A molecular dynamics simulation study of hydrogen bonding in poly(ethylene oxide) (PEO)/water solutions was performed. PEO-water and water-water hydrogen bonding manifested complex dependence on both composition and temperature. Strong water clustering in concentrated solutions was seen. Saturation of hydrogen bonding at w(p) approximately equal to 0.5 and a dramatic decrease in PEO-water hydrogen bonding with increasing temperature, consistent with experimentally observed closed-loop phase behavior, were observed. Little tendency toward intermolecular bridging of PEO chains by water molecules was seen.

The biodistribution of biodegradable poly(organo phosphazene) nanoparticles surface modified by adsorption of a novel poly(organo phosphazene)-poly(ethylene oxide) copolymer with a 5000 M(W) PEO chain (PF-PEO[5000]), following intravenous administration in rats and rabbits, is described. The data are compared to the biodistribution of poly(organo phosphazene) and poly(lactide-co-glycolide) nanoparticles coated with a tetrafunctional copolymer of poly(ethylene oxide)-poly(propylene oxide) ethylenediamine, commercially available as Poloxamine 908. This copolymer has a PEO chain of the same size as the poly(organo phosphazene)-PEO derivative used. The results in the rat model reveal that poly(organo phosphazene) nanoparticles with a Poloxamine 908 coating were mainly captured by the liver, although a retardation in clearance from the systemic circulation was seen. In contrast, the poly(organo phosphazene) nanoparticles coated with PF-PEO(5000) showed a prolonged blood circulating profile, with only a small amount of the nanoparticles sequestered by the liver. This indicates the importance of the nature of both the anchoring group and the particle surface on the biological performances of the system. Study of the biodistribution of the PF-PEO(5000)-coated poly(organo phosphazene) nanoparticles in the rabbit model also indicated a prolonged systemic circulation lifetime and reduced liver uptake, whereby a significant amount of the administered nanoparticles was targeted to the bone marrow.

The adsorption of poly(ethylene oxide) (PEO) on synthetic anisotropic clay particles (Laponite) has been investigated as a function of the molecular weight. Contrast variation small-angle neutron scattering (SANS) measurements were used to characterize the distribution and adsorbed amount of polymer on the particles. These experiments show not only that polymer is present on the face of the clay particle but that it also extends or "wraps" over the edges. The edge layer was thicker than the face layer for all the molecular weights studied. The polymer layers are unusually thin, with a thickness and adsorbed amount that show little variation with molecular weight.

The ability of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers (Poloxamers) to form "gels" (lyotropic liquid crystalline structures) in water is of interest to pharmaceutical applications. In such applications the presence of polar organic solvents is often desirable or required. The effect of such solvents on the stability of lyotropic liquid crystalline gels formed by PEO-PPO-PEO block copolymers was assessed by studying the phase behavior and structure in ternary isothermal (25 degrees C) systems of pharmaceutical interest consisting of Poloxamer 407 (EO(100)PO(70)EO(100)), water, and one of the following solvents (referred to here collectively as "glycols"): glycerol, propylene glycol, ethanol, polyethylene glycol 400, and glucose. Small-angle X-ray scattering was employed to establish the structure of the liquid crystals obtained and to determine their characteristic length scales. The stability range of the liquid crystalline gel phases in the systems studied was found to vary with the glycol type. For example, the micellar cubic structure can accommodate about 0.85:1 parts glucose per part water (in terms of weight) and up to as much as 5.5:1 parts propylene glycol per part water. A correlation between the glycol effects on the stability of the liquid crystalline phases and glycol physiochemical characteristics such as octanol/water partition coefficient or solubility parameter is proposed.

