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The secretome from mesenchymal stem cells (MSCs) have recently gained attention for new therapeutics. However, clinical application requires in vitro cell manufacturing to attain enough cells. Unfortunately, this process often drives MSCs into a senescent state that drastically changes cellular secretion activities. Antioxidants are used to reverse and prevent the propagation of senescence; however, their activity is short‐lived. Polymer‐stabilized crystallization of antioxidants has been shown to improve bioactivity, but the broad crystal size distribution (CSD) significantly increases the efficacy variation. Efforts are made to crystalize drugs in microdroplets to narrow the CSD, but the fraction of drops containing at least one crystal can be as low as 20%. To this end, this study demonstrates that in‐drop thermal cycling of hyaluronic acid‐modified antioxidant crystals, named microcrystal assembly for senescence control (MASC), can drive the fraction of microdrops containing crystals to >86% while achieving significantly narrower CSDs (13 ± 3 µm) than in bulk (35 ± 11 µm). Therefore, this approach considerably improves the practicality of CSD‐control in drops. In addition to exhibiting uniform release, MASC made with antioxidizing N‐acetylcysteine extends the release time by 40%. MASC further improves the restoration of reactive oxygen species homeostasis in MSCs, thus minimizing cellular senescence and preserving desired secretion activities. It is proposed that MASC is broadly useful to controlling senescence of a wide array of therapeutic cells during biomanufacturing. [ABSTRACT FROM AUTHOR]

Biomanufacturing, drop-microfluidics, exosomes, hyaluronic acid-dopamine, mesenchymal stem cells Furthermore, MASC can restore homeostasis, reduce senescence, and preserve paracrine secretion activities in stress-induced senescent mesenchymal stem cells. Keywords: biomanufacturing; drop-microfluidics; exosomes; hyaluronic acid-dopamine; mesenchymal stem cells EN biomanufacturing drop-microfluidics exosomes hyaluronic acid-dopamine mesenchymal stem cells 1 1 1 09/15/23 20230912 NES 230912 B Drop Microfluidics b In article number 2302232, Hee-Sun Han, Hyunjoon Kong, and co-workers report a droplet-based microfluidic approach to fabricate a microcrystal assembly for senescence control (MASC). [Extracted from the article]

Techniques to fabricate polymer membranes with improved performance have been actively developed over the past several decades. Most conventional manufacturing processes are based on amorphous phase separation, which often restricts the formation of interconnected pores, resulting in high tortuosity. Herein, we demonstrate the fabrication of polyvinylidene fluoride (PVDF)/TiO 2 composite membranes with highly interconnected pore structures. Vertically oriented pores could be produced by continuous growth of solvent crystals under a controlled temperature gradient and then removing solvent crystals via freeze drying. Crystal nucleation and growth could offer better control of pore morphology, size, and connectivity. The incorporation of TiO 2 into PVDF membranes not only improved the hydrophilicity, but also enhanced protein resistance of the membrane. The pure water flux of PVDF/TiO 2 composite membranes with interconnected porosity was excellent, six times higher than that of commercial PVDF membranes having similar pore size. This novel preparation method could expand the variety of structures and properties of such membranes and hence their areas of application. [ABSTRACT FROM AUTHOR]

Seamless encapsulation for stable storage of an active material and its controlled release when needed are the ultimate targets of all encapsulation-related technologies. However, seamless encapsulation often limits the effects of external stimuli for triggering release. Thus, systems in which release is triggered by ultrasonic waves have usually employed relatively weak encapsulation systems such as liposomes. Herein, we developed a novel triggering mechanism (uncorking) that combines sonication triggering and seamless stable encapsulation. Core–shell nanofibers were chosen as encapsulation systems and silica nanoparticles were developed as corks on the surfaces of the nanofibers. The nanoparticles were attached on the surfaces of nanofibers by a combination method of electrospinning and electrospraying, and subsequent solvent-vapor annealing embedded the nanoparticles, resulting in the formation of corks. Annealing for 30 min gave half-embedded nanoparticles, 50% of which could be uncorked by sonication for 30 min. Successful uncorking triggered zero-order release from the core of the nanofibers. Uncorking left nanocraters on the surface that acted as diffusion paths for release. This novel uncorking strategy for release will enable smart release control of nanofibers and textiles for various future applications. [ABSTRACT FROM AUTHOR]

Nanofibers have been developed as basic nanotechnology building blocks, however, unlike with conventional textiles, nanofibers have lacked the surface engineering tools. Herein, we have developed novel basic techniques used to introduce nanoscale bumps and dents on the surfaces of nanofibers. Nanoparticles were first attached uniformly onto nanofibers by electrohydrodynamic jetting, which were subsequently thermally annealed to embed the nanoparticles (bumps). The embedded nanoparticles could be further detached via ultrasonication, resulting in the formation of nano-craters (dents). Ultrasonication could change the contact angle of nanofibers in situ from 84° to 146°. These surface nanoengineering techniques could widen the utility window of nanofibers. [ABSTRACT FROM AUTHOR]

