Mitigating Cobalt Phthalocyanine Aggregation in Electrocatalyst Films through Codeposition with an Axially Coordinating Polymer.

Cobalt phthalocyanine (CoPc) is a promising molecular catalyst for aqueous electroreduction of CO2, but its catalytic activity is limited by aggregation at high loadings. Codeposition of CoPc onto electrode surfaces with the coordinating polymer poly(4-vinylpyridine) (P4VP) mitigates aggregation in addition to providing other catalytic enhancements. Transmission and diffuse reflectance UV-vis measurements demonstrate that a combination of axial coordination and π-stacking effects from pyridyl moieties in P4VP serve to disperse cobalt phthalocyanine in deposition solutions and help prevent reaggregation in deposited films. Polymers lacking axial coordination, such as Nafion, are significantly less effective at cobalt phthalocyanine dispersion in both the deposition solution and in the deposited films. SEM images corroborate these findings through particle counts and morphological analysis. Electrochemical measurements show that CoPc codeposited with P4VPonto carbon electrode surfaces reduces CO2 with higher activity and selectivity compared to the catalyst codeposited with Nafion.

Silicone-Textile Composite Resistive Strain Sensors for Human Motion-Related Parameters.

In recent years, soft and flexible strain sensors have found application in wearable devices for monitoring human motion and physiological parameters. Conductive textile-based sensors are good candidates for developing these sensors. However, their robust electro-mechanical connection and susceptibility to environmental factors are still an open challenge to date. In this work, the manufacturing process of a silicone-textile composite resistive strain sensor based on a conductive resistive textile encapsulated into a dual-layer of silicone rubber is reported. In the working range typical of biomedical applications (up to 50%), the proposed flexible, skin-safe and moisture resistant strain sensor exhibited high sensitivity (gauge factor of -1.1), low hysteresis (maximum hysteresis error 3.2%) and ease of shaping in custom designs through a facile manufacturing process. To test the developed flexible sensor, two applicative scenarios covering the whole working range have been considered: the recording of the chest wall expansion during respiratory activity and the capture of the elbow flexion/extension movements.

Disruption of Enterococcus Faecalis biofilms using individual and plasma polymer encapsulated D-amino acids.

OBJECTIVE: Our aim was to assess the anti-biofilm ability of previously unverified individual D-amino acids (DAAs), to produce plasma polymer encapsulated DAAs (PPEDAAs), to measure the shell thickness and subsequent release of DAAs, and to assess the effects of PPEDAAs on Enterococcus faecalis biofilms. MATERIALS AND METHODS: Microtitre tray assays were used to evaluate the effect of individual DAAs (D-leucine, D-methionine, D-tryptophan, and D-tyrosine) on E. faecalis biofilms of different maturity. A mixture and individual DAAs were encapsulated with a plasma polymer for 10, 20, 40, and 60 min. The shell thickness of PPEDAAs was analyzed by ultra-high-resolution scanning electron microscopy. The release of DAAs from the PPEDAAs encapsulated for 60 min was measured over 7 days using high-performance liquid chromatography. Static biofilms were used to assess the effect of PPEDAAs on E. faecalis biofilms. RESULTS: Individual DAAs reduced biofilm formation to various degrees, according to the DAA and the experimental times. The shell thicknesses of the PPEDAAs ranged between 31 and 76 nm and increased with encapsulation time. Diffusion of DAAs from the PPEDAAs occurred over 60 min for encapsulated D-leucine, D-methionine, and D-tyrosine and up to 7 days for D-tryptophan. PPEDAAs disrupted biofilms at every experimental time. CONCLUSIONS: PPEDAAs of various shell thickness can be produced with the proposed methodology, DAAs are subsequently released, and the anti-biofilm activity remains unaltered. CLINICAL RELEVANCE: Individual DAAs and PPEDAAs have anti-biofilm ability and can be considered as part of a biological strategy in endodontics.

Polymeric Encapsulation of Turmeric Extract for Bioimaging and Antimicrobial Applications.

As a herb of the ginger family, the turmeric plant has been used as spice and colorant in the Oriental countries. The rhizome part of the plant is rich in curcumin, which has been proven to be the main ingredient responsible for turmeric's biological effects. Most research endeavors have been upon the investigation of pharmaceutical activities of curcumin, yet the fluorescence of curcumin is a bit far from well-studied. The major drawbacks associated with curcumin are its poor aqueous solubility and low stability. In this communication, the encapsulation of fluorescent turmeric extract into polymeric nanoparticles (NPs) for bioimaging and antibacterial applications is reported. Through poly(d,l-lactic-co-glycolic acid) (PLGA) encapsulation, solubility of curcumin is greatly increased, and the biodegradable nature of PLGA further enhances the biocompatibility of curcumin. These Cur-PLGA NPs are successfully demonstrated to be efficient fluorescence probes for bioimaging, and promising for antibacterial application.

