Antimicrobial Peptide Conjugated on Graphene Oxide-Containing Sulfonated Polyetheretherketone Substrate for Effective Antibacterial Activities against Staphylococcus aureus.

In the present study, the antimicrobial peptide nisin was successfully conjugated onto the surface of sulfonated polyetheretherketone (SPEEK), which was decorated with graphene oxide (GO) to investigate its biofilm resistance and antibacterial properties. The PEEK was activated with sulfuric acid, resulting in a porous structure. The GO deposition fully covered the porous SPEEK specimen. The nisin conjugation was accomplished using the crosslinker 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) through a dip-coating method. The surface micrographs of the SPEEK-GO-nisin sample indicated that nisin formed discrete islets on the flat GO surface, allowing both the GO and nisin to perform a bactericidal effect. The developed materials were tested for bactericidal efficacy against Staphylococcus aureus (S. aureus). The SPEEK-GO-nisin sample had the highest antibacterial activity with an inhibition zone diameter of 27 mm, which was larger than those of the SPEEK-nisin (19 mm) and SPEEK-GO (10 mm) samples. Conversely, no inhibitory zone was observed for the PEEK and SPEEK samples. The surface micrographs of the bacteria-loaded SPEEK-GO-nisin sample demonstrated no bacterial adhesion and no biofilm formation. The SPEEK-nisin and SPEEK-GO samples showed some bacterial attachment, whereas the pure PEEK and SPEEK samples had abundant bacterial colonies and thick biofilm formation. These results confirmed the good biofilm resistance and antibacterial efficacy of the SPEEK-GO-nisin sample, which is promising for implantable orthopedic applications.

A Flexible Lithium-Ion-Conducting Membrane with Highly Loaded Titanium Oxide Nanoparticles to Promote Charge Transfer for Lithium-Air Battery.

In this research, we aim to investigate a flexible composite lithium-ion-conducting membrane (FC-LICM) consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and titanium dioxide (TiO2) nanoparticles with a TiO2-rich configuration. PVDF-HFP was selected as the host polymer owing to its chemically compatible nature with lithium metal. TiO2 (40-60 wt%) was incorporated into the polymer matrix, and the FC-LICM charge transfer resistance values (Rct) were reduced by two-thirds (from 1609 Ω to 420 Ω) at the 50 wt% TiO2 loading compared with the pristine PVDF-HFP. This improvement may be attributed to the electron transport properties enabled by the incorporation of semiconductive TiO2. After being immersed in an electrolyte, the FC-LICM also exhibited a Rct that was lower by 45% (from 141 to 76 Ω), suggesting enhanced ionic transfer upon the addition of TiO2. The TiO2 nanoparticles in the FC-LICM facilitated charge transfers for both electron transfer and ionic transport. The FC-LICM incorporated at an optimal load of 50 wt% TiO2 was assembled into a hybrid electrolyte Li-air battery (HELAB). This battery was operated for 70 h with a cut-off capacity of 500 mAh g-1 in a passive air-breathing mode under an atmosphere with high humidity. A 33% reduction in the overpotential of the HELAB was observed in comparison with using the bare polymer. The present work provides a simple FC-LICM approach for use in HELABs.

Prismatic Silver Nanoparticles Decorated on Graphene Oxide Sheets for Superior Antibacterial Activity.

Spherical silver nanoparticles (Ag NPs) and silver nanoprisms (Ag NPrsms) were synthesized and decorated on graphene oxide (GO) nanosheets. The Ag contents were 29% and 23% in the GO−Ag NPs and GO−Ag NPrsms, respectively. The Ag NPrsms exhibited stronger (111) crystal signal than Ag NPs. The GO−Ag NPrsms exhibited higher Ag (I) content (75.6%) than GO-Ag NPs (69.9%). Increasing the nanomaterial concentration from 25 to 100 µg mL−1 improved the bactericidal efficiency, and the antibacterial potency was in the order: GO−Ag NPrsms > GO−Ag NPs > Ag NPrsms > Ag NPs > GO. Gram-positive Staphylococcus aureus (S. aureus) was more vulnerable than Gram-negative Escherichia coli (E. coli) upon exposure to these nanomaterials. The GO−Ag NPrsms demonstrated a complete (100%) bactericidal effect against S. aureus at a concentration of 100 µg mL−1. The GO−Ag composites outperformed those of Ag or GO due to the synergistic effect of bacteriostatic Ag particles and GO affinity toward bacteria. The levels of reactive oxygen species produced in the bacteria−nanomaterial mixtures were highly correlated to the antibacterial efficacy values. The GO−Ag NPrsms are promising as bactericidal agents to suppress biofilm formation and inhibit bacterial infection.

