Rapid Self-Healing Hydrogel with Ultralow Electrical Hysteresis for Wearable Sensing

Self-healing hydrogels are in high demand for wearable sensing applications due to their remarkable deformability, high ionic and electrical conductivity, self-adhesiveness to human skin, as well as resilience to both mechanical and electrical damage. However, these hydrogels face challenges such as delayed healing times and unavoidable electrical hysteresis, which limit their practical effectiveness. Here, we introduce a self-healing hydrogel that exhibits exceptionally rapid healing with a recovery time of less than 0.12 s and an ultralow electrical hysteresis of less than 0.64% under cyclic strains of up to 500%. This hydrogel strikes an ideal balance, without notable trade-offs, between properties such as softness, deformability, ionic and electrical conductivity, self-adhesiveness, response and recovery times, durability, overshoot behavior, and resistance to nonaxial deformations such as twisting, bending, and pressing. Owing to this unique combination of features, the hydrogel is highly suitable for long-term, durable use in wearable sensing applications, including monitoring body movements and electrophysiological activities on the skin.

Transparent Intracellular Sensing Platform with Si Needles for Simultaneous Live Imaging

Vertically ordered Si needles are of particular interest for long-term intracellular recording owing to their capacity to infiltrate living cells with negligible damage and minimal toxicity. Such intracellular recordings could greatly benefit from simultaneous live cell imaging without disrupting their culture, contributing to an in-depth understanding of cellular function and activity. However, the use of standard live imaging techniques, such as inverted and confocal microscopy, is currently impeded by the opacity of Si wafers, typically employed for fabricating vertical Si needles. Here, we introduce a transparent intracellular sensing platform that combines vertical Si needles with a percolated network of Au-Ag nanowires on a transparent elastomeric substrate. This sensing platform meets all prerequisites for simultaneous intracellular recording and imaging, including electrochemical impedance, optical transparency, mechanical compliance, and cell viability. Proof-of-concept demonstrations of this sensing platform include monitoring electrical potentials in cardiomyocyte cells and in three-dimensionally engineered cardiovascular tissue, all while conducting live imaging with inverted and confocal microscopes. This sensing platform holds wide-ranging potential applications for intracellular research across various disciplines such as neuroscience, cardiology, muscle physiology, and drug screening.

In Situ Spray Polymerization of Conductive Polymers for Personalized E-textiles

E-textiles, also known as electronic textiles, seamlessly merge wearable technology with fabrics, offering comfort and unobtrusiveness and establishing a crucial role in health monitoring systems. In this field, the integration of custom sensor designs with conductive polymers into various fabric types, especially in large areas, has presented significant challenges. Here, we present an innovative additive patterning method that utilizes a dual-regime spray system, eliminating the need for masks and allowing for the programmable inscription of sensor arrays onto consumer textiles. Unlike traditional spray techniques, this approach enables in situ, on-the-fly polymerization of conductive polymers, enabling intricate designs with submillimeter resolution across fabric areas spanning several meters. Moreover, it addresses the nozzle clogging issues commonly encountered in such applications. The resulting e-textiles preserve essential fabric characteristics such as breathability, wearability, and washability while delivering exceptional sensing performance. A comprehensive investigation, combining experimental, computational, and theoretical approaches, was conducted to examine the critical factors influencing the operation of the dual-regime spraying system and its role in e-textile fabrication. These findings provide a flexible solution for producing e-textiles on consumer fabric items and hold significant implications for a diverse range of wearable sensing applications.

Biodegradable silicon nanoneedles for ocular drug delivery

Ocular drug delivery remains a grand challenge due to the complex structure of the eye. Here, we introduce a unique platform of ocular drug delivery through the integration of silicon nanoneedles with a tear-soluble contact lens. The silicon nanoneedles can penetrate into the cornea in a minimally invasive manner and then undergo gradual degradation over the course of months, enabling painless and long-term sustained delivery of ocular drugs. The tear-soluble contact lens can fit a variety of corneal sizes and then quickly dissolve in tear fluid within a minute, enabling an initial burst release of anti-inflammatory drugs. We demonstrated the utility of this platform in effectively treating a chronic ocular disease, such as corneal neovascularization, in a rabbit model without showing a notable side effect over current standard therapies. This platform could also be useful in treating other chronic ocular diseases.

Differential characteristics associated with progression of mitral and aortic regurgitation in patients undergoing kidney transplantation

Background

Heart valve regurgitation is common in patients with end-stage renal disease (ESRD). However, there are no data on the fate of mitral regurgitation (MR) and aortic regurgitation (AR) after kidney transplantation (KT). In this study, we sought to investigate regression or progression rates of MR and AR after KT in patients with ESRD. Moreover, we aimed to explore clinical and echocardiographic factors associated with the progression of MR and AR in patients undergoing KT.

Methods

Among 1,734 patients who underwent KT from 2005 to 2018 at a single tertiary hospital, 674 patients (407 men; mean 48±12 years) who underwent both pre- and post-KT echocardiography were analyzed comprehensively. Pre-KT echocardiography was performed within three months of KT, and post-KT echocardiography was done between 6 months and 24 months after KT. Severities of MR and AR were graded as no/trivial, mild, moderate, and severe according to the current guidelines. Regression was defined if the severity decreased by one or more grades, while progression was defined if the severity increased by one or more grades.

Results

Figure 1 shows the regression or progression of MR and AR after KT. 78 (11%) patients showed MR regression, but 41 (6%) experienced MR progression. 13 (2%) revealed AR regression, while 23 (4%) presented AR progression. In patients with MR progression, there were more cases of receiving a second KT, having mitral annular calcification, and showing lesser reduction of left atrial volume after KT. Patients with AR progression showed a longer hemodialysis duration, persistent hypertension after KT, and aortic root dilatation. Factors related to the progression of MR and AR showed statistically meaningful predictive values in a stepwise manner (Figure 2)

Conclusions

In patients undergoing KT, MR and AR may progress in patients with certain distinct characteristics. Different clinical and echocardiographic characteristics before KT, and reduction of hemodynamic loads after KT determine the progression of MR and AR. Further echocardiographic surveillances after KT are needed in patients with clinical and echocardiographic factors for progression of valve regurgitation.

Funding Acknowledgement

Type of funding sources: None.

