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1.
Environ Sci Technol ; 54(7): 3871-3880, 2020 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-32146813

RESUMO

Current mass spectrometry techniques for the online measurement of organic aerosol (OA) composition are subjected to either thermal/ionization-induced artifacts or limited mass resolving power, hindering accurate molecular characterization. Here, we combined the soft ionization capability of extractive electrospray ionization (EESI) and the ultrahigh mass resolution of Orbitrap for real-time, near-molecular characterization of OAs. Detection limits as low as tens of ng m-3 with linearity up to hundreds of µg m-3 at 0.2 Hz time resolution were observed for single- and mixed-component calibrations. The performance of the EESI-Orbitrap system was further evaluated with laboratory-generated secondary OAs (SOAs) and filter extracts of ambient particulate matter. The high mass accuracy and resolution (140 000 at m/z 200) of the EESI-Orbitrap system enable unambiguous identification of the aerosol components' molecular composition and allow a clear separation between adjacent peaks, which would be significantly overlapping if a medium-resolution (20 000) mass analyzer was used. Furthermore, the tandem mass spectrometry (MS2) capability provides valuable insights into the compound structure. For instance, the MS2 analysis of ambient OA samples and lab-generated biogenic SOAs points to specific SOA precursors in ambient air among a range of possible isomers based on fingerprint fragment ions. Overall, this newly developed and characterized EESI-Orbitrap system will advance our understanding of the formation and evolution of atmospheric aerosols.

2.
Environ Sci Technol ; 54(6): 3114-3120, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32022545

RESUMO

Northern China is regularly subjected to intense wintertime "haze events", with high levels of fine particles that threaten millions of inhabitants. While sulfate is a known major component of these fine haze particles, its formation mechanism remains unclear especially under highly polluted conditions, with state-of-the-art air quality models unable to reproduce or predict field observations. These haze conditions are generally characterized by simultaneous high emissions of SO2 and photosensitizing materials. In this study, we find that the excited triplet states of photosensitizers could induce a direct photosensitized oxidation of hydrated SO2 and bisulfite into sulfate S(VI) through energy transfer, electron transfer, or hydrogen atom abstraction. This photosensitized pathway appears to be a new and ubiquitous chemical route for atmospheric sulfate production. Compared to other aqueous-phase sulfate formation pathways with ozone, hydrogen peroxide, nitrogen dioxide, or transition-metal ions, the results also show that this photosensitized oxidation of S(IV) could make an important contribution to aerosol sulfate formation in Asian countries, particularly in China.


Assuntos
Poluentes Atmosféricos , Transtornos de Fotossensibilidade , Aerossóis , Ásia , China , Humanos , Material Particulado , Sulfatos
3.
Angew Chem Int Ed Engl ; 59(18): 7203-7208, 2020 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-32061176

RESUMO

An orthogonal combination of cationic and radical RAFT polymerizations is used to synthesize bottlebrush polymers using two distinct RAFT agents. Selective consumption of the first RAFT agent is used to control the cationic RAFT polymerization of a vinyl ether monomer bearing a secondary dormant RAFT agent, which subsequently allows side-chain polymers to be grafted from the pendant RAFT agent by a radical-mediated RAFT polymerization of a different monomer, thus completing the synthesis of bottlebrush polymers. The high efficiency and selectivity of the cationic and radical RAFT polymerizations allow both polymerizations to be conducted in one-pot tandem without intermediate purification.

4.
Angew Chem Int Ed Engl ; 59(23): 8860-8863, 2020 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-32045099

RESUMO

Typically, the morphologies of the self-assembled nanostructures from block copolymers are limited to spherical micelles, wormlike micelles and vesicles. Now, a new generation of materials with unique shape and structures, cylindrical soft matter particles (tubisomes), are obtained from the hierarchical self-assembly of cyclic peptide-bridged amphiphilic diblock copolymers. The capacity of obtained photo-responsive tubisomes as potential drug carriers is evaluated. The supramolecular tubisomes pave an alternative way for fabricating polymeric tubular structures, and will expand the toolbox for the rational design of functional hierarchical nanostructures.

