Electrospinning was employed to obtain chitosan nanofibers from blends of chitosans (CS) and poly(ethylene oxide) (PEO). Blends of chitosan (MW (weight-average molecular weight) = 102 kg/mol) and PEO (M (molecular weight) = 1000 kg/mol) were selected to optimize the electrospinning process parameters. The PEO powder was solubilized into chitosan solution at different weight ratios in 0.5 M acetic acid. The physicochemical changes of the nanofibers were determined by scanning electron microscopy (SEM), swelling capacity, and nuclear magnetic resonance (NMR) spectroscopy. For stabilization, the produced nanofibers were neutralized with K₂CO₃ in water or 70% ethanol/30% water as solvent. Subsequently, repeated washings with pure water were performed to extract PEO, potassium acetate and carbonate salts formed in the course of chitosan nanofiber purification. The increase of PEO content in the blend from 20 to 40 w% exhibited bead-free fibers with average diameters 85 ± 19 and 147 ± 28 nm, respectively. Their NMR analysis proved that PEO and the salts were nearly completely removed from the nanostructure of chitosan, demonstrating that the adopted strategy is successful for producing pure chitosan nanofibers. In addition, the nanofibers obtained after neutralization in ethanol-aqueous solution has better structural stability, at least for six months in aqueous solutions (phosphate buffer (PBS) or water).

To encourage cell adhesion on biomaterial surfaces in a more facile, safe, and low-cost fashion, we have demonstrated a noncovalent approach to spatially conjugate β-cyclodextrin (β-CD) modified peptide sequences onto self-assembled adamantane-terminated polystyrene-b-poly(ethylene oxide) (PS-PEO-Ada) films through inclusion complexing interactions between β-CDs and adamantane. By simply blending various ratios of unmodified PS-PEO with a newly synthesized PS-PEO-Ada, we produced PS polymer films that displayed well-organized adamantine-decorated cylindrical PEO domains with varying average interdomain spacings ranging from 29 to 47 nm. The presence of the adamantane moiety at the terminal end of the PEO chain permitted rapid, and importantly, oriented attachment of β-CD functionalized peptides onto these surfaces. This one-step process not only converted these proven nonadherent PS-PEO surfaces into adherent surfaces, but also permitted precisely controlled presentation and surface distribution of the conjugated peptides. The utility of these surfaces as cell culture substrates was confirmed with human mesenchymal stem cells (hMSCs). We observed that with increasing PS-PEO-Ada content in the PEO cylindrical domains, these novel polymer films displayed improved cell attachment and spreading, with notable differences in hMSC morphology. We further confirmed that this novel PS-PEO-Ada surface provides a flexible platform for facile conjugation of mixtures of β-CDs functionalized with different peptides, specifically RGD and IKVAV peptides. The cell adhesion and spreading assays on these surfaces indicated that the morphologies of hMSCs can be easily manipulated, while no significant changes in cell attachment were observed. The lock-and-key peptide conjugation technique presented in this work is applicable to any substrate that incorporates a moiety capable of forming inclusion complexes with α-, β-, and γ-CDs, providing a facile and flexible method by which to construct peptide-conjugated biomaterial substrates for a multitude of applications in fields ranging from cell bioprocessing and regenerative medicine to cell-based assays.

The urgent need for safer batteries is leading research to all-solid-state lithium-based cells. To achieve energy density comparable to liquid electrolyte-based cells, ultrathin and lightweight solid electrolytes with high ionic conductivity are desired. However, solid electrolytes with comparable thicknesses to commercial polymer electrolyte separators (~10 μm) used in liquid electrolytes remain challenging to make because of the increased risk of short-circuiting the battery. Here, we report on a polymer-polymer solid-state electrolyte design, demonstrated with an 8.6-μm-thick nanoporous polyimide (PI) film filled with polyethylene oxide/lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI) that can be used as a safe solid polymer electrolyte. The PI film is nonflammable and mechanically strong, preventing batteries from short-circuiting even after more than 1,000 h of cycling, and the vertical channels enhance the ionic conductivity (2.3 × 10^-4 S cm^-1 at 30 °C) of the infused polymer electrolyte. All-solid-state lithium-ion batteries fabricated with PI/PEO/LiTFSI solid electrolyte show good cycling performance (200 cycles at C/2 rate) at 60 °C and withstand abuse tests such as bending, cutting and nail penetration.