Here, we demonstrate the fabrication of a microporous membrane and its surface modification via solvent crystallization of a polymer solution under a temperature gradient, similar to the natural process to form permafrost and the subsequent polygonal ground pattern produced during glacier formation. This system was prepared spreading a polyvinylidene fluoride (PVDF) solution on a silicon wafer, followed by crystallization. The solvent crystals were uniformly distributed by applying a directional temperature gradient over a PVDF solution layer. Finally, the microporous membranes were formed by removing solvent crystals via freeze-drying, similar to natural landform formation, such as the patterned ground that arises from permafrost. The introduction of co-solvent systems allowed for the systematic control of the pore morphologies of resulting polymer membranes including pore size, pore wall thickness, and surface topography. Overall, the composition of solvents in the crystallization of PVDF solution was the key factor affecting crystallization behavior, thus determining the morphology, crystallinity, and even polymorph. We believe this bio-inspired approach will open the door to a range of interesting studies related to micro/nano-materials fabrication. [ABSTRACT FROM AUTHOR]

Improving the dissolution behavior of poorly or sparingly water-soluble drugs by reducing their particle size remains a critical issue in oral drug delivery. Confined nano-crystallization has many advantages over other nanocrystal preparation techniques, but also has the serious drawback of the use of uncommon excipients as porous template materials. We prepared novel porous mannitol templates with pore sizes ranging from a few microns to submicrons by directional melt crystallization of solvent; these pores served to confine the evaporative crystallization of celecoxib. Pore structures were relatively well connected, which was beneficial for infiltration of the drug solution. The particle size of the resulting crystals spanned from tens of microns to several hundreds of nanometers. Distinctly improved dissolution characteristics were obtained with retention of the stable original polymorph. We anticipate the readily dissolvable composite formulation of mannitol and celecoxib described in this study will spur the development of nanocrystal formulations for various poorly water-soluble drugs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Engineered the volume phase transition and mechanical behavior of composite hydrogels. [•] Both microfibrillated cellulose and micropores greatly enhanced volume transition. [•] Aligned micropores distinctly enhanced water infiltration speed. [•] Aligned micropores were produced by unidirectional melt crystallization. [ABSTRACT FROM AUTHOR]

Biocompatible polymers have played an integral role in the advancement of drug delivery systems. The discovery of a novel polymer with innovative properties can provide great opportunities to enhance drug efficacy as well as reduce side effects. In this study, a novel disulfide polymer was synthesized and characterized. Its mono-mer is alpha-lipoic acid (ALA), which is synthesized in all cells in the human body. The disulfide polymer was obtained by the simple thermal polymerization of crystal-line particles at a temperature higher than its melting point, followed by precipitation purification. It had rubbery and sticky characteristics. In vitro release tests demon-strated that the disulfide polymer had both pH-dependent degradation and related sustained release profiles, with a degraded form of ALA. Therefore, this novel class of responsive polymers that can be prepared by simple thermal polymerization has pronounced potential to contribute to future drug delivery systems. [ABSTRACT FROM AUTHOR]

Abstract: Pharmaceutical research and development critically rely on crystallization engineering principles since they influence the bioavailability, stability and processability of drug formulations. Although the polymer-induced crystallization has been intensively investigated in the area of inorganic materials, drug molecules have seldom been its subject. Celecoxib, which critically needed the improvement of bioavailability and processability, benefited from polymer-induced crystallization. Polyvinylpyrrolidone (PVP) and Pluronic successfully reduced the aspect ratio of celecoxib crystals to 1.5, which would improve processability. Among the polymers used, PVP distinctly improved the in vitro drug release behavior, which is consistent with the significant melting point depression and the polymorphic change in celecoxib crystallized with PVP. The strong hydrogen bonding between celecoxib and PVP is suspected as the origin of the improved crystal morphology and in vitro drug release. This polymer-induced crystallization can create new opportunities of convenient pharmaceutical particle engineering allowing reliable improvements in bioavailability and processability. [Copyright &y& Elsevier]

Abstract: The cocrystallization of adefovir dipivoxil (AD) with suberic acid (SUB) or succinic acid (SUC) was examined. X-ray diffraction was used to determine the structures of AD/SUB and AD/SUC cocrystals. Both cocrystals were formed via multiple hydrogen bonds between the adenine part of AD and the carboxylic acid groups of SUB or SUC. Longer SUB effectively dispersed AD molecules, and AD hydrogen-bonded only to SUB. When shorter SUC was used, AD formed hydrogen bonding with both SUC and adjacent AD. As a result, the cocrystal compositions were AD/SUB=1:1 and AD/SUC=2:1. Both cocrystals displayed superior thermal stability and increased aqueous solubility. The present study demonstrated that the adenine and similar structures of active pharmaceutical ingredients could be used to produce cocrystals of improved physical properties. [Copyright &y& Elsevier]

Abstract: Melt crystallization methods offer high purity and energy-efficient purification for many chemicals. The solubility of solutes in a crystal phase is extremely low, but they can be engulfed by crystal phases. Therefore, the control of crystal morphology and size is critical in melt crystallization. In this work, we investigated the crystallization behavior of dioxane in the presence of a polymer solute under a controlled temperature gradient. By controlling the movement of a sample toward a liquid nitrogen reservoir, the nucleation and growth of crystals were regulated to produce uniformly distributed cylindrical crystals. Upon cooling, two crystallization steps were observed. While the first crystallization step mainly involved solidification of the bulk solution, the second crystallization at a lower temperature was accompanied by a further reduction in transparency and micro-cracking. This two-step crystallization behavior was used to make defect-free polymer structures with a unique cylindrical morphology of through-thickness pores, regardless of the dioxane removal method. Such understanding of directional crystallization will facilitate the future development of melt crystallization routes for dioxane and novel preparation methods for porous polymeric materials. [Copyright &y& Elsevier]

