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Biliary strictures are characterized by the narrowing of the bile duct lumen, usually caused by surgical biliary injury, cancer, inflammation, and scarring from gallstones. Endoscopic stent placement is a well-established method for the management of biliary strictures. However, maintaining optimal mechanical properties of stents and designing surfaces that can prevent stent-induced tissue hyperplasia and biofilm formation are challenges in the fabrication of biodegradable biliary stents (BBSs) for customized treatment. This study proposes a novel approach to fabricating functionalized polymer BBSs with nanoengineered surfaces using 3D printing. The 3D printed stents, fabricated from bioactive silica poly(ε-carprolactone) (PCL) via a sol–gel method, exhibited tunable mechanical properties suitable for supporting the bile duct while ensuring biocompatibility. Furthermore, a nanoengineered surface layer was successfully created on a sirolimus (SRL)-coated functionalized PCL (fPCL) stent using Zn ion sputtering-based plasma immersion ion implantation (S-PIII) treatment to enhance the performance of the stent. The nanoengineered surface of the SRL-coated fPCL stent effectively reduced bacterial responses and remarkably inhibited fibroblast proliferation and initial burst release of SRL in vitrosystems. The physicochemical properties and biological behaviors, including in vitrobiocompatibility and in vivotherapeutic efficacy in the rabbit bile duct, of the Zn-SRL@fPCL stent demonstrated its potential as a versatile platform for clinical applications in bile duct tissue engineering.

Background:: Current polymer-based drug-eluting stents (DESs) have fundamental issues about inflammation and delayed re-endothelializaton of the vessel wall. Substance-P (SP), which plays an important role in inflammation and endothelial cells, has not yet been applied to coronary stents. Therefore, this study compares poly lactic-co-glycolic acid (PLGA)-based everolimus-eluting stents (PLGA-EESs) versus 2-methacryloyloxyethyl phosphorylcholine (MPC)-based SP-eluting stents (MPC-SPs) in in-vitroand in-vivomodels. Methods:: The morphology of the stent surface and peptide/drug release kinetics from stents were evaluated. The in-vitroproliferative effect of SP released from MPC-SP is evaluated using human umbilical vein endothelial cell. Finally, the safety and efficacy of the stent are evaluated after inserting it into a pig's coronary artery. Results:: Similar to PLGA-EES, MPC-SP had a uniform surface morphology with very thin coating layer thickness (2.074 μm). MPC-SP showed sustained drug release of SP for over 2 weeks. Endothelial cell proliferation was significantly increased in groups treated with SP (n = 3) compared with the control (n = 3) and those with everolimus (n = 3) (SP: 118.9 ± 7.61% vs. everolimus: 64.3 ± 12.37% vs. the control: 100 ± 6.64%, p< 0.05). In the animal study, the percent stenosis was higher in MPC-SP group (n = 7) compared to PLGA-EES group (n = 7) (MPC-SP: 28.6 ± 10.7% vs. PLGA-EES: 16.7 ± 6.3%, p< 0.05). MPC-SP group showed, however, lower inflammation (MPC-SP: 0.3 ± 0.26 vs. PLGA-EES: 1.2 ± 0.48, p< 0.05) and fibrin deposition (MPC-SP: 1.0 ± 0.73 vs. PLGA-EES: 1.5 ± 0.59, p< 0.05) around the stent strut. MPC-SP showed more increased expression of cluster of differentiation 31, suggesting enhanced re-endothelialization. Conclusion:: Compared to PLGA-EES, MPC-SP demonstrated more decreased inflammation of the vascular wall and enhanced re-endothelialization and stent coverage. Hence, MPC-SP has the potential therapeutic benefits for the treatment of coronary artery disease by solving limitations of currently available DESs.

This paper presents an evaluation method for the interruption capability of direct-current (DC) circuit breakers. We induced various hybrid types of DC circuit breakers (DCCBs) and proposed a suitable DC interruption test method to simulate the scenario of a short circuit occurring in a DC system during normal operation. To analytically estimate the interruption capability of the DCCB, we calculated the magnitude of the DC interruption current, rate of change of current (di/dt), and maximum transient recovery voltage (TIV) using an equivalent circuit model. To experimentally evaluate the interruption capability of the DCCB, we constructed a practical DC interruption test facility based on an equivalent circuit. The measured DC interruption test current was compared with the values calculated using the equivalent circuit model.

