Transport Of Poly Research Articles

Transport and Retention of Poly(Acrylic Acid-co-Maleic Acid) Coated Magnetite Nanoparticles in Porous Media: Effect of Input Concentration, Ionic Strength and Grain Size.

Understanding the physicochemical factors affecting nanoparticle transport in porous media is critical for their environmental application. Water-saturated column experiments were conducted to investigate the effects of input concentration (Co), ionic strength (IS), and sand grain size on the transport of poly(acrylic acid-co-maleic acid) coated magnetite nanoparticles (PAM@MNP). Mass recoveries in the column effluent ranged from 45.2 to 99.3%. The highest relative retention of PAM@MNP was observed for the lowest Co. Smaller Co also resulted in higher relative retention (39.8%) when IS increased to 10 mM. However, relative retention became much less sensitive to solution IS as Co increased. The high mobility is attributed to the PAM coating provoking steric stability of PAM@MNP against homoaggregation. PAM@MNP retention was about 10-fold higher for smaller grain sizes, i.e., 240 µm and 350 µm versus 607 µm. The simulated maximum retained concentration on the solid phase (Smax) and retention rate coefficient (k1) increased with decreasing Co and grain sizes, reflecting higher retention rates at these parameters. The study revealed under various IS for the first time the high mobility premise of polymer-coated magnetite nanoparticles at realistic (<10 mg L−1) environmental concentrations, thereby highlighting an untapped potential for novel environmental PAM@MNP application usage.

Mass-Based, Field-Scale Demonstration of PFAS Retention within AFFF-Associated Source Areas.

Transport of poly- and perfluoroalkyl substances (PFAS) at aqueous film-forming foam (AFFF)-impacted sites is limited by various processes that can retain PFAS mass within the source area. This study used concentration data obtained via a high-resolution sampling and analytical protocol to estimate the PFAS mass distribution in source and downgradient areas of a former firefighter training area. The total PFAS mass present at the site was approximately 222 kg, with 106 kg as perfluoroalkyl acids (PFAAs) and 116 kg as polyfluorinated precursors. Zwitterionic and cationic PFAS represented 83% of the total precursor mass and were found primarily in the source and up/side-gradient areas (75%), likely due to preferential hydrophobic partitioning, electrostatic interactions, and diffusion into lower-permeability soils. Based on the release history and the high percentage of total PFAS mass represented by precursors (primarily electrochemical fluorination-derived compounds), the estimated conversion rate of precursors to PFAAs was less than 2% annually. Eighty-two percent of the total PFAS mass was encountered in lower-permeability soils, which limited the potential for advection and transformation. This contributed to a 99% decrease in the mass discharge rate at the far-downgradient plume (0.048 kg/yr compared to the near-source area (3.6 kg/yr)). The results provide field-scale evidence of the importance of these PFAS retention processes at sites where AFFF has been released.

Correlation Between Crystallization Behavior and Mechanical Properties of Biodegradable Poly(Caprolactone-co-Cyclohexene Carbonate)

ABSTRACTThe isothermal and nonisothermal crystallization behaviors of poly(ε-caprolactone) and poly(caprolactone-co-cyclohexene carbonate) were investigated utilizing differential scanning calorimeter and polarized optical microscope. The kinetic of isothermal crystallization could be well defined by Avrami equation, while Mo model was successful to describe the nonisothermal crystallization. Based on the obtained kinetic parameters, poly(cyclohexene carbonate) segments not only act as a nucleating agent accelerating nucleating rate but also restrict the transport of poly(ε-caprolactone) segments decelerating growth rate. The mechanical properties of polymers were investigated using DMA and nanoindentation. It shows that the insertion of hard poly(cyclohexene carbonate) segments improves Young’s modulus and heat resistance but reduces hardness of copolymers.