Rapid custom prototyping of soft poroelastic biosensor for simultaneous epicardial recording and imaging

The growing need for the implementation of stretchable biosensors in the body has driven rapid prototyping schemes through the direct ink writing of multidimensional functional architectures. Recent approaches employ biocompatible inks that are dispensable through an automated nozzle injection system. However, their application in medical practices remains challenged in reliable recording due to their viscoelastic nature that yields mechanical and electrical hysteresis under periodic large strains. Herein, we report sponge-like poroelastic silicone composites adaptable for high-precision direct writing of custom-designed stretchable biosensors, which are soft and insensitive to strains. Their unique structural properties yield a robust coupling to living tissues, enabling high-fidelity recording of spatiotemporal electrophysiological activity and real-time ultrasound imaging for visual feedback. In vivo evaluations of custom-fit biosensors in a murine acute myocardial infarction model demonstrate a potential clinical utility in the simultaneous intraoperative recording and imaging on the epicardium, which may guide definitive surgical treatments.

Replicable Quasi-Three-Dimensional Plasmonic Nanoantennas for Infrared Bandpass Filtering

Quasi-three-dimensionally designed metal-dielectric hybrid nanoantennas have provided a unique capability to control light at the nanoscale beyond the diffraction limit, which has enabled powerful optical manipulation techniques. However, the fabrication of these nanoantennas has largely relied on the use of nanolithography techniques that are time- and cost-consuming, impeding their application in wide-ranging use. Herein, we report a versatile methodology enabling the repetitive replication of these nanoantennas from their silicon molds with tailored optical features for infrared bandpass filtering. Comprehensive experimental and computational analyses revealed the underlying mechanism of this methodology and also provided a technical guideline for pragmatic translation into infrared filters in multispectral imaging.

Controlled Integration of Interconnected Pores under Polymeric Surfaces for Low Adhesion and Antiscaling Performance

Low-adhesive surfaces have been highlighted due to the potentials to mitigate fouling issues by preventing unwanted substances from adhering. Realizing superhydrophobicity with 3D surface structures/chemical modifiers or fabricating lubricant-assisted slippery surfaces has been demonstrated to realize low-adhesive surfaces. However, they still need to overcome the transition to Wenzel from Cassie states of droplets on 3D surface structures or the lubricant depletion issues of slippery surfaces for sustainable operations. Herein, we report the fabrication of low-adhesive polymeric surfaces, neither assisted by 3D surface structures/chemical modifiers nor lubricants, which is realized by embedding the interconnected pore networks underneath the top smooth surface using a water steaming method. The fabricated silicone surfaces exhibit low-adhesive properties due to the stress concentration effects generated by the subsurface-structured pores, favorable for easy detachment of the adherent from the surface. Our platform can be exploited to lower adhesion of superhydrophilic surfaces or to achieve ultralow-adhesive properties upon combination with superhydrophobicity. Finally, scale precipitation tests reveal 4.2 times lower scale accumulation of our low-adhesive polymeric surfaces than that in control samples.

3D Printed Bioresponsive Devices with Selective Permeability Inspired by Eggshell Membrane for Effective Biochemical Conversion

Eggshell membrane has selective permeability that enables gas or liquid molecules to pass through while effectively preventing migration of microbial species. Herein, inspired by the architecture of the eggshell membrane, we employ three-dimensional (3D) printing techniques to realize bioresponsive devices with excellent selective permeability for effective biochemical conversion. The fabricated devices show 3D conductive carbon nanofiber membranes in which precultured microbial cells are controllably deployed. The resulting outcome provides excellent selective permeability between chemical and biological species, which enables acquisition of target responses generated by biological species confined within the device upon input signals. In addition, electrically conductive carbon nanofiber networks provide a platform for real-time monitoring of metabolism of microbial cells in the device. The suggested platform represents an effort to broaden microbial applications by constructing biologically programmed devices for desired responses enabled by designated deployment of engineered cells in a securely confined manner within enclosed membranes using 3D printing methods.

Bioresorbable, Miniaturized Porous Silicon Needles on a Flexible Water-Soluble Backing for Unobtrusive, Sustained Delivery of Chemotherapy

Conventional melanoma therapies suffer from the toxicity and side effects of repeated treatments due to the aggressive and recurrent nature of melanoma cells. Less-invasive topical chemotherapies by utilizing polymeric microneedles have emerged as an alternative, but the sustained, long-lasting release of drug cargos remains challenging. In addition, the size of the microneedles is relatively bulky for the small, curvilinear, and exceptionally sensitive cornea for the treatment of ocular melanoma. Here, we report a design of bioresorbable, miniaturized porous-silicon (p-Si) needles with covalently linked drug cargos at doses comparable to those of conventional polymeric microneedles. The p-Si needles are built on a water-soluble film as a temporary flexible holder that can be intimately interfaced with the irregular surface of living tissues, followed by complete dissolution with saline solution within 1 min. Consequently, the p-Si needles remain embedded inside tissues and then undergo gradual degradation, allowing for sustained release of the drug cargos. Its utility in unobtrusive topical delivery of chemotherapy with minimal side effects is demonstrated in a murine melanoma model.

Bactericidal Lubricating Synthetic Materials for Three-Dimensional Additive Assembly with Controlled Mechanical Properties

3D printable synthetic materials have been developed to realize desired surface and mechanical properties. Lubricating synthetic surfaces have broad technological impacts on many applications including food packaging, microfluidic systems, and biomedical devices. However, combining soft materials with lubricants leads to significant phase separation and swelling phenomena, together with lowered mechanical strength, impeding full utilization of lubricating synthetic surfaces with desired shapes in a highly controllable manner. Here, we report a new platform to create a 3D printable lubricant-polymer composite (3D-LUBRIC) for the seamless fabrication of multidimensional structures with diverse functionalities. The rationally designed lubricant-polymer mixtures including silica aerogel particles not only exhibit suitable rheological properties for direct ink writing without phase separation but also enable the deterministic additive assembly of heterogeneous materials, which have large mismatches of oil permeability, with no distinct shape distortion. While exhibiting excellent lubricating properties for a variety of liquids, 3D-LUBRIC shows tunable mechanical properties with desired functionalities, such as optical transparency, flexibility and stretchability, and anti-icing and antibacterial/bactericidal properties. We employ the proposed platform to fabricate self-cleanable containers and antibacterial/bactericidal medical tubes. Our platform can offer new opportunities for building low-adhesive, multifunctional synthetic materials with customized shapes for diverse applications.