Swelling-Resistant, Crosslinked Polyvinyl Alcohol Membranes with High ZIF-8 Nanofiller Loadings as Effective Solid Electrolytes for Alkaline Fuel Cells.

The present work investigates the direct mixing of aqueous zeolitic imidazolate framework-8 (ZIF-8) suspension into a polyvinyl alcohol (PVA) and crosslinked with glutaraldehyde (GA) to form swelling-resistant, mechanically robust and conductivity retentive composite membranes. This drying-free nanofiller incorporation method enhances the homogeneous ZIF-8 distributions in the PVA/ZIF-8/GA composites to overcome the nanofiller aggregation problem in the mixed matrix membranes. Various ZIF-8 concentrations (25.4, 40.5 and 45.4 wt.%) are used to study the suitability of the resulting GA-crosslinked composites for direct alkaline methanol fuel cell (DAMFC). Surface morphological analysis confirmed homogeneous ZIF-8 particle distribution in the GA-crosslinked composites with a defect- and crack-free structure. The increased ionic conductivity (21% higher than the ZIF-free base material) and suppressed alcohol permeability (94% lower from the base material) of PVA/40.5%ZIF-8/GA resulted in the highest selectivity among the prepared composites. In addition, the GA-crosslinked composites' selectivity increased to 1.5−2 times that of those without crosslink. Moreover, the ZIF-8 nanofillers improved the mechanical strength and alkaline stability of the composites. This was due to the negligible volume swelling ratio (<1.4%) of high (>40%) ZIF-8-loaded composites. After 168 h of alkaline treatment, the PVA/40.5%ZIF-8/GA composite had almost negligible ionic conductivity loss (0.19%) compared with the initial material. The maximum power density (Pmax) of PVA/40.5%ZIF-8/GA composite was 190.5 mW cm−2 at 60 °C, an increase of 181% from the PVA/GA membrane. Moreover, the Pmax of PVA/40.5%ZIF-8/GA was 10% higher than that without GA crosslinking. These swelling-resistant and stable solid electrolytes are promising in alkaline fuel cell applications.

Separation Mechanisms and Anti-Fouling Properties of a Microporous Polyvinylidene Fluoride-Polyacrylic Acid-Graphene Oxide (PVDF-PAA-GO) Composite Membrane with Salt and Protein Solutions.

This research demonstrates the preparation of composite membranes containing graphene oxide (GO) and investigates the separation mechanisms of various salts and bovine serum albumin (BSA) solutions. A microporous polyvinylidene fluoride-polyacrylic acid-GO (PVDF-PAA-GO) separation layer was fabricated on non-woven support. The GO-incorporating composite resulted in enlarged pore size (0.16 µm) compared with the control membrane (0.12 µm). The zeta potential of the GO composite was reduced to -31 from -19 mV. The resulting membranes with and without GO were examined for water permeability and rejection efficiency with single salt and BSA solutions. Using the non-woven/PVDF-PAA composite, the permeance values were 88-190 kg/m2hMPa, and the salt rejection coefficients were 9-28% for Na2SO4, MgCl2, MgSO4, and NaCl solutions. These salt removals were based on the Donnan exclusion mechanism considering the ion radii and membrane pore size. Incorporating GO into the separation layer exhibited limited impacts on the filtration of salt solutions, but significantly reduced BSA membrane adhesion and increased permeance. The negatively charged protein reached almost complete removal (98.4%) from the highly negatively charged GO-containing membrane. The GO additive improved the anti-fouling property of the composite membrane and enhanced BSA separation from the salt solution.