Label-free, high-throughput, and efficient separation and enrichment of rare tumor cells, such as circulating tumor cells (CTCs), from untreated whole blood is a challenging task, owing to extremely rare events of CTCs and an enormous amount of blood cells. Current strategies for CTC separation always require pre-processing steps including lysis of blood or labeling of CTCs, leading to loss or damage of CTCs. Here, we report an interfacial viscoelastic microfluidic system for size-selective separation of tumor cells directly from whole blood, without the need of cell labeling and other treatments. The sharp flow interfaces between the sample flow and viscoelastic flow (0.05% PEO solutions) in the straight microchannel allow for the penetration of large tumor cells while blocking small blood cells, through exploiting the competition between the inertial lift forces and interfacial elastic lift forces. The microfluidic paradigm does not involve external force fields or complicated fabrication procedures, while achieving 95.1% separation efficiency and 77.5% recovery rate for isolating as few as 50 tumor cells in 1 mL whole blood. The viability of tumor cells after separation is ∼100%, and normal proliferation of separated tumor cells is observed. The interfacial viscoelastic microfluidics holds great promise to facilitate the fundamental and clinical studies of CTCs.

Here, antimicrobial nanofibrous membranes were produced by electrospinning of chitosan/poly(ethylene oxide) (PEO) solution in the presence of poly(hexamethylene biguanide) hydrochloride (PHMB). The influence of PHMB on the electrospinnability and antimicrobial properties of chitosan/PEO nanofibers were studied. Further, viscosity of the solutions as well as morphology of the nanofibrous structures were investigated. Results revealed that incorporation of PHMB in chitosan/PEO solutions led to decrease in the zero-shear rate viscosity up to 20%. Moreover, increasing PHMB from 0.5 mM to 1 mM led to formation of thinner fibers with diameters ranging from 240 nm to 60 nm, respectively. Fourier transform infrared (FT-IR) spectrums indicated the functional groups of chitosan, PEO and PHMB in nanofibrous structure. Differential scanning calorimetry (DSC) thermograms indicated interaction of PHMB with PEO and chitosan through alteration in the thermal behavior of the nanofibers. Inhibition of the bacteria growth for both Escherichia coli and Staphylococcus aureus were achieved on the PHMB loaded nanofibers. Also, a burst release of PHMB from mats has been observed in the first hour. These findings suggest that there is a great potential in fabrication of biomaterials with incorporation of PHMB using electrospinning.

Titanium alloys have advanced mechanical properties jointly with high biocompatibility that make them eminently suitable for biomedical applications such as dental and orthopedic implants. Improvement of their osseointegration with human bone can be achieved by development of hydroxyapatite (HAp) on a Ti alloy surface using different methods of deposition. However, plasma electrolytic oxidation (PEO) treatment has been found to be one of the most promising techniques due to the formation of high bonding between bone and the Ti surface. Along with this high bonding, an antibacterial ability of the surface to prevent bacterial infection is also essential. Silver, which is widely applicable antibacterial agent, was used in this work. First, titanium oxide coating containing calcium and phosphorous and Ag nanoparticles was formed by PEO treatment. Then, Ti alloy was subjected to hydrothermal treatment to ensure a crystalline formation of HAp. Morphology and phase composition investigations detected the presence of HAp crystals in coating along with antibacterial agents of silver nanoparticles. Biocompatibility and bioactivity of the created coating were examined by contact angle (CS) measurement and electrochemical impedance spectroscopy (EIS). It was shown that the coating was extensively grew after alloy's exposure to simulated body fluid (SBF) solution for 7 days with no effect on it by appeared Ag nanoparticles. Antibacterial test using Staphylococcus aureus and Escherichia coli revealed that the coating contained Ag nanoparticles has more significant antibacterial effectiveness compared to this that is not contain silver.

