Nitinol Wire Research Articles

Low-Cost and Rapid Shaping of Nitinol for Medical Device Prototyping

Abstract This paper describes the methodology for rapid prototyping of nitinol structures by heat setting. Nitinol is a shape memory alloy commonly used in implantable medical devices. The proposed technique, based on 3D printing, can be used to effectively iterate multiple nitinol designs for different types of medical devices. We describe a rapid and low-cost process of ceramic replica molding of standard 3D printed parts to create high-temperature resistant fixtures, suitable for heat setting of nitinol. The technique represents a low cost (<$20 materials per fixture) and rapid (as quickly as 16 h for a volume less than 1.25 × 105 mm3) method for shaping nitinol, a technique that typically is costly, labor intensive, and requires specialized equipment. Our method satisfies a need for cost-effective, rapid prototyping of nitinol for implantable medical devices, and we show an example set of shaped nitinol wires, clips, and stents. This method is straightforward and can be easily applied by researchers to rapidly iterate medical device designs.

Direct coupling of fiber-in-tube solid-phase microextraction with tandem mass spectrometry to determine amyloid beta peptides as biomarkers for Alzheimer's disease in cerebrospinal fluid samples

Current research efforts at neurological diseases have focused on identifying novel biomarkers to aid in diagnosis, to provide accurate prognostic information, and to monitor disease progression. This study presents the direct coupling of fiber-in-tube solid-phase microextraction to tandem mass spectrometry as a reliable method to determine amyloid beta peptides (Aβ38, Aβ40, and Aβ42) as biomarkers for Alzheimer's disease in cerebrospinal fluid (CSF) samples. To obtain the biocompatible fiber-in-tube SPME capillary, a PEEK tube segment was longitudinally packed with fine fibers [nitinol wires coated with a zwitterionic polymeric ionic liquid], to act as selective extraction medium. The fiber-in-tube SPME–MS/MS method integrated analyte extraction/enrichment and sample cleanup (exclusion of interferents) into one step. The method provided lower limits of quantification (LLOQ: 0.2 ng mL−1 for Aβ38 and 0.1 ng mL−1 for Aβ40 and Aβ42), high precision (CV lower than 11.6%), and high accuracy (relative standard deviation lower than 15.1%). This method was successfully applied to determine Aβ peptides in CSF samples obtained from AD patients (n = 8) and controls (healthy volunteers, n = 10). Results showed that Aβ42 levels in the CSF samples obtained from AD patients were significantly lower compared to healthy controls (p < 0.05). On the basis of the ROC analysis results, the Aβ42/Aβ40 ratio (AUC = 0.950, p < 0.01; 95%) performed significantly better than Aβ42 alone (AUC = 0.913, p < 0.01; 95%) in discriminating between AD patients and healthy controls and presented better diagnostic ability for AD. The novelties of this study are not only related to evaluating Aβ peptides as AD biomarkers, but also to demonstrating direct online coupling of fiber-in-tube SPME with MS/MS as a quantitative high-throughput method for bioanalysis.

Experimental and numerical investigation of the transient thermal characteristics of twisted nitinol wires in a continuous torsional refrigeration system.

Twistocaloric cooling technology is a novel solid elastocaloric refrigeration to be promising alternatives to conventional compression refrigeration. The transient thermal characteristics of the twistocaloric-effect material and its cooling capacity are critical for this technology. A test rig of the continuous torsional refrigeration system (CTRS) using nitinol wires twisted by a stepping motor was built. The experimental tests show that, the surface temperatures increased as the stepping motor twisted the nitinol wires clockwise, and decreased by untwisting them counterclockwise under the stepping motor speed of 40, 45 and 45rpm. The maximum temperature rise and drop relative to the ambient temperature for the two-twisted-nitinol-wire combinations were 7.1 and 2.6°C, higher than those of 1.4 and 0.6°C for the single nitinol wire, respectively. An optimization program based on a heat conduction model was constructed to attain the potential cooling and heating capacities (PHCCs) of the nitinol wires. Then, PHCCs were introduced into the coupled flow and convective heat transfer model to predict the actual cooling and heating capacities of the CTRS. They were discovered to increase as the number of nitinol wires, the stepping motor speed, and the air velocity. The results can be referred in developing a continuous torsional refrigeration prototype.