Abstract 2073: Focused ultrasound-mediated transport of poly(alkyl) cyanoacrylate nanoparticles across the blood-brain barrier in a melanoma brain metastasis model

Abstract Drug delivery into the brain is impeded by the blood-brain barrier (BBB) - a dynamic interface that protects brain homeostasis, but also screens the brain from the vast majority of large and/or hydrophilic drug molecules. Focused ultrasound (FUS) has emerged as one of the promising methods to open the BBB safely and reversibly. We have previously reported FUS-mediated BBB opening using a novel platform consisting of microbubbles surrounded by poly(alkyl cyanoacrylate) nanoparticles that could prospectively be used for FUS- and nanoparticle-mediated drug delivery into the brain (1,2). Here, we have been investigating FUS-mediated BBB opening using a novel ultrasound system capable of generating FUS at two frequencies, 1.1 MHz and 7.8 MHz during the same experiment. This system allows a very precise selection of the exposure area. We used FUS exposure at 1 MHz to open the BBB by cavitation, while exposure at 7.8 MHz was employed to enable the action of acoustic radiation force. This force is caused by a transfer of momentum from acoustic waves to the tissues in which they propagate, and can facilitate nanoparticle transport in the extracellular matrix. FUS-mediated BBB opening was performed in NOD/SCID mice with melanoma brain metastases developed after intracardiac injection of human melanoma brain metastasis cells (3). The cells were fluorescently labeled, which enabled their detection in the brain. Poly(isohexyl) cyanoacrylate (PIHCA) nanoparticle-microbubbles similar to those reported in our earlier works (1,2) were injected immediately before the FUS exposure. Successful opening of the BBB was verified by MRI using a gadolinium-based contrast agent. An optimal window of exposure intensities that allow BBB disruption was found to be close a mechanical index of 0.3. Location of fluorescently labeled nanoparticles relative to blood vessels and tumor cells was determined in frozen sections using confocal microscopy. Tissue damage and FUS-induced changes at the cellular and molecular level were studied using histological and molecular techniques. In conclusion, the dual-frequency ultrasound transducer setup and our novel nanoparticle-microbubble platform showed promising results which will be used to develop a novel treatment of brain metastasis combining dual-frequency FUS with drug delivery using microbubbles. 1. Nanoparticle-stabilized microbubbles for multimodal imaging and drug delivery. Mørch Ý et al. Contrast Media Mol Imaging. 2015 Sep;10(5):356-66 2. Nanoparticle delivery to the brain - By focused ultrasound and self-assembled nanoparticle-stabilized microbubbles. Åslund AK et al. J Control Release. 2015 Oct 28;220(Pt A):287-294 3. Automated tracking of nanoparticle-labeled melanoma cells improves the predicted power of a brain metastasis model. Sundstrøm T et al. Cancer Res. 2013 Feb;73(8):2445-2456. Citation Format: Habib Baghirov, Andreas Åslund, Sofie Snipstad, Sigrid Berg, Rune Hansen, Frits Thorsen, Yrr Mørch, Catharina de Lange Davies. Focused ultrasound-mediated transport of poly(alkyl) cyanoacrylate nanoparticles across the blood-brain barrier in a melanoma brain metastasis model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2073.

Versatile Role of Solvent Additive for Tailoring Morphology in Polymer Solar Cells for Efficient Charge Transport.

In this work role of solvent additive namely 1,8 diiodoctane (DIO) on the nanoscale morphology and its relation with the charge transport of poly(diketopyrrolopyrrole-terthiophene) (PDPP3T):PCBM solar cells has been investigated. Addition of DIO led to enhanced structural ordering as observed from optical measurements. Photovoltaic devices processed with DIO additive showed improved efficiencies due to significant enhancement in short circuit current density. Atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) images showed that DIO led to finer phase segregation that gave rise to better photovoltaic performance in additive processed active layers. Photoinduced current extraction by linearly increasing voltage (P-CELIV) measurements on PDPP3T:PCBM solar cells revealed higher mobility and extracted charge carrier density for DIO processed devices.