The purpose of this study was to evaluate the feasibility of using a counter polymer in polyethylene oxide (PEO)/polyethylene glycol (PEG) polymeric matrices for the sustained release of a large amount of highly water-soluble drug. PEO/PEG matrix tablets (CR-A) containing four drugs with different water solubilities were prepared to investigate the effect of drug solubility on the drug-release and diffusion properties of PEO/PEG matrices. Cross-linked carboxyvinyl polymer (CVP)/PEO/PEG matrix tablets (CR-B) containing a water-soluble drug, diltiazem hydrochloride (DTZ), were also prepared, and their in vitro characteristics were compared with those of CR-A. Their in vitro drug release properties were evaluated using a dissolution test, and the polymeric erosion and drug diffusion properties of the matrices were also calculated. Drugs with higher solubility in water were released faster for the CR-A. The drug-release rate also increased with the amount of drug loaded. CR-A containing 50% DTZ (by weight) extended drug release by only 6h. This confirms the difficulty experienced when trying to formulate PEO/PEG matrices for the sustained release of a large amount of highly water-soluble drugs due to large drug diffusion. In an attempt to control this issue, a polymer bearing a charge opposite that of the drug was used to effectively decrease the diffusion of DTZ, resulting in sustained release for 24h or longer. These results suggested that including counter polymer in the PEO/PEG matrix tablet is a useful tool for achieving the sustained release of a large amount of highly water-soluble drug.

The objective of this work was to gain a better understanding of the mechanism of resistance to protein adsorption of surfaces grafted with poly(ethylene oxide) (PEO). A polyurethane-urea was used as a substrate to which PEO was grafted. Grafting was carried out by introducing isocyanate groups into the surface followed by reaction with amino-terminated PEO. Surfaces grafted with PEO of various chain lengths (PUU-NPEO) were prepared and characterized by water contact angle and X-ray photoelectron spectroscopy (XPS). XPS data indicated higher graft densities on the PUU-NPEO surfaces than on analogous surfaces prepared using hydroxy-PEO (PUU-OPEO) as reported previously [J.G. Archambault, J.L. Brash, Colloids Surf. B: Biointerf. 33 (2004) 111-120]. Protein adsorption experiments using radiolabeled myoglobin, concanavalin A, albumin, fibrinogen and ferritin as single proteins in buffer showed that adsorption was reduced on the PEO-grafted surfaces by up to 95% compared to the control. Adsorption decreased with increasing PEO chain length and reached a minimum at a PEO MW of 2000. Adsorption levels on surfaces with 5000 and 2000 MW grafts were similar. There was no clear effect of protein size on resistance to protein adsorption. Adsorption on the PUU-NPEO surfaces was significantly lower than on the corresponding PUU-OPEO surfaces, again suggesting higher graft densities on the former. Adsorption of fibrinogen from plasma was also greatly reduced on the grafted surfaces. From analysis (SDS-PAGE, immunoblotting) of the proteins eluted after plasma exposure, it was found that the grafted surfaces and the unmodified substrate adsorbed the same proteins in roughly the same proportions, suggesting that adsorption to the PEO surfaces occurs on patches of bare substrate. The PEO grafts did not apparently cause differential access to the substrate based on protein size.

Polyactive(R) [polyethylene oxide-polybuthylene terephtalate (PEO-PBT)] refers to a group of copolymers with bone-bonding properties. In reference to these properties, PEO-PBT copolymers are currently being investigated for their possible use in orthopedic surgery and dentistry. PEO-PBT copolymers exhibit hydrogel behavior. When swelling in fluid is prohibited by mechanical confinement, the copolymers exert a swelling pressure on surrounding structures. In the first part of this study, these swelling pressures were measured in vitro. Polymers with different ratios of PEO-PBT exerted a swelling pressure of more than 2 MPa when tested in fluid between the cross-heads of a Hounsfield test-bench. In the second part of the study, the biocompatibility of PEO-PBT 55-45 and the effect of continuous intramedullary pressure of these copolymers on bone was investigated. Large cylinders of dry PEO-PBT 55-45 were implanted with a tight fit in the distal part of goat femora. Preswollen cylinders of PEO-PBT implanted in the opposite femur served as a control. Although it was assumed that the pressure of dry PEO-PBT on the bone would reach more than 2 MPa with press-fit insertion, no immediate hazardous effects of the expanding polymer were noticed within the first days postoperatively. The goats were sacrificed after 3, 9, and 25 weeks. Histological examination showed good implant-bone contact at different follow-up times in the distal femora with the dry implanted implants. The femora in which the preswollen cylinders had been implanted showed a thin layer of soft tissue between the PEO-PBT implant and bone. The swelling pressure exerted by dry press-fit implanted PEO-PBT implants is an important factor in creating a strong interface bond between PEO-PBT and bone.

