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1.
Biofilm ; 5: 100124, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37153749

RESUMO

Objectives: Driveline infections are a major complication of ventricular assist device (VAD) therapy. A newly introduced Carbothane driveline has preliminarily demonstrated anti-infective potential against driveline infections. This study aimed to comprehensively assess the anti-biofilm capability of the Carbothane driveline and explore its physicochemical characteristics. Methods: We assessed the Carbothane driveline against biofilm formation of leading microorganisms causing VAD driveline infections, including Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Candida albicans, using novel in vitro biofilm assays mimicking different infection micro-environments. The importance of physicochemical properties of the Carbothane driveline in microorganism-device interactions were analyzed, particularly focusing on the surface chemistry. The role of micro-gaps in driveline tunnels on biofilm migration was also examined. Results: All organisms were able to attach to the smooth and velour sections of the Carbothane driveline. Early microbial adherence, at least for S. aureus and S. epidermidis, did not proceed to the formation of mature biofilms in a drip-flow biofilm reactor mimicking the driveline exit site environment. The presence of a driveline tunnel however, promoted staphylococcal biofilm formation on the Carbothane driveline. Physicochemical analysis of the Carbothane driveline revealed surface characteristics that may have contributed to its anti-biofilm activity, such as the aliphatic nature of its surface. The presence of micro-gaps in the tunnel facilitated biofilm migration of the studied bacterial species. Conclusion: This study provides experimental evidence to support the anti-biofilm activity of the Carbothane driveline and uncovered specific physicochemical features that may explain its ability to inhibit biofilm formation.

2.
ACS Appl Mater Interfaces ; 14(31): 35755-35768, 2022 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-35905302

RESUMO

Solid-state sensing platforms are desirable for the development of reusable sensors to promote public health measures such as testing for drinking water contamination. A bioinspired metal-organic framework (MOF)-based material has been developed by imitating metal-protein interactions in biological systems to attain high sensitivity and selectivity to Pb2+ through fluorescence sensing. A zirconium terephthalate-type framework (also known as NH2-UiO-66) was modified with both gold nanoparticles and thiol-functionalized carbon dots to give HS-C/Au(x)/UiO-66 composites with different Au content (x) and were subsequently adapted into films that show extraordinary sensitivity to Pb2+. The HS-C/Au(1.4)/UiO-66 film that consists of 1.4 wt % Au shows a quenching response with the limit of detection of 80 parts per trillion and sustained performance for five cycles. Moreover, the fluorescence response of the HS-C/Au(x)/UiO-66 film to Pb2+ can be reversed from emission quenching to enrichment of fluorescence by increasing the Au content. The performance of the HS-C/Au(x)/UiO-66 film as a solid-state sensor demonstrates its potential for application in reusable sensing devices to ensure public safety from Pb2+ contamination in drinking water.


Assuntos
Água Potável , Nanopartículas Metálicas , Estruturas Metalorgânicas , Carbono , Água Potável/análise , Fluorescência , Ouro , Íons , Chumbo , Ácidos Ftálicos
3.
Nanoscale ; 14(4): 1395-1408, 2022 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-35018401

RESUMO

The electrochemical synthesis of ammonia at ambient temperature and pressure has the potential to replace the conventional process for the production of ammonia. However, the low ammonia yield and poor long-term stability of catalysts for the synthesis of ammonia hinders the application of this technology. Herein, we endeavored to tackle this challenge by synthesizing 3-D vertical graphene (VG) on Ni foam via a one-step, low-temperature plasma process, which offered high conductivity and large surface area. Subsequently, the vertical graphene on Ni foam was loaded with nanolayers of ruthenium oxide (RuO2, ∼2 nm) and cerium oxide (CeO2, <20 nm) nanoparticles via magnetron sputtering. The incorporation of nanoparticle layers (RuO2 and CeO2/RuO2) on VG significantly increased the NH3 yield in KOH electrolyte. Finally, the performance and long-term stability of this composite material were successfully demonstrated by the addition of CeO2/RuO2 nanolayers on the VG electrocatalyst. The catalyst achieved an excellent performance with a high ammonia synthesis yield of 50.56 µg mgtotal cat.-1 h-1 (1.11 × 10-10 mol cm-2 s-1) during the performance evaluation period of 36 h. This observation was also verified by density functional theory calculation, where CeO2 exhibited the best catalytic performance compared to RuO2 and pristine graphene.