Harmonic radar tracking of individual melon flies, Zeugodacus cucurbitae, in Hawaii: Determining movement parameters in cage and field settings.

Tephritid fruit flies, such as the melon fly, Zeugodacus cucurbitae, are major horticultural pests worldwide and pose invasion risks due primarily to international trade. Determining movement parameters for fruit flies is critical to effective surveillance and control strategies, from setting quarantine boundaries after incursions to development of agent-based models for management. While mark-release-recapture, flight mills, and visual observations have been used to study tephritid movement, none of these techniques give a full picture of fruit fly movement in nature. Tracking tagged flies offers an alternative method which has the potential to observe individual fly movements in the field, mirroring studies conducted by ecologists on larger animals. In this study, harmonic radar (HR) tags were fabricated using superelastic nitinol wire which is light (tags weighed less than 1 mg), flexible, and does not tangle. Flight tests with wild melon flies showed no obvious adverse effects of HR tag attachment. Subsequent experiments successfully tracked HR tagged flies in large field cages, a papaya field, and open parkland. Unexpectedly, a majority of tagged flies showed strong flight directional biases with these biases varying between flies, similar to what has been observed in the migratory butterfly Pieris brassicae. In field cage experiments, 30 of the 36 flies observed (83%) showed directionally biased flights while similar biases were observed in roughly half the flies tracked in a papaya field. Turning angles from both cage and field experiments were non-random and indicate a strong bias toward continued "forward" movement. At least some of the observed direction bias can be explained by wind direction with a correlation observed between collective melon fly flight directions in field cage, papaya field, and open field experiments. However, individual mean flight directions coincided with the observed wind direction for only 9 out of the 25 flies in the cage experiment and half of the flies in the papaya field, suggesting wind is unlikely to be the only factor affecting flight direction. Individual flight distances (meters per flight) differed between the field cage, papaya field, and open field experiments with longer mean step-distances observed in the open field. Data on flight directionality and step-distances determined in this study might assist in the development of more effective control and better parametrize models of pest tephritid fruit fly movement.

Investigation of the damping behavior of shape memory alloy-nitinol reinforced composite

The use of Shape Memory Alloy (SMA) recently increased in smart structures. It is essential to investigate the impact of viscoelastic material, and transformation temperatures of SMA on dynamic behavior, especially the damping capability of the SMA reinforced composite. In this paper, the damping constants of SMA and viscoelastic material are evaluated experimentally, and a damping model based on experimental results is proposed for the composite. The effect of SMA wires in combination and selective activation has been studied using the proposed model and validated experimentally. It has been observed that damping predicted by the model is close to damping calculated by experimentation. Also, damping varies with the transformation temperatures of SMA. Thus, dynamic control of the SMA reinforced composite is feasible by controlling transformation temperature. The composite studied in this work can shift the damping by 9.58% by activating all nitinol wires.