Tailoring therapeutic properties of silver nanoparticles for effective bacterial keratitis treatment.

The formulation of nanoparticles with intrinsically therapeutic properties in a tailorable and appropriate manner is critical in nanomedicine for effective treatments of infectious diseases. Here, we present a biomedical strategy to formulate silver nanoparticles (AgNPs) as intrinsically therapeutic agents for the treatment of Staphylococcus aureus (S. aureus) keratitis. Specifically, AgNPs are controllably obtained as spheres, wrapped with a biopolymer, and varied in sizes. in vitro and in vivo studies indicate that biological interactions between the AgNPs and corneal keratocytes, S. aureus bacteria, and blood vessels are strongly determined by the particle sizes. As the size increased from 3.3 ±â€¯0.7 to 37.2 ±â€¯5.3 nm, the AgNPs exhibit better ocular biocompatibility and stronger antiangiogenic activity, but poorer bactericidal performance. In a rabbit model of S. Aureus-induced keratitis, intrastromal injection of AgNP formulations (single dose) show substantial influences of particle size on the treatment efficacy. As the trade-off, AgNPs with medium size of 15.0 ±â€¯3.6 nm reveal as the best therapeutic agent that could offer ∼5.6 and ∼9.1-fold greater corneal thickness recovery respectively compared to those with smaller and larger sizes at 3 days post-administration. These findings suggest an important advance in structural design for formulating intrinsically therapeutic nano-agents toward the efficient management of infectious diseases.

Graphene Oxide-Induced Protein Conformational Change in Nasopharyngeal Carcinoma Cells: A Joint Research on Cytotoxicity and Photon Therapy.

The objectives of this work aim to investigate the interaction and cytotoxicity between nanometric graphene oxide (GO) and nasopharyngeal carcinoma cells (NPC-BM1), and possible application in photon therapy. GO nanosheets were obtained in the size range of 100-200 nm, with a negative surface charge. This nanometric GO exhibited a limited (<10%) cytotoxicity effect and no significant dimensional change on NPC-BM1 cells in the tested GO concentration range (0.1-10 µg·mL-1). However, the secondary protein structure was modified in the GO-treated NPC-BM1 cells, as determined through synchrotron radiation-based Fourier transform infrared microspectroscopy (SR-FTIRM) mapping. To further study the cellular response of GO-treated NPC-BM1 cancer cells at low GO concentration (0.1 µg·mL-1), photon radiation was applied with increasing doses, ranging from 2 to 8 Gy. The low radiation energy (<5 Gy) did not cause significant cell mortality (5-7%). Increasing the radiation energy to 6-8 Gy accelerated cell apoptosis rate, especially in the GO-treated NPC-BM1 cells (27%). This necrosis may be due to GO-induced conformational changes in protein and DNA/RNA, resulting in cell vulnerability under photon radiation. The findings of the present work demonstrate the potential biological applicability of nanometric GO in different areas, such as targeted drug delivery, cellular imaging, and radiotherapy, etc.

Electrochemical Characteristics of a Polymer/Garnet Trilayer Composite Electrolyte for Solid-State Lithium-Metal Batteries.

Although solid-state Li-metal batteries (LMBs) featuring polymer-based solid electrolytes might one day replace conventional Li-ion batteries, the poor Li-ion conductivity of solid polymer electrolytes at low temperatures has hindered their practical applications. Herein, we describe the first example of using a co-precipitation method in a Taylor flow reactor to produce the metal hydroxides of both the Ga/F dual-doped Li7La3Zr2O12 (Ga/F-LLZO) ceramic electrolyte precursors and the Li2MoO4-modified Ni0.8Co0.1Mn0.1O2 (LMO@T-LNCM 811) cathode materials for LMBs. The Li/Nafion (LiNf)-coated Ga/F-LLZO (LiNf@Ga/F-LLZO) ceramic filler was finely dispersed in the poly(vinylidene fluoride)/polyacrylonitrile/lithium bis(trifluoromethanesulfonimide)/succinonitrile matrix to give a trilayer composite polymer electrolyte (denoted "Tri-CPE") through a simple solution-casting. The bulk ionic conductivity of the Tri-CPE at room temperature was approximately 4.50 × 10-4 S cm-1 and exhibited a high Li+ ion transference number (0.84). It also exhibits a broader electrochemical window of 1-5.04 V versus Li/Li+. A full cell based on a CR2032 coin cell containing the LMO@T-LNCM811-based composite cathode, when cycled under 1 C/1 C at room temperature for 300 cycles, achieved an average Columbic efficiency of 99.4% and a capacity retention of 89.8%. This novel fabrication strategy for Tri-CPE structures has potential applications in the preparation of highly safe high-voltage cathodes for solid-state LMBs.

