3D Fabrication of Fully Iron Magnetic Microrobots.

Biocompatibility and high responsiveness to magnetic fields are fundamental requisites to translate magnetic small-scale robots into clinical applications. The magnetic element iron exhibits the highest saturation magnetization and magnetic susceptibility while exhibiting excellent biocompatibility characteristics. Here, a process to reliably fabricate iron microrobots by means of template-assisted electrodeposition in 3D-printed micromolds is presented. The 3D molds are fabricated using a modified two-photon absorption configuration, which overcomes previous limitations such as the use of transparent substrates, low writing speeds, and limited depth of field. By optimizing the geometrical parameters of the 3D molds, metallic structures with complex features can be fabricated. Fe microrollers and microswimmers are realized that demonstrate motion at ≈20 body lengths per second, perform 3D motion in viscous environments, and overcome higher flow velocities than those of "conventional 3D printed helical microswimmers." The cytotoxicity of these microrobots is assessed by culturing them with human colorectal cancer (HCT116) cells for four days, demonstrating their good biocompatibility characteristics. Finally, preliminary results regarding the degradation of iron structures in simulated gastric acid liquid are provided.

Twisted Linker Effect on Naphthalene Diimide-Based Dimer Electron Acceptors for Non-fullerene Organic Solar Cells.

Naphthalene diimide (NDI) dimers, NDI-Ph-NDI with a phenyl linker and NDI-Xy-NDI with a xylene linker, are designed and synthesized. The influence of the xylene and phenyl linkers on optical properties, electrochemical properties, morphology, and device performance is systematically investigated. Non-fullerene organic solar cells (OSCs) with NDI-Ph-NDI show poor device efficiency due to aggregation of polymer chains and/or NDI dimers caused by the highly planar structure of NDI-Ph-NDI. Although NDI-Xy-NDI is a non-planar structure, uniform surface morphology and weak bimolecular recombination lead to high power conversion efficiencies of 3.11%, which is the highest value in non-fullerene OSCs with NDI small molecules.

Conservative Treatment of Multiple Keratocystic Odontogenic Tumors in a Young Patient with Nevoid Basal Cell Carcinoma Syndrome by Decompression: A 7-year Follow-up Study.

Multiple keratocystic odontogenic tumors (KCOT) occurred in a young child is challenging problem in the field of pediatric dentistry, and might have been related to nevoid basal cell carcinoma syndrome (NBCCS). Because of high recurrence rate of KCOTs, complete surgical resection is generally accepted as definitive treatment. However, complete surgical resection could induce negative effect on the development of permanent teeth and growth of jaw. Herein, we reported successful treatment case of young KCOT patient with NBCCS. Although multiple KCOTs occurred continually, the majority of the lesions healed well by decompression and important anatomical structures and permanent teeth were successfully preserved. The purpose of this paper is to report more conservative treatment of multiple keratocystic odontogenic tumors (KCOTs) by repeated decompressions with later peripheral ostectomy during a 7-year follow-up.

CO2 - and O2 -sensitive fluorophenyl end-capped poly(ethylene glycol).

Pentafluorophenyl end-capped poly(ethylene glycol) (PF-PEG-PF) aqueous solution shows a lower critical solution temperature (LCST), which is sensitive to the type of gases dissolved in the solution. LCST increases from 24.5 to 26 °C when dissolved carbon dioxide is replaced by oxygen. The transparent-to-turbid transition is reversibly observed when the dissolved carbon dioxide in the PF-PEG-PF aqueous solution is exchanged with oxygen, and vice versa, at 24.5 °C. (19) F NMR and (1) H NMR spectra of the PF-PEG-PF in D2 O suggest that 1) dehydration of PEG is the main reason of developing LCST of the PF-PEG-PF aqueous solution, 2) minute differences in the intermolecular interactions, as demonstrated by changes in the chemical shift of the PF-PEG-PF peaks, induce such a difference in LCST. This paper provides a new insight in designing a stimuli-responsive polymer in that fine tuning of a phase transition can be controlled by the type of dissolved gas.

Multipositional silica-coated silver nanoparticles for high-performance polymer solar cells.

