Self-controllable proteinic antibacterial coating with bacteria-triggered antibiotic release for prevention of periprosthetic infection.

Periprosthetic infection is a devastating postimplantation complication in which a biofilm layer harboring invasive microorganisms forms around orthopedic implants, leading to severe implant failure and patient morbidity. Despite the development of several infection-triggered antibiotic release approaches, most current antibacterial coatings are susceptible to undesired antibiotic leakage or mechanical disintegration during prosthesis installation. Herein, we propose a self-controllable proteinic antibacterial coating capable of both long-lasting adherence onto titanium implant substrates over the implant fixation period and instantaneous bacterial eradication. Importantly, the pH-dependent reversible metal coordination of mussel adhesive protein (MAP) enabled bacterial concentration-dependent antibiotic delivery in response to infection-induced acidification. In addition, the MAP coating exhibited superior self-healable adhesive properties and scratch resistance, which enabled to avert issues associated with mechanical damages, including peeling and cracking, often occurring in conventional implant coating systems. The gentamicin-loaded MAP coating exhibited complete inhibition of bacterial growth in vivo against Staphylococcus aureus penetrations during implantation surgery (immediate infection) and even 4 weeks after implantation (delayed infection). Thus, our antibiotic-loaded MAP hydrogel coating can open new avenues for self-defensive antibiotic prophylaxis to achieve instant and sustainable bacteriocidal activity in orthopedic prostheses. © 2017 Elsevier Inc. All rights reserved.

Construction of a vector-field cryogenic magnetic force microscope.

Owing to the high resolution of magnetic force microscopes (MFMs) operating at low temperatures and high-applied magnetic fields, they can be employed to study various phenomena observed in topological magnetic materials and superconductors. In this study, we constructed a low-temperature MFM equipped with a 2-2-9-T vector magnet and a three-axis fiber-optic alignment system. The three-axis alignment device enables in situ calibration of the scanner at low temperatures as well as optimizes the intensity and sensitivity of the interferometer signal. A massive homebuilt vibration isolation table lowers the resonance frequency of the system and minimizes mechanical noise. Consequently, the minimum detectable force gradient of our proposed model is close to the thermodynamic limit of the cantilever. To demonstrate the low-temperature capability of the MFM, we obtained magnetic domain images of the van der Waals ferromagnet Fe4GeTe2 and the Abrikosov superconducting vortices of an Nb film. Furthermore, we performed field angle-dependent MFM experiments in a van der Waals magnetic insulator Cr2Ge2Te6 to verify its vector-field functionality and observed a transition in the domains from the stripe to the bubble phase with respect to the magnetic field angle. The vector-field capability of our MFM can be useful for investigating various anisotropic magnetic phenomena in topological magnetic and superconducting materials.

Bone Graft Biomineral Complex Coderived from Marine Biocalcification and Biosilicification.

Bone graft materials have been mainly developed based on inorganic materials, including calcium phosphate. However, these graft materials usually act as osteoconductive rather than osteoinductive scaffolds. To improve bone reconstruction, a combination of several materials has been proposed. However, there are still no alternatives that can completely replace the existing animal-derived bone graft materials. In this work, a marine-inspired biomineral complex was suggested as a potential bone graft material. The proposed biosilicified coccolithophore-derived coccoliths using bioengineered mussel adhesive proteins show osteopromotive ability through the synergistic effects of osteoconductivity from calcium carbonate and osteoinductivity from silica. Its possibility of use as a bone substitute was determined by evaluating the in vitro osteogenic behaviors of multipotent mesenchymal stem cells and in vivo bone regeneration in a rat calvarial defect model. Therefore, the marine-inspired biomineral complex developed in this study could be successfully used for bone tissue engineering.

Understanding of the aging pattern in quantum dot light-emitting diodes using low-frequency noise.

The negative and positive aging effects of quantum dot (QD) light-emitting diodes (QLEDs) have received considerable attention in recent years and various analysis methods have been discussed. Here, we introduce a new approach to understand the aging effect of QLEDs, which is to diagnose the behavior of carriers and traps at interfaces between each layer of the QLEDs and inside the layers themselves. In particular, low-frequency noise (LFN) measurement and the analysis of current in the QLEDs were introduced to investigate the trapping/de-trapping behaviors of carriers in the defect states in the devices. A flicker noise was observed before the carriers are injected into the QD emitting layer, while the exciton generation-recombination (G-R) noise and shot noise were observed when the electrons were injected. A correlated noise, which is the correlated model of the trapping/de-trapping of the carriers near and/or inside the QDs and the exciton recombination, was also observed above the turn-on voltage. In addition, when the devices were aged with a constant current source, rapid increases in the luminance and external quantum efficiency (EQE) were observed for up to 50 h. After 100 h of the current aging, however, the devices were negatively aged with the reduced EQE. The LFN analysis results imply that the aging phenomena mainly depend on the trapping/de-trapping of carriers. In addition to the LFN analysis, we also investigated the current density-voltage-luminance and capacitance-voltage characteristics of the devices to clarify the aging behaviors in QLEDs.

Enhanced efficiency and high temperature stability of hybrid quantum dot light-emitting diodes using molybdenum oxide doped hole transport layer.

High power efficiency (PE) and stability of quantum dot (QD) light-emitting diodes (QLEDs) are important factors for practical use in various displays. However, hybrid QLEDs consisting of an organic hole transport layer (HTL) and an inorganic electron transport layer (ETL) sometimes have poor stability due to the low thermal stability of the organic HTL. To solve the problem, here, we report enhanced efficiency, lifetime, and temperature stability in inverted and hybrid structured QLEDs by adopting a MoO3-doped HTL. Also, to improve the electron-hole charge carrier balance, a thin insulating interlayer was used between QDs and the ETL. As a result, the QLED with the p-doped HTL exhibited the increased PE by ∼28% and longer lifetime compared to the pristine QLEDs. In addition, the QLED showed stable operation at the high temperature up to 400 K, whereas the control device failed to operate at 375 K. We systematically investigated the effect of the MoO3-doping on the performance and thermal stability of the QLEDs. We believe that QLEDs with the p-doped HTL can be used for further QLED researches to simultaneously improve the efficiency, lifetime, and high temperature stability, which are highly required for their use in automotive and outdoor displays.