Transport of poly(acrylic acid) coated 2-line ferrihydrite nanoparticles in saturated aquifer sediments for environmental remediation

Groundwater remediation using iron oxide and zero-valent iron nanoparticles (NPs) can be effective, but is limited in many applications due to the NP strong retention in groundwater-saturated porous media after injection, the passivation of the porous surface, and the high cost of nanomaterials versus macro scale iron. In this study, we investigated transport of bare and polymer-coated 2-line ferrihydrite NPs (30–300 nm) in saturated aquifer sediments. The influence of poly(acrylic acid) (PAA) polymer coatings was studied on the colloidal stability and transport in sediments packed column tests simulating groundwater flow in saturated sediments. In addition, the influence of calcium cations was investigated by transport measurements using sediments with calcium concentrations in the aqueous phase ranging from 0.5 (typical for most sediments) to 2 mM. Measurements were also made of zeta potential, hydrodynamic diameter, polymer adsorption and desorption properties, and bio-availability of PAA-coated NPs. We found that NP transport through the saturated aquifer sediments was improved by PAA coating and that the transport properties could be tuned by adjusting the polymer concentration. We further discovered that PAA coatings enhanced NP transport, compared to bare NPs, in all calcium-containing experiments tested, however, the presence of calcium always exhibited a negative effect on NP transport. In tests of bioavailability, the iron reduction rate of the coated and bare NPs by Geobacter sulfurreducens was the same, which shows that the PAA coating does not significantly reduce NP Fe(III) bioavailability. Our results demonstrate that much improved transport of iron oxide NP can be achieved in saturated aquifer sediments by introducing negatively charged polyelectrolytes and optimizing polymer concentrations, and furthermore, these coated NPs retain their bioavailability that is needed for applications in bio-environmental remediation.

Impact of dilution on the transport of poly(acrylic acid) supported magnetite nanoparticles in porous media

This paper investigates the impact of dilution on the mobility of magnetite nanoparticles surface coated with poly(acrylic acid) (PAA). Transport experiments were conducted in a water-saturated sand-packed column for input nanoparticle solutions with total Fe concentrations ranging from 100 to 600 mg/L. Particle size analysis of the synthesized nanoparticle solutions showed that PAA provides good size stability for Fe concentrations as low as about 1 mg/L. Time-moment analysis of the nanoparticle breakthrough curves, on the other hand, revealed that nanoparticle mass recovery from the column decreased consistently with dilution, with greater attenuation, sharper fronts and longer tails compared to that of the tracer. Particle size analysis of the eluted solutions shows that the nanoparticle size is negatively correlated with nanoparticle concentration. Modeling results suggest that the decrease in nanoparticle mobility with input concentration can be represented using a kinetic time-dependent deposition term with finite deposition capacity and a kinetic detachment term. For field applications, the increase in particle size and detachment resulting from dilution means reduced transport efficiency of nanoparticles and reaction potential with travel distance.

Transport of Poly( n-butylcyano-acrylate) nanoparticles across the blood–brain barrier in vitro and their influence on barrier integrity

In previous studies it was shown that polysorbate 80(PS80)-coated poly( n-butylcyano-acrylate) nanoparticles (PBCA-NP) are able to cross the blood–brain barrier (BBB) in vitro and in vivo. In order to explore and extend the potential applications of PBCA-NP as drug carriers, it is important to ascertain their effect on the BBB. The objective of the present study was to determine the effect of PS80-coated PBCA-NP on the BBB integrity of a porcine in vitro model. This has been investigated by monitoring the development of the transendothelial electrical resistance (TEER) after the addition of PBCA-NP employing impedance spectroscopy. Additionally, the integrity of the BBB in vitro was verified by measuring the passage of the reference substances 14C-sucrose and FITC-BSA after addition of PBCA-NP. In this study we will show that the application of PS80-coated PBCA-NP leads to a reversible disruption of the barrier after 4 h. The observed disruption of the barrier could also be confirmed by 14C-sucrose and FITC-BSA permeability studies. Comparing the TEER and permeability studies the lowest resistances and maximal values for permeabilities were both observed after 4 h. These results indicate that PS80-coated PBCA-NP might be suitable for the use as drug carriers. The reversible disruption also offers the possibility to use these particles as specific opener of the BBB. Instead of incorporating the therapeutic agents into the NP, the drugs may cross the BBB after being applied simultaneously with the PBCA-NP.