Highlights: [•] Block microfibrils were processed for the first time. [•] Block microfibrils showed chromosome-like structures upon dispersion in a medium. [•] Preparation of anisometric microfibrils used quasi-steady state electrospinning. [Copyright &y& Elsevier]

We developed a procedure for the reliable and reproducibleformation of monodispersed polymer nanocrystals whose morphologiescan be easily controlled to produce structures ranging from nanoparticlesto nanorods. The directional cooling crystallization of ferroelectricpolymer solutions under nanoconfinement allowed polyvinylidene fluorideto form single crystalline monodisperse nanocrystals without the useof surfactants or stabilizers. An important growth condition necessaryto yield highly crystalline ferroelectric polymers was a regulatedthermal gradient under nanoconfinement to induce uniform nucleationand controlled directional growth. While other methods involving thenanoconfined crystallization of polymers are restricted to yield nanofibersor nanotubes with a high aspect ratio, our unidirectional coolingmethod produced nanocrystals of ferroelectric polymers with nanosphere,nanocapsule, and nanorod structures. Field-emission scanning electronmicroscopy, transmission electron microscopy, dynamic contact electrostaticforce microscopy, grazing incidence X-ray diffraction, and differentialscanning calorimetry were used to characterize the morphologies andstructures of the nanocrystals. The results suggest that the directionalcooling method facilitates nucleation and directional growth by controllingdiffusion and promoting molecular alignment from the preferred crystalorientations due to the unidirectional thermal gradient. This studyprovides a novel method of rational material design to fabricate polymernanocrystals by directing nucleation and growth of molecular crystalsfrom solution. [ABSTRACT FROM AUTHOR]

New eco-friendly materials for soil improvement have been developed recently for construction purposes in civil engineering. An organic acid material encourages microbe proliferation over time and accelerates consolidation by biochemical penetration; soil particles are compacted by microbes and pore water is dissipated quickly. However, the effectiveness of organic acid has not yet been established. To investigate the strength characteristics of soil mixed with an organic acid, unconfined compressive strength tests were performed after aging soil samples with and without the organic acid. After 96 days of aging, the strength was generally 1.5-2.5 times greater than that without the organic acid. The pore structure of the soils was observed to change in a scanning electron microscopy analysis, and the change of total bacterial counts revealed the activity of microbes that reflects the strength characteristics. Moreover, this material is likely to be environmentally friendly according to the pH test. [ABSTRACT FROM AUTHOR]

Abstract: Nonwoven fabrics and structured particles prepared by electrohydrodynamic jetting have been attracting increasing attention in various research areas. Chitosan has been known as a poorly spinnable polymer, often electrospun using a mixed solution of polyethylene glycol. Herein, we report that a combination of electrospraying and subsequent freeze drying can produce chitosan fibrous 3D network structures from low concentration chitosan solutions, well below fiber forming concentrations. Nanoparticle suspensions of chitosan were first fabricated by a controlled electrospraying process and then freeze drying assembled the nanoparticles into fibrous networks. The formation of a columnar ice phase and subsequent drying produced chitosan fibrous structures of a few microns in diameter. The X-ray diffraction results and the surface morphologies of the fibers indicate a unique fiber formation mechanism of biaxial compression. This technique can prepare nonwoven fabrics from nanoparticles, which lead to novel opportunities in applications including tissue engineering, cell or drug delivery, and membranes. [Copyright &y& Elsevier]

Abstract: Drying nanosuspensions into redispersable powders is a critical issue in developing solid dosage forms of drug nanoparticles. The particle fusion and chain entanglement of polymeric steric stabilizers adsorbed onto the nanoparticle surface should be prevented to retain redispersibility after drying. Herein, we report that only a small amount of polymeric dispersants such as carrageenan, gelatin, and alginic acid between 0.5 and 3wt.% in various drug nanosuspensions can provide sufficient redispersibility in vacuum, convection, and freeze drying. In vacuum and freeze drying of naproxen nanosuspensions, the addition of only 0.5wt.% carrageenan resulted in the formation of redispersable nanoparticulate powders. The amounts of polymeric dispersants required for redispersibility was lowest for carrageenan and highest for gelatin. The specific interactions between the dispersants and steric stabilizers (or drugs), in addition to viscosity increase during drying, appeared to effectively prevent irreversible particle aggregation. [ABSTRACT FROM AUTHOR]

Abstract: On the basis of the synthesis of novel biodegradable amphiphilic MPEG-b-PCL-grafted chitooligosaccharide (COS-g-PCL-b-MPEG) copolymers, supramolecular hydrogels were fabricated rapidly via their inclusion complexation with α-cyclodextrin (α-CD) in aqueous solutions. The graft copolymers were characterized by 1H NMR spectroscopy, gel permeation chromatography (GPC), and fluorescence measurement, and the supramolecular structure of the resultant hydrogels was confirmed by X-ray diffraction measurements. Rheological studies of as-obtained hydrogels indicate that the physical properties could be modulated by controlling the concentration and the graft content of the graft copolymers as well as the molar feed ratio of the graft to α-CD. The in vitro release kinetics studies of bovine serum albumin (BSA) entrapped in the hydrogels show that the drug release profiles are dependent on the supramolecular hydrogel compositions. [Copyright &y& Elsevier]

