Elastomeric Devices Research Articles

Controlled Release of Small Molecules from Elastomers for Reducing Epidermal Downgrowth in Percutaneous Devices.

The elevated infection rise associated with indwelling devices can compromise the performance of percutaneous devices and increase the risk of complications. High infection rates are associated with both the high bacterial load on the skin and epidermal downgrowth at the interface of the indwelling material. Here, we propose a drug-eluting material that promotes local dermal regeneration to reduce epidermal downgrowth. Mesoporous elastomeric matrices composed of naturally occurring monomers were prepared by a combination of photo- and thermal-crosslinking. Elastomeric devices loaded with conjugated linoleic acids (CLA), a class of small molecules that promote local anti-inflammatory responses, can deliver these compounds for 7 d (DCLA-elastomer = 3.94 × 10-9 cm2/s, 95% CI [3.12 × 10-9, 4.61 × 10-9]). In a mouse model, CLA-eluting elastomeric matrices increase the M2 population (5.0 × 103 ± 1.4 × 103 cells/cm2), compared to blank devices (3.8 × 103 ± 2.2 × 103 cells/cm2), and also reduce skin contraction (98.9 ± 6.4%), compared to blank devices (70.9 ± 9.3%) at 7 d. Dermal downgrowth is also attenuated at 14 d (60.4 ± 32.4 μm) compared to blank devices (171.7 ± 93.8 μm). CLA-eluting elastomers are therefore a viable strategy to reduce epidermal downgrowth in percutaneous devices.

WHAT IS THE MAXIMUM TEMPERATURE REACHED IN ELASTOMERIC DEVICES UNDER SIMULATED OPAT CONDITIONS?

AimOutpatient parenteral antimicrobial therapy (OPAT), both in children and adults, is increasing in use as part of a cost saving measure for the NHS.1 However there is a general lack...

Redox Reducible and Hydrolytically Degradable PEG-PLA Elastomers as Biomaterial for Temporary Drug-Eluting Medical Devices.

With the aim to develop biomaterials for temporary medical devices, a series of novel reducible and/or degradable elastomers has been prepared from PLA-b-PEG-b-PLA copolymers photo-crosslinked with diallyl sulfide or pentaerythritol tetrakis(3-mercaptopropionate). Thermal and mechanical properties, including elastic limit and Young modulus, are assessed. Degradation is then evaluated under standard hydrolytic conditions. Reducibility of a selected elastomer is then illustrated using 2-mercaptoethanol or glutathione as reducing agents. The redox-sensitivity of the selected elastomer and the possibility to modulate the degradability are shown. Considering drug-eluting elastomeric devices applications, anti-inflammatory drug ibuprofen loading is illustrated with the two simplest elastomer formulations. A rapid or slow linear release is observed as a function of the low or high molecular weight of the triblock pre-polymers. Finally, the cytocompatibility of the degradable elastomers is assessed with regard to their potential to favor or inhibit L929 murine fibroblasts proliferation as a function of the hydrophilicity/hydrophobicity of the triblock copolymers.

Photoresist Design for Elastomeric Light Tunable Photonic Devices

An increasing interest in tunable photonic structures is growing within the photonic community. The usage of Liquid Crystalline Elastomer (LCE) structures in the micro-scale has been motivated by the potential to remotely control their properties. In order to design elastic photonic structures with a three-dimensional lithographic technique, an analysis of the different mixtures used in the micro-printing process is required. Previously reported LCE microstructures suffer damage and strong swelling as a limiting factor of resolution. In this article, we reported a detailed study on the writing process with four liquid crystalline photoresists, in which the percentage of crosslinker is gradually increased. The experiments reveal that exploiting the crosslinking degree is a possible means in which to obtain suspended lines with good resolution, quite good rigidity, and good elasticity, thereby preserving the possibility of deformation by light irradiation.

Safety and effectiveness of outpatient parenteral antimicrobial therapy in older people.