5.
Nat Commun ; 10(1): 4708, 2019 10 17.
Artigo em Inglês | MEDLINE | ID: mdl-31624265

RESUMO

Self-assembling peptides have the ability to spontaneously aggregate into large ordered structures. The reversibility of the peptide hydrogen bonded supramolecular assembly make them tunable to a host of different applications, although it leaves them highly dynamic and prone to disassembly at the low concentration needed for biological applications. Here we demonstrate that a secondary hydrophobic interaction, near the peptide core, can stabilise the highly dynamic peptide bonds, without losing the vital solubility of the systems in aqueous conditions. This hierarchical self-assembly process can be used to stabilise a range of different ß-sheet hydrogen bonded architectures.


Assuntos
Substâncias Macromoleculares/química , Nanotubos de Peptídeos/química , Peptídeos/química , Conformação Proteica em Folha beta , Água/química , Sobrevivência Celular , Humanos , Ligação de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Células PC-3 , Solubilidade , Termodinâmica
6.
Phys Chem Chem Phys ; 21(37): 20613-20627, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31528972

RESUMO

Atmospheric aerosol particles with a high viscosity may become inhomogeneously mixed during chemical processing. Models have predicted gradients in condensed phase reactant concentration throughout particles as the result of diffusion and chemical reaction limitations, termed chemical gradients. However, these have never been directly observed for atmospherically relevant particle diameters. We investigated the reaction between ozone and aerosol particles composed of xanthan gum and FeCl2 and observed the in situ chemical reaction that oxidized Fe2+ to Fe3+ using X-ray spectromicroscopy. Iron oxidation state of particles as small as 0.2 µm in diameter were imaged over time with a spatial resolution of tens of nanometers. We found that the loss off Fe2+ accelerated with increasing ozone concentration and relative humidity, RH. Concentric 2-D column integrated profiles of the Fe2+ fraction, α, out of the total iron were derived and demonstrated that particle surfaces became oxidized while particle cores remained unreacted at RH = 0-20%. At higher RH, chemical gradients evolved over time, extended deeper from the particle surface, and Fe2+ became more homogeneously distributed. We used the kinetic multi-layer model for aerosol surface and bulk chemistry (KM-SUB) to simulate ozone reaction constrained with our observations and inferred key parameters as a function of RH including Henry's Law constant for ozone, HO3, and diffusion coefficients for ozone and iron, DO3 and DFe, respectively. We found that HO3 is higher in our xanthan gum/FeCl2 particles than for water and increases when RH decreased from about 80% to dry conditions. This coincided with a decrease in both DO3 and DFe. In order to reproduce observed chemical gradients, our model predicted that ozone could not be present further than a few nanometers from a particle surface indicating near surface reactions were driving changes in iron oxidation state. However, the observed chemical gradients in α observed over hundreds of nanometers must have been the result of iron transport from the particle interior to the surface where ozone oxidation occurred. In the context of our results, we examine the applicability of the reacto-diffusive framework and discuss diffusion limitations for other reactive gas-aerosol systems of atmospheric importance.

7.
Biomaterials ; 217: 119249, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31279102

RESUMO

Intracellular persistence of bacteria represents a clinical challenge as bacteria can thrive in an environment protected from antibiotics and immune responses. Novel targeting strategies are critical in tackling antibiotic resistant infections. Synthetic antimicrobial peptides (SAMPs) are interesting candidates as they exhibit a very high antimicrobial activity. We first compared the activity of a library of ammonium and guanidinium polymers with different sequences (statistical, tetrablock and diblock) synthesized by RAFT polymerization against methicillin-resistant S. aureus (MRSA) and methicillin-sensitive strains (MSSA). As the guanidinium SAMPs were the most potent, they were used to treat intracellular S. aureus in keratinocytes. The diblock structure was the most active, reducing the amount of intracellular MSSA and MRSA by two-fold. We present here a potential treatment for intracellular, multi-drug resistant bacteria, using a simple and scalable strategy.

8.
Chem Sci ; 10(21): 5476-5483, 2019 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-31293730

RESUMO

Cyclic peptide nanotubes (CPNT) consisting of an even number of amino acids with an alternating chirality are highly interesting materials in a biomedical context due to their ability to insert themselves into cellular membranes. However, unwanted unspecific interactions between CPNT and non-targeted cell membranes are a major drawback. To solve this issue we have synthetized a series of CPNT-polymer conjugates with a cleavable covalent connection between macromolecule and peptide. As a result, the polymers form a stabilizing and shielding shell around the nanotube that can be cleaved on demand to generate membrane active CPNT from non-active conjugates. This approach enables us to control the stacking and lateral aggregation of these materials, thus leading to stimuli responsive membrane activity. Moreover, upon activation, the systems can be adjusted to form nanotubes with an increased length instead of aggregates. We were able to study the dynamics of these systems in detail and prove the concept of stimuli responsive membrane interaction using CPNT-polymer conjugates to permeabilize liposomes as well as mammalian cell membranes.

