Development of Organic/Inorganic Hybrid Materials for Fully Degradable Reactive Oxygen Species-Releasing Stents for Antirestenosis.

Despite innovative advances in stent technology, restenosis remains a crucial issue for the clinical implantation of stents. Reactive oxygen species (ROS) are known to potentially accelerate re-endothelialization and lower the risk of restenosis by selectively controlling endothelial cells and smooth muscle cells. Recently, several studies have been conducted to develop biodegradable polymeric stents. As biodegradable polymers are not electrically conductive, double metallic layers are required to constitute a galvanic couple for ROS generation. Here, we report a new biodegradable hybrid material composed of a biodegradable polymer substrate and double anodic/cathodic metallic layers for enhancing re-endothelialization and suppressing restenosis. Pure Zn and Mg films (3 µm thick) were deposited onto poly-l-lactic acid (PLLA) substrates by DC magnetron sputtering, and a long-term immersion test using biodegradable hybrid materials was performed in phosphate-buffered solution (PBS) for 2 weeks. The concentrations of superoxide anions and hydrogen peroxide generated by the corrosion of biodegradable metallic films were monitored every 1 or 2 days. Both superoxide anions and hydrogen peroxide were seamlessly generated even after the complete consumption of the anodic Mg layer. It was confirmed that the superoxide anions and hydrogen peroxide were formed not only by the galvanic corrosion between the anode and cathode layers but also by the corrosion of a single Mg or Zn layer. The corrosion products of the Mg and Zn films in PBS were phosphate, oxide, or chloride of the biodegradable metals. Thus, it is concluded that ROS generation by the corrosion of PLLA-based hybrid materials can be sustained until the exhaustion of the cathode metal layer.

Rapid Synthesis of Multifunctional Apatite via the Laser-Induced Hydrothermal Process.

Synthetic biomaterials are used to overcome the limited quantity of human-derived biomaterials and to impart additional biofunctionality. Although numerous synthetic processes have been developed using various phases and methods, currently commonly used processes have some issues, such as a long process time and difficulties with extensive size control and high-concentration metal ion substitution to achieve additional functionality. Herein, we introduce a rapid synthesis method using a laser-induced hydrothermal process. Based on the thermal interaction between the laser pulses and titanium, which was used as a thermal reservoir, hydroxyapatite particles ranging from nanometer to micrometer scale could be synthesized in seconds. Further, this method enabled selective metal ion substitution into the apatite matrix with a controllable concentration. We calculated the maximum temperature achieved by laser irradiation at the surface of the thermal reservoir based on the validation of three simplification assumptions. Subsequent linear regression analysis showed that laser-induced hydrothermal synthesis follows an Arrhenius chemical reaction. Hydroxyapatite and Mg2+-, Sr2+-, and Zn2+-substituted apatite powders promoted bone cell attachment and proliferation ability due to ion release from the hydroxyapatite and the selective ion-substituted apatite powders, which had a low crystallinity and relatively high solubility. Laser-induced hydrothermal synthesis is expected to become a powerful ceramic material synthesis technology.

Microscale Biosensor Array Based on Flexible Polymeric Platform toward Lab-on-a-Needle: Real-Time Multiparameter Biomedical Assays on Curved Needle Surfaces.

In vivo sensing of various physical/chemical parameters is gaining increased attention for early prediction and management of various diseases. However, there are major limitations on the fabrication method of multiparameter needle-based in vivo sensing devices, particularly concerning the uniformity between sensors. To address these challenges, we developed a microscale biosensor array for the measurement of electrical conductivity, pH, glucose, and lactate concentrations on a flexible polymeric polyimide platform with electrodeposited electrochemically active layers. The biosensor array was then transferred to a medical needle toward multiparametric in vivo sensing. The flexibility of the sensor platform allowed an easy integration to the curved surface (φ = 1.2 mm) of the needle. Furthermore, the electrodeposition process was used to localize various active materials for corresponding electrochemical sensors on the microscale electrodes with a high precision (patterning area = 150 µm × 2 mm). The biosensor array-modified needle was aimed to discriminate cancer from normal tissues by providing real-time discrimination of glucose, lactate concentration, pH, and electrical conductivity changes associated with the cancer-specific metabolic processes. The sensor performance was thus evaluated using solution samples, covering the physiological concentrations for cancer discrimination. Finally, the possibility of in vivo electrochemical biosensing during needle insertion was confirmed by utilizing the needle in a hydrogel phantom that mimicked the normal and cancer microenvironments.

Synergetic Effect of Porous Elastomer and Percolation of Carbon Nanotube Filler toward High Performance Capacitive Pressure Sensors.