Hydroxyapatite (HA) is a bioactive material that is widely used for improving the osseointegration of titanium dental implants. Titanium can be coated with HA by various methods, such as chemical vapor deposition (CVD), thermal spray, or plasma spray. HA coatings can also be grown on titanium surfaces by hydrothermal, chemical, and electrochemical methods. Plasma electrolytic oxidation (PEO), or microarc oxidation (MAO), is an electrochemical method that enables the production of a thick porous oxide layer on the surface of a titanium implant. If the electrolyte in which PEO is performed contains calcium and phosphate ions, the oxide layer produced may contain hydroxyapatite. The HA content can then be increased by subsequent hydrothermal treatment. The HA thus produced on titanium surfaces has attractive properties, such as a high porosity, a controllable thickness, and a considerable density, which favor its use in dental and bone surgery. This review summarizes the state of the art and possible further development of PEO for the production of HA on Ti implants.

Polymeric micelles based on poly(ethylene oxide)-b-poly(ε-caprolactone) PEO-b-PCL or poly(ethylene oxide)-b-poly(α-benzyl carboxylate-ε-caprolactone) PEO-b-PBCL block copolymers were prepared and decorated with either c(RGDfK) or p160, a cancer cell-specific peptide ligand, on their surface. The cellular uptake of p160-decorated PEO-b-PBCL micelles containing DiI fluorescent label by MDA-MB-435 cancer cells was assessed and compared to that for c(RGDfK)-decorated micelles. The hydrophobic anticancer drug paclitaxel (PTX) was physically encapsulated into PEO-b-PCL or PEO-b-PBCL micelles (with and without peptide ligands) using a dialysis technique. The effect of the micellar formulation on the specificity of encapsulated PTX against cancer cells was assessed by investigating the in vitro cytotoxicity of free and encapsulated PTX against MDA-MB-435 cancer cell line versus two normal cells, Human Umbilical Vein Endothelial Cells (HUVEC) and MCF10A cells, using the MTT assay. Our results showed both peptide ligands to facilitate the association of micelles with MDA-MB-435 cells. The p160-micelles, however showed better binding and internalizing in MDA-MB-435 cells than c(RGDfK)-micelles. In general, peptide decoration enhanced the selective cytotoxicity of encapsulated PTX against MDA-MB-435 cells over normal HUVEC and MCF10A cells. The extent of this increase in cancer cell specificity for encapsulated PTX was more for p160-decorated micelles than c(RGDfK)-decorated ones.

We describe robustly anchored triblock copolymers that adopt loop conformations on surfaces and endow them with unprecedented lubricating and antifouling properties. The triblocks have two end blocks with catechol-anchoring groups and a looping poly(ethylene oxide) (PEO) midblock. The loops mediate strong steric repulsion between two mica surfaces. When sheared at constant speeds of ∼2.5 μm/s, the surfaces exhibit an extremely low friction coefficient of ∼0.002-0.004 without any signs of damage up to pressures of ∼2-3 MPa that are close to most biological bearing systems. Moreover, the polymer loops enhance inhibition of cell adhesion and proliferation compared to polymers in the random coil or brush conformations. These results demonstrate that strongly anchored polymer loops are effective for high lubrication and low cell adhesion and represent a promising candidate for the development of specialized high-performance biomedical coatings.

The formation of 3D electrospun mat structures from alginate-polyethylene oxide (PEO) solution blends is reported. These unique architectures expand the capabilities of traditional electrospun mats for applications such as regenerative medicine, where a scaffold can help to promote tissue growth in three dimensions. The mat structures extend off the surface of the flat collector plate without the need of any modifications in the electrospinning apparatus, are self-supported when the electric field is removed, and are composed of bundles of nanofibers. A mechanism for the unique formations is proposed, based on the fiber-fiber repulsions from surface charges on the negatively charged alginate. Furthermore, the role of the electric field in the distribution of alginate within the nanofibers is discussed. X-ray photoelectron spectroscopy is used to analyze the surface composition of the electrospun nanofiber mats and the data is related to cast films made in the absence of the electric field. Further techniques to tailor the 3D architecture and nanofiber morphology by changing the surface tension and relative humidity are also discussed.