Extensive Lesser Toes Plantar Plate Tears Reconstruction

Category: Lesser Toes Introduction/Purpose: The plantar plate is a fibrocartilaginous structure that plays a fundamental role in the sagittal stability of the metatarsophalangeal joint (MTPJ). Traumatic and degenerative lesions affecting the plantar plate have the potential to cause instability, swelling, pain and deformity. Extensive plantar plate tears (grade IV) still challenge surgeons as primary repair is impossible, demanding a reconstructive procedure which, unfortunately, can be associated with high morbidity such as stiffness, persistence of discomfort, vascular compromise to the digit and amputation. The purpose of this work is to describe a new technique that uses a synthetic tape and one absorbable screw to achieve the MTPJ stabilization in plantar plate grade IV tears. We believe that this procedure can achieve better results than other techniques described in the literature. Methods: Two bone tunnels are made at the base of the proximal phalanx. Both medial and lateral tunnels are directed in a light oblique fashion from a distal-dorsal entry point to a proximal, justarticular plantar exit. Two new oblique dorsal-plantar bone tunnels - medial and lateral - are made at the distal metaphyseal metatarsal area. A #2 FiberTape is passed through the bone tunnels guided by a Nitinol wire, creating a mesh for the plantar stabilization of the MTPJ. Then both Fiber Tapes limbs are driven, with the help of a nitinol loop, through the plantar orifices of corresponding sides of the metatarsal bone tunnels, exiting in its dorsal aspect. One of the limbs of the tape is passed from dorsal to plantar trough the other metatarsal orifice. Both limbs are tensioned, and the toe should be kept at neutral sagittal position (flexion-extension). Fixation is made with a Biotenodesis screw. Results: Only a few patients were submitted to this technique. At one year follow up, none of them presented with complaints or complications. Conclusion: The surgical technique described in this article can change the way physicians treat plantar complex plantar plate tears when there is no viable biologic tissue to repair. A lesser complication rate it's also expected. Nonetheless comparative, and biomechanical studies are still needed to confirm our hypothesis.

The metabolic fate of oxaliplatin in the biological milieu investigated during in vivo lung perfusion using a unique miniaturized sampling approach based on solid-phase microextraction coupled with liquid chromatography-mass spectrometry.

Adjuvant chemotherapy after pulmonary metastasectomy for colorectal cancer may reduce recurrence and improve survival rates; however, the benefits of this treatment are limited by the significant side effects that accompany it. The development of a novel in vivo lung perfusion (IVLP) platform would permit the localized delivery of high doses of chemotherapeutic drugs to target residual micrometastatic disease. Nonetheless, it is critical to continuously monitor the levels of such drugs during IVLP administration, as lung injury can occur if tissue concentrations are not maintained within the therapeutic window. This paper presents a simple chemical-biopsy approach based on sampling with a small nitinol wire coated with a sorbent of biocompatible morphology and evaluates its applicability for the near-real-time in vivo determination of oxaliplatin (OxPt) in a 72-h porcine IVLP survival model. To this end, the pigs underwent a 3-h left lung IVLP with 3 doses of the tested drug (5, 7.5, and 40 mg/L), which were administered to the perfusion circuit reservoir as a bolus after a full perfusion flow had been established. Along with OxPt levels, the biocompatible solid-phase microextraction (SPME) probes were employed to profile other low-molecular-weight compounds to provide spatial and temporal information about the toxicity of chemotherapy or lung injury. The resultant measurements revealed a rather heterogeneous distribution of OxPt (over the course of IVLP) in the two sampled sections of the lung. In most cases, the OxPt concentration in the lung tissue peaked during the second hour of IVLP, with this trend being more evident in the upper section. In turn, OxPt in supernatant samples represented ∼25% of the entire drug after the first hour of perfusion, which may be attributable to the binding of OxPt to albumin, its sequestration into erythrocytes, or its rapid nonenzymatic biotransformation. Additionally, the Bio-SPME probes also facilitated the extraction of various endogenous molecules for the purpose of screening biochemical pathways affected during IVLP (i.e., lipid and amino acid metabolism, steroidogenesis, or purine metabolism). Overall, the results of this study demonstrate that the minimally invasive SPME-based sampling approach presented in this work can serve as (pre)clinical and precise bedside medical tool.

