Blood compatibility and physicochemical assessment of novel nanocomposite comprising polyurethane and dietary carotino oil for cardiac tissue engineering applications

Cardiovascular diseases (CVD) were estimated to claim 17 million lives each year. Among these, coronary heart disease almost accounts 50% deaths associated with CVD, which causes the blockage of the coronary arteries that supplies blood to the heart. Nowadays, the cardiac tissue engineering have become a promising solution to overcome the drawbacks associated with current therapies. Further, the scaffold used in cardiac tissue engineering must possess thromboresistant and anticoagulant nature to serve as a plausible candidate for cardiovascular applications. In this present investigation, a novel nanocomposite based on polyurethane (PU) and carotino oil was fabricated using electrospinning. Scanning electron microscopy images indicated that the nanocomposites have smaller fiber diameter (702 ± 130 nm) compared to the pristine PU (969 ± 217 nm). The Fourier transform infrared spectroscopy analysis confirmed the interaction between the carotino oil and PU by the formation of hydrogen bond and shifting of CH peak. The contact angle of electrospun PU/carotino oil was found to be 119°, which was increased compared to pristine PU (86°) indicating the hydrophobic nature of developed nanocomposites. Moreover, the surface roughness and thermal stability were found to be enhanced due to the presence of carotino oil in the PU matrix indicated in atomic force microscopy and thermogravimetric analysis. The enhanced surface roughness of nanocomposites resulted in delayed activation of the blood clot as revealed in activated partial thromboplastin time and prothrombin time assay. Moreover, the hemolytic index of fabricated nanocomposites was found to very low of about 1.33% compared to pristine PU (2.73%), suggesting non‐hemolytic nature and also better blood compatibility. So, the developed PU/carotino nanocomposites having desirable characteristics like better physicochemical and blood compatibility may render appropriate potentials for raw materials of cardiac tissue engineering. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45691.     

The influence of forming surface on the vacuum pressure in hydroentangling process

Hydroentangling is a process that uses waterjet curtains issued from a series of parallel jet-heads (manifolds) for entangling and interloping fibres in a loose fibre web carried on a belt or perforated surface. The efficient removal of the stagnant water remaining from each waterjet curtain is crucial for the success of fibre entanglement when the web reaches the next jet-head. In this article, we discuss different methodologies that can be used to calculate the minimum vacuum pressure required for extracting the hydroentangling water from non-woven fabrics. A distinction has been made between hydroentangling on tightly and openly woven screens and different modelling strategies are recommended for each. In particular, it is demonstrated that a one-dimensional flow pattern coupled with available analytical permeability expressions can be used to predict the required vacuum pressure in the case of tightly woven screens. In the case of open woven screens where the flow pattern becomes three-dimensional, numerical simulation is needed for calculating the vacuum pressure required for complete removal of hydroentangling water. We also demonstrated that the vacuum pressure increases by decreasing the fibre diameter or increasing the fabrics' solid volume fractions.     

A simple numerical model of the apparent loss of eddy current conductivity due to surface roughness

In light of its frequency-dependent penetration depth, the measurement of eddy current conductivity has been suggested as a possible means to allow the nondestructive evaluation of subsurface residual stresses in shot-peened specimens. This technique is based on the so-called electro-elastic effect, i.e. the stress-dependence of the electrical conductivity. Unfortunately, the relatively small change in electrical conductivity caused by shot peening is often distorted, or even completely overshadowed, by the apparent conductivity loss caused by the accompanying surface roughness. This geometrical artifact is due to the fact that as the frequency increases, and therefore the penetration depth decreases, the path of the eddy current must follow a more tortuous route in the material, which produces a reduction in the observed conductivity. This paper addresses the apparent reduction of the near-surface electrical conductivity measured by the eddy current method in the presence of surface roughness. The rough surface is modeled as a one-dimensional sinusoidal corrugation using the Rayleigh–Fourier method. The apparent conductivity is determined from the resulting change in the plane-wave reflection coefficient of the conducting half-space at normal incidence. In spite of the simplicity of the suggested analytical model, the obtained theoretical results are found to be in good qualitative agreement with recently published experimental data from shot-peened copper specimens.     