Abstract: The characteristics of various pharmaceutical dosage forms are influenced by surface properties such as the friction behavior. For example, die wall friction is a key issue in developing a solid dosage form. However, the friction properties are not completely understood mainly because of the lack of fundamental measurements. Herein, the friction behavior of pharmaceutical materials was investigated and compared with their adhesion behavior using atomic force microscopy. The sliding speed causes significant variations in the frictional force. Compared with other materials, lubricant materials showed less distinct differences in friction tests than in adhesion tests, indicating the dependence of the lubricant efficiency on the stress state. The three parameters obtained from the modified Amonton''s law, i.e., absolute frictional force, friction coefficient and residual force, showed consistent trends. Overall, the friction behavior was not a direct reflection of the adhesion forces. The intrinsic friction behavior of a single pharmaceutical particle can be quantified using atomic force microscopy. [Copyright &y& Elsevier]

Abstract: Recent advances in nanoparticle technologies have significantly enhanced the oral and parenteral delivery of poorly water-soluble active pharmaceutical ingredients (APIs). However, reports have been limited on the various drying procedures to convert a liquid nanocrystal dispersions into solid dosage forms. The solid dosage form should consist of nanocrystals that can readily reconstitute into their original size upon dissolution in water. Herein, the freeze drying process of nanocrystal dispersions was examined at varying freezing rates (speed of freezing interface). As freezing rate decreases, more particle–particle aggregation developed. A critical freezing rate, below which the dried nanocrystals cannot be re-dispersed, was identified based on the plot of the particle size of reconstituted nanocrystals versus freezing rate. Freeze drying at a freezing rate near the critical value produces dry powders of bimodal particle size distribution after re-dispersion. In addition, API concentration was found to significantly affect the critical freezing rate and therefore the re-dispersibility of dry powders. The concept of critical freezing rate is critical for the development of solid dosage forms of liquid nanocrystal dispersions. [Copyright &y& Elsevier]

Abstract: The recent advance of particle size engineering in nanometer ranges has widened the formulation opportunities of relatively water-insoluble drugs. However, the ‘nanoformulation’ suffers from a lack of systematic understanding about the requirements of polymeric stabilizers. Furthermore, the polymers that can be used for the preparation of nanocrystals are so limited that finding a proper stabilizer for a given formulation is often difficult. In this study, amino acid copolymers whose properties can systematically be tailored are developed, and their morphological and compositional effects are investigated. Copolymers containing lysine (K) as their hydrophilic segments, and phenylalanine (F) or leucine (L) as their hydrophobic segments successfully produce stable nanocrystals (200–300nm) in water, while copolymers of K and alanine (A) could not generate nanosized particles. Not the morphology but the hydrophobicity of copolymers seems to be a critical parameter in the preparation of drug nanocrystals by wet comminution. The effective stabilization performance of copolymers requires the hydrophobic moiety content to be higher than 15mol%. Comminution for only 5min is long enough for nanocrystal preparation, and the crystallinity of drug is found intact after the processing. [Copyright &y& Elsevier]

Reported are specific materials characterizations of three protein-based polymers comprised of repeating pentapeptide sequences, namely (GVGVP)[sub 251], (GVGIP)[sub 260] and (GVGVP GVGVP GEGVP GVGVP GVGVP GVGVP)[sub n]](GVGVP) where G = glycine, V = valine, P = proline, I = isoleucine, and E = glutamic acid, which had been previously prepared and γ-irradiation cross-linked into elastic matrices. These polymers exhibit a hydrophobic folding and assembling transition on raising the temperature above a critical temperature, designated by T[sub t]. Their equilibrium swelling ratio, uniaxial tensile and dynamic shear behavior were studied. The effect of the transition on swelling and mechanical properties was demonstrated. Equilibrium swelling ratio below the transition temperature decreased with the increase of γ-irradiation dose. Above the transition temperature, hysteresis and frequency dependence were found in tensile loading-unloading tests and dynamic shear measurements, respectively. The rubber elasticity theory of random chain networks was applied to the data only below the transition temperature, where they may properly be considered random network hydrogels, to estimate molecular weight between cross-links and the Flory-Huggins interaction parameter. [ABSTRACT FROM AUTHOR]

The COSMO-SAC model provides a convenient method for predicting the phase behavior of components with minimal information about molecules using quantum-mechanical principles. During the past few years, several researchers tried to improve the prediction capability with modifications to hydrogen bonding terms and other methods of calculation. In this contribution, we focused on carboxylic acid groups, which may exhibit different hydrogen-bond behavior as compared with alcohols. The calculation scheme in COSMO-SAC (2017 version) was slightly modified to encompass a hydrogen-bond term specifc to carboxylic acid groups. The parameters for the extended COSMO-SAC model were fitted using 559 data points. The characteristics of the extended model were investigated for the prediction capability of binary solubility, ternary solubility, and vapor-liquid equilibrium data. The results show that the extension correctly predicts the phase behavior of mixtures containing carboxylic acids. [ABSTRACT FROM AUTHOR]

Engineering the surface properties of a material without affecting its bulk properties is desirable for many applications, but it is often not readily achievable because it requires a complex series of processing steps. This study presents for the first time a simple and straightforward method that can convert regular flat polymer surfaces into various porous composite surfaces. The controlled dissolution of the polymer surface by a dispersion and subsequent melt crystallization allows for the successful embedding of dispersed inorganic or organic particles in the pore walls. The porous surface morphology is not significantly affected by the type of dispersed particle, but the contact and sliding angles and surface wettability are. Both superhydrophobic and oil/water separation surfaces can be conveniently fabricated from flat polymer surfaces. This novel and versatile technique could provide engineering freedom for the future development of various functional materials. [ABSTRACT FROM AUTHOR]