Transcatheter closure of secundum atrial septal defect using Cocoon septal occluder: immediate and long-term results

BackgroundAtrial septal defect (ASD) is one of the common congenital heart defects. Its management has transformed dramatically in the last 4 decades with the transition from surgical to percutaneous transcatheter closure for most secundum-type ASDs. Various devices are available for transcatheter closure of ASD with Amplatzer atrial septal occluder being most commonly used worldwide. Cocoon septal occlude has a nanocoating of platinum using nano-fusion technology over nitinol framework that imparts better radiopacity and excellent biocompatibility and prevents leaching of nickel into circulation, and by smoothening nitinol wire makes this device very soft and smooth. The aim of this study was to evaluate feasibility, effectiveness, safety, and long-term outcome of transcatheter closure of ASD using Cocoon septal occluder (Vascular Innovation, Thailand).ResultsAll patients undergoing transcatheter closure of hemodynamically significant ASD between September 2012 and July 2019 in our institute were included into this single-center, prospective study. Exclusion criteria were defect > 40 mm, unsuitable anatomy, Eisenmenger syndrome, and anomalous pulmonary venous return. Three hundred and twenty patients underwent device closure, of which 238 (74%) were female. The mean age was 14.6 years (range 6–29), and the median weight was 30.2 kg (range 10–53 kg). Procedure was performed under fluoroscopy using transthoracic and transesophageal echocardiography in 298 (93.1%) and 22(6.9%) patients, respectively. Balloon-assisted technique was used, when septal defect was ≥ 34 mm, in 9 (2.8%) patients. The mean diameter of defect and device was 21.4 mm (range 12–36 mm) and 26.9 mm (range 14–40 mm), respectively. Aortic rim was absent in 11 (3.4%) patients. Primary success was achieved in 312 (97.5%) patients. Early embolization to right ventricle was noted in 2 (0.6%) patients. In both cases, 40-mm device was attempted for defect of 36 mm with inadequate aortic rim using balloon-assisted technique. One (0.3%) patient developed perforation of right atrium. All were surgically repaired. Three (0.9%) patients developed complete heart block following device deployment requiring device retrieval. Two patients had had moderate residual shunt at 6 months of follow-up. After mean follow-up of 50.92 months (range 12.5–89 months), no erosion, allergic reactions to nickel, or other major complications were reported.ConclusionsPercutaneous transcatheter closure of ASD by Cocoon septal occluder (up to 36 mm) is safe and feasible with high success rate and without any significant device-related major complications over long-term follow-up. With unique device design and excellent long-term safety, it could be preferred dual-disk occluder for transcatheter closure of atrial septal defect. In most of the patients, ASD device can be safely deployed under transthoracic echocardiographic guidance.

A novel temporary atrioventricular sequential pacing catheter-Characteristics and first-in-human application.

Sequential synchronized atrioventricular (AV) pacing provides enhanced electrophysiologic parameters which contribute to improved hemodynamic parameters and increased cardiac performance to subsequently confer a clinical advantage over traditional ventricular pacing. Current temporary transvenous pacemaker catheters are limited to only one electrode which paces solely the right ventricle, thus lacking the capability to provide the optimal pacing mode. A new multilead pacemaker device was developed in response to the need for improved temporary pacing through the utilization of sequential synchronized atrioventricular pacing (TAVSP). It consists of seven preformed, preshaped nitinol wires electrodes, of which four are for intra-atrial and three for intraventricular positioning and endocardial contact, respectively. Each wire carries a ball tip designed to minimize tissue trauma and provide a high current density for adequate myocardial capture. The device is not yet Food and Drug Administration approved. To present the unique structural components and mechanical properties of a novel sequential synchronized AV pacing device for temporary insertion and to report its first-in-human application with an analysis of the early clinical experience. Following a process of development and proof of concept of the novel pacing modality in an animal model which demonstrated feasibility and safety, a series of patients who were candidates for the device application was identified. During left and right heart catheterization, the novel temporary pacing catheter was inserted transvenously and delivered in most patients under fluoroscopy or echocardiography. The catheter was deployed to its target right heart anatomic sites and then activated in an AV sequential mode. The technical aspects, the corresponding clinical utilization, and device performance were documented and analyzed. The series included 10 enrolled subjects. During planned left and right heart catheterization, the novel TAVSP device was inserted transvenously and then delivered and deployed successfully in a timely fashion in all patients. The pacing catheter achieved proper threshold and impedance in all (100%) patients. The performance of all ventricular leads was adequate; however, in 1 (10%)patient poor performance of the atrial leads was detected. The device was successfully retrieved in all patients. No adverse arrhythmia, impaired hemodynamics, or clinical adverse events occurred. No technical difficulties, component failure, or wires thrombosis were detected. All patients sustained the device application without sequala and were discharged home. Initial clinical experience with the utilization of a novelTAVSPdemonstrates feasibility and safety in humans. The TAVSP modality potentially offers improved pacing capability and subsequent hemodynamic benefits over the current temporary pacing catheters. Further experience with the clinical application of this pacing catheter is warranted.