We analyse the safety and effectiveness of self-outpatient parenteral antimicrobial therapy (s-OPAT) in older patients. We prospectively evaluated all adults admitted to our home hospitalization unit (HHU) for s-OPAT in the period 2008-12 in whom the bacteria responsible for the infection were identified. We divided patients into three age groups: <65, 65-79 and ≥80 years. s-OPAT was administered by patients or their caregivers using elastomeric infusion devices. Effectiveness was assessed by analysing readmissions to hospital for inadequate control of underlying infection. Safety was assessed by analysing adverse events, catheter-related complications and readmission to hospital for causes unrelated to inadequate control of underlying infection. During the study period, 420 episodes of s-OPAT were registered in 351 patients: 139 (33.1%) in patients aged <65 years, 182 (43.3%) in those aged 65-79 years and 99 (23.6%) in those aged ≥80 years. Patients aged ≥80 years had a significantly lower Barthel index. The length of stay for s-OPAT and the complete HHU stay were similar in the three groups. Older people had similar changes in antibiotic treatment and hospital readmission rates due to poor control of underlying infection but higher readmission rates due to worsening of underlying diseases than younger adults. Adverse events and catheter-related complications were similar in the three age groups. s-OPAT administered by patients or their caregivers using elastomeric devices was safe and effective in the treatment of infections in older people.

Outpatient multimodal intravenous analgesia in patients undergoing day-case surgery: description of a three year experience.

BackgroundThe use of elastomeric devices for ambulatory intravenous pain treatment in Major Ambulatory Surgery (MAS) has been described to improve postoperative pain management. The objective of the study was to describe the first 3 years experience of the use of elastomeric devices for ambulatory intravenous pain treatment in MAS implemented at our site since 2010.MethodsData were retrieved from the medical records for all patients who, between January 2010 and March 2014, underwent surgical procedures at the ambulatory surgical centre at our hospital and were prescribed a home-based continuous intravenous analgesia.ResultsData were retrieved from the medical records of 1128 patients. The most frequent surgical interventions included orthopedic and proctology surgeries. 80 % of patients were discharged home without pain; during the first 48 h after discharge roughly 40 % of subjects were completely free of pain, 50 % reported mild pain (VAS 1 to 3) and 9 % reported higher pain scores (4 and above). Peripheral nerve block was associated to better pain control in the immediate postoperative period. Vomiting in the first 24 h was 4.6 % before introducing haloperidol into the drug schemes, and 2.6 % thereafter. Complications related with the intravenous route required treatment withdrawal in 1.1 % cases. Only 3.5 % of patients returned to the hospital in the first 72 h, mainly for non-pain related reasons. Overall, 99.5 % of patients were satisfied with the treatment received at home.ConclusionOur initial experience suggest that outpatient multimodal intravenous analgesia in patients undergoing day-case surgery is a feasible alternative in our setting, that allows an effective management of postoperative pain with a small rate of adverse events and complications requiring readmission.

Tunable Microfluidic Devices for Hydrodynamic Fractionation of Cells and Beads: A Review.

The adjustable microfluidic devices that have been developed for hydrodynamic-based fractionation of beads and cells are important for fast performance tunability through interaction of mechanical properties of particles in fluid flow and mechanically flexible microstructures. In this review, the research works reported on fabrication and testing of the tunable elastomeric microfluidic devices for applications such as separation, filtration, isolation, and trapping of single or bulk of microbeads or cells are discussed. Such microfluidic systems for rapid performance alteration are classified in two groups of bulk deformation of microdevices using external mechanical forces, and local deformation of microstructures using flexible membrane by pneumatic pressure. The main advantage of membrane-based tunable systems has been addressed to be the high capability of integration with other microdevice components. The stretchable devices based on bulk deformation of microstructures have in common advantage of simplicity in design and fabrication process.

Evaluation of patient-controlled sedation (PCS) during surgical removal of impacted lower third molars.