Particle Size Distribution, Concentration, and Magnetic Attraction Affect Transport of Polymer-Modified Fe0 Nanoparticles in Sand Columns

The effect of particle concentration, size distribution (polydispersity) and magnetic attractive forces (Fe(0) content) on agglomeration and transport of poly(styrene sulfonate) (PSS) modified NZVI was studied in water-saturated sand (d(p) = 300 microm) columns. Particle concentrations ranged from 0.03 to 6 g/L in 5 mM NaCl/5 mM NaHCO3 at a pore water velocity of 3.2 x 10(-4) m/s. Three NZVI dispersions with different intrinsic particle size distributions obtained from sequential sedimentation are compared. The influence of magnetic attraction (Fe(0) content) on NZVI agglomeration and deposition in porous media is assessed by comparing the deposition behavior of PSS-modified NZVI (magnetic) having different Fe(0) contents with PSS-modified hematite (nonmagnetic) with the same surface modifier. At low particle concentration (30 mg/L) all particles were mobile in sand columns regardless of size or magnetic attractive forces. At high concentration (1 to 6 g/L), deposition of the relatively monodisperse dispersion containing PSS-modified NZVI (hydrodynamic radius (R(H)) = 24 nm) with the lowest Fe(0) content (4 wt%) is low (attachment efficiency (alpha) = 2.5 x 10(-3)), insensitive to particle concentration, and similar to PSS-modified hematite. At 1 to 6 g/L, the attachment efficiency of polydisperse dispersions containing both primary particles and sintered aggregates (R(H) from 15 to 260 nm) of PSS-modified NZVI with a range of Fe(0) content (10-60%) is greater (alpha = 1.2 x 10(-2) to 7.2 x 10(-2) and is sensitive to particle size distribution. The greater attachment for larger, more polydisperse Fe(0) nanoparticles with higher Fe(0) content is a result of their agglomeration during transport in porous media because the magnetic attractive force between particles increases with the sixth power of particle/agglomerate radius. A filtration model that considers agglomeration in porous media and subsequent deposition explains the observed transport of polydisperse PSS-modified NZVI at high concentration.

Transport of poly- l-lysine into oppositely charged poly(acrylic acid) microgels and its effect on gel deswelling

The interaction between poly- l-lysine (pLys) and oppositely charged poly(acrylic acid) (pAA) microgels (Ø ∼ 80–120 μm) was studied by micromanipulator-assisted light microscopy and confocal laser scanning microscopy. The aim of this study was to investigate effects of peptide size, pH, and salt concentration on binding, transport, and distribution of pLys in pAA microgel particles and thereby also to outline the details of the gel deswelling in response to pLys binding and incorporation. Both peptide distribution and gel deswelling kinetics were found to be strongly influenced by the pLys molecular weight, originating partly from limited entry of large peptides into the gel particle core. Also pH was shown to influence both deswelling and pLys incorporation kinetics, with a decreased deswelling rate observed with increasing pH. These effects are determined by a complex interplay between the pH-dependence of both pLys and the gel network, also influencing volume transitions of the latter. Finally, salt concentration was shown to have a significant effect on both gel deswelling rate and pLys transport, with an increased electrolyte concentration resulting in decreased deswelling rate but also in an increased peptide transport rate within the microgel particles.

Interaction and Transport of Poly(l-lysine) Dendrigrafts through Liposomal and Cellular Membranes: The Role of Generation and Surface Functionalization

Two generations of poly(l-lysine) dendrigrafts (DGLs) were studied with regard to their ability to interact with and translocate through liposomal and cellular membranes. Partial guanidinylation of the surface amino groups of the starting dendrigrafts afforded the guanidinylated derivatives whose membrane translocation properties were also assessed. Mixed liposomes, consisting of dihexadecyl phosphate, phosphatidylcholine, and cholesterol, were employed as model membranes, while A549 human lung carcinoma cells were used for cellular uptake studies. At high surface group/liposomal phosphate molar ratios and depending on the structure of the DGL, the interaction led to aggregation. Dendrigraft liposomal internalization was achieved, however, at low molar ratios. Thus translocation of the second generation dendrigrafts was rather limited at 25 degrees C, which, however, was enhanced when the bilayer was in the liquid-crystalline phase. In contrast, third-generation counterparts exhibited minor translocational ability. Furthermore, the introduction of a guanidinium group to dendrigrafts was found to enhance their transport through liposomal membranes. On the other hand, cellular uptake by A549 cells was monitored up to 3 h incubation time via fluorescence registration employing fluorescein-labeled dendrigrafts. The efficiency of dendrigraft internalization was enhanced by the presence of the guanidinium groups, while DGLs were preferentially localized in the nucleus and nuclear membrane, as revealed by fluorescence microscopy.