Nanofibers represent an attractive novel drug delivery system for prolonged and controlled release. However, sustained release of hydrophilic drugs, like ciprofloxacin hydrochloride (CIP), from polymeric nanofibers is not an easy task. The present study investigates the effect of different hydrophobic polymers (PCL and PMMA) alone in monolithic nanofibers or with hydrophilic polymers (PVA, PEO, and chitosan) in blended nanofibers aiming to achieve sustained CIP release. CIP release from PCL nanofibers was 46% and from PMMA just 1.5% over 40 day period. Thus, PMMA holds great promise for modification of CIP release from blended nanofibers. PMMA blends with 10% PEO, PVA, or chitosan were used to electrospin nanofibers from solution in the mixture of acetic and formic acid. These nanofibers exhibited different drug-release profiles: PEO containing nanofiber mats demonstrated high burst effect, chitosan containing mats revealed very slow gradual release, and PVA containing mats yielded smaller burst effect with favorable sustained release. We have also shown that gradual sustain release of antibiotic like CIP can be additionally tuned over 18 days with various blend ratios of PMMA with PVA or chitosan reaching almost 100%. A mathematical model in agreement with the experimental observation revealed that the sustained CIP release from the blended nanofibers corresponded to the two-stage desorption process.

This research was aimed at investigating the growth mechanism of TiO(2)-Ag antibacterial coatings during plasma electrolytic oxidation (PEO) of Ti6Al7Nb biomedical alloy in an electrolyte based on calcium acetate/calcium glycerophosphate bearing Ag nanoparticles. The focus was on the mechanism of incorporation of Ag nanoparticles, their distribution and chemical composition within the porous coatings using high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) imaging techniques combined with energy dispersive X-ray spectroscopy (EDX) for chemical analyses. The PEO coatings were grown using different oxidation times, 10, 30, 60, 90, 120, 180, 240 and 300 s. The electron microscopy results confirmed the formation of a porous coating with incorporated Ag nanoparticles from the initial stages of oxidation (i.e. 10 s), with further Ag incorporation as the PEO process was continued for longer durations. The Ag nanoparticles were embedded in the dense oxide layer, fused into the pore walls and on the surface of the coatings without any change in their morphology or chemistry as detected by HRTEM, SEM and EDX. Ag seems to be delivered to the sites of coating growth (where dielectric breakdown occurs) through different transport pathways, i.e. open pores, cracks and short-circuit channels.

Stable, pendant polyethylene oxide (PEO) layers were formed on medical-grade Pellethane® and Tygon® polyurethane surfaces, by adsorption and gamma-irradiation of PEO-polybutadiene-PEO triblock surfactants. Coated and uncoated polyurethanes were challenged individually or sequentially with nisin (a small polypeptide with antimicrobial activity) and/or fibrinogen, and then analyzed with time-of-flight secondary ion mass spectrometry (TOF-SIMS). Data reduction by robust principal components analysis (PCA) allowed detection of outliers, and distinguished adsorbed nisin and fibrinogen. Fibrinogen-contacted surfaces, with or without nisin, were very similar on uncoated polymer surfaces, consistent with nearly complete displacement or coverage of previously-adsorbed nisin by fibrinogen. In contrast, nisin-loaded PEO layers remained essentially unchanged upon challenge with fibrinogen, suggesting that the adsorbed nisin is stabilized within the pendant PEO layer, while the peptide-loaded PEO layer retains its ability to repel large proteins. Coatings of PEO loaded with therapeutic polypeptides on medical polymers have the potential to be used to produce anti-fouling and biofunctional surfaces for implantable or blood-contacting devices.

The competitive interactions between the poly-[propylene oxide] (POO)-poly-[ethylene oxide] (PEO) block copolymer poloxamer 407 (Pluronic F127) and two drugs, triamcinolone acetonide and ciclopirox olamine, by the formation of inclusion complexes with two cyclodextrin hydrophilic derivatives, hydroxypropyl-β-cyclodextrin (HPβCD; molar substitution (MS) 0.65) and partially methylated-β-cyclodextrin (MβCD; MS 0.57), were studied by means of one-dimensional (1)H NMR, 2D ROESY experiments, solubility studies and drug release studies. 1D and 2D NMR and solubility studies indicate that both triamcinolone acetonide and ciclopirox olamine form stable inclusion complexes with the cyclodextrin derivatives. In the case of ciclopirox olamine the complex was more stable at pH 1. Effective complexation of poloxamer with the two cyclodextrins (CDs) was also evidenced by NMR analysis, and competitive displacement of the drugs from the CD cavity by the polymer was observed. Drug solubility in CD solutions was not modified by the addition of polymers, indicating that a decrease in solubility due to the competitive displacement is probably compensated by the solubilizing effect of polymer micellization. Finally, polypseudorotaxanes formation has a significant influence on the release of the drugs studied. Changes in the release rate depend on the stability of drug-CD inclusion complex and on cyclodextrin concentration in the bulk solution; so polypseudorotaxane formation can be employed to modulate drug controlled release from thermosensitive hydrogels.