Facilitating GL13K Peptide Grafting on Polyetheretherketone via 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide: Surface Properties and Antibacterial Activity.

In the present work, the antimicrobial peptide (AMP) of GL13K was successfully coated onto a polyetheretherketone (PEEK) substrate to investigate its antibacterial activities against Staphylococcus aureus (S. aureus) bacteria. To improve the coating efficiency, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) was mixed with a GL13K solution and coated on the PEEK surface for comparison. Both energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) data confirmed 30% greater peptide coating on PEEK/GL13K-EDC than PEEK without EDC treatment. The GL13K graft levels are depicted in the micrograms per square centimeter range. The PEEK/GL13K-EDC sample showed a smoother and lower roughness (Rq of 0.530 µm) than the PEEK/GL13K (0.634 µm) and PEEK (0.697 µm) samples. The surface of the PEEK/GL13K-EDC was more hydrophilic (with a water contact angle of 24°) than the PEEK/GL13K (40°) and pure PEEK (89°) samples. The pure PEEK disc did not exhibit any inhibition zone against S. aureus. After peptide coating, the samples demonstrated significant zones of inhibition: 28 mm and 25 mm for the PEEK/GL13K-EDC and PEEK/GL13K samples, respectively. The bacteria-challenged PEEK sample showed numerous bacteria clusters, whereas PEEK/GL13K contained a little bacteria and PEEK/GL13K-EDC had no bacterial attachment. The results confirm that the GL13K peptide coating was able to induce antibacterial and biofilm-inhibitory effects. To the best of our knowledge, this is the first report of successful GL13K peptide grafting on a PEEK substrate via EDC coupling. The present work illustrates a facile and promising coating technique for a polymeric surface to provide bactericidal activity and biofilm resistance to medical implantable devices.

Size-Dependent Antibacterial Activity of Silver Nanoparticle-Loaded Graphene Oxide Nanosheets.

A series of graphene oxide (GO) suspensions with different particle sizes (<100 nm, ~100 nm, ~1 µm and >1 µm) were successfully fabricated after 0, 30, 60 and 120 min of sonication, respectively. The antibacterial properties of GO suspensions showed that >1 µm GO size resulted in a loss of nearly 50% of bacterial viability, which was higher than treatment by ~100 nm GO size (25%) towards Escherichia coli (E. coli). Complete entrapment of bacteria by the larger GO was observed in transmission electron microscopy (TEM). Silver nanoparticles (Ag NPs) were doped onto GO samples with different lateral sizes to form GO-Ag NP composites. Resulting larger GO-Ag NPs showed higher antibacterial activity than smaller GO-Ag NPs. As observed by Fourier transform infrared spectroscopy (FTIR), the interaction between E. coli and GO occurred mainly at the outer membrane, where membrane amino acids interact with hydroxyl and epoxy groups. The reactive oxygen species (ROS) and the considerable penetration of released Ag+ into the inner bacterial cell membrane result in loss of membrane integrity and damaged morphology. The present work improves the combined action of GO size effect with constant Ag loadings for potential antibacterial activity.

Synergistic Antibacterial Activity of Silver-Loaded Graphene Oxide towards Staphylococcus Aureus and Escherichia Coli.