Force-Bioreactor for Assessing Pharmacological Therapies for Mechanobiological Targets.

Tissue fibrosis is a major health issue that impacts millions of people and is costly to treat. However, few effective anti-fibrotic treatments are available. Due to their central role in fibrotic tissue deposition, fibroblasts and myofibroblasts are the target of many therapeutic strategies centered primarily on either inducing apoptosis or blocking mechanical or biochemical stimulation that leads to excessive collagen production. Part of the development of these drugs for clinical use involves in vitro prescreening. 2D screens, however, are not ideal for discovering mechanobiologically significant compounds that impact functions like force generation and other cell activities related to tissue remodeling that are highly dependent on the conditions of the microenvironment. Thus, higher fidelity models are needed to better simulate in vivo conditions and relate drug activity to quantifiable functional outcomes. To provide guidance on effective drug dosing strategies for mechanoresponsive drugs, we describe a custom force-bioreactor that uses a fibroblast-seeded fibrin gels as a relatively simple mimic of the provisional matrix of a healing wound. As cells generate traction forces, the volume of the gel reduces, and a calibrated and embedded Nitinol wire deflects in proportion to the generated forces over the course of 6 days while overhead images of the gel are acquired hourly. This system is a useful in vitro tool for quantifying myofibroblast dose-dependent responses to candidate biomolecules, such as blebbistatin. Administration of 50 μM blebbistatin reliably reduced fibroblast force generation approximately 40% and lasted at least 40 h, which in turn resulted in qualitatively less collagen production as determined via fluorescent labeling of collagen.

Minimally Invasive Mid-Substance Achilles Tendon Repair Using the Percutaneous Achilles Repair System (PARS).

Minimally Invasive Mid-Substance Achilles Tendon Repair Using the Percutaneous Achilles Repair System (PARS).

Stent-in-stent technique under fluoroscopy for removal of embedded esophageal stent: a retrospective case series

Treatment of complications after esophageal stent placement and methods for removal of stents need to be improved. The purpose of this study was to evaluate the safety and efficacy of stent-in-stent (SIS) removal of esophageal stent under fluoroscopy. This study analyzed the clinical data of consecutive patients undergoing esophageal stent removal by the SIS technique under fluoroscopy. The procedure was performed under local anesthesia on conscious sedated patients. Under fluoroscopy, a second esophageal stent was released within the lumen of the first esophageal stent. The second stent was larger than the first, with both ends protruding 1-2 cm beyond the ends of the first stent. Four weeks later, both esophageal stents were removed by the SIS technique under fluoroscopy. All procedures were performed by the same interventional radiologist (with >10 years of experience). A total of 25 patients were treated by the SIS removal technique. In 23 patients, the first esophageal stent was easily removed by the SIS technique; in the other 2 patients, stent fracture occurred, and some residual nitinol wire had to be removed endoscopically. No serious complications occurred in any patient. The SIS removal technique appears to be a safe and effective method for removal of embedded esophageal metallic stents.