We demonstrate high-performance polymer solar cells using the plasmonic effect of multipositional silica-coated silver nanoparticles. The location of the nanoparticles is critical for increasing light absorption and scattering via enhanced electric field distribution. The device incorporating nanoparticles between the hole transport layer and the active layer achieves a power conversion efficiency of 8.92% with an external quantum efficiency of 81.5%. These device efficiencies are the highest values reported to date for plasmonic polymer solar cells using metal nanoparticles.

Large-Area Printed Oxide Film Sensors Enabling Ultrasensitive and Dual Electrical/Colorimetric Detection of Hydrogen at Room Temperature.

Commercial hydrogen (H2) sensors operate at high temperatures, which increases power consumption and poses a safety risk owing to the flammable nature of H2. Here, a polymer-noble metal-metal oxide film is fabricated using the spin-coating and printing methods to realize a highly sensitive, low-voltage operation, wide-operating-concentration, and near-monoselective H2 sensor at room temperature. The H2 sensors with an optimized thickness of Pd nanoparticles and SnO2 showed an extremely high response of 16,623 with a response time of 6 s and a recovery time of 5 s at room temperature and 2% H2. At the same time, printed flexible sensors demonstrate excellent sensitivity, with a response of 2300 at 2% H2. The excellent sensing performance at room temperature is due to the optimal SnO2 thickness, corresponding to the Debye length and the oxygen and H2 spillover caused by the optimized coverage of the Pd catalyst. Furthermore, multistructures of WO3 and SnO2 films are used to fabricate a new type of dual-signal sensor, which demonstrated simultaneous conductance and transmittance, i.e., color change. This work provides an effective strategy to develop robust, flexible, transparent, and long-lasting H2 sensors through large-area printing processes based on polymer-metal-metal oxide nanostructures.

Multifunctional conjugated polymers with main-chain donors and side-chain acceptors for dye sensitized solar cells (DSSCs) and organic photovoltaic cells (OPVs).

A novel multifunctional conjugated polymer (RCP-1) composed of an electron-donating backbone (carbazole) and an electron-accepting side chain (cyanoacetic acid) connected through conjugated vinylene and terthiophene has been synthesized and tested as a photosensitizer in two major molecule-based solar cells, namely dye sensitized solar cells (DSSCs) and organic photovoltaic cells (OPVs). Promising initial results on overall power conversion efficiencies of 4.11% and 1.04% are obtained from the basic structure of DSSCs and OPVs based on RCP-1, respectively. The well-defined donor (D)-acceptor (A) structure of RCP-1 has made it possible, for the first time, to reach over 4% of power conversion efficiency in DSSCs with an organic polymer sensitizer and good operation stability.

Membrane perturbation by the antimicrobial peptide PMAP-23: a fluorescence and molecular dynamics study.

Several bioactive peptides exert their biological function by interacting with cellular membranes. Structural data on their location inside lipid bilayers are thus essential for a detailed understanding of their mechanism of action. We propose here a combined approach in which fluorescence spectroscopy and molecular dynamics (MD) simulations were applied to investigate the mechanism of membrane perturbation by the antimicrobial peptide PMAP-23. Fluorescence spectra, depth-dependent quenching experiments, and peptide-translocation assays were employed to determine the location of the peptide inside the membrane. MD simulations were performed starting from a random mixture of water, lipids and peptide, and following the spontaneous self-assembly of the bilayer. Both experimental and theoretical data indicated a peptide location just below the polar headgroups of the membrane, with an orientation essentially parallel to the bilayer plane. These findings, together with experimental results on peptide-induced leakage from large and giant vesicles, lipid flip-flop and peptide exchange between vesicles, support a mechanism of action consistent with the "carpet" model. Furthermore, the atomic detail provided by the simulations suggested the occurrence of an additional, more specific and novel mechanism of bilayer destabilization by PMAP-23, involving the unusual insertion of charged side chains into the hydrophobic core of the membrane.

Foveal Microvascular Structures in Eyes with Silicone Oil Tamponade for Rhegmatogenous Retinal Detachment: A Swept-source Optical Coherence Tomography Angiography Study.