Background:: Biodegradable poly (l-lactic acid) (PLLA), a bio safe polymer with a large elastic modulus, is widely used in biodegradable medical devices. However, because of its poor mechanical properties, a PLLA strut must be made twice as thick as a metal strut for adequate blood vessel support. Therefore, the mechanical properties of a drug-eluting metal-based stents (MBS) and a bioresorbable vascular scaffolds (BVS) were evaluated and their safety and efficacy were examined via a long-term rabbit iliac artery model. Methods:: The surface morphologies of the MBSs and BVSs were investigated via optical and scanning electron microscopy. An everolimus-eluting (EE) BVS or an EE-MBS was implanted into rabbit iliac arteries at a 1.1:1 stent-to-artery ratio. Twelve months afterward, stented iliac arteries from each group were analyzed via X-ray angiography, optical coherence tomography (OCT), and histopathologic evaluation. Results:: Surface morphology analysis of the EE coating on the MBS confirmed that it was uniform and very thin (4.7 μm). Comparison of the mechanical properties of the EE-MBS and EE-BVS showed that the latter outperformed the former in all aspects (radial force (2.75 vs. 0.162 N/mm), foreshortening (0.24% vs. 1.9%), flexibility (0.52 vs. 0.19 N), and recoil (3.2% vs. 6.3%). At all time points, the percent area restenosis was increased in the EE-BVS group compared to the EE-MBS group. The OCT and histopathological analyses indicate no significant changes in strut thickness. Conclusion:: BVSs with thinner struts and shorter resorption times should be developed. A comparable long-term safety/efficacy evaluation after complete absorption of BVSs should be conducted.

Background:: We have designed a reinforced drug-loaded vascular graft composed of polycaprolactone (PCL) and polydioxanone (PDO) via a combination of electrospinning/3D printing approaches. To evaluate its potential for clinical application, we compared the in vivoblood compatibility and performance of PCL/PDO + 10%DY grafts doped with an antithrombotic drug (dipyridamole) with a commercial expanded polytetrafluoroethylene (e-PTFE) graft in a porcine model. Methods:: A total of 10 pigs (weight: 25–35 kg) were used in this study. We made a new 5-mm graft with PCL/PDO composite nanofiber via the electrospinning technique. We simultaneously implanted a commercially available e-PTFE graft (n= 5) and our PCL/PDO + 10%DY graft (n= 5) into the carotid arteries of the pigs. No anticoagulant/antiplatelet agent was administered during the follow-up period, and ultrasonography was performed weekly to confirm the patency of the two grafts in vivo. Four weeks later, we explanted and compared the performance of the two grafts by histological analysis and scanning electron microscopy (SEM). Results:: No complications, such as sweating on the graft or significant bleeding from the needle hole site, were seen in the PCL/PDO + 10%DY graft immediately after implantation. Serial ultrasonographic examination and immunohistochemical analysis demonstrated that PCL/PDO + 10%DY grafts showed normal physiological blood flow and minimal lumen reduction, and pulsed synchronously with the native artery at 4 weeks after implantation. However, all e-PTFE grafts occluded within the study period. The luminal surface of the PCL/PDO + 10%DY graft in the transitional zone was fully covered with endothelial cells as observed by SEM. Conclusion:: The PCL/PDO + 10%DY graft was well tolerated, and no adverse tissue reaction was observed in porcine carotid models during the short-term follow-up. Colonization of the graft by host endothelial and smooth muscle cells coupled with substantial extracellular matrix production marked the regenerative capability. Thus, this material may be an ideal substitute for vascular reconstruction and bypass surgeries. Long-term observations will be necessary to determine the anti-thrombotic and remodeling potential of this device.