Poly(ether ester) block copolymers based on polyethylene oxide (PEO) and polylactic acid (PLA) segments were synthesized and characterized, with the aim of developing a new family of bioadsorbable polymers. The materials developed were tailored to meet various mechanical and degradation requirements, and overcome the limitations of the few existing biodegradable polymers. The copolymeric matrices were characterized by means of infrared spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance spectroscopy. The composition of the copolymers synthesized varied between 20 and 84 mol% lactic acid, with PEO chains in the 600-6000 molecular weight range. The solubility properties of the copolymers in a series of organic solvents are described. The equilibrium water content and the water contact angle of various matrices were determined and related to their composition and structure. The incorporation of PEO into the chain yielded highly hydrophilic materials, with equilibrium water contents higher than 60%. Stress/strain curves are presented.

The monolithic osmotic tablet system, which is composed of a monolithic tablet coated with cellulose acetate (CA) membrane drilled with two orifices on both side surfaces, has been described. The influences of tablet formulation variables including molecular weight (MW) and amount of polyethylene oxide (PEO), amount of potassium chloride (KCl), and amount of rice starch as well as nifedipine loading have been investigated. The optimal tablet formulation and the osmotic-suspending co-controlled delivery mechanisms have been proposed. Orifice size and membrane variables including nature and amount of plasticizers as well as thickness on drug release have also been studied. The in vitro release profiles of the optimal system have been evaluated in various release media and different agitation rates, and compared with commercialized conventional capsule and push-pull osmotic tablet. It was found that PEO with MW of 300000 g/mol was suitable to be thickening agent, both amount of KCl and amount of PEO had comparable and profoundly positive effects, while nifedipine loading had a strikingly negative influence on drug release. It could be found that the optimal orifice size was in the range of 0.25-1.41 mm. It has also been observed that hydrophilic plasticizer polyethylene glycol (PEG) improved drug release, whereas hydrophobic plasticizer triacetin depressed drug release when they were incorporated in CA membrane. The monolithic osmotic tablet system was found to be able to deliver nifedipine at the rate of approximate zero-order up to 24 h, independent of both environmental media and agitation rate, and substantially comparable with the push-pull osmotic tablet. The monolithic osmotic tablet system was simple to be prepared as exempting from push layer and simplifying in the orifice drilling compared with the push-pull osmotic tablet. The monolithic osmotic tablet system may be used in drug controlled delivery field, especially suitable for water-insoluble drugs.

OBJECTIVE

The surface coating of a synthetic surface is currently investigated to decrease the harmful effects of cardiopulmonary bypass (CPB). This study was designed to study the effects of the surface coating of a hollow fiber membrane oxygenator on coagulation, inflammation markers, and clinical outcomes. The biomaterials used to coat the membrane include heparin, polyethylene oxide chains (PEO), and sulfate/sulfonate groups. The coated membrane was compared to an uncoated oxygenator made of polypropylene.

METHODS

Two hundred patients who were scheduled to undergo valve repair and/or replacement surgery with or without coronary surgery were enrolled in the study. The patients were randomized to undergo CPB with either the Avecor oxygenator with Trillium (Medtronic, Minneapolis, MN, USA), a biopassive surface, or the Monolyth (Sorin, Irvine, CA, USA) oxygenator without coating. The primary and secondary endpoints were the differences between these oxygenators in regard to patients' biochemistry, coagulation profiles, inflammatory mediators, and clinical outcomes, including blood loss and neurological events.

RESULTS

There were no differences between the two groups in terms of biochemistry, coagulation profile, inflammatory mediator release, and blood loss. Five patients in the Avecor group showed clinical evidence of a stroke confirmed with computerized tomography (CT) scan imaging, and none in the noncoated oxygenator group.

