells. Here, we show that the marine pathogen Vibrio harveyi packages one of its QS molecules, the long-chain ketone CAI-1, into outer membrane vesicles (OMVs). Isolated CAI-1-containing vesicles trigger a QS phenotype in CAI-1 nonproducing V. harveyi and also in Vibrio cholerae cells. Packaging of CAI-1 into OMVs not only solubilizes, stabilizes, and concentrates this class of molecules, but facilitate their distribution between bacteria that live in aqueous environments.


Assuntos
Membrana Celular/fisiologia , Cetonas/metabolismo , Vesículas Transportadoras/fisiologia , Vibrio/fisiologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Transporte Biológico , Regulação Bacteriana da Expressão Gênica/fisiologia , Vibrio/ultraestrutura
7.
Diabetologia ; 61(4): 954-958, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29128936

RESUMO

AIMS/HYPOTHESIS: Diabetes research studies routinely rely upon the use of tissue samples from human organ donors. It remains unclear whether the length of hospital stay prior to organ donation affects the presence of cells infiltrating the pancreas or the frequency of replicating beta cells. METHODS: To address this, 39 organ donors without diabetes were matched for age, sex, BMI and ethnicity in groups of three. Within each group, donors varied by length of hospital stay immediately prior to organ donation (<3 days, 3 to <6 days, or ≥6 days). Serial sections from tissue blocks in the pancreas head, body and tail regions were immunohistochemically double stained for insulin and CD45, CD68, or Ki67. Slides were electronically scanned and quantitatively analysed for cell positivity. RESULTS: No differences in CD45+, CD68+, insulin+, Ki67+ or Ki67+/insulin+ cell frequencies were found when donors were grouped according to duration of hospital stay. Likewise, no interactions were observed between hospitalisation group and pancreas region, age, or both; however, with Ki67 staining, cell frequencies were greater in the body vs the tail region of the pancreas (∆ 0.65 [unadjusted 95% CI 0.25, 1.04]; p = 0.002) from donors <12 year of age. Interestingly, frequencies were less in the body vs tail region of the pancreas for both CD45+ cells (∆ -0.91 [95% CI -1.71, -0.10]; p = 0.024) and insulin+ cells (∆ -0.72 [95% CI -1.10, -0.34]; p < 0.001). CONCLUSIONS/INTERPRETATION: This study suggests that immune or replicating beta cell frequencies are not affected by the length of hospital stay prior to donor death in pancreases used for research. DATA AVAILABILITY: All referenced macros (adopted and developed), calculations, programming code and numerical dataset files (including individual-level donor data) are freely available on GitHub through Zenodo at https://doi.org/10.5281/zenodo.1034422.


Assuntos
Hospitalização , Tempo de Internação , Transplante de Pâncreas , Pâncreas/patologia , Adolescente , Índice de Massa Corporal , Criança , Morte , Diabetes Mellitus/patologia , Feminino , Humanos , Imuno-Histoquímica , Insulina/metabolismo , Células Secretoras de Insulina/metabolismo , Masculino , Doadores de Tecidos , Obtenção de Tecidos e Órgãos , Resultado do Tratamento , Adulto Jovem
8.
Biomacromolecules ; 18(3): 808-818, 2017 03 13.
Artigo em Inglês | MEDLINE | ID: mdl-28199098

RESUMO

Polycations are popular agents for nonviral delivery of DNA to mammalian cells. Adding hydrophobic, biodegradable, or cell-penetrating functions could help to improve their performance, which at present is below that of viral agents. A crucial first step in gene delivery is the complexation of the DNA. The characteristics of these "polyplexes" presumably influence or even determine the subsequent steps of membrane passage, intracellular traveling/DNA release, and nuclear uptake. Herein, polyplexes formed with linear poly(ethylenimine) (l-PEI) are compared to complexes generated with functionalized diblock copolymers. While l-PEI interacts only electrostatically with the DNA, interaction in the case of the diblock polymers may be mixed-mode. In certain cases, transfection efficiency improved when the polyplexes were formed in hypertonic solution. Moreover, whereas conventional PEI-based polyplexes enter the cells via endocytosis, at least one of the diblock agents seemed to promote entry via transient destabilization of the plasma membrane.