Poly(ethylene oxide)-block-poly(epsilon-caprolactone) (PEO-b-PCL) copolymers bearing paclitaxel (PTX) side groups on PCL (PEO-b-P(CL-PTX) were synthesized and assembled to particles of 123 nm average diameter. At 20% (w/w) PTX to polymer conjugation, PEO-b-P(CL-PTX) demonstrated only 5.0 and 6.7% PTX release after 72 h incubation at pH 7.4 and 5.0, respectively, but revealed signs of chain cleavage at pH 5.0. The cytotoxicity of PEO-b-P(CL-PTX) against MDA-MB-435 cancer cells increased as incubation time was raised from 72 to 96 h (IC(50) of 680 and 475 ng/mL, respectively), but it was still significantly lower than the cytotoxicity of free PTX (IC(50) of 3.5 ng/mL at 72 h). In further studies, micelles of PEO-b-PCL and those bearing benzyl or PTX on PCL were used for physical encapsulation of PTX, where maximum level of loading was achieved by PEO-b-P(CL-PTX) (2.22%, w/w). The release of PTX from this carrier was rapid; however. The in vitro cytotoxicity of physically loaded PTX was independent of carrier and similar to that of free PTX. This was attributed to the low concentration of polymers which fell below their critical micellar concentration in the cytotoxicity study. The results point to the potential of chemically tailored PEO-b-PCL for optimum PTX solubilization and delivery.

Intramuscular (i.m.) DNA vaccination induces strong cellular immune responses in the mouse, but only at DNA doses that cannot be achieved in humans. Because antigen expression is weak after naked DNA injection, we screened five nonionic block copolymers of poly(ethyleneoxide)-poly(propyleneoxide) (PEO-PPO) for their ability to enhance DNA vaccination using a beta-galactosidase (betaGal) encoding plasmid, pCMV-betaGal, as immunogen. At a high DNA dose, formulation with the tetrafunctional block copolymers 304 (molecular weight [MW] 1,650) and 704 (MW 5,500) and the triblock copolymer Lutrol (MW 8,600) increased betaGal-specific interferon-gamma enzyme-linked immunosorbent spot (ELISPOT) responses 2-2.5-fold. More importantly, 704 allowed significant reductions in the dose of antigen-encoding plasmid. A single injection of 2 microg pCMV-betaGal with 704 gave humoral and ELISPOT responses equivalent to those obtained with 100 microg naked DNA and conferred protection in tumor vaccination models. However, 704 had no adjuvant properties for betaGal protein, and immune responses were only elicited by low doses of pCMV-betaGal formulated with 704 if noncoding carrier DNA was added to maintain total DNA dose at 20 microg. Overall, these results show that formulation with 704 and carrier DNA can reduce the dose of antigen-encoding plasmid by at least 50-fold.

We investigated the influence of tetrahydrofuran (THF) addition on the structure of poly(1,2-butadiene-b-ethylene oxide) [PB-PEO] micelles in aqueous solution. Our studies showed that while the micelles remained starlike, the micelle core-corona interfacial tension and micelle size decreased upon THF addition. The detailed effects of the reduction in interfacial tension were probed using contrast variations in small angle neutron scattering (SANS) experiments. At low THF contents (high interfacial tensions), the SANS data were fit to a micelle form factor that incorporated a radial density distribution of corona chains to account for the starlike micelle profile. However, at higher THF contents (low interfacial tensions), the presence of free chains in solution affected the scattering at high q and required the implementation of a linear combination of micelle and Gaussian coil form factors. These SANS data fits indicated that the reduction in interfacial tension led to broadening of the core-corona interface, which increased the PB chain solvent accessibility at intermediate THF solvent fractions. We also noted that the micelle cores swelled with increasing THF addition, suggesting that previous assumptions of the micelle core solvent content in cosolvent mixtures may not be accurate. Control over the size, corona thickness, and extent of solvent accessible PB in these micelles can be a powerful tool in the development of targeting delivery vehicles.