In this study, the physicochemical and surface properties of the GO-Ag composite promote a synergistic antibacterial effect towards both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. Aureus) bacteria. GO-Ag NPs have a better bactericidal effect on E. coli (73%) and S. Aureus (98.5%) than pristine samples (pure Ag or GO). Transmission electron microscopy (TEM) confirms that the GO layers folded entire bacteria by attaching to the membrane through functional groups, while the Ag NPs penetrated the inner cell, thus damaging the cell membrane and leading to cell death. Cyclic voltammetry (CV) tests showed significant redox activity in GO-Ag NPs, enabling good catalytic performance towards H2O2 reduction. Strong reactive oxygen species (ROS) in GO-Ag NPs suggests that ROS might be associated with bactericidal activity. Therefore, the synergy between the physicochemical effect and ROS production of this material is proposed as the mechanism of its antibacterial activity.

The role of aromatic ring number in phenolic compound-conjugated chitosan injectables for sustained therapeutic antiglaucoma efficacy.

The development of long-lasting therapeutic drug delivery system is greatly desired for effective treatment of glaucoma, a chronic and multifactorial disease. Herein, the roles of aromatic ring number in phenolic compound-conjugated chitosan injectables are exploited for achieving an advanced drug carrier with potent anti-inflammatory and anti-oxidant properties. Low and high number of aromatic rings can induce deleterious impacts on the pharmaceutical applications of injectables, whereas the compound with a moderate ring number is proved as the most efficient agent for boosting drug delivery performances and endowing the chitosan injectables with therapeutic properties. Kaempferol-conjugated injectable formulation reveals a remarkable effectiveness for intracameral pilocarpine administration, which can alleviate progressive glaucoma via simultaneously exerting multiple pharmacological activities to suppress ocular hypertension, inflammation, and oxidative stress. These findings provide a significant advance in understanding structure-property relationship of the phenolic compound-conjugated chitosan injectables as long-lasting therapeutic drug delivery systems for medical management of glaucoma.

The Preparation of Graphene Oxide-Silver Nanocomposites: the Effect of Silver Loads on Gram-Positive and Gram-Negative Antibacterial Activities.

In this work, silver nanoparticles (Ag NPs) were decorated on thiol (-SH) grafted graphene oxide (GO) layers to investigate the antibacterial activities in Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Pseudomonas aeruginosa). The quasi-spherical, nano-sized Ag NPs were attached to the GO surface layers, as confirmed by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), respectively. The average size of GO-Ag nanocomposites was significantly reduced (327 nm) from those of pristine GO (962 nm) while the average size of loaded Ag NPs was significantly smaller than the Ag NPs without GO. Various concentrations of AgNO3 solutions (0.1, 0.2, and 0.25 M) were loaded into GO nanosheets and resulted in the Ag contents of 31, 43, and 65%, respectively, with 1-2 nm sizes of Ag NPs anchored on the GO layers. These GO-Ag samples have negative surface charges but the GO-Ag 0.2 M sample (43% Ag) demonstrated the highest antibacterial efficiency. At 10 ppm load of GO-Ag suspension, only a GO-Ag 0.2 M sample yielded slight bacterial inhibition (5.79-7.82%). As the GO-Ag content was doubled to 20 ppm, the GO-Ag 0.2 M composite exhibited ~49% inhibition. When the GO-Ag 0.2 M composite level was raised to 100 ppm, almost 100% inhibition efficiencies were found on both Staphylococcus aureus (S.A.) and Pseudomonas aeruginosa (P.A.), which were significantly higher than using pristine GO (27% and 33% for S.A. and P.A.). The combined effect of GO and Ag nanoparticles demonstrate efficient antibacterial activities.

Highly Zeolite-Loaded Polyvinyl Alcohol Composite Membranes for Alkaline Fuel-Cell Electrolytes.