Compromised integrity of excised porcine intestinal epithelium obtained from the abattoir affects the outcome of in vitro particle uptake studies

Excised porcine intestinal tissue obtained from the local abattoir was studied for its suitability to examine the uptake and transport of poly(lactic–co-glycolic acid) (PLGA) nanoparticles in Peyer’s (PP) and non-Peyer’s patch (NPP) tissue in vitro. Incubation of such tissue with fluorescent PLGA and polystyrene particles revealed negligible uptake into the intercellular space with no noticeable difference between PP and NPP tissue. Similarly, yeast cells, which were used as a positive control for selective uptake into PP tissue, were found in the subepithelial area of both PP and NPP tissue. Therefore we examined the morphological integrity of the tissue for the duration of the experiments. For this purpose, excised intestinal tissue from the abattoir transported to the laboratory was examined for morphological changes by light microscopy and compared to intestinal tissue from freshly slaughtered piglets. Already after 25 min postmortem, we observed lysis and defoliation of the epithelial cell layer followed by a complete loss of villus architecture and, consequently, resulting in a complete loss of the integrity of the intestinal tissue. This may explain the limited and non-selective particle uptake when using excised intestinal tissue from the abattoir. It is suggested to avoid small intestine obtained from the abattoir and to use tissue from freshly sacrificed animals within a few minutes postmortem. Experiments should then be performed under adequate oxygenation of the excised intestinal tissue.

Crystal structure of the two RNA binding domains of human hnRNP A1 at 1.75 A resolution.

Heterogeneous ribonucleoprotein A1 (hnRNP A1) is an abundant eukaryotic nuclear RNA binding protein. A1 is involved in the packaging of pre-mRNA into hnRNP particles, transport of poly A+ mRNA from the nucleus to the cytoplasm and may modulate splice site selection. The crystal structure of A1(RBD1,2) reveals two independently-folded RNA binding domains (RBDs) connected by a flexible linker. Both RBDs are structurally homologous to the U1A(RBD1), and have their RNA binding platforms oriented in an anti-parallel fashion. The anti-parallel arrangement of the A1 RNA binding platforms suggests mechanisms for RNA condensation and ways of bringing together distant RNA sequences for RNA metabolism such as splicing or transport.

Effects of Simple Salts on the Transport of Poly(vinylpyrrolidone) in Dextran Solutions

Effects of Simple Salts on the Transport of Poly(vinylpyrrolidone) in Dextran Solutions

In vivo analysis of the stability and transport of nuclear poly(A)+ RNA.

We have studied the distribution of poly(A)+ RNA in the mammalian cell nucleus and its transport through nuclear pores by fluorescence and electron microscopic in situ hybridization. Poly(A)+ RNA was detected in the nucleus as a speckled pattern which includes interchromatin granule clusters and perichromatin fibrils. When cells are fractionated by detergent and salt extraction as well as DNase I digestion, the majority of the nuclear poly(A)+ RNA was found to remain associated with the nonchromatin RNP-enriched fraction of the nucleus. After inhibition of RNA polymerase II transcription for 5-10 h, a stable population of poly(A)+ RNA remained in the nucleus and was reorganized into fewer and larger interchromatin granule clusters along with pre-mRNA splicing factors. This stable population of nuclear RNA may play an important role in nuclear function. Furthermore, we have observed that, in actively transcribing cells, the regions of poly(A)+ RNA which reached the nuclear pore complexes appeared as narrow concentrations of RNA suggesting a limited or directed pathway of movement. All of the observed nuclear pores contained poly(A)+ RNA staining suggesting that they are all capable of exporting RNA. In addition, we have directly visualized, for the first time in mammalian cells, the transport of poly(A)+ RNA through the nuclear pore complexes.