48-GHz digital ICs and 85-GHz baseband amplifiers usingtransferred-substrate HBT's

Using substrate transfer processes, we have fabricated heterojunction bipolar transistors with submicrometer emitter-base and collector-base junctions, minimizing RC parasitics and increasing f_max to 500 GHz. The process also provides a microstrip wiring environment on a low-ϵ_r dielectric substrate. First design iterations of emitter-coupled-logic master-slave flip-flops exhibit 48 GHz maximum clock frequency when connected as static frequency dividers. Baseband amplifiers have been demonstrated with bandwidths up to 85 GHz     

A new dynamic model for drilling and reaming processes

This paper presents a new computer simulation model for drilling and reaming processes. The model is made of four parts: the force model for the cutting lips, the force model for the chisel edge, the dynamic model for the machine tool (including the cutter) and the regenerative correlation between the force and machine tool vibration. The models for the forces and the machine tool are similar to the existing models. The key to the model is the regeneration correlation between the cutting forces and the machine tool vibration. It uses a new 3D chip formation model to describe the interaction between the cutter and the workpiece. The model can predict the dynamic forces and chatter limit. It also reveals several interesting phenomena, such as how the feed and the point angle of the drill affect the chatter limit. The model is implemented using C++ language with an interface to I-DEAS™ CAE software system. The simulation results are validated experimentally by both drilling and reaming under various cutting conditions. The experiment results show that the simulation is accurate with average error about 10%. A number of research issues are also proposed for the future work.     

Improvement of passivity of Fe–<Emphasis Type="Italic">x</Emphasis>Cr Alloys (<Emphasis Type="Italic">x</Emphasis> < 10%) by cycling through the reactivation potential

Classically, 13% Cr is required for stable passivity of a Fe–Cr alloy in acidic and neutral solutions not containing inhibitors. Some authors (Mansfeld, Fujimoto) have published potential cycling procedures that generate thick Cr-rich films. In this work, a similar technique, but with a far smaller potential cycle, was used to enrich a surface layer in chromium, thereby increasing corrosion-resistance in otherwise non-passivating steels. This was achieved by potential stepping across the iron reactivation potential, firstly forming passive iron(III) oxide, then reducing it to soluble iron(II) ions, while ensuring the passivity of chromium. The use of potential stepping was found to result in a more robust film than that formed through a single continuous passivation step.     

ABCB1 Does Not Require the Side-Chain Hydrogen-Bond Donors Gln347, Gln725, Gln990 to Confer Cellular Resistance to the Anticancer Drug Taxol

The multidrug efflux transporter ABCB1 is clinically important for drug absorption and distribution and can be a determinant of chemotherapy failure. Recent structure data shows that three glutamines donate hydrogen bonds to coordinate taxol in the drug binding pocket. This is consistent with earlier drug structure-activity relationships that implicated the importance of hydrogen bonds in drug recognition by ABCB1. By replacing the glutamines with alanines we have tested whether any, or all, of Gln³⁴⁷, Gln⁷²⁵, and Gln⁹⁹⁰ are important for the transport of three different drug classes. Flow cytometric transport assays show that Q347A and Q990A act synergistically to reduce transport of Calcein-AM, BODIPY-verapamil, and OREGON GREEN-taxol bisacetate but the magnitude of the effect was dependent on the test drug and no combination of mutations completely abrogated function. Surprisingly, Q725A mutants generally improved transport of Calcein-AM and BODIPY-verapamil, suggesting that engagement of the wild-type Gln⁷²⁵ in a hydrogen bond is inhibitory for the transport mechanism. To test transport of unmodified taxol, stable expression of Q347/725A and the triple mutant was engineered and shown to confer equivalent resistance to the drug as the wild-type transporter, further indicating that none of these potential hydrogen bonds between transporter and transport substrate are critical for the function of ABCB1. The implications of the data for plasticity of the drug binding pocket are discussed.     

Advanced nanofibrous textile-based dressing material for treating chronic wounds

In the present work, an electrospun nanofibrous textile composed of polyurethane (PU), sodium bicarbonate (\(\hbox {NaHCO}_{3}\)) and pantothenic acid (PA) is developed for treating chronic wounds. Wounds are a common health problem and in particular, the chronic wounds such as vascular ulcers, diabetic ulcers and pressure ulcers cause a large number of morbidity and mortality. The main problems of the chronic wounds are prolonged inflammation phase and presence of acidic environment. These events deactivate the operation of growth factors and also the progression of natural healing mechanism. Hence, various types of advanced textile-based dressings are developed to address the clinical complications associated with chronic wound management. The prepared electrospun scaffolds were characterized to study their physicochemical and haemocompatible properties. The scanning electron microscopy micrographs depicted continuous, smooth-interconnected nanofibrous morphology of PU–NaHCO\(_{3}\)–PA scaffolds. The Fourier transform infrared spectroscopy spectra indicated the addition of NaHCO\(_{3}\) and PA-based hydrophilic chemical groups, which significantly enhanced the wettability of the composites. Further, the PU–NaHCO\(_{3}\)–PA composite membrane inferred to have a highly porous structure with the mean porosity of 79.4 ± 4.8%, which may provide a conducive environment for adherence and proliferation of skin cells. The composite scaffold also offers a highly haemocompatible surface by delaying coagulation of blood through contact activation pathways and by limiting red blood cells damage. Therefore, the excellent physicochemical properties, blood compatibility and the delivery of PA are anticipated to speed up the impaired healing process of chronic wounds.