9.
Chem Commun (Camb) ; 55(49): 7045-7048, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31143905

RESUMO

A robust method for preparing controlled poly(vinyl ethers) utilizing commercially available reagents under visible light is reported. Pentacarbonylbromomanganese (Mn(CO)5Br), generated from the conventional photolysis of manganese carbonyl and halide abstraction, is considered as a catalyst to oxidize carbon radical to carbenium ion in this polymerization. Polymerization behavior including the effects of solvents and monomers have been investigated.

10.
Chem Commun (Camb) ; 55(36): 5291-5294, 2019 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-30994130

RESUMO

A supramolecular strategy of switching the self-assembly of cyclic peptide-polymer conjugates using host-guest chemistry is proposed. The formation of tubular supramolecular polymers based on cyclic peptide-polymer conjugates can be controlled by reversibly attaching cucurbit[7]uril onto the cyclic peptide via host-guest interactions.


Assuntos
Peptídeos Cíclicos/química , Polímeros/química , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Cinética , Compostos Macrocíclicos/química , Substâncias Macromoleculares/química , Estrutura Molecular , Nanopartículas/química , Tamanho da Partícula , Solventes/química , Relação Estrutura-Atividade , Propriedades de Superfície , Termodinâmica
11.
Biomacromolecules ; 20(3): 1297-1307, 2019 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-30694656

RESUMO

A synthetic cell mimic in the form of giant glycosylated polymersomes (GGPs) comprised of a novel amphiphilic diblock copolymer is reported. A synthetic approach involving a poly(dimethylsiloxane) (PDMS) macro-chain transfer agent (macroCTA) and postpolymerization modification was used to marry the hydrophobic and highly flexible properties of PDMS with the biological activity of glycopolymers. 2-Bromoethyl acrylate (BEA) was first polymerized using a PDMS macroCTA ( Mn,th ≈ 4900 g·mol-1, D = 1.1) to prepare well-defined PDMS- b-pBEA diblock copolymers ( D = 1.1) that were then substituted with 1-thio-ß-d-glucose or 1-thio-ß-d-galactose under facile conditions to yield PDMS- b-glycopolymers. Compositions possessing ≈25% of the glycopolymer block (by mass) were able to adopt a vesicular morphology in aqueous solution (≈210 nm in diameter), as indicated by TEM and light scattering techniques. The resulting carbohydrate-decorated polymersomes exhibited selective binding with the lectin concanavalin A (Con A), as demonstrated by turbidimetric experiments. Self-assembly of the same diblock copolymer compositions using an electroformation method yielded GGPs (ranging from 2-20 µm in diameter). Interaction of these cell-sized polymersomes with fimH positive E. coli was then studied via confocal microscopy. The glucose-decorated GGPs were found to cluster upon addition of the bacteria, while galactose-decorated GGPs could successfully interact with (and possibly immobilize) the bacteria without the onset of clustering. This demonstrates an opportunity to modulate the response of these synthetic cell mimics (protocells) toward biological entities through exploitation of selective ligand-receptor interactions, which may be readily tuned through a considered choice of carbohydrate functionality.

12.
Biomacromolecules ; 20(1): 285-293, 2019 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-30543415

RESUMO

Fibroblast growth factors (FGF) are involved in a wide range of biological processes such as cell proliferation and differentiation. In living organisms, the binding of FGF to its receptors are mediated through electrostatic interactions between FGF and naturally occurring heparin. Despite its prevalent use in medicine, heparin carries notable limitations; namely, its extraction from natural sources (expensive, low yield and extensive purification), viral contamination, and batch-to-batch heterogeneity. In this work a range of synthetic homopolymers and copolymers of sodium 2-acrylamido-2-methylpropanesulfonate were evaluated as potential FGF stabilizers. This was studied by measuring the proliferation of BaF3-FR1c cells, as a model assay, and the results will be compared with the natural stabilization and activation of FGF by heparin. This study explores the structure-activity relationship of these polysulfonated polymers with a focus on the effect of molecular weight, comonomer type, charge dispersion, and polymer architecture on protein stabilization.