Adaptive Laboratory Evolution of Eubacterium limosum ATCC 8486 on Carbon Monoxide

Acetogens are naturally capable of metabolizing carbon monoxide (CO), a component of synthesis gas (syngas), for autotrophic growth in order to produce biomass and metabolites such as acetyl-CoA via the Wood–Ljungdahl pathway. However, the autotrophic growth of acetogens is often inhibited by the presence of high CO concentrations because of CO toxicity, thus limiting their biosynthetic potential for industrial applications. Herein, we implemented adaptive laboratory evolution (ALE) for growth improvement of Eubacterium limosum ATCC 8486 under high CO conditions. The strain evolved under syngas conditions with 44% CO over 150 generations, resulting in a significant increased optical density (600 nm) and growth rate by 2.14 and 1.44 folds, respectively. In addition, the evolved populations were capable of proliferating under CO concentrations as high as 80%. These results suggest that cell growth is enhanced as beneficial mutations are selected and accumulated, and the metabolism is altered to facilitate the enhanced phenotype. To identify the causal mutations related to growth improvement under high CO concentrations, we performed whole genome resequencing of each population at 50-generation intervals. Interestingly, we found key mutations in CO dehydrogenase/acetyl-CoA synthase (CODH/ACS) complex coding genes, acsA and cooC. To characterize the mutational effects on growth under CO, we isolated single clones and confirmed that the growth rate and CO tolerance level of the single clone were comparable to those of the evolved populations and wild type strain under CO conditions. Furthermore, the evolved strain produced 1.34 folds target metabolite acetoin when compared to the parental strain while introducing the biosynthetic pathway coding genes to the strains. Consequently, this study demonstrates that the mutations in the CODH/ACS complex affect autotrophic growth enhancement in the presence of CO as well as the CO tolerance of E. limosum ATCC 8486.

Genome Engineering of Eubacterium limosum Using Expanded Genetic Tools and the CRISPR-Cas9 System

Eubacterium limosum is one of the important bacteria in C1 feedstock utilization as well as in human gut microbiota. Although E. limosum has recently garnered much attention and investigation on a genome-wide scale, a bottleneck for systematic engineering in E. limosum is the lack of available genetic tools and an efficient genome editing platform. To overcome this limitation, we here report expanded genetic tools and the CRISPR-Cas9 system. We have developed an inducible promoter system that enables implementation of the CRISPR-Cas9 system to precisely manipulate target genes of the Wood-Ljungdahl pathway with 100% efficiency. Furthermore, we exploited the effectiveness of CRISPR interference to reduce the expression of target genes, exhibiting substantial repression of several genes in the Wood-Ljungdahl pathway and fructose-PTS system. These expanded genetic tools and CRISPR-Cas9 system comprise powerful and widely applicable genetic tools to accelerate functional genomic study and genome engineering in E. limosum.

Sensor-Instrumented Scaffold Integrated with Microporous Spongelike Ultrabuoy for Long-Term 3D Mapping of Cellular Behaviors and Functions

Real-time monitoring of cellular behaviors and functions with sensor-instrumented scaffolds can provide a profound impact on fundamental studies of the underlying biophysics and disease modeling. Although quantitative measurement of predictive data for in vivo tests and physiologically relevant information in these contexts is important, the long-term reliable monitoring of cellular functions in three-dimensional (3D) environments is limited by the required set under wet cell culture conditions that are unfavorable to electronic instrument settings. Here, we introduce an ultrabuoyant 3D instrumented scaffold that can remain afloat on the surface of culture medium and thereby provides favorable environments for the entire electronic components in the air while the cells reside and grow underneath. This setting enables high-fidelity recording of electrical cell-substrate impedance and electrophysiological signals for a long period of time (weeks). Comprehensive in vitro studies reveal the utility of this platform as an effective tool for drug screening and tissue development.

Hierarchical Macroporous Particles for Efficient Whole-Cell Immobilization: Application in Bioconversion of Greenhouse Gases to Methanol

A viable approach for methanol production under ambient physiological conditions is to use greenhouse gases, methane (CH₄) and carbon dioxide (CO₂), as feed for immobilized methanotrophs. In the present study, unique macroporous carbon particles with pore sizes in the range of ∼1-6 μm were synthesized and used as support for the immobilization of Methylocella tundrae. Immobilization was accomplished covalently on hierarchical macroporous carbon particles. Maximal cell loading of covalently immobilized M. tundrae was 205 mg_DCM g^-1 of particles. Among these particles, the cells immobilized on 3.6 μm pore size particles showed the highest reusability with the least leaching and were chosen for further study. After immobilization, M. tundrae showed up to 2.4-fold higher methanol production stability at various pH and temperature values because of higher stability and metabolic activity than free cells. After eight cycles of reuse, the immobilized cells retained 18.1-fold higher relative production stability compared to free cells. Free and immobilized cells exhibited cumulative methanol production of 5.2 and 9.5 μmol mg_DCM^-1 under repeated batch conditions using simulated biogas [CH₄ and CO₂, 4:1 (v/v)] as feed, respectively. The appropriate pore size of macroporous particles favors the efficient M. tundrae immobilization to retain better biocatalytic properties. This is the first report concerning the covalent immobilization of methanotrophs on the newly synthesized macroporous carbon particles and its subsequent application in repeated methanol production using simulated biogas as a feed.

Genome-scale analysis of Acetobacterium bakii reveals the cold adaptation of psychrotolerant acetogens by post-transcriptional regulation

Acetogens synthesize acetyl-CoA via CO2 or CO fixation, producing organic compounds. Despite their ecological and industrial importance, their transcriptional and post-transcriptional regulation has not been systematically studied. With completion of the genome sequence of Acetobacterium bakii (4.28-Mb), we measured changes in the transcriptome of this psychrotolerant acetogen in response to temperature variations under autotrophic and heterotrophic growth conditions. Unexpectedly, acetogenesis genes were highly up-regulated at low temperatures under heterotrophic, as well as autotrophic, growth conditions. To mechanistically understand the transcriptional regulation of acetogenesis genes via changes in RNA secondary structures of 5'-untranslated regions (5'-UTR), the primary transcriptome was experimentally determined, and 1379 transcription start sites (TSS) and 1100 5'-UTR were found. Interestingly, acetogenesis genes contained longer 5'-UTR with lower RNA-folding free energy than other genes, revealing that the 5'-UTRs control the RNA abundance of the acetogenesis genes under low temperature conditions. Our findings suggest that post-transcriptional regulation via RNA conformational changes of 5'-UTRs is necessary for cold-adaptive acetogenesis.