Ultra-Low Power Wearable Infant Sleep Position Sensor.

Numerous wearable sensors have been developed for a variety of needs in medical/healthcare/wellness/sports applications, but there are still doubts about their usefulness due to uncomfortable fit or frequent battery charging. Because the size or capacity of battery is the major factor affecting the convenience of wearable sensors, power consumption must be reduced. We developed a method that can significantly reduce the power consumption by introducing a signal repeater and a special switch that provides power only when needed. Antenna radiation characteristics are an important factor in wireless wearable sensors, but soft material encapsulation for comfortable fit results in poor wireless performance. We improved the antenna radiation characteristics by a local encapsulation patterning. In particular, ultra-low power operation enables the use of paper battery to achieve a very thin and flexible form factor. Also, we verified the human body safety through specific absorption rate simulations. With these methods, we demonstrated a wearable infant sleep position sensor. Infants are unable to call for help in unsafe situations, and it is not easy for caregivers to observe them all the time. Our wearable sensor detects infants' sleep positions in real time and automatically alerts the caregivers when needed.

Polymer/Iron Oxide Nanoparticle Composites--A Straight Forward and Scalable Synthesis Approach.

Magnetic nanoparticle systems can be divided into single-core nanoparticles (with only one magnetic core per particle) and magnetic multi-core nanoparticles (with several magnetic cores per particle). Here, we report multi-core nanoparticle synthesis based on a controlled precipitation process within a well-defined oil in water emulsion to trap the superparamagnetic iron oxide nanoparticles (SPION) in a range of polymer matrices of choice, such as poly(styrene), poly(lactid acid), poly(methyl methacrylate), and poly(caprolactone). Multi-core particles were obtained within the Z-average size range of 130 to 340 nm. With the aim to combine the fast room temperature magnetic relaxation of small individual cores with high magnetization of the ensemble of SPIONs, we used small (<10 nm) core nanoparticles. The performed synthesis is highly flexible with respect to the choice of polymer and SPION loading and gives rise to multi-core particles with interesting magnetic properties and magnetic resonance imaging (MRI) contrast efficacy.

Effect of Polymer Encapsulation on the Mechanoluminescence of Mn2+-Doped CaZnOS.

Rare earth and transition metal ion-doped CaZnOS has garnered significant attention for its exceptional mechanoluminescence (ML) performance under mild mechanical stimuli and its capability for multicolor emissions. Since powdered phosphors are not directly usable, they require encapsulation within with polymers to create stable structures. This study investigates Mn2+-doped CaZnOS (CaZnOS:Mn2+) as the ML phosphor, optimizing its performance by varying the Mn2+ content, resulting in bright orange-red emissions from the d-d transitions of the Mn2+ activator. A quantum efficiency of 59.08% was achieved through the self-sensitization of the matrix lattice and energy transfer to the Mn2+ luminescent centers. The enhancement in ML due to Mn2+ doping is attributed to the reduced trap depth and increased trap concentration. Encapsulation with four polymers-PDMS, PU, SIL, and RTV-2-was explored to further optimize ML performance. Among these, PDMS provides the best ML output and sensitivity, owing to its slightly cross-linked structure and good triboelectric properties. The optimized CaZnOS:0.03Mn2+/PDMS composite, featuring excellent flexibility and recoverability, shows great potential for applications in anti-counterfeiting encryption, stress sensors, and wearable devices.

Transferred Polymer-Encapsulated Metal Electrodes for Electrical Transport Measurements on Ultrathin Air-Sensitive Crystals.

Owing to rapid property degradation after ambient exposure and incompatibility with conventional device fabrication process, electrical transport measurements on air-sensitive 2D materials have always been a big issue. Here, for the first time, a facile one-step polymer-encapsulated electrode transfer (PEET) method applicable for fragile 2D materials is developed, which showed great advantages of damage-free electrodes patterning and in situ polymer encapsulation preventing from H2 O/O2 exposure during the whole electrical measurements process. The ultrathin SmTe2 metals grown by chemical vapor deposition (CVD) are chosen as the prototypical air-sensitive 2D crystals for their poor air-stability, which will become highly insulating when fabricated by conventional lithographic techniques. Nevertheless, the intrinsic electrical properties of CVD-grown SmTe2 nanosheets can be readily investigated by the PEET method instead, showing ultralow contact resistance and high signal/noise ratio. The PEET method can be applicable to other fragile ultrathin magnetic materials, such as (Mn,Cr)Te, to investigate their intrinsic electrical/magnetic properties.