Objectives: The current study was conducted to evaluate the safety of patient-controlled sedation (PCS) and the efficiency of elastomeric infusion device during surgical removal of impacted lower third molars and its impact on patients regarding level of sedation, patients’ satisfaction and psycho-motor recovery. Materials and methods:Twenty patients were equally divided into two groups chosen randomly. In both groups, 0.03 mg/kg Midazolam and 0.5 mg/kg Propofol were administered IV as a bolus dose. Group 1 was then given 0.3 mg/kg/hr Ketamine and 1.2 mg/kg/hr Propofol as a maintenance dose delivered through the PCS pump. Group 2 was then given 0.3 µg/kg/hr Fentanyl and 1.2 mg/kg/hr Propofol as a maintenance dose delivered through the PCS pump. For all patients’ surgical procedure were done under local anesthesia. Before going to the operating theatre all patients were instructed about the PCS pump and familiarized with it. Patients in both groups were evaluated for hemodynamic stability, patient's &surgeon's satisfaction, psychomotor recovery and adverse effects. Results: The results of this study showed no statistical difference between the two groups. The use of different drug combinations in both groups showed hemodynamic stability, patients’& surgeon's satisfaction and rapid psychomotor recovery. None of the patients in both groups suffered from any adverse reactions such as: nausea, vomiting, hallucinations, involuntary movements, or over-sedation. Conclusion: PCS can be considered as a safe option in minor oral surgeries providing the majority of patients with high satisfaction and relaxation, also providing the surgeons with good operating conditions and the cooperation of the majority of the patients. Fentanyl-Propofol and Ketamine-Propofol combinations were both safe with respect to hemodynamic changes with rapid recovery of psychomotor functions in all patients.

Dynamic Analysis of a Base Isolated Building Having Zener Rheological Connections at Seismic Unidirectional Translations

The paper presents the physical model and the experimental results of a building having its base isolated with elastomeric and dissipative devices arranged in a functional configuration equivalent to that of the Zener rheological model.The harmonic motion of excitation at dominant frequency, which corresponds to a narrow band portion of the seismic composition spectrum, generates an inertial excitation force for the building modeled as a rigid-body with unidirectional displacement. Thus, the parameters of the unidirectional translation motion function of the inertial and of the linear viscoelastic characteristics of the Zener rheological model are analyzed.In essence, the amplitude of the displacement of the mass function of the fundamental spectral amplitude of the ground during an earthquake and the transmissibility or the isolation degree of the Zener rheological system are determined.

Parametric analysis of a highly dynamical phenomena caused by a propeller blade loss

Dynamic phenomena can jeopardize the structural integrity of aerospace structures and engineers have developed different strategies to analyze them. One of the most highly dynamical and severe failures in an aircraft provided with turboprops is an airscrew blade loss. This article analyzes this event using implicit and explicit finite element methods including non-linear behaviors, damages, and several types of failures trying to identify the key parameters in the failure sequence. The model includes non-deterministic variables and studies its stochastic behavior through series of Monte Carlo simulations. The influence of lost blade size is studied in detail as well as the effect of stiffness and strength variations on the engine mounting system through elastomeric devices. In the paper, different parameters that can influence the phenomenon are studied, including propeller rotational frequency, structural damping, and angular position where the blade is lost.

Robust and Soft Elastomeric Electronics Tolerant to Our Daily Lives.

Clothes represent a unique textile, as they simultaneously provide robustness against our daily activities and comfort (i.e., softness). For electronic devices to be fully integrated into clothes, the devices themselves must be as robust and soft as the clothes themselves. However, to date, no electronic device has ever possessed these properties, because all contain components fabricated from brittle materials, such as metals. Here, we demonstrate robust and soft elastomeric devices where every component possesses elastomeric characteristics with two types of single-walled carbon nanotubes added to provide the necessary electronic properties. Our elastomeric field effect transistors could tolerate every punishment our clothes experience, such as being stretched (elasticity: ∼ 110%), bent, compressed (>4.0 MPa, by a car and heels), impacted (>6.26 kg m/s, by a hammer), and laundered. Our electronic device provides a novel design principle for electronics and wide range applications even in research fields where devices cannot be used.

