Layer‐by‐Layer Coated Gold Nanoparticles: Size‐Dependent Delivery of DNA into Cells

Because nanoparticles are finding uses in myriad biomedical applications, including the delivery of nucleic acids, a detailed knowledge of their interaction with the biological system is of utmost importance. Here the size‐dependent uptake of gold nanoparticles (AuNPs) (20, 30, 50 and 80 nm), coated with a layer‐by‐layer approach with nucleic acid and poly(ethylene imine) (PEI), into a variety of mammalian cell lines is studied. In contrast to other studies, the optimal particle diameter for cellular uptake is determined but also the number of therapeutic cargo molecules per cell. It is found that 20 nm AuNPs, with diameters of about 32 nm after the coating process and about 88 nm including the protein corona after incubation in cell culture medium, yield the highest number of nanoparticles and therapeutic DNA molecules per cell. Interestingly, PEI, which is known for its toxicity, can be applied at significantly higher concentrations than its IC₅₀ value, most likely because it is tightly bound to the AuNP surface and/or covered by a protein corona. These results are important for the future design of nanomaterials for the delivery of nucleic acids in two ways. They demonstrate that changes in the nanoparticle size can lead to significant differences in the number of therapeutic molecules delivered per cell, and they reveal that the toxicity of polyelectrolytes can be modulated by an appropriate binding to the nanoparticle surface.     

Self‐Collapsing of Single Molecular Poly‐Propylene Oxide (PPO) in a 3D DNA Network

On the basis of DNA self‐assembly, a thermal responsive polymer polypropylene oxide (PPO) is evenly inserted into a rigid 3D DNA network for the study of single molecular self‐collapsing process. At low temperature, PPO is hydrophilic and dispersed uniformly in the network; when elevating temperature, PPO becomes hydrophobic but can only collapse on itself because of the fixation and separation of DNA rigid network. The process has been characterized by rheological test and Small Angle X‐Ray Scattering test. It is also demonstrated that this self‐collapsing process is reversible and it is believed that this strategy could provide a new tool to study the nucleation‐growing process of block copolymers.     

An Investigation of PS‐b‐PEO Polymersomes for the Oral Treatment and Diagnosis of Hyperammonemia

Ammonia‐scavenging transmembrane pH‐gradient poly(styrene)‐b‐poly(ethylene oxide) polymersomes are investigated for the oral treatment and diagnosis of hyperammonemia, a condition associated with serious neurologic complications in patients with liver disease as well as in infants with urea cycle disorders. While these polymersomes are highly stable in simulated intestinal fluids at extreme bile salt and osmolality conditions, they unexpectedly do not reduce plasmatic ammonia levels in cirrhotic rats after oral dosing. Incubation in dietary fiber hydrogels mimicking the colonic environment suggests that the vesicles are probably destabilized during the dehydration of the intestinal chyme. The findings question the relevance of commonly used simulated intestinal fluids for studying vesicular stability. With the encapsulation of a pH‐sensitive dye in the polymersome core, the local pH increase upon ammonia influx could be exploited to assess the ammonia concentration in the plasma of healthy and cirrhotic rats as well as in other fluids. Due to its high sensitivity and selectivity, this polymersome‐based assay could prove useful in the monitoring of hyperammonemic patients and in other applications such as drug screening tests.     

Ultrahigh‐Conductivity Polymer Hydrogels with Arbitrary Structures

A poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) hydrogel is prepared by thermal treatment of a commercial PEDOT:PSS (PH1000) suspension in 0.1 mol L^?1 sulfuric acid followed by partially removing its PSS component with concentrated sulfuric acid. This hydrogel has a low solid content of 4% (by weight) and an extremely high conductivity of 880 S m^?1. It can be fabricated into different shapes such as films, fibers, and columns with arbitrary sizes for practical applications. A highly conductive and mechanically strong porous fiber is prepared by drying PEDOT:PSS hydrogel fiber to fabricate a current‐collector‐free solid‐state flexible supercapacitor. This fiber supercapacitor delivers a volumetric capacitance as high as 202 F cm^?3 at 0.54 A cm^?3 with an extraordinary high‐rate performance. It also shows excellent electrochemical stability and high flexibility, promising for the application as wearable energy‐storage devices.     