Polymeric Nanoshell-Stabilized Liquid Metal for Bactericidal Photonanomedicine.

Liquid metals (LMs), typically gallium and its alloys, are emerging functional materials for nanotechnology, yet the applications of LM nanoparticles (LMNPs) in biomedical areas are still in their infancy. This predicament occurs primarily because LMNPs are generally synthesized with inadequately protected surfaces rendering rapid uncontrollable oxidation in physiological conditions. Herein, we show that depositing a polymeric supra-nanoparticle shell on LMNPs through sonochemical assembly can alleviate their oxidation kinetics and maintain their designed functionalities, even during hyperthermia processing. The LMNPs with polymer encapsulation promise to be excellent candidate materials for stable, biocompatible, and reusable photothermal converters under near-infrared (NIR) laser irradiation, showing doubled photothermal conversion efficiency compared with unprotected ones. Besides, they are employed, alone or synergistically with a hydrogel matrix, as potent photothermal bactericidal agents, both in vitro and in vivo. Specifically, the LMNPs-embedded agarose hydrogel allows the disinfection and concurrently accelerated healing of full-thickness skin wounds. The nanoshell-enabled heat resistance of LMNPs is expected to broaden the horizons of LM-based nano/biomedicine, potentially against superbugs and cancer.

Low-cost nano-TiO2 composites for remediation of textile dyes: Appraisal on the effect of solar and ultraviolet irradiations.

The study evaluates the azo dye degradation potential of nano-TiO2 ; its composites with low-cost substrates in the form of powder and encapsulated bead for two widely used azo dyes, methyl orange (MO) and congo red (CR) under solar and ultraviolet (UV) irradiation. Degradation potential varied according to the dye concentration, chemistry of dye, light source, and the formulation of the photocatalyst. Both the dyes were completely decolorized at 100 mg/L concentration and to some extent at 1,000 mg/L concentration. The activated charcoal-titanium dioxide (AC-TiO2 ) nanocomposite in the presence of solar radiations proved to be an economic and efficient substrate for degradation of the test dyes exhibiting combined action of adsorption and photocatalytic phenomena.

Polymer and Crosslinker Content Influences Performance of Encapsulated Live Biotherapeutic Products.

INTRODUCTION: Live biotherapeutic products (LBPs), or therapeutic microbes, are an emerging therapeutic modality for prevention and treatment of gastrointestinal diseases. Since LBPs are living, they are uniquely sensitive to external stresses (e.g., oxygen, acid) encountered during manufacturing, storage, and delivery. Here, we systematically evaluate how polymer and crosslinker concentration affects the performance of an encapsulated LBP toward developing a comprehensive framework for the characterization and optimization of LBP delivery systems. METHODS: We encapsulate a model LBP, Lactobacillus casei ATCC 393, in calcium chloride (CaCl2)-crosslinked alginate beads, and evaluate how alginate and CaCl2 concentrations influence LBP formulation performance, including: (i) encapsulation efficiency, (ii) shrinkage upon drying, (iii) survival upon lyophilization, (iv) acid resistance, (v) release, and (vi) metabolite secretion. Approaches from microbiology (e.g., colony forming unit enumeration), materials science (e.g., scanning electron microscopy), and pharmaceutical sciences (e.g., release assays) are employed. RESULTS: LBP-encapsulating alginate beads were systematically evaluated as a function of alginate and CaCl2 concentrations. Specifically: (i) encapsulation efficiency of all formulations was >50%, (ii) all alginate beads shrunk (after lyophilization) and recovered (after rehydration) similarly, (iii) at 10% alginate concentration, lower CaCl2 concentration decreased survival upon lyophilization, (iv) 10% alginate improved acid resistance, (v) sustained release was enabled by increasing alginate and CaCl2 concentrations, and (vi) encapsulation did not impair secretion of l-lactate as compared to free LBP. CONCLUSIONS: This research demonstrates that polymer content and crosslinking extent modulate the performance of polymer-based LBP delivery systems, motivating research into the optimization of material properties for LBP delivery systems.