Medial Patellofemoral Reconstruction With a Hamstring Allograft

Background: Lateral patellar instability is common in young, active patients. Patients who fail conservative treatment may benefit from medial patellofemoral ligament (MPFL) reconstruction. Indications: Recurrent lateral patellar instability. Technique Description: Examination assesses patellar translation, eversion and range of instability. Diagnostic arthroscopy is performed for loose bodies, cartilage damage, trochlear dysplasia, and tracking. A longitudinal incision is made from superomedial to mid-body of the patella. The plane between the capsule and retinaculum is developed for palpation of the medial epicondyle and adductor tubercle. Electrocautery and rongeur are used to create a trough on the patella from centromedially to superomedially. Two suture anchors are placed at the proximal and distal trough. Fluoroscopy is utilized to identify Schöttle point with a perfect lateral radiograph. A 3-centimeter incision is made, and blunt dissection connects the 2 incisions in the developed plane. A guidepin is advanced at Schöttle point, and suture anchor sutures are shuttled through the plane, posterior to the guidepin. There should be loosening of tension with knee flexion. A semitendinosus allograft is whipstitched with terminal tapering. The whipstitched end is tunneled around the guidepin and brought back to the patella, so that both ends have an excess of 20 to 25 millimeters, and excess graft is trimmed from the free end prior to whipstitching. The doubled graft is sized. The midportion of the tendon is tagged and passed through both anchors. The graft is tensioned to the patellar trough and the graft ends are advanced through the developed plane. The femoral tunnel is reamed, and the graft is tensioned into the tunnel after nitinol wire placement with the knee in full extension. Isometry and lateral patellar translation are assessed, aiming for 1 quadrant with firm endpoint. The patella is proximalized and the tensioned graft is secured with an interference screw. Results: MPFL reconstruction is successful for the majority of patients, with 1.2% reporting instability, 3.6% apprehension, and 3.1% reoperation. Possible complications include patellar fracture, patellofemoral pain, and knee stiffness (loss of range of motion). Discussion/Conclusion: Lateral patellar instability is common, and MPFL reconstruction is typically successful for the majority of patients.

Optimisation of performance characteristics in laser welding of Nitinol wires using Taguchi and grey relation analysis

ABSTRACT NiTi Shape Memory Alloy (SMA) finds wide applications in high-performance engineering industries such as medical devices, micro-electrical and electronic components, aerospace, aircraft structure, and so on, to name a few. This is owing to its superior properties like shape memory effect (SME), superelasticity, and biocompatibility. However, getting a proper joining of NiTi alloys is hard considering its unique characteristics. Therefore, joining this alloy has been a domain of great attention for scientists. The current research work investigates the weldability of NiTi wires using Laser spot welding. The microhardness and the tensile strength of the weld joint are acquired according to Taguchi’s design of experiment. The significance of the control factors (laser power, scan speed, and focal length) is identified through ANOVA, and an ideal factor setting for optimum individual responses is established. Moreover, simultaneous optimisation of multi-performance characteristics is also attempted through Grey Relational Analysis (GRA) method. From the GRA, 300 W laser power, 1 mm/sec scan speed, and 0.5 mm focal position are found to be giving optimum results for both the responses. The result from the confirmation runs showed that the predicted optimal welding parameters improve the individual as well as the multiple performance characteristics.

Early Repair of Aortic Wall Structural Defect by "Net" Endoprosthesis to Arrest the Aneurysm without Interference with Aortic Branch Vessel Perfusion.