4.
ACS Sens ; 5(10): 3226-3236, 2020 10 23.
Artigo em Inglês | MEDLINE | ID: mdl-32938190

RESUMO

Desorption/ionization on porous silicon mass spectrometry (DIOS-MS) is shown to be a powerful technique for the sensing of low-molecular-weight compounds, including drugs and their metabolites. Surface modification of DIOS surfaces is required to increase analytical performance and ensure stability. However, common wet chemical modification techniques use fluorosilanes, which are less suitable for high-throughput manufacturing and analytical repeatability. Here, we report an alternative, rapid functionalization technique for DIOS surfaces using plasma polymerization (ppDIOS). We demonstrate the detection of drugs, metabolites, pesticides, and doping agents, directly from biological matrices, with molecular confirmation performed using the fragmentation capabilities of a tandem MS instrument. Furthermore, the ppDIOS surfaces were found to be stable over a 162 day period with no loss of reproducibility and sensitivity. This alternative functionalization technique is cost-effective and amenable to upscaling, ensuring avenues for the high-throughput manufacture and detection of hundreds of analytes across various applications while still maintaining the gold-standard clinical technique using mass spectrometry.


Assuntos
Fluorocarbonos , Preparações Farmacêuticas , Porosidade , Reprodutibilidade dos Testes , Silício , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
6.
Nano Lett ; 20(2): 1240-1251, 2020 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-31960676

RESUMO

3D/2D hybrid perovskite systems have been intensively investigated to improve the stability of perovskite solar cells (PSCs), whereas undesired crystallization of 2D perovskite during the film formation process could undermine the structural stability of 2D perovskite materials, which causes serious hysteresis of PSCs after aging. This issue is, however, rarely studied. The stability study for 3D/2D hybrid systems to date is all under the one-direction scan, and the lack of detailed information on the hysteresis after aging compromises the credibility of the stability results. In this work, by correlating the hysteresis of the hybrid PSCs with the 2D crystal structure, we find that the prompt 2D perovskite formation process easily induces numerous crystal imperfections and structural defects. These defects are susceptible to humidity attack and decompose the 2D perovskite to insulating long-chain cations and 3D perovskite, which hinder charge transfer or generate charge accumulation. Therefore, a large hysteresis is exhibited after aging the 3D/2D hybrid PSCs in an ambient environment, even though the reverse-scan power conversion efficiency (PCE) is found to be well-preserved. To address this issue, alkali cations, K+ and Rb+, are introduced into the 2D perovskite to exquisitely modulate the crystal formation, which gives rise to a higher crystallinity of 2D perovskite and a better film morphology with fewer defects. We achieved PCE beyond 21% due to the preferable charge transfer process and reduced nonradiative recombination losses. The structural features also bring about impressive moisture stability, which results in the corresponding PSCs retaining 93% of its initial PCE and negligible hysteresis after aging in an ambient atmosphere for 1200 h.

7.
iScience ; 23(1): 100761, 2020 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-31887660

RESUMO

Effective design of bifunctional catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is important but remains challenging. Herein, we report a three-dimensional (3D) hierarchical structure composed of homogeneously distributed Ni-Fe-P nanoparticles embedded in N-doped carbons on nickel foams (denoted as Ni-Fe-P@NC/NF) as an excellent bifunctional catalyst. This catalyst was fabricated by an anion exchange method and a low-temperature phosphidation of nanotubular Prussian blue analogue (PBA). The Ni-Fe-P@NC/NF displayed exceptional catalytic activity toward both HER and OER and delivered an ultralow cell voltage of 1.47 V to obtain 10 mA cm-2 with extremely excellent durability for 100 h when assembled as a practical electrolyser. The extraordinary performance of Ni-Fe-P@NC/NF is attributed to the abundance of unsaturated active sites, the well-defined hierarchical porous structure, and the synergistic effect between multiple components. Our work will inspire more rational designs of highly active non-noble electrocatalysts for industrial energy applications.