Programmed self-assembly of well-defined molecular building blocks enables the fabrication of precisely structured nanomaterials. In this work, we explore a new class of giant polymeric surfactants (Mn = (0.7-4.4) × 10(6) g/mol) with bottlebrush architecture and show that their persistent molecular shape leads to the formation of uniform aggregates in a predictable manner. Amphiphilic bottlebrush block copolymers containing polylactide (PLA) and poly(ethylene oxide) (PEO) side chains were synthesized by a grafting-from method, and their self-assembly in aqueous environment was studied by cryogenic transmission electron microscopy. The produced micelle structures with varying interfacial curvatures and core radii (19-55 nm) boasted rod-like hydrophilic PEO brushes protruding from the hydrophobic PLA cores normal to the interface. Highly uniform spherical micelles with low dispersities were obtained from bottlebrush amphiphiles with packing parameters of ∼0.3, estimated from the polymer structural data. Long cylindrical micelles and other nonspherical aggregates were observed for the first time for compositionally less asymmetric bottlebrush surfactants. Critical micelle concentration values of 1 nM, measured for PEO-rich bottlebrush amphiphiles, indicated an enhanced thermodynamic stability of the produced micelle aggregates. Shape-dependent assembly of bottlebrush surfactants allows for the rational fabrication of a range of micelle structures in narrow morphological windows.

Sulphonated poly(ethylene oxide) (PEO-SO3) and PEO-SO3-grafted polyurethane (PU-PEO-SO3) were prepared by bulk modification and their anticoagulant and heparin-like activities were investigated. Anticoagulant activity measured by activated partial thromboplastin time of PU-PEO-SO3 displayed 2%, whereas that of PEO-SO3 itself reached 14% as compared to free heparin. In addition, the anticoagulant effects of these sulphonated polymers were not due to factor Xa inhibition but mainly thrombin inhibition. From the clotting time measurements using reptilase instead of thrombin and antithrombin III (AT III), PEO-SO3 and PU-PEO-SO3 indicated heparin-like activity which represents both prolonged thrombin time (TT) and normal reptilase time and increased TT in the presence of AT III. Thrombin was also neutralized by sulphonated polymers to a great extent. Therefore, the anticoagulant and heparin-like activities of PEO-SO3 and PU-PEO-SO3 seem to contribute to their improved blood compatibility.

Vesicles whose bilayer membranes contain phospholipids mixed with co-polymers or surfactants comprise new hybrid materials having potential applications in drug delivery, sensors, and biomaterials. Here we describe a model polymer-phospholipid hybrid membrane system exhibiting strong similarities to binary phospholipid mixtures, but with more robust membrane mechanics. A lamella-forming graft copolymer, PDMS-co-PEO (polydimethylsiloxane-co-polyethylene oxide) was blended with a high melting temperature phospholipid, DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine), over a broad compositional range. The resulting giant hybrid unilamellar vesicles were compared qualitatively and quantitatively to analogous mixed phospholipid membranes in which a low melting temperature phospholipid, DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine), was blended with DPPC. The mechanical properties of the hybrid vesicles, even when phase separated, were robust with high lysis stresses and strains approaching those of the pure copolymer vesicles. The temperature-composition phase diagram of the hybrid vesicles closely resembled that of the mixed phospholipids; with only slightly greater nonidealities in the hybrid compared with DOPC/DPPC mixed membranes. In both systems, it was demonstrated that tension could be used to manipulate DPPC solidification into domains of patchy or striped morphologies that exhibited different tracer incorporation. The patch and stripe-shaped domains are thought to be different solid DPPC polymorphys: ripple and tilt (or gel). This work demonstrates that in mixed-phospholipid bilayers where a high-melting phospholipid solidifies on cooling, the lower-melting phospholipid may be substituted by an appropriate copolymer to improve mechanical properties while retaining the underlying membrane physics.

Block copolymer lithography holds promise as a next-generation technique to achieve the sub-20 nm feature sizes demanded by semiconductor roadmaps. While molecular weight and block immiscibility have traditionally been used to control feature size, this study demonstrates that macromolecular architecture is also a powerful tool for tuning domain spacing. To demonstrate this concept, a new synthetic strategy for cyclic block polymers based on highly efficient "click" coupling of difunctional linear chains is developed, and the thin film self-assembly of cyclic polystyrene-block-polyethylene oxide (cPS-b-PEO) is compared with the corresponding linear analogues. The reduced hydrodynamic radii of the cyclic systems result in ~30% decrease in domain spacing over the corresponding linear polymers.