Genome-scale analysis of syngas fermenting acetogenic bacteria reveals the translational regulation for its autotrophic growth

Background

Acetogenic bacteria constitute promising biocatalysts for the conversion of CO₂/H₂ or synthesis gas (H₂/CO/CO₂) into biofuels and value-added biochemicals. These microorganisms are naturally capable of autotrophic growth via unique acetogenesis metabolism. Despite their biosynthetic potential for commercial applications, a systemic understanding of the transcriptional and translational regulation of the acetogenesis metabolism remains unclear.

Results

By integrating genome-scale transcriptomic and translatomic data, we explored the regulatory logic of the acetogenesis to convert CO₂ into biomass and metabolites in Eubacterium limosum. The results indicate that majority of genes associated with autotrophic growth including the Wood-Ljungdahl pathway, the reduction of electron carriers, the energy conservation system, and gluconeogenesis were transcriptionally upregulated. The translation efficiency of genes in cellular respiration and electron bifurcation was also highly enhanced. In contrast, the transcriptionally abundant genes involved in the carbonyl branch of the Wood-Ljungdahl pathway, as well as the ion-translocating complex and ATP synthase complex in the energy conservation system, showed decreased translation efficiency. The translation efficiencies of genes were regulated by 5′UTR secondary structure under the autotrophic growth condition.

Conclusions

The results illustrated that the acetogenic bacteria reallocate protein synthesis, focusing more on the translation of genes for the generation of reduced electron carriers via electron bifurcation, rather than on those for carbon metabolism under autotrophic growth.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5238-0) contains supplementary material, which is available to authorized users.

Flexible elastomer patch with vertical silicon nanoneedles for intracellular and intratissue nanoinjection of biomolecules

Vertically ordered arrays of silicon nanoneedles (Si NNs), due to their nanoscale dimension and low cytotoxicity, could enable minimally invasive nanoinjection of biomolecules into living biological systems such as cells and tissues. Although production of these Si NNs on a bulk Si wafer has been achieved through standard nanofabrication technology, there exists a large mismatch at the interface between the rigid, flat, and opaque Si wafer and soft, curvilinear, and optically transparent biological systems. Here, we report a unique methodology that is capable of constructing vertically ordered Si NNs on a thin layer of elastomer patch to flexibly and transparently interface with biological systems. The resulting outcome provides important capabilities to form a mechanically elastic interface between Si NNs and biological systems, and simultaneously enables direct imaging of their real-time interactions under the transparent condition. We demonstrate its utility in intracellular, intradermal, and intramuscular nanoinjection of biomolecules into various kinds of biological cells and tissues at their length scales.

Synthesis of cross-linked protein-metal hybrid nanoflowers and its application in repeated batch decolorization of synthetic dyes

Herein, we report the preparation of a cross-linked protein-metal hybrid nanoflower (NF) system for laccase immobilization. The immobilized laccase showed effective encapsulation yield and activity recovery of 78.1% and 204%, respectively. The catalytic efficiency (k_catV_max^-1) of cross-linked NF (CL-NF) was 2.2-fold more than that of free laccase. The CL-NF also exhibited significantly higher stability towards pH and temperature changes. It exhibited excellent storage stability and tolerance towards solvents and inhibitors as compared with the free enzyme. After 10 cycles of reuses, the NF and CL-NF laccase showed 41.2% and 92.3% residual activity, respectively. The CL-NF showed high oxidation potential, 265% that of the free enzyme, towards phenolic compounds. The CL-NF laccase retained the residual decolorization efficiency of up to 84.6% for synthetic dyes under repeated batch conditions of 10 cycles. These results suggested that the preparation of CL-NF is an effective approach to enhance the enzymatic properties and has great potential in many industrial applications.

Three-Dimensional Hetero-Integration of Faceted GaN on Si Pillars for Efficient Light Energy Conversion Devices

An important pathway for cost-effective light energy conversion devices, such as solar cells and light emitting diodes, is to integrate III-V (e.g., GaN) materials on Si substrates. Such integration first necessitates growth of high crystalline III-V materials on Si, which has been the focus of many studies. However, the integration also requires that the final III-V/Si structure has a high light energy conversion efficiency. To accomplish these twin goals, we use single-crystalline microsized Si pillars as a seed layer to first grow faceted Si structures, which are then used for the heteroepitaxial growth of faceted GaN films. These faceted GaN films on Si have high crystallinity, and their threading dislocation density is similar to that of GaN grown on sapphire. In addition, the final faceted GaN/Si structure has great light absorption and extraction characteristics, leading to improved performance for GaN-on-Si light energy conversion devices.

Facile Fabrication of Superomniphobic Polymer Hierarchical Structures for Directional Droplet Movement

We report a facile method for fabricating polymer hierarchical structures, which are the engineered, ratchet-like microscale structures with nanoscale dimples, for the directional movement of droplets. The fabricated polymer hierarchical structures with no surface modifier show hydrophobic, superhydrophobic, or omniphobic characteristics depending on their intrinsic polymer properties. Further treatment with a surface modifier endows the polymer surfaces with superomniphobicity. The fabricated polymer substrates with no surface modifier enable the movement of the water droplet along the designed track at almost no inclination of the substrate.