8.
ACS Appl Mater Interfaces ; 11(44): 41617-41625, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31601101

RESUMO

Colored and color-changing materials are central to perception and interaction in nature and have been exploited in an array of modern technologies such as sensors, visual displays, and smart materials. Attempts to introduce color into carbon fiber materials have been limited by deleterious impacts on fiber properties, and the extension of colored fibers toward "smart composites" remains in its infancy. We present carbon fibers incorporating structural color, similar to that observed on the surface of soap bubbles and various insects and birds, by modifying the fiber surface through in situ polymerization grafting. When dry, the treated fibers exhibit a striking blue color, but when exposed to a volatile solvent, a cascade of colors across the visible light region is observed as the film first swells and then shrinks as the solvent evaporates. The treated fibers not only possess a unique color and color-changing ability but also can be reversibly formed into complex shapes and bear significant loads even without being encased in a supporting polymer. The tensile strength of treated fibers shows a statistically significant increase (+12%), and evaluation of the fiber-to-matrix adhesion of these polymers to an epoxy resin shows more than 300% improvement over control fibers. This approach creates a new platform for the multifaceted advance of smart composites.


Assuntos
Fibra de Carbono/química , Resinas Acrílicas/química , Adesivos/química , Cor , Compostos de Diazônio/química , Microscopia de Força Atômica , Espectroscopia Fotoeletrônica , Resistência ao Cisalhamento , Solventes/química , Propriedades de Superfície , Resistência à Tração
9.
Chem Commun (Camb) ; 55(55): 8001-8004, 2019 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-31225547

RESUMO

We report the first method to introduce differential functionalities in the interior pore walls and exterior surface of highly stable thermally hydrocarbonised porous silicon (THCpSi) films. The approach exploits the hydrophobicity of the hydrosilylated THCpSi to, first, selectively functionalise the external surface, and subsequently derivatise the hydrophobic internal pore walls.

10.
J Biomed Mater Res B Appl Biomater ; 107(1): 112-121, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-29504237

RESUMO

A series of siloxane poly(urethane-urea) (SiPUU) were developed by incorporating a macrodiol linked with a diisocyanate to enhance mixing of hard and soft segments (SS). The effect of this modification on morphology, surface properties, surface elemental composition, and creep resistance was investigated. The linked macrodiol was prepared by reacting α,ω-bis(6-hydroxyethoxypropyl) poly(dimethylsiloxane)(PDMS) or poly(hexamethylene oxide) (PHMO) with either 4,4'-methylenediphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), or isophorone diisocyanate (IPDI). SiPUU with PHMO-MDI-PHMO and PHMO-IPDI-PHMO linked macrodiols showed enhanced creep resistance and recovery when compared with a commercial biostable polyurethane, Elast-Eon™ 2A. Small and wide-angle X-ray scattering data were consistent with significant increase of hydrogen bonding between hard and SS with linked-macrodiols, which improved SiPUU's tensile stress and tear strengths. These SiPUU were hydrophobic with contact angle higher than 101° and they had low water uptake (0.7%·w/w of dry mass). They also had much higher siloxane concentration on the surface compared to that in the bulk. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 112-121, 2019.


Assuntos
Próteses Valvulares Cardíacas , Poliuretanos/química , Siloxanas/química , Humanos , Propriedades de Superfície
11.
Langmuir ; 35(5): 1266-1272, 2019 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-29801414

RESUMO

Development of antifouling films which selectively capture or target proteins of interest is essential for controlling interactions at the "bio/nano" interface. However, in order to synthesize biofunctional films from synthetic polymers that incorporate chemical "motifs" for surface immobilization, antifouling, and oriented biomolecule attachment, multiple reaction steps need to be carried out at the solid/liquid interface. EKx is a zwitterionic peptide that has previously been shown to have excellent antifouling properties. In this study, we recombinantly expressed EKx peptides and genetically encoded both surface attachment and antibody-binding motifs, before characterizing the resultant biopolymers by traditional methods. These peptides were then immobilized to organosilica nanoparticles for binding IgG, and subsequently capturing dengue NS1 as a model antigen from serum-containing solution. We found that a mixed layer of a short peptide (4.9 kDa) "backfilled" with a longer peptide terminated with an IgG-binding Z-domain (18 kDa) demonstrated selective capture of dengue NS1 protein down to ∼10 ng mL-1 in either PBS or 20% serum.