Photosensitive Nanoparticles Combining Vascular‐Independent Intratumor Distribution and On‐Demand Oxygen‐Depot Delivery for Enhanced Cancer Photodynamic Therapy

In drug delivery, the poor tumor perfusion results in disappointing therapeutic efficacy. Nanomedicines for photodynamic therapy (PDT) greatly need deep tumor penetration due to short lifespan and weak diffusion of the cytotoxic reactive oxygen species (ROS). The damage of only shallow cells can easily cause invasiveness and metastasis. Moreover, even if the nanomedicines enter into deeper lesion, the effectiveness of PDT is limited due to the hypoxic microenvironment. Here, a deep penetrating and oxygen self‐sufficient PDT nanoparticle is developed for balanced ROS distribution within tumor and efficient cancer therapy. The designed nanoparticles (CNPs/IP) are doubly emulsified (W/O/W) from poly(ethylene glycol)‐poly(ε‐caprolactone) copolymers doped with photosensitizer IR780 in the O layer and oxygen depot perfluorooctyl bromide (PFOB) inside the core, and functionalized with the tumor penetrating peptide Cys‐Arg‐Gly‐Asp‐Lys (CRGDK). The CRGDK modification significantly improves penetration depth of CNPs/IP and makes the CNPs/IP arrive at both the periphery and hypoxic interior of tumors where the PFOB releases oxygen, effectively alleviating hypoxia and guaranteeing efficient PDT performance. The improved intratumoral distribution of photosensitizer and adequate oxygen supply augment the sensitivity of tumor cells to PDT and significantly improve PDT efficiency. Such a nanosystem provides a potential platform for improved therapeutic index in anticancer therapy.     

Desktop‐Stereolithography 3D‐Printing of a Poly(dimethylsiloxane)‐Based Material with Sylgard‐184 Properties

The advantageous physiochemical properties of poly(dimethylsiloxane) (PDMS) have made it an extremely useful material for prototyping in various technological, scientific, and clinical areas. However, PDMS molding is a manual procedure and requires tedious assembly steps, especially for 3D designs, thereby limiting its access and usability. On the other hand, automated digital manufacturing processes such as stereolithography (SL) enable true 3D design and fabrication. Here the formulation, characterization, and SL application of a 3D‐printable PDMS resin (3DP‐PDMS) based on commercially available PDMS‐methacrylate macromers, a high‐efficiency photoinitiator and a high‐absorbance photosensitizer, is reported. Using a desktop SL‐printer, optically transparent submillimeter structures and microfluidic channels are demonstrated. An optimized blend of PDMS‐methacrylate macromers is also used to SL‐print structures with mechanical properties similar to conventional thermally cured PDMS (Sylgard‐184). Furthermore, it is shown that SL‐printed 3DP‐PDMS substrates can be rendered suitable for mammalian cell culture. The 3DP‐PDMS resin enables assembly‐free, automated, digital manufacturing of PDMS, which should facilitate the prototyping of devices for microfluidics, organ‐on‐chip platforms, soft robotics, flexible electronics, and sensors, among others.     