CONCLUSIONS

The oxygenator Avecor offers similar results in terms of inflammation and coagulation profiles and blood loss during valvular surgery compared to a standard uncoated control oxygenator. The rate of neurological events was unusually elevated in the former group of patients, with only speculative explanation at this point. Further studies are warranted to clarify this aspect.

Films containing polyethylene oxide (PEO) and a model drug, either guaifenesin (GFN) or ketoprofen (KTP), were prepared by hot-melt extrusion. The thermal properties of the hot-melt extruded films were investigated using differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) was used to examine the surface morphology of the films, and wide angle X-ray diffraction (XRD) was used to investigate the crystalline properties of the polymer, drugs and physical mixtures as well as the solid state structure of the films. The stability of the polymer was studied using gel permeation chromatography. The mechanical properties, including percent elongation and tensile strength of the films, were determined on an Instron according to American Society for Testing Materials (ASTM) procedures. The Hansen solubility parameter was calculated using the Hoftyzer or van Krevelen method to estimate the likelihood of drug--polymer miscibility. Both GFN and KTP were stable during the extrusion process. Melting points corresponding to the crystalline drugs were not observed in the films. Crystallization of GFN on the surface of the film was observed at all concentrations studied, however KTP crystallization did not occur until reaching the 15% level. Guaifenesin and ketoprofen were found to decrease drive load, increase PEO stability and plasticize the polymer during extrusion. The Hansen solubility parameters predicted miscibility between PEO and KTP and poor miscibility between PEO and GFN. The predictions of the solubility parameters were in agreement with the XRD and SEM results. The percent elongation decreased with increasing GFN concentrations and significantly increased with increasing levels of KTP. Both GFN and KTP decreased the tensile strength of the extruded film.

We have studied the effects of polymer molar mass and concentration on the electrophoretic migration modalities of individual molecules of DNA in LPA, HEC, and PEO solutions via epifluorescent videomicroscopy. While both transient entanglement coupling (TEC) and reptation have been studied in the past, the transition between them has not. Understanding this transition will allow for polymer network properties to be optimized to enhance the speed and resolution of DNA separations in microfluidic devices. Near the overlap threshold concentration, C*, TEC is the dominant observed mode of DNA migration, and the observation frequency of TEC increases with increasing polymer molar mass. As polymer concentration is increased, observed TEC events reduce to zero while DNA reptation events become the only detected mechanism. Individual DNA molecules undergoing both migration mechanisms were counted in solutions of varying polymer molar masses and concentrations and were plotted against a dimensionless polymer concentration, C/C*. The data for LPA reduce to form universal curves with a sharp increase in DNA reptation at approximately 6.5C*. Analogous transition concentrations for PEO and HEC were observed at 5C* and 3.5C*, respectively, reflecting the different physical properties of these polymers. This transition correlates closely with the polymer network entanglement concentration, Ce, as measured by rheological techniques. The electrophoretic mobility of lambda-DNA in LPA polymer solutions was also measured and shows how a balance can be struck between DNA resolution and separation speed by choosing the desired prevalence of DNA reptation.

The effects of chitosan hydrochloride (CH-HCl) on in vitro release of ofloxacin (OFX) from mucoadhesive erodible ocular inserts and on the relevant ocular pharmacokinetics have been studied both to contribute evidence of the ability of CH-HCl to enhance transcorneal penetration of drugs and to increase the therapeutic efficacy of topically applied OFX. Circular inserts of 6 mm in diameter, 0.8-0.9 mm in thickness and 20 mg in weight, medicated with 0.3 mg drug, were prepared by powder compression. The addition of 10, 20 or 30% medicated CH-HCl microparticles, obtained by spray-drying, to formulations based on poly(ethylene oxide) of MW 900 kDa (PEO 900) or 2000 kDa (PEO 2000) produced changes in the insert microstructure which accelerated both insert erosion and OFX release from inserts. The effect was stronger with higher CH-HCl fractions. Of the CH-HCl-containing formulations based on either PEO 900 or PEO 2000, PEO 900-CH-HCl (9:1 w/w) was more suitable for a prolonged OFX release. Following insertion in the lower conjunctival sac of the rabbit's eye, such an insert produced no substantial increase of AUC(eff) (AUC in the aqueous humour for concentrations>>MIC(90%)) with respect to inserts based on plain PEO; however, it produced a concentration peak in the aqueous significantly higher than that produced by any of the CH-HCl-free PEO inserts, and well higher than the MIC(90%) for the more resistant ocular pathogens (7 microg/ml vs. 4 microg/ml). It has been argued that the increase was due to the ability of CH-HCl to enhance the transcorneal permeability of the drug.