Assuntos
Acrilamidas/química , Alcanossulfonatos/química , Materiais Biomiméticos/química , Fatores de Crescimento de Fibroblastos/química , Heparina/química , Células 3T3 , Acrilamidas/farmacologia , Alcanossulfonatos/farmacologia , Animais , Materiais Biomiméticos/farmacologia , Proliferação de Células/efeitos dos fármacos , Fatores de Crescimento de Fibroblastos/metabolismo , Heparina/farmacologia , Camundongos , Ligação Proteica , Enxofre/química
13.
Macromol Rapid Commun ; 40(2): e1800335, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30175483

RESUMO

Polymerization-induced self-assembly of 2-hydroxypropyl methacrylate is conducted in water and water/MeOH using a CO2 -responsive macroRAFT agent in the form of a statistical copolymer comprising N,N-diethylaminoethyl methacrylate (DEAEMA) and poly(ethylene glycol) methyl ether methacrylate (M n  = 475 g mol-1 ). Pressurization with CO2 leads to protonation of DEAEMA units within the stabilizer block, thereby offering a means of adjusting the charge density of the coronal layer. It is demonstrated that a wide range of tunable particle morphologies are accessible by simply varying the CO2 pressure during polymerization in the range of 10-45 bar.


Assuntos
Dióxido de Carbono/química , Metacrilatos/química , Polimerização , Polímeros/química , Técnicas de Química Sintética/métodos , Microscopia Eletrônica de Transmissão , Modelos Químicos , Estrutura Molecular , Polietilenoglicóis/química , Polímeros/síntese química , Prótons , Água/química
14.
Macromol Rapid Commun ; 40(2): e1800314, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29999558

RESUMO

Heparin plays a significant role in wound healing and tissue regeneration applications, through stabilization of fibroblast growth factors (FGF). Risks associated with batch-to-batch variability and contamination from its biological sources have led to the development of synthetic, highly sulfonated polymers as promising heparin mimics. In this work, a systematic study of an aqueous polymerization-induced self-assembly (PISA) of styrene from poly(2-acrylamido-2-methylpropane sodium sulfonate) (P(AMPS)) macro reversible addition-fragmentation chain transfer (macro-RAFT) agents produced a variety of spherical heparin-mimicking nanoparticles, which were further characterized with light scattering and electron microscopy techniques. None of the nanoparticles tested showed toxicity against mammalian cells; however, significant hemolytic activity was observed. Nonetheless, the heparin-mimicking nanoparticles outperformed both heparin and linear P(AMPS) in cellular proliferation assays, suggesting increased bFGF stabilization efficiencies, possibly due to the high density of sulfonated moieties at the particle surface.


Assuntos
Técnicas de Química Sintética/métodos , Heparina/química , Nanopartículas/química , Polimerização , Polímeros/química , Ácidos Sulfônicos/química , Animais , Materiais Biomiméticos/síntese química , Materiais Biomiméticos/química , Materiais Biomiméticos/farmacologia , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Difusão Dinâmica da Luz , Hemólise/efeitos dos fármacos , Heparina/síntese química , Camundongos , Microscopia Eletrônica de Transmissão , Modelos Químicos , Estrutura Molecular , Células NIH 3T3 , Nanopartículas/ultraestrutura , Polímeros/síntese química , Estireno/química , Ácidos Sulfônicos/síntese química
15.
Angew Chem Int Ed Engl ; 57(51): 16678-16682, 2018 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-30383920

RESUMO

The properties and structures of viruses are directly related to the three-dimensional structure of their capsid proteins, which arises from a combination of hydrophobic and supramolecular interactions, such as hydrogen bonds. The design of synthetic materials demonstrating similar synergistic interactions still remains a challenge. Herein, we report the synthesis of a polymer/cyclic peptide conjugate that combines the capability to form supramolecular nanotubes via hydrogen bonds with the properties of an amphiphilic block copolymer. The analysis of aqueous solutions by scattering and imaging techniques revealed a barrel-shaped alignment of single peptide nanotubes into a large tubisome (length: 260 nm (from SANS)) with a hydrophobic core (diameter: 16 nm) and a hydrophilic shell. These systems, which have a structure that is similar to those of viruses, were tested in vitro to elucidate their activity on cells. Remarkably, the rigid tubisomes are able to perforate the lysosomal membrane in cells and release a small molecule into the cytosol.