Having a secure and stable energy supply is a top priority for the global community. Fuel-cell technology is recognized as a promising electrical energy generation system for the twenty-first century. Polyvinyl alcohol/zeolitic imidazolate framework-8 (PVA/ZIF-8) composite membranes were successfully prepared in this work from direct ZIF-8 suspension solution (0⁻45.4 wt %) and PVA mixing to prevent filler aggregation for direct methanol alkaline fuel cells (DMAFCs). The ZIF-8 fillers were chosen for the appropriate cavity size as a screening aid to allow water and suppress methanol transport. Increased ionic conductivities and suppressed methanol permeabilities were achieved for the PVA/40.5% ZIF-8 composites, compared to other samples. A high power density of 173.2 mW cm-2 was achieved using a KOH-doped PVA/40.5% ZIF-8 membrane in a DMAFC at 60 °C with 1⁻2 mg cm-2 catalyst loads. As the filler content was raised beyond 45.4 wt %, adverse effects resulted and the DMAFC performance (144.9 mW cm-2) was not improved further. Therefore, the optimal ZIF-8 content was approximately 40.5 wt % in the polymeric matrix. The specific power output was higher (58 mW mg-1) than most membranes reported in the literature (3⁻18 mW mg-1).

Effect of matrix nanostructure on the functionality of carbodiimide cross-linked amniotic membranes as limbal epithelial cell scaffolds.

Carbodiimide cross-linked amniotic membrane (AM) can potentially serve as an artificial corneal epithelial stem cell niche in ocular surface wound healing. For the first time, this study was performed to investigate the relationship between nanostructure and functionality of carbodiimide cross-linked AM tissues as limbal epithelial cell (LEC) scaffold biomaterials. The triple-helical molecular conformation of AM collagen was checked after chemical treatment for varying cross-linking durations (1-4 h). Our data indicated that the unraveling of the helical structure into a more random globular state is accompanied by an increase in the cross-linking index of AM samples. The cross-linker-mediated alterations in tissue ultrastructure and substrate nanotopography of these proteinaceous matrices were confirmed by transmission electron and atomic force microscopy studies. With increasing treatment time, the chemically cross-linked AM possessed larger nanofiber diameter and exhibited rougher texture. Marked increases in the water content, light transmittance, and resistance to enzymatic degradation were found, probably due to collagen fibril aggregation in biological tissues. All the test AM materials were not toxic to the human corneal epithelial cell cultures and retained anti-inflammatory activity, indicating the tolerability and safety of carbodiimide (i.e., a zero-length cross-linker). In addition, the enhanced LEC growth and increased p63 and ABCG2 gene expressions were significantly noted on the AM samples with greater cross-linking degree. In summary, the findings reported in this paper suggest that a specific limbal epithelial stem cell-biomaterial interaction may occur in response to biophysical cue such as nanostructure of carbodiimide cross-linked AM matrix.

Micron- and nano-sized poly(N-isopropylacrylamide-co-acrylic acid) latex syntheses and their applications for controlled drug release.

Thermo-sensitive poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAAm-co-AAc)) latex particles were prepared with and without sodium dodecyl sulfate (SDS) surfactant via an emulsion polymerization method. The P(NIPAAm-co-AAc) latex particle sizes were approximately 1.1 microm without SDS addition and the particle sizes were in the nanometer range (59 nm) with SDS at its critical micelle concentration (CMC) of 8 mM. We propose a scheme to demonstrate how the SDS concentration affects the synthesized latex particle size. The lower critical solution temperature (LCST) was hardly influenced by the SDS level but increased with the AAc concentration. The PNIPAAm-co-AAc latex particles were employed as thermo-sensitive drug carriers and 4-acetamidophenol was loaded to study the drug release rates from the nano-gels. The effective drug diffusion coefficients within the nano-gels varied as a function of particle size, AAc content, and temperature. The smaller or AAc-rich hydrogel particles provided sustainable drug release property and have potential use in biomedical applications.

Time-resolved polymer propagation for acrylic acid-mediated nanolatexes containing magnetic Fe3O4 cores.