Assuntos
DNA/química , Plasmídeos/química , Polietilenoimina/química , Animais , Materiais Biocompatíveis/química , Células CHO , Linhagem Celular , Cricetulus , Endocitose/efeitos dos fármacos , Técnicas de Transferência de Genes , Células HEK293 , Humanos , Interações Hidrofóbicas e Hidrofílicas , Camundongos , Tamanho da Partícula , Poliaminas/química , Polieletrólitos , Eletricidade Estática , Transfecção
9.
Soft Matter ; 12(39): 8098-8103, 2016 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-27550638

RESUMO

A block copolymer-based assembly approach for the creation of nano-patterned polyelectrolyte multilayers over cm2-scale areas is presented. Up to 5 bi-layers were selectively assembled on top of specific nano-domains featuring different morphologies. The successful isolation of nanoscale objects corresponding in shape to the template features is also demonstrated. This methodology is applicable to different types of polyelectrolytes, and opens up a new dimension for layer-by-layer construction.

10.
Soft Matter ; 12(20): 4595-602, 2016 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-27104854

RESUMO

Nano-patterned materials are beneficial for applications such as solar cells, opto-electronics, and sensing owing to their periodic structure and high interfacial area. Here, we present a non-lithographic approach for assembling polyelectrolytes into periodic nanoscale patterns over cm(2)-scale areas. Chemically modified block copolymer thin films featuring alternating charged and neutral domains are used as patterned substrates for electrostatic self-assembly. In-depth characterization of the deposition process using spectroscopy and microscopy techniques, including the state-of-the-art scanning transmission X-ray microscopy (STXM), reveals both the selective deposition of the polyelectrolyte on the charged copolymer domains as well as gradual changes in the film topography that arise from further penetration of the solvent molecules and possibly also the polyelectrolyte into these domains. Our results demonstrate the feasibility of creating nano-patterned polyelectrolyte layers, which opens up new opportunities for structured functional coating fabrication.

11.
EMBO J ; 30(14): 2972-81, 2011 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-21673657

RESUMO

The bacterial flagellum is one of nature's most amazing and well-studied nanomachines. Its cell-wall-anchored motor uses chemical energy to rotate a microns-long filament and propel the bacterium towards nutrients and away from toxins. While much is known about flagellar motors from certain model organisms, their diversity across the bacterial kingdom is less well characterized, allowing the occasional misrepresentation of the motor as an invariant, ideal machine. Here, we present an electron cryotomographical survey of flagellar motor architectures throughout the Bacteria. While a conserved structural core was observed in all 11 bacteria imaged, surprisingly novel and divergent structures as well as different symmetries were observed surrounding the core. Correlating the motor structures with the presence and absence of particular motor genes in each organism suggested the locations of five proteins involved in the export apparatus including FliI, whose position below the C-ring was confirmed by imaging a deletion strain. The combination of conserved and specially-adapted structures seen here sheds light on how this complex protein nanomachine has evolved to meet the needs of different species.


Assuntos
Bactérias/química , Bactérias/metabolismo , Flagelos/química , Proteínas Motores Moleculares/química , Proteínas Motores Moleculares/metabolismo , Movimento Celular , Flagelos/metabolismo , Modelos Moleculares
12.
Biochem Soc Trans ; 43(5): 1011-7, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26517916

RESUMO

ATP-binding cassette (ABC) transporters, although being ubiquitous in biology, often feature a subunit that is limited primarily to bacteria and archaea. This subunit, the substrate-binding protein (SBP), is a key determinant of the substrate specificity and high affinity of ABC uptake systems in these organisms. Most prokaryotes have many SBP-dependent ABC transporters that recognize a broad range of ligands from metal ions to amino acids, sugars and peptides. Herein, we review the structure and function of a number of more unusual SBPs, including an ABC transporter involved in the transport of rare furanose forms of sugars and an SBP that has evolved to specifically recognize the bacterial cell wall-derived murein tripeptide (Mtp). Both these examples illustrate that subtle changes in binding-site architecture, including changes in side chains not directly involved in ligand co-ordination, can result in significant alteration of substrate range in novel and unpredictable ways.


Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Trifosfato de Adenosina/metabolismo , Bactérias/metabolismo , Proteínas de Bactérias/metabolismo , Transportadores de Cassetes de Ligação de ATP/química , Proteínas de Bactérias/química , Sítios de Ligação , Evolução Biológica , Modelos Moleculares , Monossacarídeos/química , Monossacarídeos/metabolismo , Ligação Proteica , Estrutura Terciária de Proteína
13.
Anal Bioanal Chem ; 407(20): 6181-90, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26100547

RESUMO

In Campylobacterales and related ε-proteobacteria with N-linked glycosylation (NLG) pathways, free oligosaccharides (fOS) are released into the periplasmic space from lipid-linked precursors by the bacterial oligosaccharyltransferase (PglB). This hydrolysis results in the same molecular structure as the oligosaccharide that is transferred to a protein to be glycosylated. This allowed for the general elucidation of the fOS-branched structures and monosaccharides from a number of species using standard enrichment and mass spectrometry methods. To aid characterization of fOS, hydrazide chemistry has often been used for chemical modification of the reducing part of oligosaccharides resulting in better selectivity and sensitivity in mass spectrometry; however, the removal of the unreacted reagents used for the modification often causes the loss of the sample. Here, we develop a more robust method for fOS purification and characterize glycostructures using complementary tandem mass spectrometry (MS/MS) analysis. A cationic cysteine hydrazide derivative was synthesized to selectively isolate fOS from periplasmic fractions of bacteria. The cysteine hydrazide nicotinamide (Cyhn) probe possesses both thiol and cationic moieties. The former enables reversible conjugation to a thiol-activated solid support, while the latter improves the ionization signal during MS analysis. This enrichment was validated on the well-studied Campylobacter jejuni by identifying fOS from the periplasmic extracts. Using complementary MS/MS analysis, we approximated data of a known structure of the fOS from Campylobacter concisus. This versatile enrichment technique allows for the exploration of a diversity of protein glycosylation pathways.


Assuntos
Campylobacter/química , Cisteína/análogos & derivados , Oligossacarídeos/análise , Espectrometria de Massas em Tandem/métodos , Cisteína/química , Oligossacarídeos/isolamento & purificação , Extração em Fase Sólida/métodos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos
14.
Phys Chem Chem Phys ; 17(17): 11490-8, 2015 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-25855146

RESUMO

The formation of copper nanoparticles (Cu-NPs) in irradiated aqueous solutions of star-shaped poly(acrylic acid) (PAA) were studied at two pH values. Transmission electron microscopy (TEM) demonstrates that the star-shaped macromolecules loaded with Cu(2+) ions can act as individual nanosized containers providing a perfect control over the size and size distribution of Cu-NPs. Electron paramagnetic resonance (EPR) and optical spectroscopy show a transformation of mechanisms controlling the reduction of Cu(2+) ions and the further formation of Cu-NPs. At pH 2.9, Cu-NPs are formed from the aquacomplexes of Cu(2+) ions through homogeneous nucleation. At pH 4.3, the formation of Cu-NPs occurs inside macromolecular containers loaded with Cu(2+) ions, which are bound to carboxylic groups of the polyelectrolyte. In the latter case, Cu-NPs apparently ripen from preformed hydrated Cu2O seeds, which are thought to result from the ultrasmall (Cu(2+))m(OH(-))k(COO(-))n species, thus implying a heterogeneous nucleation.