BiVO4/WO3/SnO2 Double-Heterojunction Photoanode with Enhanced Charge Separation and Visible-Transparency for Bias-Free Solar Water-Splitting with a Perovskite Solar Cell

Coupling dissimilar oxides in heterostructures allows the engineering of interfacial, optical, charge separation/transport and transfer properties of photoanodes for photoelectrochemical (PEC) water splitting. Here, we demonstrate a double-heterojunction concept based on a BiVO₄/WO₃/SnO₂ triple-layer planar heterojunction (TPH) photoanode, which shows simultaneous improvements in the charge transport (∼93% at 1.23 V vs RHE) and transmittance at longer wavelengths (>500 nm). The TPH photoanode was prepared by a facile solution method: a porous SnO₂ film was first deposited on a fluorine-doped tin oxide (FTO)/glass substrate followed by WO₃ deposition, leading to the formation of a double layer of dense WO₃ and a WO₃/SnO₂ mixture at the bottom. Subsequently, a BiVO₄ nanoparticle film was deposited by spin coating. Importantly, the WO₃/(WO₃+SnO₂) composite bottom layer forms a disordered heterojunction, enabling intimate contact, lower interfacial resistance, and efficient charge transport/transfer. In addition, the top BiVO₄/WO₃ heterojunction layer improves light absorption and charge separation. The resultant TPH photoanode shows greatly improved internal quantum efficiency (∼80%) and PEC water oxidation performance (∼3.1 mA/cm² at 1.23 V vs RHE) compared to the previously reported BiVO₄/WO₃ photoanodes. The PEC performance was further improved by a reactive-ion etching treatment and CoO_x electrocatalyst deposition. Finally, we demonstrated a bias-free and stable solar water-splitting by constructing a tandem PEC device with a perovskite solar cell (STH ∼3.5%).

Peru-15 (Choleragarde(®)), a live attenuated oral cholera vaccine, is safe and immunogenic in human immunodeficiency virus (HIV)-seropositive adults in Thailand

BACKGROUND

Many areas with endemic and epidemic cholera report significant levels of HIV transmission. According to the World Health Organization (WHO), over 95% of reported cholera cases occur in Africa, which also accounts for nearly 70% of people living with HIV/AIDS globally. Peru-15, a promising single dose live attenuated oral cholera vaccine (LA-OCV), was previously found to be safe and immunogenic in cholera endemic areas. However, no data on the vaccine's safety among HIV-seropositive adults had been collected.

METHODS

This study was a double-blinded, individually randomized, placebo-controlled trial enrolling HIV-seropositive adults, 18-45 years of age, conducted in Bangkok, Thailand, to assess the safety of Peru-15 in a HIV-seropositive cohort.

RESULTS

32 HIV infected subjects were randomized to receive either a single oral dose of the Peru-15 vaccine with a buffer or a placebo (buffer only). No serious adverse events were reported during the follow-up period in either group. The geometric mean fold (GMF) rise in V. cholerae O1 El Tor specific antibody titers between baseline and 7 days after dosing was 32.0 (p<0.001) in the vaccine group compared to 1.6 (p<0.14) in the placebo group. Among the 16 vaccinees,14 vaccinees (87.5%) had seroconversion compared to 1 of 16 placebo recipients (6.3%). V. cholerae was isolated from the stool of one vaccinee, and found to be genetically identical to the Peru-15 vaccine strain. There were no significant changes in HIV viral load or CD4 T-cell counts between vaccine and placebo groups.

CONCLUSION

Peru-15 was shown to be safe and immunogenic in HIV-seropositive Thai adults.

Transfer printing methods for flexible thin film solar cells: basic concepts and working principles

Fabricating thin film solar cells (TFSCs) on flexible substrates will not only broaden the applications of solar cells, but also potentially reduce the installation cost. However, a critical challenge for fabricating flexible TFSCs on flexible substrates is the incompatibility issues between the thermal, mechanical, and chemical properties of these substrates and the fabrication conditions. Transfer printing methods, which use conventional substrates for the fabrication and then deliver the TFSCs onto flexible substrates, play a key role to overcome these challenges. In this review, we discuss the basic concepts and working principles of four major transfer printing methods associated with (1) transfer by sacrificial layers, (2) transfer by porous Si layer, (3) transfer by controlled crack, and (4) transfer by water-assisted thin film delamination. We also discuss the challenges and opportunities for implementing these methods for practical solar cell manufacture.

Electroassisted transfer of vertical silicon wire arrays using a sacrificial porous silicon layer

An electroassisted method is developed to transfer silicon (Si) wire arrays from the Si wafers on which they are grown to other substrates while maintaining their original properties and vertical alignment. First, electroassisted etching is used to form a sacrificial porous Si layer underneath the Si wires. Second, the porous Si layer is separated from the Si wafer by electropolishing, enabling the separation and transfer of the Si wires. The method is further expanded to develop a current-induced metal-assisted chemical etching technique for the facile and rapid synthesis of Si nanowires with axially modulated porosity.

Shrinking and growing: grain boundary density reduction for efficient polysilicon thin-film solar cells

Polycrystalline Si (poly-Si) thin-film, due to its low Si consumption, low substrate cost, and good stability, is an attractive candidate for cost-effective solar cells, but the as-deposited poly-Si typically has a columnar structure with grain boundaries in between, severely limiting the efficiency of the poly-Si. Here, we report a micropillar poly-Si solar cell that utilizes the columnar structure of the as-deposited poly-Si grains. We first formed submicrometer diameter poly-Si pillars, smaller than the initial grain sizes, and used these pillars as the seeds for the subsequent epitaxial growth of Si, which effectively reduces grain boundary density in the final poly-Si crystal. In addition, the vertically aligned micropillar arrays form radial p-n junctions that further mitigate the grain boundary recombination losses by improving the light absorption and charge-carrier collection efficiencies. Consequently, the maximum efficiency of micropillar poly-Si thin-film solar cells is 6.4%, that is, ∼1.5 times higher than that of the planar cells.

Thermal conductivity in porous silicon nanowire arrays

The nanoscale features in silicon nanowires (SiNWs) can suppress phonon propagation and strongly reduce their thermal conductivities compared to the bulk value. This work measures the thermal conductivity along the axial direction of SiNW arrays with varying nanowire diameters, doping concentrations, surface roughness, and internal porosities using nanosecond transient thermoreflectance. For SiNWs with diameters larger than the phonon mean free path, porosity substantially reduces the thermal conductivity, yielding thermal conductivities as low as 1 W/m/K in highly porous SiNWs. However, when the SiNW diameter is below the phonon mean free path, both the internal porosity and the diameter significantly contribute to phonon scattering and lead to reduced thermal conductivity of the SiNWs.

Fabrication of flexible and vertical silicon nanowire electronics

Vertical silicon nanowire (SiNW) array devices directly connected on both sides to metallic contacts were fabricated on various non-Si-based substrates (e.g., glass, plastics, and metal foils) in order to fully exploit the nanomaterial properties for final applications. The devices were realized with uniform length Ag-assisted electroless etched SiNW arrays that were detached from their fabrication substrate, typically Si wafers, reattached to arbitrary substrates, and formed with metallic contacts on both sides of the NW array. Electrical characterization of the SiNW array devices exhibits good current-voltage characteristics consistent with the SiNW morphology.