The development of antioxidant polymers through the chemical conjugation of natural polyphenols onto polysaccharides has important applications in biomedical, pharmaceutical, food, and cosmetic fields. Due to their labile characteristics, the covalent conjugation of polyphenols while retaining antioxidant properties has been a challenging task. Herein, four structurally different polyphenols, three with and one without a catechol group, were conjugated onto pectin macromolecules via a simple and efficient preparation method involving epichlorohydrin chemistry. The conjugation reactions were confirmed by FT-IR and UV–vis characterization, and the free radical scavenging assay confirmed that the polyphenols maintained their antioxidant activity after the reaction. The conventional structure-antioxidant property relationship can be applied to the assay results, and hesperidin without a catechol group showed the lowest antioxidant capability. The coordination of multivalent metal ions with polyphenols enabled ionic crosslinking and the moduli of hydrogels depend on the type of polyphenols and their molecular interactions with metal ions. The simplicity of preparation and the resulting unique properties could make the pectin conjugates useful in a wide range of application areas. [ABSTRACT FROM AUTHOR]

Porous materials with surprisingly diverse structures have been utilized in nature for many functional purposes. However, the structures and applications of porous man-made polymer materials have been limited by the use of processing techniques involving foaming agents. Herein, we demonstrate for the first time the outstanding hardness and modulus properties of an elastomer that originate from the novel processing approach applied. Polyurethane films of 100-μm thickness with biomimetic ordered porous structures were prepared using directional melt crystallization of a solvent and exhibited hardness and modulus values that were 6.8 and 4.3 times higher than those of the random pore structure, respectively. These values surpass the theoretical prediction of the typical model for porous materials, which works reasonably well for random pores but not for directional pores. Both the ordered and random pore structures exhibited similar porosities and pore sizes, which decreased with increasing solution concentration. This unexpectedly significant improvement of the hardness and modulus could open up new application areas for porous polymeric materials using this relatively novel processing technique. [ABSTRACT FROM AUTHOR]

Bioactive hydrogels have been extensively studied as a platform for 3D cell culture and tissue regeneration. One of the key desired design parameters is the ability to control spatial organization of biomolecules and cells and subsequent tissue in a 3D matrix. To this end, this study presents a simple but advanced method to spatially organize microchanneled, cell adherent gel blocks and non-adherent ones in a single construct. This hydrogel system was prepared by first fabricating a bimodal hydrogel in which the microscale, alginate gel blocks modified with cell adhesion peptides containing Arg-Gly-Asp sequence (RGD peptides), and those free of RGD peptides, were alternatingly presented. Then, anisotropically aligned microchannels were introduced by uniaxial freeze-drying of the bimodal hydrogel. The resulting gel system could drive bone marrow stromal cells to adhere to and differentiate into neuron and glial cells exclusively in microchannels of the alginate gel blocks modified with RGD peptides. Separately, the bimodal gel loaded with microparticles releasing vascular endothelial growth factor stimulated vascular growth solely into microchannels of the RGD-alginate gel blocks in vivo . These results were not attained by the bimodal hydrogel fabricated to present randomly oriented micropores. Overall, the bimodal gel system could regulate spatial organization of nerve-like tissue or blood vessels at sub-micrometer length scale. We believe that the hydrogel assembly demonstrated in this study will be highly useful in developing a better understanding of diverse cellular behaviors in 3D tissue and further improve quality of a wide array of engineered tissues. [ABSTRACT FROM AUTHOR]

Abstract: Drug nanoparticles prepared in a liquid medium are commonly freeze-dried for the preparation of an oral dosage in solid dosage form. The freezing rate is known to be a critical parameter for redispersible nanoformulations. However, there has been controversy as to whether a fast or slow freezing rate prevents irreversible aggregation. A systematic investigation is presented herein regarding the effect of both the molecular weight of the cryoprotectant and the freezing rate in order to elucidate the mechanism underlying irreversible aggregation. It was found that irreversible aggregation occurred during drying rather than freezing, although a proper freezing rate is critical. A more homogeneous distribution of the cryoprotectant and drug nanoparticles led to more redispersible powders. Thus, keeping the local concentration distribution of the nanoparticles and cryoprotectant fixed during the freezing step plays a critical role in how the freezing rate affects the redispersibility. The kinetic approach of excluding the tendency of ice crystal growth permitted an explanation of the controversial results. This study will facilitate an in-depth understanding of the aggregation process of nanoparticles or proteins during freeze-drying. [Copyright &y& Elsevier]

Abstract: Recently, researchers have tried to produce non-spherical and anisotropic particles to be used in the next generation of multi-functional materials. Of key interest is the red blood cell-like particle. The torus structure was produced under the relatively fast consolidation of monodisperse droplets, and its parameters were found to be tunable by temperature as well as solvent type and concentration. The observation of consolidation demonstrated that the polymers were accumulated and solidified in the torus structure, naturally, whereas there was the critical droplet size to induce the asymmetry diffusivities. The torus structures could be simply tuned by the flow rate and concentration. The coaxial nozzle system produced the core/shell torus particles. These results state that the consolidation mechanism can hold important clues to enhance the range of tuning capabilities. [Copyright &y& Elsevier]

