Multifunctional polymer/porous boron nitride nanosheet membranes for superior trapping emulsified oils and organic molecules

Effective oil/water separation and removal of organic molecules from water are of worldwide importance for water source protection. Multifunctional sorbent materials with excellent sorption capacity, stability, and recyclability properties need to be developed. Here, flexible and multifunctional polymer/porous boron nitride nanosheets (BNNSs) membranes with high water permeability, exhibiting high effectiveness and stability in the purification of simulated wastewater tainted with either oil/water emulsion or organic molecules, are reported. Remarkably, the flexible nature of these porous membranes enables simplicity of operation for water remediation processing and ease of post-processing collection. The composite membrane also displays a remarkably high permeability of 8 × 10⁴ L μm m^-2 h^-1 bar^-1, roughly three orders of magnitude higher than pure polymer, and excellent filter efficiencies for the pharmaceuticals ciprofloxacin, chlortetracycline, and carbamazepine (up to 14.2 L g^-1 of BNNSs in the composite membrane for a concentration of 10 mg L^-1 ciprofloxacin) and the dye methylene blue (up to 9.3 L g^-1 of BNNSs in the composite membrane at a concentration of 30 mg L^-1). Exhausted membranes can be readily rejuvenated by simple washing with retention of their high-performance characteristics. The results demonstrate the potential efficacy and practicality of these membranes for water cleaning.

Evaluation of polyvinyl alcohol composite membranes containing collagen and bone particles

Composite biomaterials provide alternative materials that improve on the properties of the individual components and can be used to replace or restore damaged or diseased tissues. Typically, a composite biomaterial consists of a matrix, often a polymer, with one or more fillers that can be made up of particles, sheets or fibres. The polymer matrix can be chosen from a wide range of compositions and can be fabricated easily and rapidly into complex shapes and structures. In the present study we have examined three size fractions of collagen-containing particles embedded at up to 60% w/w in a poly(vinyl alcohol) (PVA) matrix. The particles used were bone particles, which are a mineral-collagen composite and demineralised bone, which gives naturally cross-linked collagen particles. SEM showed well dispersed particles in the PVA matrix for all concentrations and sizes of particles, with FTIR suggesting collagen to PVA hydrogen bonding. Tg of membranes shifted to a slightly lower temperature with increasing collagen content, along with a minor amount of melting point depression. The modulus and tensile strength of membranes were improved with the addition of both particles up to 10 wt%, and were clearly strengthened by the addition, although this effect decreased with higher collagen loadings. Elongation at break decreased with collagen content. Cell adhesion to the membranes was observed associated with the collagen particles, indicating a lack of cytotoxicity.

Self-assembly of monolayered lipid membranes for surface-coating of a nanoconfined Bombyx mori silk fibroin film

Regenerated Bombyx mori (B. mori) silk fibroin is a type of widely used biomaterial. The β-sheet structure of it after methanol treatment provides water-insolubility and mechanical stability while on the other side leads to a hydrophobic surface which is less preferred by biological systems. In this work we prepare a novel type of nanoconfined silk fibroin film with a thickness below 100 nm. The film has a flat while hydrophobic surface because of its β-sheet structure due to the z-direction confinement during formation. Different types of lipid monolayers, DOPC, DPPC and MO, are assembled on the silk film surface. The lipid coating, especially the DPPC membrane, provides a much smoother and more hydrophilic surface due to the gel phase tails of the lipids, in comparison with the DOPC and MO ones which are in a liquid phase and have a much stronger interfacial association between silk film surface and lipid tails. Such a lipid coating preserves the biocompatibility and cellular affinity of the silk film which promises potential applications as surface coatings for materials for biological use.

Electrospun fibrous membranes with super-large-strain electric superhydrophobicity

Large-strain elastic superhydrophobicity is highly desirable for its enhanced use performance and functional reliability in mechanically dynamic environments, but remains challenging to develop. Here we have, for the first time, proven that an elastic fibrous membrane after surface hydrophobization can maintain superhydrophobicity during one-directional (uniaxial) stretching to a strain as high as 1500% and two-direction (biaxial) stretching to a strain up to 700%. The fibrous membrane can withstand at least 1,000 cycles of repeated stretching without losing the superhydrophobicity. Stretching slightly increases the membrane air permeability and reduces water breakthrough pressure. It is highly stable in acid and base environments. Such a permeable, highly-elastic superhydrophobic membrane may open up novel applications in membrane separation, healthcare, functional textile and energy fields.