Assuntos
Nanotubos/química , Peptídeos Cíclicos/química , Polímeros/química , Linhagem Celular Tumoral , Sobrevivência Celular , Células HEK293 , Humanos , Ligação de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Lisossomos/química , Substâncias Macromoleculares/síntese química , Substâncias Macromoleculares/química
16.
Chemistry ; 24(71): 19066-19074, 2018 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-30338575

RESUMO

Breaking away from the linear structure of previously reported peptide-based gelators, this study reports the first example of gel formation based on the use of cyclic peptides made of alternating d- and l-amino acids, known to self-assemble in solution to form long nanotubes. Herein, a library of cyclic peptides was systemically studied for their gelation properties in various solvents, uncovering key parameters driving both organogel and hydrogel formation. The hierarchical nature of the self-assembly process in water was characterised by a combination of electron microscopy imaging and small-angle X-ray scattering, revealing a porous network of entangled nanofibres composed by the aggregation of several cyclic peptide nanotubes. Rheology measurements then confirmed the formation of soft hydrogels.


Assuntos
Hidrogéis/química , Nanotubos/química , Peptídeos Cíclicos/química , Nanotubos/ultraestrutura , Biblioteca de Peptídeos , Reologia , Espalhamento a Baixo Ângulo , Solventes , Água/química , Difração de Raios X
18.
Anal Chem ; 90(19): 11710-11715, 2018 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-30199232

RESUMO

With increasing focus on the structural elucidation of polymers, advanced tandem mass spectrometry techniques will play a crucial role in the characterization of these compounds. In this contribution, synthesis and analysis of methyl-initiated and xanthate-terminated poly(2-ethyl-2-oxazoline) using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) was achieved. Electron capture dissociation (ECD) produced full end group characterization as well as backbone fragmentation including complete sequence coverage of the polymer. A method of fragment ion characterization is also presented with the use of the high-resolution-modified Kendrick mass defect plots as a means of grouping fragments from the same fragmentation pathways together. This type of data processing is applicable to all tandem mass spectrometry techniques for polymer analysis but is made more effective with high mass accuracy methods. ECD FT-ICR MS demonstrates its promising role as a structural characterization technique for polyoxazoline species.

19.
Macromol Biosci ; 18(10): e1800213, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30085410

RESUMO

Current approaches to generate core-shell nanoparticles for biomedical applications are limited by factors such as synthetic scalability and circulatory desorption of cytotoxic surfactants. Developments in controlled radical polymerization, particularly in dispersed states, represent a promising method of overcoming these challenges. In this work, well-defined PEGylated nanoparticles are synthesized using reversible addition fragmentation chain transfer emulsion polymerization to control particle size and surface composition and were further characterized with light scattering, electron microscopy, and size exclusion chromatography. Importantly, the nanoparticles are found to be tolerated both in vitro and in vivo, without the need for any purification after particle synthesis. Pharmacokinetic and biodistribution studies in mice, following intraperitoneal injection of the nanoparticles, reveal a long (>76 h) circulation time and accumulation in the liver.


Assuntos
Látex , Teste de Materiais , Nanopartículas/química , Polimerização , Animais , Células CACO-2 , Emulsões , Humanos , Látex/química , Látex/farmacocinética , Látex/farmacologia , Masculino , Camundongos
20.
Soft Matter ; 14(30): 6320-6326, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30019044

RESUMO

Self-assembling cyclic peptides (CP) consisting of amino acids with alternating d- and l-chirality form nanotubes by hydrogen bonding, hydrophobic interactions, and π-π stacking in solution. These highly dynamic materials are emerging as promising supramolecular systems for a wide range of biomedical applications. Herein, we discuss how varying the polymer conformation (linear vs. brush), as well as the number of polymer arms per peptide unimer affects the self-assembly of PEGylated cyclic peptides in different solvents, using small angle neutron scattering. Using the derived information, strong correlations were drawn between the size of the aggregates, solvent polarity, and its ability to compete for hydrogen bonding interactions between the peptide unimers. Using these data, it could be possible to engineer cyclic peptide nanotubes of a controlled length.

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