Branched TiO₂ nanorods for photoelectrochemical hydrogen production

We report a hierarchically branched TiO(2) nanorod structure that serves as a model architecture for efficient photoelectrochemical devices as it simultaneously offers a large contact area with the electrolyte, excellent light-trapping characteristics, and a highly conductive pathway for charge carrier collection. Under Xenon lamp illumination (UV spectrum matched to AM 1.5G, 88 mW/cm(2) total power density), the branched TiO(2) nanorod array produces a photocurrent density of 0.83 mA/cm(2) at 0.8 V versus reversible hydrogen electrode (RHE). The incident photon-to-current conversion efficiency reaches 67% at 380 nm with an applied bias of 0.6 V versus RHE, nearly two times higher than the bare nanorods without branches. The branches improve efficiency by means of (i) improved charge separation and transport within the branches due to their small diameters, and (ii) a 4-fold increase in surface area which facilitates the hole transfer at the TiO(2)/electrolyte interface.

Fabrication of nanowire electronics on nonconventional substrates by water-assisted transfer printing method

We report a simple, versatile, and wafer-scale water-assisted transfer printing method (WTP) that enables the transfer of nanowire devices onto diverse nonconventional substrates that were not easily accessible before, such as paper, plastics, tapes, glass, polydimethylsiloxane (PDMS), aluminum foil, and ultrathin polymer substrates. The WTP method relies on the phenomenon of water penetrating into the interface between Ni and SiO(2). The transfer yield is nearly 100%, and the transferred devices, including NW resistors, diodes, and field effect transistors, maintain their original geometries and electronic properties with high fidelity.

Hybrid Si microwire and planar solar cells: passivation and characterization

We report an efficient hybrid Si microwire (radial junction) and planar solar cell with a maximum efficiency of 11.0% under AM 1.5G illumination. The maximum efficiency of the hybrid cell is improved from 7.2% to 11.0% by passivating the top surface and p-n junction with thin a-SiN:H and intrinsic poly-Si films, respectively, and is higher than that of planar cells of the identical layers due to increased light absorption and improved charge-carrier collections in both wires and planar components.

Vertical transfer of uniform silicon nanowire arrays via crack formation

Vertical transfer of silicon nanowire (SiNW) arrays with uniform length onto adhesive substrates was realized by the assistance of creating a horizontal crack throughout SiNWs. The crack is formed by adding a water soaking step between consecutive Ag-assisted electroless etching processes of Si. The crack formation is related to the delamination, redistribution, and reattachment of the Ag film during the water soaking and subsequent wet etching steps. Moreover, the crack facilitates embedding SiNWs inside polymers.

Orientation-controlled alignment of axially modulated pn silicon nanowires

We demonstrate orientation-controlled alignment of axially modulated pn SiNWs by applying dc electric fields across metal electrodes. The as-aligned pn SiNWs exhibit rectifying behaviors with a 97.7% yield, and about 35% of them exhibit no hysteresis in their current-voltage curves that can be directly used to construct AND/OR logic gates. Moreover, the as-aligned pn SiNWs can be packaged either with polydimethylsiloxane or additional metal layer to protect and even improve the quality of these NW diodes.

Direct growth of nanowire logic gates and photovoltaic devices

Bottom-up nanowires are useful building blocks for functional devices because of their controllable physical and chemical properties. However, assembling nanowires into large-scale integrated systems remains a critical challenge that becomes even more daunting when different nanowires need to be simultaneously assembled in close proximity to one another. Herein, we report a new method to directly grow nanowire devices consisting of different nanowires. The method is based on the epitaxial growth of nanowires from the sidewalls of electrodes and on the matching of electrode design with synthesis conditions to electrically connect different nanowires during growth. Specifically, the method was used to grow silicon nanowire-based AND and OR diode logic gates with excellent rectifying behaviors, and photovoltaic elements in parallel and in series, with tunable power output.

Probing flow velocity with silicon nanowire sensors

We report our experimental efforts to quantify the impact of fluidic and ionic transport on the conductance level of silicon nanowire (SiNW) sensors configured as field effect transistors (FETs). Specifically, the conductance of SiNW FETs placed in a microfluidic channel was observed to change linearly with the flow velocity of electrolytic solutions. The direction of conductance change depends on the doping type of the SiNWs and their location inside the microfluidic channel, and the magnitude of the conductance change varies with the ionic strength and compositions of the electrolytic solution. Our quantitative analysis suggests that the flow velocity sensing is a consequence of the streaming potential that is generated by the movement of counterions inside the electrical double layer (EDL) of the silica substrate. The streaming potential, which varies with the flow velocity and the ionic properties of the electrolytic solution, acts in the same way as the charged analytes in affecting the conductance of SiNWs by changing the surface potential. This study highlights the importance of considering the ionic transport in analyzing and optimizing nanowire FET sensors, which can significantly change the conductance of NWs. Moreover, SiNWs were demonstrated for the first time to be able to detect the streaming potential, the flow velocity and the ionic strength, opening up their new application potentials in microfluidics.

Single and tandem axial p-i-n nanowire photovoltaic devices

Nanowires represent a promising class of materials for exploring new concepts in solar energy conversion. Here we report the first experimental realization of axial modulation-doped p-i-n and tandem p-i-n(+) -p(+)-i-n silicon nanowire (SiNW) photovoltaic elements. Scanning electron microscopy images of selectively etched nanowires demonstrate excellent synthetic control over doping and lengths of distinct regions in the diode structures. Current-voltage (I-V) characteristics reveal clear and reproducible diode characteristics for the p-i-n and p-n SiNW devices. Under simulated one-sun solar conditions (AM 1.5G), optimized p-i-n SiNW devices exhibited an open circuit voltage (Voc) of 0.29 V, a maximum short-circuit current density of 3.5 mA/cm(2), and a maximum efficiency of 0.5%. The response of the short-circuit current versus Voc under varying illumination intensities shows that the diode quality factor is improved from n=1.78 to n=1.28 by insertion of the i-type SiNW segment. The temperature dependence of Voc scales as -2.97 mV/K and extrapolates to the crystalline Si band gap at 0 K, which is in excellent agreement with bulk properties. Finally, a novel single SiNW tandem solar cell consisting of synthetic integration of two photovoltaic elements with an overall p-i-n(+) -p(+)-i-n structure was prepared and shown to exhibit a Voc that is on average 57% larger than that of the single p-i-n device. Fundamental studies of such well-defined nanowire photovoltaics will enable their intrinsic performance limits to be defined.