Assuntos
Incrustação Biológica/prevenção & controle , Imunoglobulina G/metabolismo , Peptídeos/metabolismo , Proteínas Recombinantes/metabolismo , Vírus da Dengue/química , Escherichia coli/genética , Proteínas Imobilizadas/genética , Proteínas Imobilizadas/metabolismo , Imunoglobulina G/química , Nanopartículas/química , Peptídeos/genética , Ligação Proteica , Domínios Proteicos , Engenharia de Proteínas/métodos , Proteínas Recombinantes/genética , Dióxido de Silício/química , Proteínas não Estruturais Virais/metabolismo
12.
Sci Total Environ ; 646: 1440-1447, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30235629

RESUMO

Although electrochemical oxidation (ECO) has shown excellent potential for disinfecting wastewater and surface waters, its application on urban stormwater has been rarely tested. In order to improve stormwater ECO design, this paper explores the major inactivation processes using Boron Doped Diamond (BDD) and titanium Dimensional Stable Anodes (DSA). Both BDD and DSA showed comparable disinfection rates. The mechanism study suggested that BDD relied on hydroxyl radical and the presence of chloride ions, while DSA disinfected stormwater mainly via the production of free­chlorine. A deterioration study carried out at a catchment in Melbourne, showed a steady performance for BDD and revealed that DSA's performance degraded with time, likely linked to the high operational voltage required for specific chemistry of stormwater. Scanning Electron Microscopes and an Energy Dispersive X-ray Detector tests confirmed elemental losses occurred on the DSA surface, together with an aluminium/silicon coating layer potentially sourced from the stormwater clayish sediments. Furthermore, disinfection by-products in electrochemical disinfected stormwater using either BDD or DSA were at least one order of magnitude lower than the Australia Drinking Water Guidelines limits. The mechanism and long-term study demonstrated that careful anode selection is required as some anodes will deteriorate in stormwater matrices faster than others.

13.
Nat Commun ; 9(1): 5070, 2018 11 29.
Artigo em Inglês | MEDLINE | ID: mdl-30498194

RESUMO

Silicon-based impurities are ubiquitous in natural graphite. However, their role as a contaminant in exfoliated graphene and their influence on devices have been overlooked. Herein atomic resolution microscopy is used to highlight the existence of silicon-based contamination on various solution-processed graphene. We found these impurities are extremely persistent and thus utilising high purity graphite as a precursor is the only route to produce silicon-free graphene. These impurities are found to hamper the effective utilisation of graphene in whereby surface area is of paramount importance. When non-contaminated graphene is used to fabricate supercapacitor microelectrodes, a capacitance value closest to the predicted theoretical capacitance for graphene is obtained. We also demonstrate a versatile humidity sensor made from pure graphene oxide which achieves the highest sensitivity and the lowest limit of detection ever reported. Our findings constitute a vital milestone to achieve commercially viable and high performance graphene-based devices.

14.
Biomater Sci ; 7(1): 233-246, 2018 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-30511062

RESUMO

Nanogels were prepared by ionotropic gelation of chitosan (CS) with tripolyphosphate (TPP). The use of such nanogels to prepare coatings by layer-by-layer deposition (LbL) was studied. The nanogels were characterized in terms of particle size, zeta-potential and stability. Nanogel suspensions were used to build polyelectrolyte multilayers on silicon wafers and on PCL fiber mats by LbL-deposition. Three different polysaccharides were used as polyanions, namely chondroitin sulfate, alginate and hyaluronic acid. The ellipsometric thickness was demonstrated to depend significantly on the type of polyanion. XPS analysis with depth profiling further substantiated the differences in the chemical composition of the films with the different polyanions. Furthermore, XPS data clearly indicated a strong penetration of the polyanions into the CS-TPP layer, resulting in a complete exchange and release of the TPP ions. The LbL-deposition also was studied with PCL fiber mats, which were modified with a chitosan-PCL-graft polymer and alginate. The possibility to create graded coatings on the fiber mats was shown employing fluorescently labelled CS-TPP nanoparticles. The potential of the coatings as drug delivery system for therapeutic proteins was exemplified with the release of Transforming Growth Factor ß3 (TGF-ß3). The CS-TPP nanogels were shown to encapsulate and release therapeutic proteins. In combination with the layer-by-layer deposition they will allow the creation of PCL fiber mat implants having with drug gradients for applications at tissue transitions.