The Effect of Encapsulation on Crack-Based Wrinkled Thin Film Soft Strain Sensors.

Practical wearable applications of soft strain sensors require sensors capable of not only detecting subtle physiological signals, but also of withstanding large scale deformation from body movement. Encapsulation is one technique to protect sensors from both environmental and mechanical stressors. We introduced an encapsulation layer to crack-based wrinkled metallic thin film soft strain sensors as an avenue to improve sensor stretchability, linear response, and robustness. We demonstrate that encapsulated sensors have increased mechanical robustness and stability, displaying a significantly larger linear dynamic range (~50%) and increased stretchability (260% elongation). Furthermore, we discovered that these sensors have post-fracture signal recovery. They maintained conductivity to the 50% strain with stable signal and demonstrated increased sensitivity. We studied the crack formation behind this phenomenon and found encapsulation to lead to higher crack density as the source for greater stretchability. As crack formation plays an important role in subsequent electrical resistance, understanding the crack evolution in our sensors will help us better address the trade-off between high stretchability and high sensitivity.

Waterproof lithium metal anode enabled by cross-linking encapsulation.

Lithium (Li) metal is considered as the ultimate anode choice for developing next-generation high-energy batteries. However, the poor tolerance against moist air and the unstable solid electrolyte interphases (SEI) induced by the intrinsic high reactivity of lithium bring series of obstacles such as the rigorous operating condition, the poor electrochemical performance, and safety anxiety of the cell, which to a large extent hinder the commercial utilization of Li metal anode. Here, an effective encapsulation strategy was reported via a facile drop-casting and a following heat-assisted cross-linking process. Benefiting from the inherent hydrophobicity and the compact micro-structure of the cross-linked poly(vinylidene-co-hexafluoropropylene) (PVDF-HFP), the as-encapsulated Li metal exhibited prominent stability toward moisture, as well corroborated by the evaluations both under the humid air at 25 °C with 30% relative humidity (RH) and pure water. Moreover, the encapsulated Li metal anode exhibits a decent electrochemical performance without substantially increasing the cell polarization due to the uniform and unblocked ion channels, which originally comes from the superior affinity of the PVDF-HFP polymer toward non-aqueous electrolyte. This work demonstrates a novel and valid encapsulation strategy for humidity-sensitive alkali metal electrodes, aiming to pave the way for the large-scale and low-cost deployment of the alkali metal-based high-energy-density batteries.

Quantum dot encapsulated nanocolloidal bioconjugates function as bioprobes for in vitro intracellular imaging.

Bioimaging probes incorporating quantum dots (QDs) are important for identifying organelles and monitoring their movement/location in living cells. Organelle specificity can be accomplished by functionalizing probe surfaces with chemical groups that can react with antibodies capable of targeting specific organelle-protein epitopes. Here, such a bioprobe is generated by encapsulating ZnS-capped CdSe QDs within polystyrene (PS) nanocolloids via Pickering miniemulsion using laponite nanoclay platelets as solid-stabilizers. The surfaces of these platelets are modified with aminopropyltriethoxysilane (APTES), and biotinylated by reacting sulfo-NHS-Biotin via the APTES amine group. Surface functionalization and bioconjugation are confirmed using X-ray photoelectron spectroscopy. The number of sites available on Streptavidin for Biotin binding is determined using a competitive HABA assay to optimize the bioconjugation protocol. The PS-encapsulated QDs (PS-QDs) nanocolloids are 50-200 nm in diameter and colloidally stable, as evidenced by transmission electron microscopy and ζ-potential measurements, respectively. Spherical particle shape is confirmed by scanning electron microscopy. Transmission electron microscopy also showed the nanoclay platelets on the surface of QD-encapsulating latex particles. The PS-QDs particles are easily dispersed in water and exhibit long-term photostability over various conditions. Cell viability of >95% is observed for NIH-3T3 cells after 72-h exposure to PS-QDs nanocolloids, with no cytotoxicity to living cells, even at 0.1 mg mL-1. NIH-3T3 cellular uptake and internalization are confirmed by confocal microscopy, with PS-QDs fluorescence within cells remaining high even after 24-h exposure, demonstrating the applicability of PS-QDs nanocolloids as long-lived fluorescent bioprobes for in vitro intracellular imaging.

Small protein sequences can induce cellular uptake of complex nanohybrids.

In this letter, we report on the ability of functional fusion proteins presenting a lytic gamma peptide, to promote interactions with HeLa cells and delivery of large hybrid nanostructures.