Uptake and transport of poly( N-vinylpyrrolidone-co-maleic acid) by the adult rat small intestine cultured in vitro: Effect of chemical structure

To study the structure-activity relationships of polymer uptake and transfer across the gastrointestinal mucosa, poly( N-vinylpyrrolidone-co-maleic acid) (NVP MA) polymers of standardised molecular mass (20000 Da) were synthesised to contain side-chains of different charge or hydrophobicity. All polymers additionally contained tyrosinamide residues to permit radioiodination. Using an improved everted gut sac prepared from adult rat small intestine, the tissue accumulation and serosal transport of the polymers was measured in vitro over a 2 h incubation period. All polymers were captured by the tissue linearly with time (endocytic indices between 1.6 and 16 μl/mg protein per h), and then transferred slowly to the serosal fluid (endocytic indices between 0.18 and 2 μl/mg protein per h). The neutral NVP MA polymer showed the lowest rate of tissue association, but this was increased 5-fold by the presence of either negatively or positively charged groups. The maximum rate of transport across the mucosa was seen for the most negatively charged polymer derivative, this being equivalent to approx. 26% its rate of tissue accumulation. Increasing hydrophobicity of the polymer derivatives had a more pronounced effect on the rate of tissue capture, increasing it by up to 10-fold for the most hydrophobic derivative. However, in this case, the serosal transfer was only 10–15% the rate of tissue uptake. The data presented indicate that NVP MA polymers can be tailor-made for use in oral delivery systems. Substituent groups can be incorporated to promote tissue uptake or translocation across the gastrointestinal mucosa, or a combination of the two.

Polymer diffusion in semicrystalline polymers. 1. Poly(ether imide)/poly(aryl ether ketone ketone)

The transport of poly(ether imide) (PEI) into amorphous and semicrystalline matrices of poly(aryl ether ketone ketone) (PEKK) has been characterized quantitiatively. Diffusion measurements were performed by an ATR-IR technique and the semicrystalline morphology investigated both before and after transport via DSC, TEM, SEM, WAXS, SAXS, and microtomy/FTIR. Fickian interdiffusion occurs when these polymers are in contacts as melts. Two distinct time scales of sorption kinetics are observed during PEI transport into PEKK with a stable semicrystalline morphology.

Modulation of the nuclear-envelope nucleoside triphosphatase by poly(A)-rich mRNA and by microtubule protein.

Nuclear envelopes contain a nucleoside triphosphatase which is thought to be involved in the supply of energy for nucleo‐cytoplasmic RNA transport. This enzyme is stimulated most efficiently by poly(A) and to a lesser extent by poly(G) and poly(dT). Half‐maximal stimulation of the enzyme from rat liver nuclei, which was associated with the poly(A)‐specific endoribonuclease IV and was free from poly(A) polymerase and endoribonuclease V activity, was determined to occur at a concentration of 1.1 × 106 poly(A) molecules/nuclear ghost. Double‐reciprocal plot analyses revealed a 2.8‐fold stimulation of the enzyme by poly(A). Poly(A) in the hybrid form had no influence on the activity of the nucleoside triphosphatase. Stimulation by oligo(A) required a minimum chain length of 18 nucleotide units. Naturally occurring RNA species enhanced the nucleoside triphosphatase activity, provided that they contained a poly(A) segment. Using poly(A)‐rich mRNA, half‐maximal stimulation was determined to proceed at 0.5 × 106 molecules/nuclear ghost. Removal of the poly(A) segment from mRNA abolished the stimulatory effect on the enzyme.Microtubule protein was found to inhibit the nucleoside triphosphatase efficiently. At a concentration of 2.0 mg/ml, polymerized microtubule protein reduced the enzyme activity by 96%. Dimeric tubulin was less inhibitory, while actin was without any significant effect.From these findings it is suggested that a possible nucleoside‐triphosphatase‐mediated transport of poly(A)‐rich mRNA through nuclear envelopes is controlled, first, by the poly(A) segment of this RNA species and, secondly, by cytoplasmic microtubules.