Silicone oil (SO) is widely used as a long-term intravitreal tamponading agent for rhegmatogenous retinal detachment (RRD) repair. This study investigated the structural changes of the foveal microvasculature using optical coherence tomography angiography (OCTA) in patients with RRD treated with vitrectomy and SO tamponade. Thirty-eight patients with unilateral RRD who were treated with vitrectomy and SO tamponade and were followed up for ≥3 months after SO removal were included. En face OCTA images were obtained and foveal avascular zone (FAZ) area and vascular density (VD) were compared between study eyes and unaffected contralateral eyes. The FAZ area in deep capillary plexus (DCP) was larger (P < 0.001) and the VD in DCP was lower (P = 0.022) in the study eyes than in the fellow eyes. The duration of SO tamponade was significantly correlated with the enlargement of FAZ area (P = 0.034) and reduction of VD in DCP (P = 0.015). These changes could reflect vascular insufficiency in eyes with SO tamponade and may represent a potential explanation for the pathogenesis of retinal thinning and unexplained visual loss.

Development of inlaid electrodes for whole column electrochemical detection in HPLC.

An electrochemical microfluidic device has been fabricated on PET (polyethylene terephthalate) substrate using an imprinting method. The imprinting transfers patterns from a stamp into a substrate mechanically. However, a blanket mould imprinting process has been introduced to embed the photolithographically produced gold metal electrode lines into the PET substrate resulting in an individually addressable array flush to better than 100 nm. The device formed one wall of a packed chromatography column. The array was electrochemically characterised using standard redox probes in both stagnant conditions and under flow. Both numerical modelling and experimental data show improved sensitivity under flow and a limiting current which scaled linearly with the cube root of the volume flow rate. A chromatographic separation of the bioanalytical significant neurotransmitter dopamine (DA) and its metabolite DOPAC was achieved and electrochemically detected at multiple locations within the column. The PET device was stable and robust to leaks to pressures well in excess of those required for chromatographic separations.

Magnetically Actuated Degradable Microrobots for Actively Controlled Drug Release and Hyperthermia Therapy.

Microrobots facilitate targeted therapy due to their small size, minimal invasiveness, and precise wireless control. A degradable hyperthermia microrobot (DHM) with a 3D helical structure is developed, enabling actively controlled drug delivery, release, and hyperthermia therapy. The microrobot is made of poly(ethylene glycol) diacrylate (PEGDA) and pentaerythritol triacrylate (PETA) and contains magnetic Fe3 O4 nanoparticles (MNPs) and 5-fluorouracil (5-FU). Its locomotion is remotely and precisely controlled by a rotating magnetic field (RMF) generated by an electromagnetic actuation system. Drug-free DHMs reduce the viability of cancer cells by elevating the temperature under an alternating magnetic field (AMF), a hyperthermic effect. 5-FU is released from the proposed DHMs in normal-, high-burst-, and constant-release modes, controlled by the AMF. Finally, actively controlled drug release from the DHMs in normal- and high-burst-release mode results in a reduction in cell viability. The reduction in cell viability is of greater magnitude in high-burst- than in normal-release mode. In summary, biodegradable DHMs have potential for actively controlled drug release and hyperthermia therapy.

Magnetically Actuated SiCN-Based Ceramic Microrobot for Guided Cell Delivery.

A silicon carbonitride (SICN) ceramic microrobot, biocompatible and magnetically activable, is developed for the delivery of viable cells to defective tissue by sequential steps of microstructuring, magnetization, and cell loading. The ceramic carrier of porous cylindrical framework is fabricated by 3D laser lithography using a photocurable preceramic polymer, chemically modified polyvinylsilazane, and subsequent pyrolysis at 600 °C under an inert atmosphere. Magnetic nanoparticles (MNP) are integrated into the surface-modified ceramic carrier by thiol-ene click reaction. Finally, the microrobot is loaded with fibroblast cells, which can be guided by a rotating external magnetic field. The proposed ceramic microrobot is mechanically durable, adequately controllable with external magnetic field, and quite compatible with mammalian cells.

A 3D Microscaffold Cochlear Electrode Array for Steroid Elution.