We report a novel class of amphiphilic conjugated block copolymers composed of poly(3-octylthiophene) and poly(ethylene oxide) (POT-b-PEO) that exhibit highly tunable photoluminescence colors spanning from blue to red. POT-b-PEO self-assembles into various well-defined core/shell-type nanostructures as a result of its amphiphilicity. The self-assembly structure can be readily controlled by altering the solvent composition or by other external stimuli. The color change was completely reversible, demonstrating that the strategy can be used to manipulate the light-emission properties of conjugated polymers in a highly controllable manner without having to synthesize entirely new sets of molecules.

Novel reduction-sensitive micelles based on poly(ethylene oxide)-b-poly(N-methacryloyl-N'-(t-butyloxycarbonyl)cystamine) (PEO-b-PMABC) diblock copolymers were developed and applied for triggered intracellular drug release. PEO-b-PMABC block copolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of MABC with dithioester-capped PEO as macroRAFT agent. Gel permeation chromatography (GPC) and (1)H NMR analysis showed that the copolymers have controlled compositions and molecular weights, indicating the living nature of polymerization. These copolymers were self-assembled into micelles. The physicochemical characteristics and reduction-sensitivity of the resultant micelles were investigated by fluorescence measurement, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The results showed that PEO-b-PMABC micelles are stable at normal physiologic condition but readily cleaved into free copolymers under reducing environment. In vitro release of doxorubicin (DOX) and cell experiments showed that the drug-loaded PEO-b-PMABC micelles accomplished much faster drug release under reducing condition and higher anticancer efficacy as compared to the control without reduction-sensitivity, indicating great potential of PEO-b-PMABC micelles for efficient intracellular drug delivery.

As a member of the organic-inorganic hybrid family, silica/organosilica cross-linked block copolymer micelles are becoming increasingly attractive due to the combined features of excellent self-assembly properties of amphiphilic block copolymers and the high stability and the easy surface modification of silica/organosilica components. Compared to the traditional cross-linking route with organic components, the silica/organosilica cross-linking approach could offer more advantages, such as quick reaction under mild conditions, a much stronger barrier to the diffusion of both encapsulated small molecules and functional nanoparticles and the substantial improvement in the stability of the whole micelles against the ambient environment. In this tutorial review, we will focus on the recent developments in the design, synthesis and biomedical applications of silica/organosilica cross-linked block copolymer micelles based on the self-assembly of amphiphilic block copolymers and the hydrolysis and condensation of silanes in aqueous solution. First, we will summarize the synthesis of three typical kinds of silica/organosilica cross-linked block copolymer micelles based on the self-assembly of non-ionic polyethylene oxide (PEO)-based, cationic and anionic poly(acrylic acid) (PAA)-based block copolymer micelles. Then, a series of multifunctional silica/organosilica cross-linked block copolymer micelles by encapsulating various functional nanoparticles/molecules in the hydrophobic polymer cores or hydrophilic silica/organosilica cross-linked shells are introduced and their biomedical applications in controlled drug delivery, bio-imaging (magnetic resonance, fluorescence and multimodal imaging) and imaging-guided therapies (photothermal and high intensity focused ultrasound therapies) will be discussed. Finally, the challenges and prospects of silica/organosilica cross-linked micellar nanostructures and their biological applications are discussed and assessed. It is highly expected that the silica/organosilica cross-linked micelles may provide a new and promising kind of carrier system for enhanced bio-imaging and efficient cancer therapy.