The recognition capability of the identification system using Raman spectroscopy is increasing with the demands in the field. Among the various approaches that determine the identity of a target, signal correlation using a moving window is one of the most effective and intuitive methods. In this paper, we report a new correlation method that is robust to spectral intensity variations. Using the peak distribution of a given spectrum, this method adaptively determines meaningful spectral regions for the identification target. Three commercial Raman spectrometer and a 14 033 library were included in the study, which was used for a library-based chemical discrimination test and mixed material analysis experiments. According to the identification experimental results, the proposed method correctly identified all of the spectra and maintained a mean correlation score above 0.95 while maintaining the correlation score of nontarget materials as low as possible.

Hydrophobic–hydrophilic hybrid surfaces, sometimes termed biphilic surfaces, have shown potential to enhance condensation and boiling heat transfer, anti-icing, and fog harvesting performance. However, state of art techniques to develop these surfaces have limited substrate selection, poor scalability, and lengthy and costly fabrication methods. Here, we develop a simple, scalable, and rapid stamping technique for hybrid surfaces with spatially controlled wettability. To enable stamping, rationally designed and prefabricated polydimethylsiloxane (PDMS)stamps, which are reusable and independent of the substrate and functional coating, were used. To demonstrate the stamping technique, we used silicon wafer, copper, and aluminum substrates functionalized with a variety of hydrophobic chemistries including heptadecafluorodecyltrimethoxy-silane, octafluorocyclobutane, and slippery omniphobic covalently attached liquids. Condensation experiments and microgoniometric characterization demonstrated that the stamped surfaces have global hydrophobicity or superhydrophobicity with localized hydrophilicity (spots) enabled by local removal of the functional coating during stamping. Stamped surfaces with superhydrophobic backgrounds and hydrophilic spots demonstrated stable coalescence induced droplet jumping. Compared to conventional techniques, our stamping method has comparable prototyping cost with reduced manufacturing time scale and cost. Our work not only presents design guidelines for the development of scalable hybrid surfaces for the study of phase change phenomena, it develops a scalable and rapid stamping protocol for the cost-effective manufacture of next-generation hybrid wettability surfaces.

Scalable and cost-effective protocols to pattern and integrate colloidal quantum dots (QDs) with high resolution have been challenging to establish. While their solubility can facilitate certain processes such as spin-casting into thin films, it also makes them incompatible with many conventional patterning techniques including photolithography that require solution processing. In this work, we present “photoresist (PR) contact patterning”, a dry means to pattern QD films over large areas with high resolution while maintaining desired properties. Here, a PR layer on an elastomer substrate is patterned by conventional photolithography and used as a dry contact stamp to selectively peel off QDs in the contact regions, leaving behind a QD film with the negative of the PR pattern. Once patterned, QD films are readily transferred and integrated on foreign substrates by subsequent transfer printing processes. Patterned PR layers can also be transferred from elastomer substrates onto QD films and used as masking layers for subsequent deposition and patterning of additional materials, e.g., patterned metal electrodes or charge transport layers for QD-based devices. The study of the interfacial mechanics and energy of materials associated with PR contact patterning reveals why a lithographically patterned PR is superior for high-resolution QD film patterning. Applicability of PR contact patterning is demonstrated through the fabrication of red, green, and blue (RGB) QD light-emitting diode pixels. PR contact patterning presented in this work not only allows dry patterning of QD films but also enables high-resolution integration of functional multistack structures for future QD-based electronic and optoelectronic devices.

The aim of this study was to evaluate the effect of ion implantation on the surface of anti-thrombogenic coronary stent. Nitrogen (N) was implanted into the cobalt–chromium surface by using an ion source under a plasma environment to enhance its hardness and surface modification. The N ion dosage was 1 × 10 15 ions/cm 2 . All analysis results of the ion implanted stent were compared with those of bare metal stent. The N component and distribution were confirmed by auger electron spectroscopy. Microhardness was significantly increased after 40 min of implantation (415.3 ± 12.38 HV, 18.9 ± 2.62%). The surface was altered to hydrophobic status through ion implantation (30.6 ± 1.12% in contact angle increment). Platelet adhesion, and smooth muscle cell migration and proliferation were prevented in the ion implanted group (43.9%, 11.2%, and 45.1%, respectively). To verify the in vitro result, stents were implanted to rabbit iliac artery and isolated at 4 weeks post implantation. Then, the stents were subjected to histological analysis. No significant differences in injury score, internal elastic lamina, lumen area, and restenosis rate were found. However, the fibrin score was more significantly decreased in the ion beam-implanted group (2.5 ± 0.15) than in the bare metal stent group (1.8 ± 0.31, n = 10, p < 0.05). Taken together, ion beam implantation may be an efficient accessorial tool for preventing in-stent restenosis and in-stent thrombosis. [ABSTRACT FROM AUTHOR]