In cochlear implants, the electrode insertion trauma during surgery can cause damage residual hearing. Preserving the residual hearing is an important challenge and the localized administration of drugs, such as steroids, is one of the most promising ways, but remains a challenge. Here, a microscaffold cochlear electrode array (MiSCEA) consisting of a microfabricated flexible electrode array and a 3D microscaffold for steroid reservoir is reported. The MiSCEA without loaded drug is tested by measuring the electrically evoked auditory brainstem response of the cochlea in guinea pigs (n = 4). The scaffold is then coated with steroid (dexamethasone) encapsulated in polylactic-co-glycolic acid and the continuous release of the steroid into artificial perilymph during six weeks is monitored. The steroid-containing scaffolds are then implanted into guinea pigs (n = 4) and threshold shifts are analyzed for four weeks by measuring the acoustically evoked auditory brainstem response. The threshold shifts tend to be lower in the group implanted with the steroid-containing MiSCEAs. The feasibility of 3D MiSCEA opens up the development of potential next-generation cochlear electrode with improved steroid release dynamics into cochlea.

Two-axis polydimethylsiloxane-based electromagnetic microelectromechanical system scanning mirror for optical coherence tomography.

Compact size and fast imaging abilities are key requirements for the clinical implementation of an optical coherence tomography (OCT) system. Among the various small-sized technology, a microelectromechanical system (MEMS) scanning mirror is widely used in a miniaturized OCT system. However, the complexities of conventional MEMS fabrication processes and relatively high costs have restricted fast clinical translation and commercialization of the OCT systems. To resolve these problems, we developed a two-axis polydimethylsiloxane (PDMS)-based MEMS (2A-PDMS-MEMS) scanning mirror through simple processes with low costs. It had a small size of 15×15×15??mm3, was fast, and had a wide scanning range at a low voltage. The AC/DC responses were measured to evaluate the performance of the 2A-PDMS-MEMS scanning mirror. The maximum scanning angles were measured as ±16.6??deg and ±11.6??deg along the X and Y axes, respectively, and the corresponding field of view was 29.8??mm×20.5??mm with an optical focal length of 50 mm. The resonance frequencies were 82 and 57 Hz along the X and Y axes, respectively. Finally, in vivo B-scan and volumetric OCT images of human fingertips and palms were successfully acquired using the developed SD-OCT system based on the 2A-PDMS-MEMS scanning mirror.

Soft network composite materials with deterministic and bio-inspired designs.

Hard and soft structural composites found in biology provide inspiration for the design of advanced synthetic materials. Many examples of bio-inspired hard materials can be found in the literature; far less attention has been devoted to soft systems. Here we introduce deterministic routes to low-modulus thin film materials with stress/strain responses that can be tailored precisely to match the non-linear properties of biological tissues, with application opportunities that range from soft biomedical devices to constructs for tissue engineering. The approach combines a low-modulus matrix with an open, stretchable network as a structural reinforcement that can yield classes of composites with a wide range of desired mechanical responses, including anisotropic, spatially heterogeneous, hierarchical and self-similar designs. Demonstrative application examples in thin, skin-mounted electrophysiological sensors with mechanics precisely matched to the human epidermis and in soft, hydrogel-based vehicles for triggered drug release suggest their broad potential uses in biomedical devices.

Correlation between dispersion properties of TiO2 colloidal sols and photoelectric characteristics of TiO2 films.

TiO2 film for use as dye-sensitized solar cell was prepared using the TiO2 colloidal sols (unpeptized sol and peptized sol). The optical properties and photocurrent-voltage characteristics of the resultant films were investigated. The optical transmittance of TiO2 thin film prepared from the peptized colloidal sol was over 90%, while that of TiO2 film from the unpeptized sol was under 80%. The TiO2 photoelectrode prepared from the peptized colloidal sol showed low photoelectric conversion efficiency (eta), 1.30%, whereas the efficiency of photoelectrode from the unpeptized sol was 2.21%. The high optical transmittance and low conversion efficiency of TiO2 film from the peptized sol are discussed in terms of dense microstructure due to the drying nature of well-dispersed colloidal sol.

Nonallergenic urushiol derivatives inhibit the oxidation of unilamellar vesicles and of rat plasma induced by various radical generators.