Current treatments of aortic aneurysm include surgical or endovascular, respectively, anatomical or functional, substitution of the aneurysm tract; however, with these methods, perfusion of at least some collateral branches cannot be fully restored, leading to the risk of paraplegia. We present a novel endovascular "net" prosthesis to strengthen the aortic wall while preserving perfusion of collateral branches. This consists of a polyester mesh "net"-layered conduit in a variable cylindrical shape, which is personalized based on patient computed tomography scan images, and is defined by circular crossing spirals of a thin nitinol wire. The prosthetic conduit, shrunk by compressing the nitinol spirals, can be inserted into the vascular lumen and expanded in situ. Then, the insertion control device can be fully removed. Thus, the, "net" prosthesis, positioned inside the aorta in stable contact with the intimal wall for 2 to 5 months, is colonized by neointima and spontaneously moved deeper into the aortic wall in contact with the media, thus being ideally able to stabilize aortic diameter without interference with collateral branch blood perfusion. This new, (ideally) paraplegia-free procedure is aimed at curing the aortic wall structural defect, thus arresting the aneurysm from further progression. This contrasts with current treatments, indicated by aneurysm dimensions for their implied complication risk, which are actually for prophylaxis of impending rupture or dissection rather than fortification of the natural aorta. Moreover, this new approach can be used alongside open surgical procedures (personalized external aortic root support) as well as a frozen "net" elephant trunk technique, for full aortic stabilization.

Nitinol Release of Nickel under Physiological Conditions: Effects of Surface Oxide, pH, Hydrogen Peroxide, and Sodium Hypochlorite.

Nitinol is a nickel-titanium alloy widely used in medical devices for its unique pseudoelastic and shape-memory properties. However, nitinol can release potentially hazardous amounts of nickel, depending on surface manufacturing yielding different oxide thicknesses and compositions. Furthermore, nitinol medical devices can be implanted throughout the body and exposed to extremes in pH and reactive oxygen species (ROS), but few tools exist for evaluating nickel release under such physiological conditions. Even in cardiovascular applications, where nitinol medical devices are relatively common and the blood environment is well understood, there is a lack of information on how local inflammatory conditions after implantation might affect nickel ion release. For this study, nickel release from nitinol wires of different finishes was measured in pH conditions and at ROS concentrations selected to encompass and exceed literature reports of extracellular pH and ROS. Results showed increased nickel release at levels of pH and ROS reported to be physiological, with decreasing pH and increasing concentrations of hydrogen peroxide and NaOCl/HOCl having the greatest effects. The results support the importance of considering the implantation site when designing studies to predict nickel release from nitinol and underscore the value of understanding the chemical milieu at the device-tissue interface.

Vesico-amniotic shunt insertion prior to the completion of 16 weeks results in improved preservation of renal function in surviving fetuses with isolated severe lower urinary tract obstruction (LUTO)

This retrospective study by Kohl et al. highlights the feasibility of vesico-amniotic shunting (VAS) before 16 weeks gestation using a Cook pigtail catheter, or the Somatex® nitinol wire mesh shunt. The authors report a technical success rate of 80% before 16 weeks, which they state is similar to the success rates of VAS later in pregnancy. Fetal intervention before 16 weeks is known to be hazardous due to an increased risk of chorioamniotic separation or shunt dislodgement into the fetal abdominal cavity, that can occur with fetal growth, resulting in fetal ascites and requiring further urgent intervention.

Ultrasound Localization of Nitinol Wire of Sub-Wavelength Dimension

Goal: To enhance endovascular navigation using surgical guidewires and the use of ionizing radiation, we demonstrate a method for ultrasonic localization of wires with diameters less than the wavelength of ultrasound in the medium. Methods: Nitinol wires with diameters ranging from 50 μm to 250 μm were imaged ultrasonically in a 0.25-in-diameter water-filled tube in a gelatin medium. Imaging frequencies were 5 MHz, 7.5 MHZ, and 10 MHz. Results: For the full range of diameters traversing the phantom, the wires were localized successfully via visual inspection of both regular and difference ultrasound images. Similarly, two convolutional neural networks were trained, and both achieved an accuracy of over 95%. Conclusions: Wires with diameters as small as 50 μm were localized successfully in a water-based gelatin phantom, indicating the potential use of ultrasound to enhance endovascular navigation and surgical treatment.