Aging of Transition Metal Dichalcogenide Monolayers.

Two-dimensional sheets of transition metal dichalcogenides are an emerging class of atomically thin semiconductors that are considered to be "air-stable", similar to graphene. Here we report that, contrary to current understanding, chemical vapor deposited transition metal dichalcogenide monolayers exhibit poor long-term stability in air. After room-temperature exposure to the environment for several months, monolayers of molybdenum disulfide and tungsten disulfide undergo dramatic aging effects including extensive cracking, changes in morphology, and severe quenching of the direct gap photoluminescence. X-ray photoelectron and Auger electron spectroscopy reveal that this effect is related to gradual oxidation along the grain boundaries and the adsorption of organic contaminants. These results highlight important challenges associated with the utilization of transition metal dichalcogenide monolayers in electronic and optoelectronic devices. We also demonstrate a potential solution to this problem, featuring encapsulation of the monolayer sheet by a 10-20 nm thick optically transparent polymer (parylene C). This strategy is shown to successfully prevent the degradation of the monolayer material under accelerated aging (i.e., high-temperature, oxygen-rich) conditions.

Encapsulated cell therapy for neurodegenerative diseases: from promise to product.

Delivering therapeutic molecules, including trophic factor proteins, across the blood brain barrier to the brain parenchyma to treat chronic neurodegenerative diseases remains one of the great challenges in biology. To be effective, delivery needs to occur in a long-term and stable manner at sufficient quantities directly to the target region in a manner that is selective but yet covers enough of the target site to be efficacious. One promising approach uses cellular implants that produce and deliver therapeutic molecules directly to the brain region of interest. Implanted cells can be precisely positioned into the desired region and can be protected from host immunological attack by encapsulating them and by surrounding them within an immunoisolatory, semipermeable capsule. In this approach, cells are enclosed within a semiporous capsule with a perm selective membrane barrier that admits oxygen and required nutrients and releases bioactive cell secretions while restricting passage of larger cytotoxic agents from the host immune defense system. Recent advances in human cell line development have increased the levels of secreted therapeutic molecules from encapsulated cells, and membrane extrusion techniques have led to the first ever clinical demonstrations of long-term survival and function of encapsulated cells in the brain parenchyma. As such, cell encapsulation is capable of providing a targeted, continuous, de novo synthesized source of very high levels of therapeutic molecules that can be distributed over significant portions of the brain.

Addressing Key Technical Aspects of Quantum Dot Probe Preparation for Bioassays.

Fluorescent semiconductor nanoparticles, or quantum dots, have become a promising platform for the engineering of biofunctional probes for a variety of biomedical applications, ranging from multicolor imaging to single-molecule tracking to traceable drug delivery. Advances in organometallic synthesis have enabled preparation of hydrophobic quantum dots with high quantum yields and narrow size distribution, offering bright optical materials with narrow size-tunable emission profiles. At the same time, polymer encapsulation procedures provided a simple and versatile methodology for transferring hydrophobic nanoparticles into physiologically-relevant aqueous buffers. Taken together, hydrophobic nanoparticle platforms and polymer encapsulation should offer great flexibility for implementation of novel probe designs. However, the success of the encapsulation and purification depends on many factors often overlooked in the scientific literature, such as close match between nanoparticle and polymer physicochemical properties and dimensions, slow dynamics of polymer arrangement on the nanoparticle surface, and the size and charge similarity of resultant polymer-coated quantum dots and empty byproduct polymer micelles. To make this general hydrophobic nanoparticle modification strategy accessible by a broad range of biomedical research groups, we focus on the important technical aspects of nanoparticle polymer encapsulation, purification, bioconjugation, and characterization.

A polymer encapsulation approach to prepare zwitterion-like, biocompatible quantum dots with wide pH and ionic stability.

A surface modification approach adopting polymer encapsulation was developed to prepare zwitterion-like quantum dots (ZWL-QDs). The fundamental physical, chemical, and biological properties of the ZWL-QDs were characterized. It is found that the ZWL-QDs almost preserve the quantum yield (QY) of native hydrophobic QDs in organic solvents, and also are compact in size (7 ~ 10 nm hydrodynamic diameter) and stable over wide pHs or in high salinity solutions. Further cellular study shows that the ZWL-QDs with a concentration less than 100 nM have a minimal cytotoxicity and thus are biocompatible. Characterizing and understanding these essential properties of the ZWL-QDs are an important step before employing them for various applications.