Assuntos
Quitosana/análogos & derivados , Materiais Revestidos Biocompatíveis/química , Portadores de Fármacos/química , Nanofibras/química , Nanopartículas/química , Poliésteres/química , Fator de Crescimento Transformador beta3/administração & dosagem , Alginatos/química , Quitosana/química , Sulfatos de Condroitina/química , Sistemas de Liberação de Medicamentos , Liberação Controlada de Fármacos , Humanos , Ácido Hialurônico/química , Nanofibras/ultraestrutura , Nanopartículas/ultraestrutura , Fator de Crescimento Transformador beta3/química
15.
Front Chem ; 6: 161, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29868563

RESUMO

Paper and cellulosic films are used in many designs of low-cost diagnostics such as paper-based blood grouping devices. A major issue limiting their commercialization is the short stability of the functional biomolecules. To address this problem, the effect of relative humidity (RH) and bovine serum albumin (BSA) on the antibody bioactivity and the surface chemical composition of a paper blood typing biodiagnostic were studied. An IgM blood typing antibody was physisorbed from solution onto paper - with or without BSA pretreatment, and aged for periods up to 9 weeks under various conditions with a series of RH. The blood typing efficiency of the antibodies and the substrate surface chemical composition were analyzed by image analysis and X-ray photoelectron spectroscopy (XPS), respectively. This study tests two hypotheses. The first is that the hydroxyl groups in paper promote antibody denaturation on paper; the second hypothesis is that proteins such as BSA can partially block the hydroxyl groups within paper, thus preserving antibody bioactivity. Results show that high RH is detrimental to antibody longevity on paper, while BSA can block hydroxyl groups and prolong antibody longevity by almost an order of magnitude-regardless of humidity. This study opens up new engineering concepts to develop robust and marketable paper diagnostics. The simplest is to store paper and antibody based diagnostics in moisture proof packages.

16.
Eur J Pharm Biopharm ; 127: 213-222, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29486303

RESUMO

This study aimed to assess the robustness of using a spray drying approach and formulation design in producing inhalable phage powders. Two types of Pseudomonas phages, PEV2 (Podovirus) and PEV40 (Myovirus) in two formulations containing different amounts of trehalose (70% and 60%) and leucine (30% and 40%) were studied. Most of the surface of the produced powders was found to be covered in crystalline leucine. The powders were stored at 4 °C and 20 °C under vacuum. The phage stability and in vitro aerosol performance of the phage powders were examined on the day of production and after 1, 3 and 12 months of storage. A minor titer loss during production was observed for both phages (0.2-0.8 log10 pfu/ml). The storage stability of the produced phage powders was found to be phage and formulation dependent. No further reduction in titer occurred for PEV2 powders stored at 4 °C across the study. The formulation containing 30% leucine maintained the viability of PEV2 at 20 °C, while the formulation containing 40% leucine gradually lost titer over time with a storage reduction of ∼0.9 log10 pfu/ml measured after 12 months. In comparison, the PEV40 phage powders generally had a ∼ 0.5 log10 pfu/ml loss upon storage regardless of temperature. When aerosolized, the total in vitro lung doses of PEV2 were of the order of 107 pfu, except the formulation containing 40% leucine stored at 20 °C which had a lower lung dose. The PEV40 powders also had lung doses of 106-107 pfu. The results demonstrate that spray dried Myoviridae and Podoviridae phage in a simple formulation of leucine and trehalose can be successfully stored for one year at 4 °C and 20 °C with vacuum packaging.


Assuntos
Bacteriófagos/química , Pós/química , Administração por Inalação , Aerossóis/química , Química Farmacêutica/métodos , Dessecação/métodos , Estabilidade de Medicamentos , Inaladores de Pó Seco/métodos , Excipientes/química , Pulmão/efeitos dos fármacos , Tamanho da Partícula , Temperatura , Trealose/química
17.
Chempluschem ; 83(7): 704-710, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31950620

RESUMO

The possibility of efficient water electrooxidation sustained by continuous (re)generation of catalysts derived from the oxidative electrodeposition of transition-metal contaminants is examined herein for three natural water samples from Australia and China. The metal composition of the solutions has been determined by inductively coupled plasma optical emission spectrometry, and a range of strategies to produce water-splitting catalysts by means of in situ electrodeposition have been applied. The performance of the resulting electrocatalysts is below the state-of-the-art level owing to large amounts of impurities in the solutions and non-optimal concentrations of naturally available catalyst precursors. Nevertheless, these studies have identified the FePb-based system as a rare example of an electrocatalyst for water oxidation that forms in situ and maintains reasonable activity (≥4.5 mA cm-2 at an overpotential of 0.8 V) in weakly acidic solutions (pH 2.9).