Wearable pressure sensors have been attracting great attention for a variety of practical applications, including electronic skin, smart textiles, and healthcare devices. However, it is still challenging to realize wearable pressure sensors with sufficient sensitivity and low hysteresis under small mechanical stimuli. Herein, we introduce simple, cost-effective, and sensitive capacitive pressure sensor based on porous Ecoflex-multiwalled carbon nanotube composite (PEMC) structures, which leads to enhancing the sensitivity (6.42 and 1.72 kPa-1 in a range of 0-2 and 2-10 kPa, respectively) due to a synergetic effect of the porous elastomer and percolation of carbon nanotube fillers. The PEMC structure shows excellent mechanical deformability and compliance for an effective integration with practical wearable devices. Also, the PEMC-based pressure sensor shows not only the long-term stability, low-hysteresis, and fast response under dynamic loading but also the high robustness against temperature and humidity changes. Finally, we demonstrate a prosthetic robot finger integrated with a PEMC-based pressure sensor and an actuator as well as a healthcare wristband capable of continuously monitoring blood pressure and heart rate.

Femtosecond laser induced nano-textured micropatterning to regulate cell functions on implanted biomaterials.

Posterior capsular opacification (PCO) is the most common complication of cataract surgery. PCO is due to the proliferation, migration, and epithelial-to-mesenchymal transition of the residual lens epithelial cells (LECs) within the lens capsule. As surface topography influences cellular response, we investigated the effect of modulating the dimensions of periodic nano-textured patterns on the surface of an intraocular lens material to regulate lens epithelial cell functions such as cell adhesion, migration, orientation, and proliferation. Patterned poly(HEMA) samples were prepared by a femtosecond laser microfabrication, and the behaviors of human B-3 LECs were observed on groove/ridge patterns with widths varying from 5 to 40 µm. In the presence of ridge and groove patterns, the adherent cells elongated along the direction of the patterns, and f-actin of the cells was spread to a lesser extent on the nano-textured groove surfaces. Both single and collective cell migrations were significantly inhibited in the perpendicular direction of the patterns on the nano-textured micro-patterned samples. We also fabricated the patterns on the curved surface of a commercially available intraocular lens for in vivo evaluation. In vivo results showed that a patterned IOL could help suppress the progression of PCO by inhibiting cell migration from the edge to the center of the IOL. Our reports demonstrate that nano- and microscale topographical patterns on a biomaterial surface can regulate cellular behavior when it is implanted into animals.

Airway obstruction by dissection of the inner layer of a reinforced endotracheal tube in a patient with Ludwig's angina: A case report.

Intraoperative airway obstruction is perplexing to anesthesiologists because the patient may fall into danger rapidly. A 74-year-old woman underwent an emergency incision and drainage for a deep neck infection of dental origin. She was orally intubated with a 6. 0 mm internal diameter reinforced endotracheal tube by video laryngoscope using volatile induction and maintenance anesthesia (VIMA) with sevoflurane, fentanyl (100 µg), and succinylcholine (75 mg). During surgery, peak inspiratory pressure increased from 22 to 38 cmH2O and plateau pressure increased from 20 to 28 cmH2O. We maintained anesthesia because we were unable to access the airway, which was covered with surgical drapes, and tidal volume was delivered. At the end of surgery, we found a longitudinal fold inside the tube with a fiberoptic bronchoscope. The patient was reintubated with another tube and ventilation immediately improved. We recognized that the tube was obstructed due to dissection of the inner layer.

Ultrathin Metal Films with Defined Topographical Structures as In Vitro Cell Culture Platforms for Unveiling Vascular Cell Behaviors.

Implanted material surfaces make direct contact with body tissues to work on its own purpose. Therefore, studies of the surface properties of implantable materials that determine cell fate are very important for successful implantation. Although numerous studies have addressed the relationship between cells and material surfaces, nonmetallic surfaces and metallic surfaces likely produce different cellular responses because of their intrinsic differences in surface energy, roughness, and chemical composition. Moreover, given the nontransparent property of metal materials, which hampers the real-time imaging of cellular behavior, a detailed cellular-level analysis at the metal-tissue interface has not been performed. In this study, metal-based cell culture platforms (MCPs) with defined microscale topographical patterns are developed using a combination of photolithography and direct current magnetron sputtering techniques. The MCPs allow to observe vascular cells on metals in real time and identify the selective regulation of human aortic smooth muscle cells and Human umbilical vein endothelial cells (HUVECs) by metallic surface topography. Additionally, atomic force microscopy, contact angles, and energy-dispersive X-ray spectroscopy analyses show that the MCPs exhibit nearly identical chemical properties with their bulk counterparts, demonstrating that MCPs can be utilized as an in vitro cell culture platform system for understanding the cellular behavior on metal substrates.