This study reports on the time-resolved polymer propagation of thermal-sensitive latex nanoparticles containing Fe3O4 cores. The latex shells are made with poly(N-isopropylacrylamide-co-acrylic acid) (Fe3O4/P(NIPAAm-co-AAc)) at different reaction times. The Fe3O4 particles are first modified using AAc monomers. The AAc-modified Fe3O4 cores are then copolymerized with NIPAAm to form the latex shell. The Fe3O4 cores in the latex nanoparticles are confirmed using X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectroscopy (XRD), and thermo gravimetric analyzer (TGA). As the reaction time is increased from 0.5 h to 2 h, the particle size enlarges from 100 to 250 nm and the Fe3O4 content decreases from 46.4% to 2.6%. The thermal responses are more pronounced in the 2 h sample with the phase transition temperature (lower critical solution temperature, LCST) about 35 degrees C. The nanoparticles show a gradient concentration distribution of AAc as the particles propagate. A higher AAc concentration is observed near'the Fe3O4 core and the AAc content deceases as the degree of polymerization increases in the latex particles. This declining AAc concentration is beneficial for profound thermal responses in the synthesized nanoparticle.

In vitro biocompatibility of magnetic thermo-responsive nanohydrogel particles of poly(N-isopropylacrylamide-co-acrylic acid) with Fe3O4 cores: effect of particle size and chemical composition.

Biocompatibility is a critical factor in the design and development of candidate materials for biomedical use. This paper reports on the in vitro biocompatibility of magnetic stimuli-sensitive nanohydrogel particles composed of magnetite cores in poly(N-isopropylacrylamide-co-acrylic acid) shells referred to Fe(3)O(4)/P(NIPAAm-co-AAc). The AAc concentration and polymerization time were varied to fabricate magnetic nanoparticles with various AAc levels (1.80-2.37%) and particle sizes (74-213 nm). The P(NIPAAm-co-AAc) shell exhibited thermo-sensitive properties and the Fe(3)O(4) core constituted 2.25-4.10% of the particles by weight. After a 2-day incubation of L929 cells with extract media that had been conditioned with various test samples, the cellular responses were monitored in terms of cell viability and growth. The Live/Dead assays showed that high levels of cellular viability (97.3-98.1%) were observed in all groups, indicating that none of the nanoparticles were cytotoxic. However, the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymetho-xyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays demonstrated that the activity of mitochondrial dehydrogenase varied significantly in cultures exposed to different magnetic nanohydrogel particles. The murine fibroblasts exposed to the NIP-(AAc5.1-Fe)-2 sample, which contained the highest AAc content and largest particle sizes, were the least metabolically active. In contrast, the activity levels in the cultures treated with the low AAc content and small size particles (NIP-(AAc2.6-Fe)-1) were not significantly different from those in the control group. Our findings suggest that smaller magnetic stimuli-sensitive nanohydrogel particles with a lower AAc content may have little inhibitory impact on cell proliferation. Overall, the in vitro biocompatibilities of the nanoparticles depend on the chemical composition and size of the Fe(3)O(4)/P(NIPAAm-co-AAc) particles.

Correlation between free-volume properties and pervaporative flux of polyurethane-zeolite composites on organic solvent mixtures.

Micron-sized zeolite particles were incorporated into a polyurethane (PU) matrix to prepare ethylbenzene-selective membranes. The resulting composite membranes were used in the pervaporation (PV) of ethylbenzene/styrene (EB/ST) mixtures. The sorption, diffusion, and PV permeation behaviors as a result of zeolite addition were elucidated. Zeolite is less chemically compatible with organic solvents than PU and the PU-zeolite composites, which exhibited suppressed solvent solubilities compared with pristine PU. However, these membranes favor EB transport by diffusion selectivity. The diffusivity and permeation flux increases in parallel with the enlarged radius of the free-volume hole size (R(4) increasing from 3.46 to 3.64 Å using positron annihilation lifetime spectroscopy analysis) by increasing the zeolite content from 0 to 23%. The enlarged free volume at a zeolite loading of 23% promoted pure solvent diffusivities by 10% higher than that of the unfilled film. During the PV operation on the EB/ST mixture, a significant diffusion-coupling was observed, and the permeant diffusion coefficients from the binary mixture exceeded the pure solvent diffusivity. The permeation flux was greatly improved (up to 0.72 kg/m(2)·h) by zeolite addition without any detrimental effect on the separation efficiency.