A technique of optimization of microfiltration using a tunable platform

The optimum efficiency of size-based filtration in microfluidic devices is highly dependent on characteristics of design, deformability of microparticles/cells, and fluid flow. The effects of filter pores and flow rate, which are the two major determining and related factors of characterization in the separation of particles and cells are investigated in this work. An elastomeric microfluidic device consisting of parallel arrays of pillars with mechanically tunable spacings is employed as an adjustable microfiltration platform. The tunable filtration system is used for finding the best conditions of separation of solid microbeads or deformable blood cells in a crossflow pillar-based method. It is demonstrated that increasing flow rate in the range of 1.0–80.0 µl min−1 has an adverse effect on the device performance in terms of decreased separation efficiency of deformable blood cells. However, by tuning the gap size in the range of 2.5–7.5 µm, the selectivity of the separation is controlled from about 5.0 to 95.0% for white blood cells (WBCs) and 40.0 to 95.0% for red blood cells (RBCs). Finally, the best range of trapping and passing efficiencies of ~70–80.0% simultaneously for WBCs and RBCs in whole blood sample is achieved at optimum gap size of ~3.5–4.0 µm.

Mechanics of mechanochemically responsive elastomers

Mechanochemically responsive (MCR) polymers have been synthesized by incorporating mechanophores – molecules whose chemical reactions are triggered by mechanical force – into conventional polymer networks. Deformation of the MCR polymers applies force on the mechanophores and triggers their reactions, which manifest as phenomena such as changing colors, varying fluorescence and releasing molecules. While the activation of most existing MCR polymers requires irreversible plastic deformation or fracture of the polymers, we covalently coupled mechanophores into the backbone chains of elastomer networks, achieving MCR elastomers that can be repeatedly activated over multiple cycles of large and reversible deformations. This paper reports a microphysical model of MCR elastomers, which quantitatively captures the interplay between the macroscopic deformation of the MCR elastomers and the reversible activation of mechanophores on polymer chains with non-uniform lengths. Our model consistently predicts both the stress–strain behaviors and the color or fluorescence variation of the MCR elastomers under large deformations. We quantitatively explain that MCR elastomers with time-independent stress–strain behaviors can give time-dependent variation of color or fluorescence due to the kinetics of mechanophore activation and that MCR elastomers with different chain-length distributions can exhibit similar stress–strain behaviors but very different colors or fluorescence. Implementing the model into ABAQUS subroutine further demonstrates our model's capability in guiding the design of MCR elastomeric devices for applications such as large-strain imaging and color and fluorescence displays.

Stability of colistimethate sodium in a disposable elastomeric infusion device

Infections of the respiratory tract with Pseudomonas aeruginosa in cystic fibrosis patients are frequently treated with colistimethate sodium (CMS). For the intravenous administration of CMS a disposable elastomeric pump is a convenient option. To date, there are no data available on the chemical stability of CMS solutions stored in elastomeric pumps. We evaluated the chemical stability of 0.8mg/mL solutions of CMS by measuring the degradation over a period of 7 days. Test samples were prepared by diluting CMS with saline solution (0.9%). The preparations were transferred to 100-mL elastomeric pumps and stored at 4°C. The chemical stability was measured by a high-performance liquid chromatography method with UV detection. There was no degradation of CMS (<0.5% of CMS present as colistin) for at least 3 day at 4°C, and after 7 days all test samples remained chemically stable (<5% of CMS present as colistin). Since colistin formed in pharmacy-compounded CMS solutions prior to administration may cause toxicity, we advise that the solution should be used before the hydrolysis of CMS occurs. Therefore, we recommend that the 0.8mg/mL solution of CMS can be stored for up to 3 days at 4°C in an elastomeric pump.