Assuntos
Cobre/química , Nanopartículas Metálicas/química , Polímeros/química , Eletrólitos/química , Tamanho da Partícula , Soluções , Propriedades de Superfície , Água/química
15.
Langmuir ; 30(44): 13152-63, 2014 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-25196970

RESUMO

The morphologies and corona compositions in aggregates of mixtures of PS-b-PAA and PS-b-P4VP diblock copolymers are influenced by controllable assembly parameters such as water content, block copolymer molar ratios, and solvent effects as well as the hydrophilic block lengths and block length ratios. All these factors can affect the morphology of the aggregates as well as their corona composition, the latter especially in vesicles, where two interfaces are involved. The morphologies and corona compositions of the aggregates were investigated by transmission electron microscopy and electrophoretic mobility, respectively. They depend, to a large extent, on the solubility of P4VP and PAA in the given organic solvent (e.g., DMF, THF, or dioxane), which influences the coil dimensions of the hydrophilic chains. The water content affects both the size and the shape of the block copolymer aggregates as well as the corona composition. Water acts as a precipitant for the hydrophobic block in the common solvent and, therefore, its progressive addition to the solution changes the interaction parameter with the hydrophobic block. The block copolymer molar ratio has an effect on both the morphology and the corona composition of the aggregates. With increasing PS-b-P4VP content in the mixture, the morphology transforms gradually from large compound micelles (LCMs), through coexistence of LCMs and small spherical micelles (SSMs), and eventually to vesicles. As expected, the corona composition of the aggregates is also affected by the block copolymer molar ratio, and changes progressively from pure PAA to a mixture of PAA and P4VP and to pure P4VP with increasing PS-b-P4VP content. It is clear that the use of mixtures of the soluble chains offers the opportunity of fine-tuning the corona composition in block copolymer aggregates under assembly conditions.

16.
Langmuir ; 30(17): 5031-40, 2014 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-24725167

RESUMO

The corona compositions and morphologies in aggregates of mixtures of amphiphilic polystyrene-block-poly(acrylic acid) (PS-b-PAA) and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymers are influenced by controllable assembly parameters such as the hydrophilic block length and solution pH. The morphologies and corona compositions of the aggregates were investigated by transmission electron microscopy and electrophoretic mobility, respectively. When mineral acids or bases are present during aggregate formation, they can exert a strong influence on the corona composition. Morphology changes were also seen with changing pH, as well as changes in corona composition, specifically for vesicles. Because of complications introduced by the presence of ions, the general hypothesis that the external corona of the vesicles is composed of the longer chains, while the shorter chains form the inner corona, which is valid only in mixtures containing only nonionic chains without any additives (no acids or bases) or within a well-defined narrow pH range. In addition to the numerical block lengths and the pH, the solubility of the hydrophilic blocks can also influence the morphology and as well as the interfacial composition of vesicles; as the numerically longer chains become less soluble, they can contract and move to the interior, while the numerically shorter but more soluble chains go to the external corona. A remarkable morphological feature of the pH continuum is that for some compositions vesicles are observed in four distinct pH regions, separated by pH ranges in which other morphologies dominate. The effect of pH and microion content on coil dimensions of the PVP and PAA chains in the block copolymers is most likely responsible for the observed behavior.

17.
Macromol Rapid Commun ; 35(2): 234-241, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24115272

RESUMO

The synthesis of well-defined cylindrical polymer brushes (CPBs) from a linear polymer backbone with a high density of RAFT functionalities ("grafting from" approach) is challenging when the chain transfer agent (CTA) is attached to the backbone via its R-group. It is proposed that the difficulties of the R-group approach in controlling the grafting polymerization are induced by the "entrapment" of active free radicals within individual growing CPBs. A facile "CTA-shuttled" R-group approach overcoming this entrapment effect is developed, and used to synthesize well-defined CPBs with polystyrene or poly(tert-butyl acrylate) branches and core-shell CPBs with polystyrene-block-poly(N-isopropylacrylamide) branches. The polydispersity index (PDI = 1.23) of the obtained CPBs with polystyrene branches is much lower than that from the conventional R-group approach (PDI = 2.18). Monte Carlo simulations confirm that the advantage of the "CTA-shuttled" R-group approach consists in the release of the active radicals from the trapping CPB systems.