Numerical characterization and optimization of the microfluidics for nanowire biosensors

The present study aims to enhance the analyte transport to the surface of nanowires (NWs) through optimizing the sensing configuration and the flow patterns inside the microfluidic channel, and hence to reduce the response time of NW biosensors. Specifically, numerical simulations were carried out to quantitatively investigate the effects of the fundamental surface reaction, convection, and diffusion processes on the sensing performance. Although speeding up all these processes will reduce the sensing response time, enhancing the diffusional transport was found to be most effective. Moreover, the response time of NW biosensors is inversely proportional to the local concentration of the analyte in the vicinity of the NWs, which suggests that the sensing response time can be significantly reduced by replenishing the local analyte rapidly. Therefore, the following three optimization strategies were proposed and their effects on the time response of NWs were characterized systematically: device substrate passivation, microfluidic channel modification, and suspending NWs. The combination of these three optimization methods was demonstrated to be able to reduce the response time of NW biosensors by more than 1 order of magnitude.

Upregulation and function of GADD45gamma in unilateral ureteral obstruction

We performed differential display analysis to determine transcriptional activity in the rat kidney, following unilateral ureteral obstruction and found a 12-fold increase in the expression of Growth Arrest and DNA Damage-45gamma (GADD45gamma), a stress-responsive molecule that interacts with cell-cycle proteins. GADD45gamma was strongly expressed in as little as 6 h following ureteric obstruction in the renal tubules, and was also found in kidney tissue of patients with chronic glomerulonephritis. Adenovirus-mediated expression of GADD45gamma in cultured renal tubular cells activated p38 along with a significant upregulation of C-C and C-X3-C chemokine ligands and fibrosis-related factors such as several matrix metalloproteinases, transforming growth factor-beta1, decorin, and bone morphogenetic protein 2. Silencing of GADD45gamma expression significantly blunted the upregulation of these inflammatory and fibrogenic mediators and monocyte infiltration in the ureteral obstructed rat kidney. Our study shows that GADD45gamma is quickly upregulated in the kidney with an obstructed ureter, enhancing the production of factors regulating the pathogenesis of kidney disease.

The burden of cholera in the slums of Kolkata, India: data from a prospective, community based study

AIMS

To conduct a prospective, community based study in an impoverished urban site in Kolkata (formerly Calcutta) in order to measure the burden of cholera, describe its epidemiology, and search for potential risk factors that could be addressed by public health strategies.

METHODS

The study population was enumerated at the beginning and end of the study period. Surveillance through five field outposts and two referral hospitals for acute, watery, non-bloody diarrhoea was conducted from 1 May 2003 to 30 April 2004. Data and a stool sample for culture of Vibrio cholerae were collected from each patient. Treatment was provided in accordance with national guidelines.

RESULTS

From 62 329 individuals under surveillance, 3284 diarrhoea episodes were detected, of which 3276 (99%) had a stool sample collected and 126 (4%) were culture confirmed cholera. Nineteen (15%) were children less than 2 years of age, 29 (23%) had severe dehydration, and 48 (38%) were hospitalised. Risk factors for cholera included a household member with cholera during the period of surveillance, young age, and lower educational level.

CONCLUSIONS

There was a substantial burden of cholera in Kolkata with risk factors not easily amenable to intervention. Young children bear the brunt not only of diarrhoeal diseases in general, but of cholera as well. Mass vaccination could be a potentially useful tool to prevent and control seasonal cholera in this community.

Fermented mushroom milk-supplemented dietary fibre prevents the onset of obesity and hypertriglyceridaemia in Otsuka Long-Evans Tokushima fatty rats

AIM

Fermented milk product containing edible mushroom water extracts (mushroom yogurt; MY) has been reported to have glycaemic control and triglyceride-lowering effects in streptozotocin (STZ)-induced diabetic rats and Zucker diabetic fatty (ZDF) rats. Here, we investigated how MY-supplemented dietary fibre (10 and 20%, v/w) influences the onset of obesity and hypertriglyceridaemia in Otsuka Long-Evans Tokushima fatty (OLETF) rats.

METHODS

The OLETF rats were fed a powdered chow diet supplemented with MY at the levels of 10 (v/w) and 20% for 6 weeks from 10 weeks of age, but the OLETF control rats were not supplemented. Their weight, fat distribution and lipid profile have been determined.

RESULTS

The body weights in MY-fed rats were reduced compared with the control rats. The perirenal fat was decreased in both MY groups, but the visceral and epididymal fats reduced only in the MY 20% group. The concentrations of serum triglyceride and non-esterified fatty acid in MY-fed rats were decreased in a dose-dependent manner. However, the levels of other serum lipid profiles [total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol] were comparable among all rats.

CONCLUSION

Anti-obesity and triglyceride lowering by MY-supplemented dietary fibre in OLETF rats might have resulted from the synergistic effect of components in the fermented mushroom-milk product.

Incidence of Haemophilus influenzae type b and other invasive diseases in South Korean children

To determine incidence of invasive Haemophilus influenzae type b (Hib) disease in a defined population of Jeonbuk Province, Korea, children <5 years were evaluated in prospective, population-based surveillance of invasive bacterial diseases using standardized methods for patient referral, clinical evaluation and laboratory testing (optimized culture, latex agglutination, polymerase chain reaction). Vaccine utilization was assessed with vaccination histories of patients in surveillance, monthly data on Hib vaccine distribution and a coverage survey of clinic patients in study population. From September 1999 to December 2001, 2176 children were evaluated for possible meningitis, 1541 had no cerebrospinal fluid (CSF) findings of meningitis, 605 had CSF abnormalities (suspected bacterial meningitis) but no pathogen identified; six patients had probable Hib meningitis and eight had confirmed Hib meningitis. The annual suspected bacterial meningitis incidence was 258.4/100,000 <5 years and the probable/confirmed Hib meningitis incidence was 6.0/100,000 <5 years. Pneumococcal meningitis incidence was 2.1/100,000 <5 years and Group B streptococcal meningitis incidence was 0.17/1000 live births. A total of 69,589 Hib vaccine doses were distributed during the study. Hib vaccine coverage was negligible initially but increased to 16% (complete Hib immunization) and 27% (partial immunization) in final months of study. Suspected bacterial meningitis incidence was high but proven invasive Hib meningitis incidence was low. Hib was leading cause of bacterial meningitis yet bacterial pathogens were identified in only 4% of abnormal CSF. These findings may reflect truly low incidence, presumptive antibiotic treatment, partial Hib immunization, or incomplete clinical evaluations. Given the apparent Hib meningitis burden in Jeonbuk Province, additional studies to describe other invasive Hib syndromes, Hib-associated mortality and disability, and economic impact of Hib disease will be useful to guide public health decisions regarding routine Hib vaccine introduction.