Consideration of Nonuniformity in Elongation of Microstructures in a Mechanically Tunable Microfluidic Device for Size-Based Isolation of Microparticles

This paper presents an investigation of the nonlinearity behavior in deformation that appears during the linear stretching of the elastomeric microstructures in a pillar-based microfilter. Determining the impact of the nonuniformity in strain on the geometry and performance of such a planar device under in-plane stretch is the motivation for this study. A semiempirical model is used to explain the physical strain-stress behavior from the root to the tip of the micropillars in the linear arrays in the device. For microfabrication of the device, the main substrate is elastomeric polyurethane methacrylate, which is utilized in an ultraviolet-molding method. Optical imaging and scanning electron microscopy were used to evaluate the deformation of the microstructures under different loading conditions. It was demonstrated that by applying mechanical strains of <;20% (ΔL/L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> ) on the elastomeric device using a modified syringe pump, the spacing of the pillars is increased effectively to about three times the size of the initial setting of 5.5 μm, which corresponds to a strain of above 180% in the absence of nonuniformity effects. This simple yet interesting behavior can be exploited to rapidly adjust a microfluidic device for application to the separation of microbeads or blood cells, which would normally require the geometrical redesign and fabrication of a new device.

Experimental investigation of a low-cost elastomeric anti-seismic device using recycled rubber

The dynamic performances of a new typology of rubber isolators are discussed in this paper. The devices are denominated recycled rubber-fiber reinforced bearings (RR-FRBs). RR-FRBs are made by replacing natural rubber, commonly used for the production of structural bearings, with a recycled rubber-like material obtained by the reuse of exhausted tires and/or industrial leftovers. In RR-FRBs, steel transversal reinforcements are replaced by fiber sheets and vulcanization is avoided by using a polyurethane adhesive for bonding of the different layers. Thanks to the aforementioned characteristics, devices are extremely low-cost and lightweight if compared to traditional bearings for structural control. This paper presents an overview of theoretical models for the analysis of the compressive and shear behavior of the isolators. Moreover, the paper describes the findings of an experimental campaign conducted to assess the behavior of RR-FRBs both in compression and shear. Different reinforcement materials, geometries and configurations were tested. The study constitutes a deep assessment of the technology’s potentiality. The work underlines the possibility of using RR-FRBs for seismic risk mitigation of low-cost housing in seismic prone regions of the world.

Étude in vitro de la durée d’écoulement de solutions antibiotiques préparées dans des diffuseurs portables élastomériques : effet du stockage au froid pendant trois à sept jours

Within the cystic fibrosis patients' home care, EMERAA network ("Together against Cystic fibrosis in Rhone-Alpes and Auvergne") organizes parenteral antibiotics cures at home prepared in elastomeric infusion devices by hospital pharmacies. However, patients and nurses found that the durations of infusion with these devices were often longer than the nominal duration of infusion indicated by their manufacturer. This study aimed to identify the potential different causes in relation to these discordances. Three hundred and ninety devices of two different manufacturers are tested in different experimental conditions: three antibiotics each at two different doses, duration of cold storage (three days or seven days) or immediate tests without cold storage, preparation and storage of the solution in the device (protocol Device) or transfer in the device just before measurement (protocol Pocket). All tests highlighted a longer flow duration for devices prepared according to the protocol Device versus the protocol Pocket (P=0.004). Flow duration is increased in the case of high doses of antibiotics with high viscosity such as piperacilline/tazobactam. The results of this in vitro study showed the impact of: (1) the time between the filling of the device and the flow of the solution; (2) cold storage of elastomeric infusion devices; (3) concentration of antibiotics and therefore the viscosity of the solution to infuse. It is therefore essential that health care teams are aware of factors, which may lead to longer infusion durations with these infusion devices. When the additional time for infusion remain acceptable, it should be necessary to inform the patient and to relativize these lengthening compared to many benefits that these devices provide for home care.

Safety and effectiveness of home intravenous antibiotic therapy for multidrug-resistant bacterial infections.