Mid-Term Preliminary Results for Safety and Patency of the Occlutech Atrial Flow Regulator in an Animal Model

Objective: The Atrial Flow Regulator (AFR) is a double disc device made of self-expanding Nitinol wire mesh, structured around a central lumen. Once deployed via the transfemoral route, the device stents the atrial septum leaving a preselected fixed diameter atrial communication. We sought to evaluate the mid-term performance of the AFR by implanting the device in 5 healthy porcine hearts to assess safety and patency of the device fenestration over a period of 150 days. Method: Five AFR devices were implanted in 5 female Yucatan adult minipigs. The animals were survived to 150 days with periodic assessments at days +3, +30, +60, +90, +120, and +150. These assessments consisted of transesophageal echocardiography and fluoroscopic evaluation. The animals were sacrificed at day +150. Histological and pathological assessments were carried out to characterize neointimal tissue growth, inflammation, thrombus formation, endothelial coverage, endothelial maturity, and the presence of any luminal thrombus. Result: There were no unscheduled deaths. Patency was maintained in all 5 animals across the 150-day study. There was no statistically significant difference in the lumen diameter over the study duration. Neointimal growth was mild to moderate in all specimens and occurred mostly on the surfaces of the device in direct contact with the atrial septum. There was no evidence of any significant inflammatory response on routine blood work or by imaging or histological assessment. Scanning electron microscope (SEM) examination showed nearly complete surface coverage with endothelial tissue. The animals were in a healthy condition for the duration of the study with no attributable pathology and no adverse effects noted on distant organs in any of the 5 animals. Conclusion: As a continuation of our earlier work, this 150-day midterm animal study provides important safety and feasibility information. Our preliminary results show that the AFR is both safe and effective in maintaining a sustainable atrial level communication for the duration of the study.

Crosslinked zwitterionic polymeric ionic liquid-functionalized nitinol wires for fiber-in-tube solid-phase microextraction and UHPLC-MS/MS as an amyloid beta peptide binding protein assay in biological fluids

Alzheimer disease (AD) is a neurodegenerative disorder characterized by extracellular accumulation of amyloid-β peptide (Aβ) in the brain interstitium. Human serum albumin (HSA) highly binds to Aβ in blood plasma and is thought to inhibit plaque formation in peripheral tissue. Thus, the evaluation of albumin binding to Aβ is an important key to understand the dynamics of these molecules in the biological system of patients with AD. In this work, a fiber-in-tube solid-phase microextraction (fiber-in-tube SPME) and ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed to estimate Aβ fraction binding to HSA in cerebrospinal fluid (CSF) and plasma samples. Crosslinked zwitterionic polymeric ionic liquid (zwitterionic PIL)-coated nitinol wires were developed and packed into a polyether ether ketone (PEEK) capillary for a fiber-in-tube SPME and UHPLC-MS/MS method. Zwitterionic PIL sorbent was synthetized from 1-vinyl-3-(butanesulfonate)imidazolium ([VIm+C4SO3−]) and 1,12-di(3-vinylimidazolium)dodecane dibromide ([(VIm)2C12]2[Br]) monomers by in-situ thermally-initiated polymerization. Morphological characterization by scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed a decrease in the surface roughness of the nitinol wires from ∼17 nm to 1 nm after the in-situ polymerization. The zwitterionic PIL sorbent selectively preconcentrates Aβ through a two-pronged interaction mechanism. The fiber-in-tube SPME and UHPLC-MS/MS method presented lower limits of quantification (LLOQ) of 0.4 ng mL−1 for Aβ38 and 0.3 ng mL−1 for Aβ40 and Aβ42, a linear range from LLOQ values to 15 ng mL−1 with coefficients of determination higher than 0.99, precision with coefficient of variation (CV) values ranging from 2.1 to 7.3% and accuracy with relative standard deviation (RSD) values from −0.3 to 7.4. This method was successfully applied to evaluate the binding of HSA to Aβ in cerebrospinal fluid (CSF) and plasma samples.