In the literature, many papers deal with the behavior of proteins in aqueous media in the presence of poly(ethylene glycol) (PEG) molecules or poly(ethylene oxide) (PEO) segments, physically adsorbed onto, or covalently attached to, macromolecules or to solid surfaces. In particular, it is well known that PEO segments make foreign materials stealthy, i.e. they are much less detected by the immune system either through humoral reactions or, at the cell level, through opsonins. Revisiting the literature led us to challenge the largely accepted opinion that the decreased recognition of PEO segment-bearing foreign macromolecules and particles by the mononuclear phagocyte system is primarily the consequence of the repulsion of all blood proteins by PEG segments through the excluded volume effect. This challenge is based on the finding that albumin and PEG are compatible in phosphate-buffered saline at room temperature and at concentrations comparable to those measured by others on the surface of PEO segment-bearing species, whereas fibrinogen and PEG phase-separated and were incompatible despite the much lower concentration of the latter protein. According to literature and to these observations, it is proposed that the stealth effect induced by PEO segments is primarily due to the compatibility between PEO segments of intermediate molar mass and albumin, thus rendering PEO-bearing macromolecules or surfaces to look like native albumin. Under such conditions, the hospitality offered by PEG macromolecules or PEO segments to albumin, the dominant plasma protein, results in a 'chameleon' effect that prevents the activation of other PEG-compatible or -incompatible plasma proteins or cells involved in foreign body recognition and elimination. PEG with molar masses>> or = 8000 did not accommodate albumin in agreement with the excluded volume phenomenon.

The properties of bicontinuous microemulsions, consisting of water, oil, and a surfactant, can be modified by the addition of diblock copolymers (boosting effect) and homopolymers (inverse boosting effect) or a combination of both. Here, the influence of the addition of homopolymers (PEP(X) and PEO(X), X=5k or 10k molecular weight) on the dynamics of the surfactant layer is studied with neutron spin echo spectroscopy (NSE). Combining the results with the previous findings for diblock copolymers allows for a better separation of viscosity and bending modulus effects. With the addition of homopolymers, a significant increase of the relaxation rate compared to the pure microemulsion has been observed. The influence on the bending rigidity kappa is measured with NSE experiments. Homopolymer addition reduces kappa by up to Deltakappa approximately -0.5k(B)T, whereas the diblock copolymer yields an increase of kappa by approximately 0.3k(B)T. Comparison of the bending moduli that are obtained by analysis of the dynamics to those obtained from small angle neutron scattering (SANS) sheds light on the different renormalization length scales for NSE and SANS. Variation of the surfactant concentration at otherwise constant conditions of homopolymer or diblock-copolymer concentration shows that NSE results are leading to the pure bending rigidity, while the renormalized one is measured with SANS.

BACKGROUND

The aim of this study was to determine the effects of plant essential oil supplementation on growth performance, immune function and antioxidant activities in weaned pigs.

METHODS

In the study, 24 weaned pigs were used to explore the effects of plant essential oil (<em>PEO</em>) on growth performance, immune properties and antioxidant activities. Pigs were fed with a basal diet (CON) or basal diet containing different concentrations of <em>PEO</em> (<em>PEO</em>50: 50 ppm; <em>PEO</em>100: 100 ppm; <em>PEO</em>200: 200 ppm). After 3 weeks, all pigs were slaughtered and blood and tissue samples were collected for biochemical analysis.

RESULTS

The results showed that PEO supplementation quadratically increased body weight gain (BWG) (P = 0.031), linearly (P < 0.05) and quadratically (P < 0.05) decreased F:G. In addition, IgG increased linearly (P < 0.05) and IgM increased linearly (P < 0.05) and quadratically (P < 0.05) as PEO supplementation. Similarly, MDA in serum, jejunal mucosa and pancreas were linearly decreased (P < 0.05) and GSH in serum (linear and quadratic, P < 0.05), duodenal mucosa (linear and quadratic, P < 0.05) and in ileal mucosa (linear and quadratic, P < 0.05) were notably increased. Futhermore, antioxidant-related genes expression levels of GST in spleen (linear and quadratic, P < 0.05), GPX1 (quadratic, P < 0.05) and SOD1 (linear, P < 0.05) in spleen and GST in liver (quadratic, P < 0.05) were markedly upregulated by PEO supplementation increasing.

CONCLUSIONS

These results suggest that PEO improves growth performance, immune function, and antioxidant activities in weaned pigs, and it may also relieve weaning stress if used as a feed additive in the livestock industry. And that supplementation 200 ppm PEO in diet would seem to be economically feasible.