The aim of the study was to develop a polymeric nano-carrier based on methoxy poly(ethylene oxide)-b-poly(epsilon-caprolactone) (MePEO-b-PCL) for the optimum solubilization and delivery of Amphotericin B (AmB). For this purpose, MePEO-b-PCL block co-polymers containing palmitoyl substituent on PCL (at a 100% substitution level) were synthesized through preparation of substituted monomer, that is, alpha-palmitoyl-epsilon-caprolactone, and further ring opening polymerization of this monomer by methoxy PEO (5000 g mol(-1)) using stannous octoate as catalyst. Prepared block co-polymers were characterized for their molecular weight by (1)H NMR and gel permeation chromatography, and assembled to polymeric nano-carriers. The self-assembly of synthesized MePEO-b-PPaCL to spherical particles of nanometer size range was shown by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The efficacy of nano-carriers formed from this structure (abbreviated as MePEO-b-PPaCL) in comparison to unmodified MePEO-b-PCL and those with benzyl and cholesteryl substituent on PCL (abbreviated as MePEO-b-PBCL and MePEO-b-PChCL, respectively) on the solubilization and hemolytic activity of AmB against rat red blood cells was assessed. Under identical conditions, the maximum solubilization of AmB was achieved by nano-carriers prepared from MePEO-b-PPaCL (436 microg/mL), followed by MePEO-b-PChCL (355 microg/mL), MePEO-b-PBCL (296 microg/mL) and MePEO-b-PCL (222 microg/mL). The hemolytic activity of AmB was reduced the most by its encapsulation in MePEO-b-PChCL nano-particles which showed only 7% hemolysis at 30 microg/mL AmB concentration. This was followed by MePEO-b-PCL nano-particles which illustrated 15% hemolysis, MePEO-b-PPaCL with 40% hemolysis and MePEO-b-PBCL with 60% hemolysis at 30 microg/mL AmB concentrations, respectively. In contrast Fungizone showed 90% hemolysis at 30 microg/mL AmB concentration. Based on the improved solubility and reduced hemolytic activity, the MePEO-b-PChCL nano-carriers are considered as optimum structures for AmB delivery.

An N-heterocyclic carbene (NHC), namely, 1,3-bis-(diisopropyl)imidazol-2-ylidene (1), was demonstrated to bring about the metal-free ring-opening polymerization of ethylene oxide at 50 degrees C in dimethyl sulfoxide, in absence of any other reagents. Poly(ethylene oxide) (PEO) of polydispersities <1.2 and molar masses perfectly matching the [monomer]/[(1)] ratio could thus be obtained in quantitative yields, attesting to the controlled/living character of such carbene-initiated polymerizations. It is argued that (1) adds to ethylene oxide to form a zwitterionic species, namely 1,3-bis-(diisopropyl)imidazol-2-ylidinium alkoxide, that further propagates by a zwitterionic ring-opening polymerization (ZROP) mechanism. Through an appropriate choice of terminating agent NuH or NuSiMe(3) at the completion of the polymerization, a variety of end-functionalized PEO chains could be generated. In particular, alpha,omega-bis(hydroxy)-telechelic PEO, alpha-benzyl,omega-hydroxy, and alpha-azido,omega-hydroxy-difunctionalized PEOs were synthesized by NHC (1)-initiated ZROP, using H(2)O, PhCH(2)OH, and N(3)SiMe(3) as terminating agent, respectively. Characterization of these alpha,omega-difunctionalized PEOs by techniques such as (1)H NMR spectroscopy, MALDI-TOF spectrometry, and size exclusion chromatography confirmed the quantitative introduction of functional groups at both alpha and omega positions of the PEO chains and the formation of very narrow molar mass polymers. Finally, the synthesis of a poly(ethylene oxide)-b-poly(epsilon-caprolactone) diblock copolymer by sequential ZROP of the corresponding monomers was successfully achieved using (1) as organic initiator without isolation of the PEO block intermediate.