Abstract: Physical gelation between two polymers of opposite charges has potential applications in hydrogel delivery systems. However, issues associated with physical gelation, such as gelation control, effective drug loading, and stability before delivery, have limited the application of this technique. We, therefore, investigated gelable composite particles, because drugs can be effectively loaded inside a core with a less hydrophilic protective shell, and, later, the composite particles can be gelled into any shape in water. A modified spray drying apparatus was built by introducing a customized coaxial nozzle and applying a high electric potential between the nozzle and a ground in the air flow channel for convenient preparation of gelable composite particles. The resulting particles were molded into more elastic hydrogels by the addition of water than those prepared by the gelation of powder physical mixtures, and their pH-dependent equilibrium swelling could be tailored to a wide range. The release rate of a model drug (lipoic acid) appears to reflect the composite structures. As the applied voltage was increased, more sustained release and lower equilibrium swelling resulted. This novel preparation technique and the resulting gelable structured particles have potential applications in drug (proteins) delivery systems, wound healing hydrogels, protein-releasing scaffolds, etc. [Copyright &y& Elsevier]

Abstract: Directional freezing is a simple and environmentally friendly method for producing aligned porous materials. Porous structures of uniaxially aligned nanoparticles can be produced by unidirectional freezing a concentrated nanoparticle dispersion and subsequent freeze-drying. However, mechanically strong through-thickness membranes have seldom been reported. The film prepared by directional freezing and subsequent freeze-drying is usually too weak to be a free-standing membrane. By using precise control of freezing rate and direction, we successfully produced free-standing films (with 20–200 μm thickness and 40–60 vol% through-thickness porosity) from inorganic particles/polymer (polytetrafluoroethylene and polyvinylidene fluoride) composites. The pore size could be conveniently controlled by freezing rate and dispersion concentration. The use of composite materials, emulsion states, and post-annealing processes facilitated the preparation of free-standing two-dimensional particulate networks due to enhanced interparticulate coherence. This method could provide novel porous networks with controlled morphology, reduced tortuosity, and enhanced mechanical properties, which have broad applications such as separation/purification, fuel cells, nanocomposites, catalysts, tissue engineering, controlled delivery, and other medical applications. [ABSTRACT FROM AUTHOR]

Novel water-soluble amphiphilic graft copolymers (COS-g-PCL-b-MPEG) were synthesized by the coupling reaction between chitooligosaccharide (COS) and MPEG-b-PCL-COOH, which was synthesized via ring-opening polymerization of ε-caprolactone (CL) using MPEG as an initiator and subsequent carboxylation by succinic anhydride. The chemical composition of the graft copolymers was confirmed by 1H-NMR spectra and FT-IR spectrometry. The thermal properties and crystallinity of the copolymers were observed by DSC and XRD measurements, which showed the existence of separate backbone and graft chain phases in the copolymer. The micellar behavior via self-assembly of the graft copolymers in aqueous solution was studied using pyrene fluorescence dye technique. AFM measurements showed that the micelles had a spherical morphology at the critical micelle concentration (CMC) and ranged in size from 20-45 nm. The amphiphilic ternary biodegradable graft copolymer endows the hydrophilic outer shell of micelles with structural and functional diversification, which might be desirable for drug delivery applications. [ABSTRACT FROM AUTHOR]

Abstract: This study was undertaken to examine the chemical compositions of essential oil and tested the efficacy of oil and organic extracts from seeds of Zizyphus jujuba against food-borne pathogens. The chemical compositions of the oil was analysed by Null. Twenty three compounds representing 91.59% of the total oil were identified. The oil (5μl of 1:5 (v/v) dilution of oil with methanol) and extracts of hexane, chloroform, ethyl acetate and methanol (300μg/disc) of Z. jujuba displayed a remarkable antibacterial activity against Staphylococcus aureus (ATCC 6538 and KCTC 1916), Listeria monocytogenes ATCC 19166, Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa KCTC 2004, Salmonella typhimurium KCTC 2515 and Escherichia coli ATCC 8739. The scanning electron microscopic studies also demonstrated the effect of essential oil on the morphology of Staph. aureus ATCC 6538 at the MIC value, along with the potential effect on cell viabilities of the tested bacteria. [Copyright &y& Elsevier]

The reduction of particle size to nanometers has been an important tool used for efficient drug delivery. Solid drug nanoparticles can be conveniently prepared by nanocomminution. This process relies on mechanical energy and the selection of a proper polymeric stabilizer. The long chains of polymers provide steric stabilization for drug nanoparticles. In this research, itraconazole and hydroxypropyl cellulose were used to study the effect of the molecular weight of a polymer on particle size reduction. In principle, an increase in molecular weight produces two counteracting effects: a decrease in the diffusion rate of chains and an increase in the physical adsorption of a polymer. The effects of particle size reduction are more pronounced in systems involving smaller molecular weights, and the effects of changing molecular weights disappear with time. Systems of higher molecular weight show larger aggregates in their redispersion after drying. Based on the results of our research, it appears that polymers of smaller molecular weight are more suitable than larger polymers for efficient nanocomminution. This indicates that the kinetic aspects of molecular weight are important. [ABSTRACT FROM AUTHOR]

Examines the efficiency of microencapsulated L-ascorbic acid by polyglycerol monostearate (PGMS). Evaluation of the changes in the chemical and sensorial aspects of L-ascorbic acid and/or iron-fortified milk during storage; Efficiency of microencapsulation; Increase in the release of ascorbic acid from the microcapsules; Application of microencapsulated L-ascorbic acid with PGMS in milk fortification.