Enhancement of the antifouling properties and filtration performance of poly(ethersulfone) ultrafiltration membranes by incorporation of nanoporous titania nanoparticles

Nanoporous titania nanoparticles (NTNs) were synthesized and used as an additive at a low concentration of 0.1-1 wt % in the fabrication of poly(ethersulfone) (PES) ultrafiltration membranes via non-solvent-induced phase separation. The structure and properties of nanoparticles were characterized using nitrogen sorption, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The NTNs have a size distribution with a particle size of mainly <100 nm and have a Brunauer, Emmett, and Teller surface area of ∼100 m2 g-1. The modified membranes were fabricated and investigated in terms of their pure water flux, solute rejection, and fouling resistance. The water permeability and molecular weight cutoffs (MWCOs) of membranes were determined under constant-pressure filtration in dead-end mode at 100 kPa. The membrane fouling resistance was characterized under constant flux operation using bovine serum albumin as a model foulant. The membranes were characterized in terms of morphology, porosity, pore size distribution, energy-dispersive X-ray spectroscopy, contact angle goniometry, surface free energy, and viscosity of the dope solution. Overall, the modified membrane showed increased wettability and reduced surface free energy and pore size. The modified UF membrane with 0.5 wt % NTN loading exhibited improved fouling resistance (fouling rate of 0.58 kPa/min compared to a rate of 0.70 kPa/min for the control membrane) with ∼80% water flux recovery. The same membrane showed an ∼20% increase in water flux, an improvement in MWCO, and a narrower pore size distribution.

Boron nitride colloidal solutions, ultralight aerogels and freestanding membranes through one-step exfoliation and functionalization

Manufacturing of aerogels and membranes from hexagonal boron nitride (h-BN) is much more difficult than from graphene or graphene oxides because of the poor dispersibility of h-BN in water, which limits its exfoliation and preparation of colloidal solutions. Here, a simple, one-step mechano-chemical process to exfoliate and functionalize h-BN into highly water-dispersible, few-layer h-BN containing amino groups is presented. The colloidal solutions of few-layer h-BN can have unprecedentedly high concentrations, up to 30 mg ml(-1), and are stable for up to several months. They can be used to produce ultralight aerogels with a density of 1.4 mg cm(-3), which is ∼1,500 times less than bulk h-BN, and freestanding membranes simply by cryodrying and filtration, respectively. The material shows strong blue light emission under ultraviolet excitation, in both dispersed and dry state.

Comparison of the properties of compacted and porous lamellar chitosan-xanthan membranes as dressings and scaffolds for the treatment of skin lesions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

On the release of metronidazole from natural rubber latex membranes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of thermal behavior of latex membranes from genetically improved rubber tree (Hevea brasiliensis)

Thermal stability, thermal decomposition process, residual mass, temperature of glass transition (T-g) and temperature dependence of storage modulus (E'), were determined for latex membranes prepared from six clones of Hevea brasiliensis: IAC 331, IAC 332, IAC 333 and IAC 334 grown at experimental plantations of Instituto Agronomico de Campinas (IAC) in Votuporanga, São Paulo State, Brazil. Latex membranes from GT1 and RRIM 600 Asian matrix clones were used as references. The thermal behavior of latex membranes from genetically improved rubber trees was characterized using thermogravimetry/derivative thermogravimetry (TG/DTG), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The thermal behavior of latex from clones studied in the present work showed similar features of the clones previously reported (IAC 40, IAC 300, IAC 301, IAC 328, IAC 329 and IAC 330), with mass loss in four consecutive steps, except IAC 333, which showed an additional mass loss step. (c) 2006 Elsevier B.V. All rights reserved.

The influence of natural rubber/Au nanoparticle membranes on the physiology of Leishmania brasiliensis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and characterization of Fe(III)-doped ceramic membranes of titanium dioxide and its application in photoelectrocatalysis of a textile dye

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cervical Lactobacillus and leukocyte infiltration in preterm premature rupture of membranes

Objectives: To evaluate the possible association between microorganisms present in the cervical secretions and amniotic fluid of pregnant women with preterm premature rupture of membranes (PPROM), and histologic chorioamnionitis. Methods: Thirty-seven pregnant women with PPROM and 21 healthy pregnant women were studied. Secretions from the cervical canal and amniotic fluid were collected to isolate microorganisms present in the genital tract. Cervical smears were Gram stained and evaluated microscopically. At delivery, chorioamniotic membranes were collected for histopathologic analysis. Results: Microscopic examination of the cervical secretion smears obtained from the PPROM group showed a low rate of Lactobacillus species, large numbers of leukocytes, and a wide diversity of microorganisms compared with the control group. The PPROM group presented an 80% rate of chorioamnionitis. Staphylococcus aureus isolation in cervical secretion was associated with intense inflammatory infiltrate in the membranes and might play a role in the pathogenesis of PPROM. Conclusions: the low colonization of cervical flora by Lactobacillus species associated with an intense leukocyte infiltrate detected in Gram-stained cervical smears can be considered a rapid method of detecting chorioamnionitis in pregnant women with PPROM. (C) 2003 International Federation of Gynecology and Obstetrics. Published by Elsevier B.V. Ireland Ltd. All rights reserved.

Interleukin 18 messenger RNA and proIL-18 protein expression in chorioamniotic membranes from pregnant women with preterm prelabor rupture of membranes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)