In this study, the formulation and process parameters that determine successful production and long-term stability of freeze-dried poly(lactic acid) (PLA) nanoparticles with "hairy-like" poly(ethylene oxide) (PEO) surfaces were investigated. Nanoparticles with grafted (covalently bound) PEO coatings were produced by the salting-out method from blends of PLA and PLA-PEO diblock or triblock copolymers. PLA nanoparticles with physically adsorbed PEO were also produced. The redispersibility of the nanoparticles after freeze-drying under various conditions was assessed. The surface of the nanoparticles was characterized and classified in terms of "brush" and "loop" conformations. Upon freeze-drying, it appeared that the presence of PEO at the nanoparticle surface could severely impair the redispersibility of the particles, especially in the PEO-grafted systems. This effect was shown to be related to the amount and molecular weight of PEO in the various formulations. In most cases, particle aggregation was prevented by use of trehalose as lyoprotective agent. Increasing the concentration of particles in the suspension to be freeze-dried was shown to induce much less damage to the nanoparticles, and freezing the suspension at a very low temperature (-196 degrees C) was found to further improve the lyoprotective effect. Most of the lyoprotected nanoparticles remained stable for at least 12 weeks at 4 and -25 degrees C. The production and preservation of freeze-dried PLA-PEO diblock and triblock copolymer nanoparticles is feasible under optimized lyoprotective conditions.

The design of targeted oral liposomes is anticipated to improve the systemic delivery of poorly absorbed agents, such as proteins and peptides. A poly(ethylene oxide) (PEO)-folic acid (FA) derivative was prepared and evaluated for improving liposome transport across a model gastrointestinal cell line (Caco-2). FA-PEO-cholesterol (Chol) derivatives were synthesized and adsorbed at liposome surfaces encapsulating Texas Red((R))-Dextran 3000 (TR-dex), a poorly-absorbed, neutral, hydrophilic, large molecular weight (M(w)) marker. Apparent permeabilities (P(app)) of Caco-2 cells to FA-PEO conjugates, TR-dex, uncoated TR-dex liposomes, and FA-coated TR-dex liposomes were compared at 2 h post-administration. Intracellular delivery of TR-dex was detected by fluorescence microscopy. An increase in intracellular accumulation of TR-dex associated with FA-PEO-coated liposomes, but not other formulations, was evidence of the potential of FA-targeted liposomes in the oral delivery of poorly absorbed, large M(w) agents.

Recombinant adeno-associated viral (rAAV) vectors are clinically adapted gene transfer vectors for direct human cartilage regenerative medicine. Their appropriate use in patients is still limited by a relatively low efficacy of vector penetration inside the cells, by the pre-existing humoral immune responses against the viral capsid proteins in a large part of the human population, and by possible inhibition of viral uptake by clinical compounds such as heparin. The delivery of rAAV vectors to their targets using optimized vehicles is therefore under active investigation. Here, we evaluated the possibility of providing rAAV to human bone marrow-derived mesenchymal stem cells (hMSCs), a potent source of cartilage regenerative cells, via self-assembled poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymers as linear poloxamers or X-shaped poloxamines. Encapsulation in poloxamer PF68 and poloxamine T908 polymeric micelles allowed for an effective, durable, and safe modification of hMSCs via rAAV to levels similar to or even higher than those noted upon direct vector application. The copolymers were capable of restoring the transduction of hMSCs with rAAV in conditions of gene transfer inhibition, i.e. in the presence of heparin or of a specific antibody directed against the rAAV capsid, enabling effective therapeutic delivery of a chondrogenic sox9 sequence leading to an enhanced chondrocyte differentiation of the cells. The present findings highlight the value of PEO-PPO copolymers as powerful tools for rAAV-based cartilage regenerative medicine.

UNASSIGNED

While recombinant adeno-associated viral (rAAV) vectors are adapted vectors to treat a variety of human disorders, their clinical use is still restricted by pre-existing antiviral immune responses, by a low efficacy of natural vector entry in the target cells, and by inhibition of viral uptake by clinically used compounds like heparin. The search for alternative routes of rAAV delivery is thus becoming a new field of investigation. In the present study, we describe the strong benefits of providing rAAV to human mesenchymal stem cells, a potent source of cells for regenerative medicine, encapsulated in polymeric micelles based on poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymers as novel, effective and safe delivery systems for human gene therapy.