The article discusses the study of the electrothermal soft manipulator enabling safe transport and handling of thin cell/tissue sheets and bioelectronic devices. Topics discusses include this study presents a soft manipulator that can manipulate and transport cell/tissue sheets and ultrathin wearable biosensing devices seamlessly; and the soft manipulator consists of an ultrafast thermo-responsive, microchanneled hydrogel layer with tissue-like softness and an electric heater layer.

Abstract The recent rapid development of soft electronics and wearable technology has demanded materials with the function of combining mechanical deformation and electronics. Particularly, materials simultaneously having memory shape characteristics in which mechanical deformation repeatedly occurs in response to stimulus, high stretchability and excellent electric/heat transfer characteristics are interesting actuator materials in future applications. As a stretchable and conductive platform, we fabricated a reentrant micro-honeycomb structure from graphene-CNT, which had structural stretchability due to the accordion-like reentrant structure and continuous conductive paths in the vertical and horizontal directions. To impart shape memory properties, we fabricated composites by simply infiltrating shape memory polyurethane (SMPU) into a stable graphene/CNT framework. Our resulting reentrant micro-honeycomb graphene-CNT/SMPU composites simultaneously exhibited a relatively low resistivity of 5 Ω cm, a change in resistance of less than 10% in the 50% stretching/releasing states, long term stability, and superior tensile shape memory properties, including 95.6% shape fixity and a 90.6% recovery ratio. Regularly distributed graphene-CNT structures offer heterogeneous nucleation sites and undisturbed crystal growth in neat SMPU pillars, resulting in superior shape memory properties. We also constructed a circuit with portable batteries to demonstrate that our reentrant graphene-CNT/SMPU composite offers potential applications as an emergency circuit breaker. [ABSTRACT FROM AUTHOR]

Abstract: Silicone‐based polymers have been widely used for many applications, but their extremely low surface energies and the resulting poor adhesion have been the cause for continuous problems. Herein, a novel adhesion improvement technique using an interlocked finger structure is demonstrated, which enables up to 24.8 and 7.3‐fold increases in adhesion compared to the untreated and conventional plasma‐treated cases, respectively. The interlocked finger structure is fabricated by surface‐confined dissolution and subsequent directional melt crystallization of a solvent. After removing the solvent crystals, porous surfaces are prepared from polyurethane, polyvinyl alcohol, and polystyrene, and these are used to fabricate interfaces of interlocked finger structures with polydimethylsiloxane. The improvement in adhesion strength linearly depends on the pore depth of the prepared surfaces. This novel technique of surface adhesion could improve the performance of polymers with intrinsically poor adhesion in future applications. [ABSTRACT FROM AUTHOR]

Recently, numerous attempts have been made to engineer micro- and nano-porous surface patterns or to develop convenient preparation methods for the practical applications of self-cleaning surfaces, water-repellent surfaces, novel textures, etc. Herein, we introduce a simple, cheap, and repeatable crystallization-based method to produce porous surface structures, on any surface of already fabricated polymeric materials. Contact of the solvent phase with cooled polymer surfaces enabled the limited dissolution of the surfaces and the subsequent extremely fast melt crystallization of the solvent. After removing the crystals, various micro- and nano-porous patterns were obtained, whose pore sizes ranged over three orders of magnitude. Pore depth was linearly dependent on the dissolution time. Crystal growth was mainly directed normal to the surfaces, but it was also controlled in-plane, resulting in cylindrical or lamellar structures. Superhydrophobic surfaces were successfully prepared on both polystyrene and polycarbonate. This process offers a novel surface engineering tool for a variety of polymer surfaces, whose topology can be conveniently controlled over a wide range by crystal engineering. [ABSTRACT FROM AUTHOR]

A three dimensional reduced graphene oxide/polyurethane (RGO-PU) porous material with connected pores was prepared by physical adsorption of RGO onto the surface of porous PU. The porous PU was prepared by directional melt crystallization of a solvent, which produced high pores with controlled orientation. The prepared RGO-PU was characterized by scanning electron microscopy, spectroscopy and electro-chemical methods. The RGO-PU porous material revealed better electrochemical performance, which might be attributed to the robust structure, superior conductivity, large surface area, and good flexibility. Differential pulse voltammetry (DPV) analysis of DA using the RGO-PU exhibited a linear response range over a wide DA concentration of 100–1150 pM, with the detection limit of 1 pM. This sensor exhibited outstanding anti-interference ability towards co-existing molecules with good stability, sensitivity, and reproducibility. Furthermore, the fabricated sensor was successfully applied for the quantitative analysis of DA in human serum and urine samples with acceptable recovery, which indicates its feasibility for practical application. [ABSTRACT FROM AUTHOR]

Polystyrene (PS)/TiO 2 composite nanofiber membranes have been fabricated by electrospinning process for Cu 2+ ions removal from water. The surface properties of the polystyrene nanofibers were modulated by introducing TiO 2 nanoparticles. The contact angle of the PS nanofiber membrane was found to be decreased with increasing concentration of TiO 2 , depicted enhanced hydrophilicity. These membranes were highly effective in adsorbing Cu 2+ ions from water. The adsorption capacity of these membranes was found to be 522 mg/g, which is significantly higher than the results reported by other researchers. This was attributed to enhanced hydrophilicity of the PS/TiO 2 composite nanofiber membranes and effective adsorption property of TiO 2 nanoparticles. [ABSTRACT FROM AUTHOR]