Molecular transport characteristics of poly (ethylene‐co‐vinyl acetate) membranes in the presence of normal alkanes

Solvent transport into poly (ethylene‐co‐vinyl acetate) membranes exposed to n‐alkanes has been studied in the temperature interval of 30–60°C. Pure and cross‐linked membranes were prepared. Membranes with different loading of cross‐linking agent were also prepared. It was found that for all liquids, the equilibrium penetrant uptake was influenced by the introduction of cross links. The mechanism of transport has been found to deviate from the regular Fickian behaviour. Transport parameters such as diffusion coefficient, sorption constant and permeability coefficient have been calculated. The influence of temperature on transport was analysed. Transport parameters and activation parameters for the process of diffusion have been calculated. The transport coefficients and the activation parameters showed a dependence on cross‐link density. The Van't Hoff's relationship was used to compute the entropy change. The values of polymer–solvent interaction parameters have been used to calculate the molar mass between cross links of the network polymer. The phantom and affine models were used to analyse the deformation of the networks during swelling. A correlation between theoretical and experimental results was also done. Copyright © 2007 John Wiley & Sons, Ltd.     

Practical Approach in Developing Desirable Peel–Seal and Clear Lidding Films Based on Poly(Lactic Acid) and Poly(Butylene Adipate‐Co‐Terephthalate) Blends

In this research, poly(lactic acid) (PLA) blend with poly(butylene adipate‐co‐terephthalate) (PBAT) were selected to fabricate peelable lidding films. In general, blending PLA with PBAT results in hazy films; however, desirable low haze films (<10%) could be achieved in this study by designing proper blend composition and cast film process under optimum conditions. Based on various blends containing PBAT ranging from 15 to 30% by weight, it could be seen that a PBAT/PLA blend of 20/80 showed desired optical and peel–seal property, which had a haze of <10% and low peel strength in an easy‐peel characteristic. It was also observed that not only the blend composition but also the film thickness could influence both optical and peel–seal behaviours because the bulk morphology and surface irregularities of the films could vary by changing films' thicknesses. Thus, cast extruded pristine and PBAT/PLA (20/80) blend films of three different thicknesses (20, 35 and 50 μm) were studied. Peel–seal behaviour and optical properties of these films were examined. An I‐peel test (180°) of films sealed on PLA sheet (thickness of ~350 μm) with different interfacial sealing temperature illustrated failure mechanism of four types, i.e. tearing, partial tearing, cohesive and adhesive failure. Based on this study, the PBAT/PLA of 20/80 wt% films with thickness of 20 μm can be used as easy‐peel lidding film sealed with PLA container. Such PBAT/PLA blend films possess a low haze of ~4% and a low peel strength of 8–10 N/15 mm at a broad range of interfacial sealing temperature of 76–105°C. Copyright © 2017 John Wiley & Sons, Ltd.     

Self‐Suppression of Lithium Dendrite in All‐Solid‐State Lithium Metal Batteries with Poly(vinylidene difluoride)‐Based Solid Electrolytes

Polymer‐based electrolytes have attracted ever‐increasing attention for all‐solid‐state lithium (Li) metal batteries due to their ionic conductivity, flexibility, and easy assembling into batteries, and are expected to overcome safety issues by replacing flammable liquid electrolytes. However, it is still a critical challenge to effectively block Li dendrite growth and improve the long‐term cycling stability of all‐solid‐state batteries with polymer electrolytes. Here, the interface between novel poly(vinylidene difluoride) (PVDF)‐based solid electrolytes and the Li anode is explored via systematical experiments in combination with first‐principles calculations, and it is found that an in situ formed nanoscale interface layer with a stable and uniform mosaic structure can suppress Li dendrite growth. Unlike the typical short‐circuiting that often occurs in most studied poly(ethylene oxide) systems, this interface layer in the PVDF‐based system causes an open‐circuiting feature at high current density and thus avoids the risk of over‐current. The effective self‐suppression of the Li dendrite observed in the PVDF–LiN(SO₂F)₂ (LiFSI) system enables over 2000 h cycling of repeated Li plating–stripping at 0.1 mA cm^?2 and excellent cycling performance in an all‐solid‐state LiCoO₂||Li cell with almost no capacity fade after 200 cycles at 0.15 mA cm^?2 at 25 °C. These findings will promote the development of safe all‐solid‐state Li metal batteries.