The complex tumor microenvironment constitutes a variety of barriers to prevent nanoparticles (NPs) delivery and results in extremely low accumulation of nanomedicines in solid tumors. Here, a newly developed size-changeable collagenase-modified polymer micelle is employed to enhance the penetration and retention of nanomedicine in deep tumor tissue. The TCPPB micelle is first formed by self-assembly of maleimide-terminated poly(ethylene glycol)-block-poly(β-amino ester) (MAL-PEG-PBAE) and succinic anhydride-modified cisplatin-conjugated poly(ε-caprolactone)-block-poly(ethylene oxide)-triphenylphosphonium (CDDP-PCL-PEO-TPP). Next, Col-TCPPB NPs are prepared through a "click" chemical combination of thiolated collagenase and maleimide groups on TCPPB micelle. Finally, biocompatible chondroitin sulfate (CS) is coated to obtain CS/Col-TCPPB NPs for avoiding collagenase inactivation in blood circulation. In tumor acidic microenvironment, the hydrophobic PBAE segments of the resultant micelles become hydrophilic, leading to a dissociation and subsequent dissolution of partial collagenase-containing components (Col-PEG-PBAE) from NPs. The dissolved Col-PEG-PBAE promotes the digestion of collagen fibers in tumor tissue like a scavenger, which enhances the NPs penetration. Simultaneously, the increased hydrophilicity of residual Col-PEG-PBAE in the micellar matrix causes an expansion of the NPs, resulting in an enhanced intratumoral retention. In tumor cells, the NPs target to release the cisplatin drugs into mitochondria, achieving an excellent anticancer efficacy.

The dispersion of polymer-covered gold nanoparticles in high molecular weight (MW) polymer matrixes is reported. Complete particle dispersion was achieved for PS125-Au in the polystyrene (PS) matrixes studied (up to and including Mn = 80 000 g/mol). PS19-Au, on the other hand, exhibits complete dispersion in a low MW PS matrix (Mn = 2000 g/mol) but only partial dispersion in higher MW matrixes (up to 80 000 g/mol). Similarly, <em>PEO</em>45-Au is fully dispersed in a low MW poly(ethylene oxide) (<em>PEO</em>) matrix (Mn = 1000 g/mol) but only partially in a higher MW <em>PEO</em> matrix (Mn = 15 000 g/mol). Wetting of the polymer-Au brushes by the polymer matrix is associated with dispersibility. Theory predicts that, for dense polymer brushes, wetting is achieved when the MW of the polymer brush equals (and is greater than) that of the polymer matrix. The observed partial dispersion of the PS19-Au and <em>PEO</em>45-Au nanoparticles in matrixes whose MW is greater than the brush MW is attributable to the existence of a high volume fraction of voids within the brush. These voids arise from the unique geometry of the nanoparticle surface arising from the juxtaposed facets of the gold nanoparticle. PS125-Au brushes are wetted by PS matrixes whose degree of polymerization is larger than 125, probably because of their lower grafting density on the gold core or the high fraction of void volumes caused by the facets on the gold cores. Dispersion thus occurs when the matrix MW is greater than that of the brush.

This work describes the effect of cold nitrogen plasma to enhance the antibacterial activity of poly(ethylene oxide) (PEO) nanofibers containing antibacterial agent. Beta-cyclodextrin (β-CD) and tea tree oil (TTO) were used as a host-guest to form water-soluble inclusion complex. The encapsulation efficiency of TTO in inclusion complex could reach 73.23% at 60°C. As antibacterial agent, the inclusion complex was encapsulated into PEO matrix by electrospun. After plasma treatment, the release efficiency of antibacterial agent from PEO nanofibers was improved. As a result, the antibacterial activity of PEO nanofibers was enhanced accordingly. The plasma-treated nanofiber membranes achieved the highest antibacterial activity against Escherichia coli O157:H7, which was tested on the beef for 7d, with inhibition efficiently of 99.99% whether at 4°C or 12°C. The plasma-treated PEO nanofiber membranes containing TTO/β-CD inclusion complex (TTO/β-CD-IC) can prolong the shelf-life of beef, suggesting it has potential application in active food packaging.