Assuntos
Polímeros/química , Polimerização
18.
Macromol Rapid Commun ; 35(1): 52-5, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24327396

RESUMO

Imitating the natural "energy cascade" architecture, we present a single-molecular rod-like nano-light harvester (NLH) based on a cylindrical polymer brush. Block copolymer side chains carrying (9,9-diethylfluoren-2-yl)methyl methacrylate units as light absorbing antennae (energy donors) are tethered to a linear polymer backbone containing 9-anthracenemethyl methacrylate units as emitting groups (energy acceptors). These NLHs exhibit very efficient energy absorption and transfer. Moreover, we manipulate the energy transfer by tuning the donor-acceptor distance.


Assuntos
Luz , Nanotecnologia , Transferência de Energia , Polímeros/química , Análise Espectral/métodos
19.
Langmuir ; 29(5): 1388-94, 2013 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-23311383

RESUMO

We investigate the self-assembly behavior of Janus particles with different geometries at a liquid-liquid interface. The Janus particles we focus on are characterized by a phase separation along their major axis into two hemicylinders of different wettability. We present a combination of experimental and simulation data together with detailed studies elucidating the mechanisms governing the adsorption process of Janus spheres, Janus cylinders, and Janus discs. Using the pendant drop technique, we monitor the assembly kinetics following changes in the interfacial tension of nanoparticle adsorption. According to the evolution of the interfacial tension and simulation data, we will specify the characteristics of early to late stages of the Janus particle adsorption and discuss the effect of Janus particle shape and geometry. The adsorption is characterized by three adsorption stages which are based on the different assembly kinetics and different adsorption mechanisms depending on the particle shape.


Assuntos
Tolueno/química , Água/química , Adsorção , Nanopartículas/química , Tamanho da Partícula , Propriedades de Superfície , Molhabilidade
20.
Biomacromolecules ; 14(9): 3081-90, 2013 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-23889326

RESUMO

Monodisperse, magnetic nanoparticles as vectors for gene delivery were successfully synthesized via the grafting-from approach. First, oleic acid stabilized maghemite nanoparticles (γ-Fe2O3) were encapsulated with silica utilizing a reverse microemulsion process with simultaneous functionalization with initiating sites for atom transfer radical polymerization (ATRP). Polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) from the core-shell nanoparticles led to core-shell-corona hybrid nanoparticles (γ-Fe2O3@silica@PDMAEMA) with an average grafting density of 91 polymer chains of DP(n) = 540 (PDMAEMA540) per particle. The permanent attachment of the arms was verified by field-flow fractionation. The dual-responsive behavior (pH and temperature) was confirmed by dynamic light scattering (DLS) and turbidity measurements. The interaction of the hybrid nanoparticles with plasmid DNA at various N/P ratios (polymer nitrogen/DNA phosphorus) was investigated by DLS and zeta-potential measurements, indicating that for N/P ≥ 7.5 the complexes bear a positive net charge and do not undergo secondary aggregation. The hybrids were tested as transfection agents under standard conditions in CHO-K1 and L929 cells, revealing transfection efficiencies >50% and low cytotoxicity at N/P ratios of 10 and 15, respectively. Due to the magnetic properties of the hybrid gene vector, it is possible to collect most of the cells that have incorporated a sufficient amount of magnetic material by using a magnetic activated cell sorting system (MACS). Afterward, cells were further cultivated and displayed a transfection efficiency of ca. 60% together with a high viability.


Assuntos
Separação Celular/métodos , Compostos Férricos/química , Metacrilatos/química , Nanopartículas/química , Ácidos Polimetacrílicos/síntese química , Animais , Células CHO , Sobrevivência Celular/efeitos dos fármacos , Cricetinae , Cricetulus , Concentração de Íons de Hidrogênio , Dose Letal Mediana , Fenômenos Magnéticos , Camundongos , Nanopartículas/toxicidade , Tamanho da Partícula , Polimerização , Ácidos Polimetacrílicos/química , Transfecção/métodos
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