Although many recent studies demonstrate surfaces with switchable wettability under various external stimuli, a deliberate effort to self-propel liquid droplets utilizing a surface wetting mode switch between slippery lotus and adhesive rose petal states via a mechanical strain has not been made yet, which would otherwise further benefit microfluidic applications. In this work, we present a black silicon/elastomer (bSi/elastomer) composite surface which shows switchable wettability and adhesion across the two wetting modes by mechanical stretching. The composite surface is composed of a scale-like nanostructured silicon platelet array that covers an elastomer surface. The gap between the neighboring silicon platelets is reversibly changeable as a function of a mechanical strain, leading to the transition between the two wetting modes. Moreover, the composite surface is highly flexible although its wetting properties primarily originate from superhydrophobic bSi platelets. Different wetting characteristics of the composite surface in various mechanical strains are studied, and droplet manipulation such as droplet self-propulsion and pick-and-place using the composite surface is demonstrated, which highlights its potentials for microfluidic applications.

Blood-contacting devices must be designed to minimize the risk of bloodstream-associated infections, thrombosis, and intimal lesions caused by surface friction. However, achieving effective prevention of both bloodstream-associated infections and thrombosis poses a challenge due to the conflicting nature of antibacterial and antithrombotic activities, specifically regarding electrostatic interactions. This study introduced a novel biocompatible hydrogel of sodium alginate and zwitterionic carboxymethyl chitosan (ZW@CMC) with antibacterial and antithrombotic activities for use in catheters. The ZW@CMC hydrogel demonstrates a superhydrophilic surface and good hygroscopic properties, which facilitate the formation of a stable hydration layer with low friction. The zwitterionic-functionalized CMC incorporates an additional negative sulfone group and increased negative charge density in the carboxyl group. This augmentation enhances electrostatic repulsion and facilitates the formation of hydration layer. This leads to exceptional prevention of blood clotting factor adhesion and inhibition of biofilm formation. Subsequently, the ZW@CMC hydrogel exhibited biocompatibility with tests of in vitrocytotoxicity, hemolysis, and catheter friction. Furthermore, in vivotests of antithrombotic and systemic inflammation models with catheterization indicated that ZW@CMC has significant advantages for practical applications in cardiovascular-related and sepsis treatment. This study opens a new avenue for the development of chitosan-based multifunctional hydrogel for applications in blood-contacting devices.

In this study, our own stent designed by Chonnam National University Hospital (designated as CNUH stent) which is considered an elastic behavior as second trial was subjected to mechanical performance tests and in vivo histological analysis. Four commercialized stents (PROMUS Element™, Cypher ® , Resolute Integrity, Xience PRIME) stents were employed as control. In the flat plate and compression test for measuring radial force, the lowest (2.40 ± 0.27 N) and moderate (31.27 ± 4.84 N) performance was shown in CNUH stent compared to others. On the other hand, In the 3-point bending test for measuring flexibility, CNUH stent showed the greatest flexibility (0.46 ± 0.08 N) among competitors (range between 0.66 ± 0.03 in Cypher ® and 1.14 ± 0.04 Resolute Integrity), In both foreshortening and recoil test, CNUH stent showed reasonable result (2.13 ± 0.15% and 3.29 ± 0.41%, respectively). However, histological analysis showed that CNUH stent has any significant difference to Coroflex ® Blue BMS on various parameters. Although the radial force of CNUH stent was slightly lower than that of other products, it showed the greatest performance in its flexibility. It can be utilized for developing drug-eluting stent as a basic structure. [ABSTRACT FROM AUTHOR]