18.
Nanoscale ; 9(44): 17349-17356, 2017 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-29095460

RESUMO

We successfully synthesized a novel electro-catalyst with a unique structure of Ni2P nanoparticles decorating the surface of MoO2@MoS2 sub-microwires on titanium foil (denote as NiMoO-SP/Ti) via a facile temperature-programmed sulfuration-phosphorization from its nickel molybdate precursor. The metallic MoO2 core facilitates electron transfer, and the interfaces between MoS2 nanosheets and Ni2P nanoparticles enhance catalytic activity both for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Due to this unique structure, the obtained NiMoO-SP/Ti showed an enhanced OER performance in alkaline solution with a small Tafel slope of 85 mV dec-1 and a low overpotential of 280 and 360 mV to achieve 10 and 100 mA cm-2 in 1.0 M KOH, respectively. The catalyst also exhibited an excellent stability in 1.0 M KOH, with just 12 mV shift after electrolysis at 10 mA cm-2 for 16 h and 27 mV shift after electrolysis at 20 mA cm-2 for another 24 h. In addition, the NiMoO-SP/Ti also displayed high catalytic properties towards HER with a small Tafel slope of 77 mV dec-1 and a low overpotential of 159 mV to obtain 10 mA cm-2 in 1.0 M KOH. After electrolysis at -10 mA cm-2 for 40 h, the overpotential increased by just 25 mV, which demonstrated its high stability for HER in 1.0 M KOH. This work provides an effective route to designing a high-performance catalyst with a favorable structure for the development of electro-catalysts for water splitting.

19.
Chemistry ; 23(54): 13482-13492, 2017 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-28722330

RESUMO

Influence of the conditions for aerobic oxidation of Mn2+(aq) catalysed by the MnxEFG protein complex on the morphology, structure and reactivity of the resulting biogenic manganese oxides (MnOx ) is explored. Physical characterisation of MnOx includes scanning and transmission electron microscopy, and X-ray photoelectron and K-edge Mn, Fe X-ray absorption spectroscopy. This characterisation reveals that the MnOx materials share the structural features of birnessite, yet differ in the degree of structural disorder. Importantly, these biogenic products exhibit strikingly different morphologies that can be easily controlled. Changing the substrate-to-protein ratio produces MnOx either as nm-thin sheets, or rods with diameters below 20 nm, or a combination of the two. Mineralisation in solutions that contain Fe2+(aq) makes solids with significant disorder in the structure, while the presence of Ca2+(aq) facilitates formation of more ordered materials. The (photo)oxidation and (photo)electrocatalytic capacity of the MnOx minerals is examined and correlated with their structural properties.

20.
Int J Pharm ; 530(1-2): 30-39, 2017 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-28709940

RESUMO

The aim of this study was to investigate the ability of L-leucine (LL) in preventing moisture-induced deterioration in the in vitro aerosolization performance of spray-dried (SD) salbutamol sulfate (SS). Increasing mass fraction of LL (5-80%) were co-spray dried with SS, and the physicochemical properties of the powders were characterized by laser diffraction, X-ray powder diffraction (XRD) and dynamic vapour sorption (DVS). Furthermore, the surface morphology and chemistry of fine particles was analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The in vitro aerosolization performance of powders stored at different relative humidity (RH) was evaluated by a next generation impactor (NGI). The SD SS powders were moderately hygroscopic and amorphous, of which the uptake of moisture upon storage caused a drop in the aerosolization performance. The results showed that 40% (w/w) LL was sufficient to eliminate the effect of moisture on the aerosolization performance at 60% RH. The formulation containing 40% (w/w) LL also maximized the aerosolization performance of SD SS powders (stored in desiccator) with the emitted fraction being 90.0±1.8%, and the fine particle fraction based on the recovered dose (FPFrecovered) and emitted dose (FPFemitted) being 78.0±3.7% and 86.6±2.9%, respectively. The underlying mechanisms were that the crystalline LL increased the degree of particle surface corrugation, and reduced particle fusion and cohesiveness to facilitate dispersion. However, there is still a great challenge to prevent the moisture-induced deterioration in the aerosolization performance at 75% RH due to the recrystallization of SD SS. In conclusion, LL is a potential excipient for reducing moisture-induced deterioration in the aerosolization performance of SD amorphous powders, but still has drawbacks in preventing the recrystallization-induced deterioration.


Assuntos
Administração por Inalação , Albuterol/administração & dosagem , Leucina/química , Pós , Aerossóis , Química Farmacêutica , Tamanho da Partícula
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