Urushiols consist of an o-dihydroxybenzene (catechol) structure and an alkyl chain of 15 or 17 carbons in the 3-position of a benzene ring and are allergens found in the family Anacardiaceae. We synthesized various veratrole (1,2-dimethoxybenzene)-type and catechol-type urushiol derivatives that contained alkyl chains of various carbon atom lengths, including -H, -C1H3, -C5H11, -C10H21, -C15H31, and -C20H41, and investigated their contact hypersensitivities and antioxidative activities. 3-Decylcatechol and 3-pentadecylcatechol displayed contact hypersensitivity, but the other compounds did not induce an allergic reaction, when the ears of rats were sensitized by treatment with the compounds every day for 20 days. Catechol-type urushiol derivatives (CTUDs) exerted very high radical-scavenging activity on the 1,1-diphenyl-2-picrylhydrazyl radical and inhibited lipid peroxidation in a methyl linoleate solution induced by 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN). However, veratrole-type urushiol derivatives did not scavenge or inhibit lipid peroxidation. CTUDs also acted as effective inhibitors of lipid peroxidation of the egg yolk phosphatidylcholine large unilamellar vesicle (PC LUV) liposome system induced by various radical generators such as AMVN, 2,2'-azobis(2-amidino-propane) dihydrochloride, and copper ions, although their efficiencies differed slightly. In addition, CTUDs suppressed formation of cholesteryl ester hydroperoxides in rat blood plasma induced with copper ions. CTUDs containing more than five carbon atoms in the alkyl chain showed excellent lipophilicity in a n-octanol/water partition experiment. These compounds also exhibited high affinities to the liposome membrane using the ultrafiltration method of the PC LUV liposome system. Therefore, CTUDs seem to act as efficient antioxidative compounds against membranous lipid peroxidation owing to their localization in the phospholipid bilayer. These results suggest that nonallergenic CTUDs act as antioxidants to protect against oxidative damage of cellular and subcellular membranes.

Hypoxia promotes CEMP1 expression and induces cementoblastic differentiation of human dental stem cells in an HIF-1-dependent manner.

Cementum covering the tooth root provides attachment for the tooth proper to the surrounding alveolar bone via non-mineralized periodontal ligament (PDL). Cementum protein 1 (CEMP1) has been shown to induce a cementoblastic phenotype in cementoblast precursors cells of PDL. Oxygen availability is a critical signal for correct development of many tissues; however, its role in tooth root and periodontium development remains poorly understood. In this study, we demonstrated that reduced oxygen tension increased CEMP1 expression, mineral deposition, and alkaline phosphatase activity in human dental stem cells such as PDL stem cells and periapical follicular stem cells. Since an oxemic state is transduced by the transcription factor, hypoxia-inducible factor-1 (HIF-1), we performed experiments to determine whether this protein was responsible for the observed changes. We noted that when HIF-1 was activated by gene introduction or chemically, CEMP1 expression and mineralization increased. In contrast, when HIF-1α was silenced, CEMP1 expression and mineralization did not increase in vitro. Furthermore, we showed for the first time that mouse tooth root and periodontium development occurs partly under hypoxic conditions, particularly at the apical part and latently at the PDL space in vivo. Desferrioxamine, an HIF-1 stimulator, enhances CEMP1 expression in the mouse PDL space, suggesting that hypoxia affects cementogenesis of PDL cells lining the surface of the developing tooth root in an HIF-1-dependent manner. These results suggest that HIF-1 activators may have the ability to stimulate regeneration of the tooth root and cementum formation.

Graphene oxide nanoribbon as hole extraction layer to enhance efficiency and stability of polymer solar cells.

Graphene oxide nanoribbons for efficient and stable polymer solar cells are discussed. With controllable bandgap, good solubility and film forming property, graphene oxide nanoribbons serve as a new class of excellent hole extraction materials for efficient and stable polymer solar cells outperforming their counterparts based on conventional hole extraction materials, including PEDOT:PSS.

Redox-active charge carriers of conducting polymers as a tuner of conductivity and its potential window.

Electric conductivity of conducting polymers has been steadily enhanced towards a level worthy of being called its alias, "synthetic metal". PEDOT:PSS (poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate)), as a representative conducting polymer, recently reached around 3,000 S cm(-1), the value to open the possibility to replace transparent conductive oxides. The leading strategy to drive the conductivity increase is solvent annealing in which aqueous solution of PEDOT:PSS is treated with an assistant solvent such as DMSO (dimethyl sulfoxide). In addition to the conductivity enhancement, we found that the potential range in which PEDOT:PSS is conductive is tuned wider into a negative potential direction by the DMSO-annealing. Also, the increase in a redox-active fraction of charge carriers is proposed to be responsible for the enhancement of conductivity in the solvent annealing process.