Recent efforts to design a synthetic extracellular matrix for cell culture, engineering, and therapies greatly contributed to addressing biological roles of types and spatial organization of cell adhesion ligands. It is often suggested that ligand–matrix bond strength is another path to regulate cell adhesion and activities; however tools are lacking. To this end, this study demonstrates that a hydrogel coupled with integrin-binding deoxyribonucleic acid (DNA) tethers with pre-defined rupture forces can modulate cell adhesion, differentiation, and secretion activities due to the changes in the number and, likely, force of cells adhered to a gel. The rupture force of DNA tethers was tuned by altering the spatial arrangement of matrix-binding biotin groups. The DNA tethers were immobilized on a hydrogel of alginate grafted with biotin using avidin. Mesenchymal stem cells showed enhanced adhesion, neural differentiation, and paracrine secretion when cultured on the gel coupled with DNA tethers with higher rupture forces. Such innovative cell–matrix interface engineering would be broadly useful for a series of materials used for fundamental and applied studies on biological cells. [ABSTRACT FROM AUTHOR]

Micro- and nanoparticle-supported lipid assemblies have significant potential for being used in biology and medicine for sensing, mimicking cellular membranes, and delivering drugs or cosmetic agents. Here, we introduce a new type of nanohydrogels based on the modification of a polysaccharide with lipid moieties, followed by the formation of nanoparticles and assembling lipid bilayers on the particle surfaces. The lipophilic compound 1,2-ditetradecanoyl- sn -glycero-3-phosphoethanolamine (DMPE) and the UV-crosslinkable methacrylic anhydride were covalently attached to hyaluronic acid (HA) and the formation of hydrogel nanoparticles via a surfactant-free inverse emulsion mechanism was demonstrated. As an anchoring group, the lipophilic DMPE moiety enables the formation of hydrogel nanoparticles with a spherical morphology in nonpolar media and allows for the stable assembly of lipid bilayers bearing amphiphiles on HA nanohydrogel surfaces. The conjugated oligoelectrolyte, 4,4′-bis[4′-( N , N -bis(6″-( N , N , N -trimethylammonium)hexyl)amino)styryl] stilbene tetraiodide (DSSN+), was incorporated into the nanohydrogel-supported lipid bilayers, resulting in the formation of stable multilamellar peripheral vesicular structures due to the similarity in chemical structure of DMPE and the assembled lipid molecules. [ABSTRACT FROM AUTHOR]

Living organisms secrete minerals composed of peptides and proteins, resulting in 'mesocrystals' of three-dimensional-assembled composite structures. Recently, this biomimetic polymer-directed crystallization technique has been widely applied to inorganic materials, although it has seldom been used with drugs. In this study, the technique was applied to the drowning-out crystallization of atorvastatin using various polymers. Nucleation and growth at optimized conditions successfully produced composite crystals with significant polymer contents and unusual characteristics. Atorvastatin composite crystals containing polyethylene glycol, polyacrylic acid, polyethylene imine, and chitosan showed a markedly decreased melting point and heat of fusion, improved stability, and sustained-release patterns. The use of hydroxypropyl cellulose yielded a unique combination of enhanced in vitro release and improved drug stability under a forced degradation condition. The formation hypothesis of unique mesocrystal structures was strongly supported by an X-ray diffraction pattern and substantial melting point reduction. This polymer-directed crystallization technique offers a novel and effective way, different from the solid dispersion approach, to engineer the release, stability, and processability of drug crystals. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:2941-2951, 2012 [ABSTRACT FROM AUTHOR]

Abstract: Nanoparticle engineering of drug crystals is an important basic tool for efficient and intelligent drug delivery. Recently, the wet comminution process of drug nanocrystals in the presence of polymeric stabilizers has been successfully developed, but it has not been well understood yet how to select a proper stabilizer for a drug. In this study, the nature of interactions between polymeric stabilizers and drugs was investigated by analyzing the steady state particle sizes of 7 drugs obtained by wet comminution. The surface energy of drugs and polymers measured by contact angle measurement was found to be an important factor, although it could not solely determine the steady state values of particle size. In addition to surface energy, specific interactions between functional groups appeared to play a certain role. The stabilization ability of polymers and the subsequent steady state particle size of drug nanocrystals depend on various parameters including surface energy and specific interactions. [Copyright &y& Elsevier]

Hydrogels are being extensively used for three-dimensional immobilization and culture of cells in fundamental biological studies, biochemical processes, and clinical treatments. However, it is still a challenge to support viability and regulate phenotypic activities of cells in a structurally stable gel, because the gel becomes less permeable with increasing rigidity. To resolve this challenge, this study demonstrates a unique method to enhance the permeability of a cell-laden hydrogel while avoiding a significant change in rigidity of the gel. Inspired by the grooved skin textures of marine organisms, a hydrogel is assembled to present computationally optimized micro-sized grooves on the surface. Separately, a gel is engineered to preset aligned microchannels similar to a plant's vascular bundles through a uniaxial freeze-drying process. The resulting gel displays significantly increased water diffusivity with reduced changes of gel stiffness, exclusively when the microgrooves and microchannels are aligned together. No significant enhancement of rehydration is achieved when the microgrooves and microchannels are not aligned. Such material design greatly enhances viability and neural differentiation of stem cells and 3D neural network formation within the gel. [ABSTRACT FROM AUTHOR]