Home intravenous antibiotic therapy is an alternative to hospital admission for moderately severe infections. However, few studies have analyzed its safety and effectiveness in the treatment of infections caused by multidrug-resistant bacteria. The purpose of this study is to analyze the safety and effectiveness of home intravenous antibiotic therapy in multidrug-resistant bacterial infections. We analyzed prospectively all patients admitted to our service who underwent home intravenous antibiotic therapy during the period 2008-2012. All the treatments were administered by caretakers or self-administered by patients, through elastomeric infusion devices. Effectiveness was evaluated by analyzing the readmission rate for poor infection control. Safety was evaluated by analyzing adverse events, catheter-related complications, and readmissions not related to poor infection control. There were 433 admissions (in 355 patients) for home intravenous antibiotic therapy during the study period. There were 226 (52.2 %) admissions due to multidrug-resistant bacterial infections and 207 (47.8 %) due to non-multidrug-resistant infections. Hospital readmissions in patients with multidrug-resistant infections were uncommon. Multidrug-resistant enterococcal infections, healthcare-associated infections, and carbapenem therapy were independent variables associated with increased readmissions due to poor infection control. Readmissions not related to poor infection control, adverse events, and catheter-related complications were similar in multidrug-resistant compared to non-multidrug-resistant bacterial infections. Home intravenous therapy, administered by patients or their caretakers using elastomeric infusion pumps, was safe and effective for the treatment of most multidrug-resistant bacterial infections.

A Combined HPLC and LC-MS Approach for Evaluating Drug Stability in Elastomeric Devices: A Challenge for the Sustainability in Pharmacoeconomics

Objectives A longer postoperative care, needed for patients admitted to the hospital, is expensive and associated with increased morbidity and mortality, when compared with the outpatient setting. Outpatient therapy with continuous infusion of drugs with elastomeric pumps represents an effective method to address this problem. The aim of this work is to analyse the benefits in using elastomeric devices and to test their their behaviour towards drugs to changes during storage that could influence quality, safety and efficacy of the therapy. Methods Several drugs belonging to different therapeutic classes, including anticancer, analgesic opioids, local anesthetics and Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) have been studied using a combined HPLC/LC-MS approach. Each drug was loaded in three different brands of elastomeric devices and the samples were withdrawn over 7 days and submitted to HPLC/LC-MS analyses. Key-Findings All tested drugs showed high stability in each filled device, in fact only a low variability, less than 5 %, in term of percentage change in chromatographic areas, was observed. Moreover additional peaks, due to degradation of drug and/or to medical device-drug interaction, have not been detected both in HPLC and LC-MS analysis. Conclusion Thanks to the implementation, within clinical protocols, of the use of these infusion systems, two important goals can be achieved: a) the keeping of the quality of care also out of hospitals and b) the reduction of tangible costs as well as intangible costs in health care.

Experimental Correlations with Calculus Parameters for a Dynamic System Equipped with Antiseismic Elastomeric Devices

Rezumat Lucrarea prezintă rezultatul încercărilor efectuate la cicluri cinematice cu deplasări instantanee armonice pentru elemente elastomerice cu rol de izolare dinamică în conformitate cu SR EN 1337-3 şi SR EN 15129. Valorile amortizării interne determinate pe standuri de încercare în condiţiile din documentele de referinţă trebuie corelate cu valorile sistemului de dispozitive antiseismice elastomerice ce echipează un sistem dinamic supus acţiunilor seismice exterioare. În acest caz, pentru fiecare situaţie reală, proiectantul trebuie să realizeze corelaţia dintre cele două valori ale amortizării obţinute în laborator cu amortizarea specifică sistemului structural care este supus acţiunilor dinamice exterioare. Din lucrare rezultă echivalenţa necesară astfel încât, valorile experimentale să poată fi corectate în mod riguros şi să poată reprezenta parametrii reali ce trebuie luaţi în calcul.