Pressure activation of the chaperone function of small heat shock proteins

Small heat shock proteins play an important role in the stress response of cells and in several other cellular functions. They possess chaperone-like activity; i.e. they can bind and protect damaged proteins from aggregation and maintain them in a folding-competent state. Two members of this family were investigated in this work: bovine alpha-crystallin and heat shock protein (HSP)16.5 from the thermophilic archaebacteria Methanococcus jannaschii. We reported earlier the enhancement of chaperone potency of alpha-crystallin by high pressure. We now report the completion of the work with results on HSP16.5. The chaperone potency of both proteins can be enhanced significantly by applying high pressure. Evidence by light scattering, Fourier transform infrared (FT-IR) and tryptophan fluorescence experiments show that while the secondary and tertiary structure of these proteins are not influenced by high pressure, their quatemary structure becomes affected: H bonds between subunits are weakened or broken, tryptophan environments become more polar, oligomers dissociate to some extent. We conclude that the oligomeric structure of both proteins is loosened, resulting in stronger dynamics and in more accessible hydrophobic surfaces. These properties lead to increased chaperone potency.

Premenstrual dysphoric disorder and psychiatric co-morbidity

Premenstrual dysphoric disorder (PMDD) can occur co-morbidly with other axis I disorders, particularly mood and anxiety disorders. The data supporting this diagnostic dilemma are reviewed in terms of methodological comparisons between studies. The point prevalence of the co-occurrence of PMDD and other psychiatric disorders is discussed as well as implications for treatment and further study.

Factor analysis of the metabolic syndrome among elderly Koreans--the South-west Seoul Study

AIMS

To examine the relationship between the components of the metabolic syndrome and to explore whether insulin resistance unifies the clustering of components of the metabolic syndrome among urban elderly Koreans using exploratory factor analysis.

METHODS

We included 1314 non-diabetic subjects over the age of 60 years, selected from a cross-sectional study, which was conducted in 1999 in Seoul, Korea. Factor analysis was carried out using the principle components analysis with Varimax orthogonal rotation of the components of the metabolic syndrome.

RESULTS

We found four major factors of cardiovascular disease risk variables in our study subjects. Impaired glucose tolerance, dyslipidaemia, hypertension and obesity aggregated as the major domain. Obesity and dyslipidaemia variables were closely related and loaded on the same factor. However, hypertension was not linked closely with other factors of the metabolic syndrome.

CONCLUSIONS

Insulin resistance is not the only contributor to the metabolic syndrome among urban elderly Koreans. Although the components of the metabolic syndrome were closely related, the finding of more than one factor suggests that more than one pathophysiological mechanism underlies full expression of the metabolic syndrome among elderly Koreans.

Comparison of ADA and WHO criteria for the diagnosis of diabetes in elderly Koreans

AIMS

This study was conducted to compare the prevalence and cardiovascular risk factors of different categories of glucose tolerance in the elderly Korean population using World Health Organization (WHO) and American Diabetes Association (ADA) criteria.

METHODS

This study included 1456 non-diabetic subjects over the age of 60 years, selected from a cross-sectional study, which was conducted in 1999 in Seoul, Korea. Fasting and post-challenge 2-h plasma glucose, insulin levels, body mass index (BMI), waist-hip ratio (WHR), blood pressure, and lipid profiles were examined. Prevalence of glucose tolerance categories and the level of agreement (kappa statistics) were obtained using WHO 2-h criteria and ADA fasting criteria. Comparison of cardiovascular risk factors among several concordant and discordant glucose intolerance groups was done.

RESULTS

The prevalence rates of newly diagnosed diabetes of elderly men defined by WHO 2-h criteria and ADA fasting criteria were 11.8% and 4.8%, respectively. That of elderly women was 8.1% by WHO 2-h criteria and 3.1% by ADA fasting criteria. The prevalence of impaired glucose tolerance (IGT) by WHO criteria was also higher than that of impaired fasting glucose (IFG) by ADA criteria (23.5% vs. 10.0% men, 23.7% vs. 7.5% women). The level of agreement between ADA fasting criteria and WHO 2-h criteria was low (weighted kappa = 0.228 men, weighted kappa = 0.301 women). The concordant diabetic women by both ADA fasting criteria and WHO 2-h criteria showed higher BMI, WHR, diastolic blood pressure, total cholesterol and triglyceride levels than concordant normal subjects. However, the isolated post-challenge hyperglycaemia (IPH) women group was not different significantly from the concordant normal women group except in BMI.

CONCLUSIONS

Our results clearly show that the 1997 ADA fasting criteria are less sensitive for diagnosing diabetes than oral glucose tolerance test (OGTT)-based WHO criteria in elderly Koreans. Also, there is a poor agreement of different categories of glucose tolerance between ADA and WHO criteria; therefore, the OGTT remains a valuable test in diagnosing diabetes and classifying various categories of glucose intolerance, especially in elderly Koreans.

Cloning and expression of novel mosaic serine proteases with and without a transmembrane domain from human lung

Two cDNAs encoding novel mosaic proteins with a serine protease domain and potential regulatory modules, consisting of a protein kinase substrate and a low-density lipoprotein receptor, were cloned from a human lung cDNA library by PCR. One with a transmembrane domain (MSPL) and the other without one (MSPS) comprise 581 and 537 amino acids, respectively. Except for the C-terminal ends, the two isoforms had an identical serine protease domain exhibiting 42, 39 and 43% identity with those of plasma kallikrein, hepsin and transmembrane protease serine 2, respectively. Both genes were predominantly expressed in human lung, placenta, pancreas and prostate.