Predicting Corrosion Delamination Failure in Active Implantable Medical Devices: Analytical Model and Validation Strategy

The ingress of body fluids or their constituents is one of the main causes of failure of active implantable medical devices (AIMDs). Progressive delamination takes its origin at the junctions where exposed electrodes and conductive pathways enter the implant interior. The description of this interface is considered challenging because electrochemically-diffusively coupled processes are involved. Furthermore, standard tests and specimens, with clearly defined 3-phase boundaries (body fluid-metal-polymer), are lacking. We focus on polymers as substrate and encapsulation and present a simple method to fabricate reliable test specimens with defined boundaries. By using silicone rubber as standard material in active implant encapsulation in combination with a metal surface, a corrosion-triggered delamination process was observed that can be universalised towards typical AIMD electrode materials. Copper was used instead of medical grade platinum since surface energies are comparable but corrosion occurs faster. The finding is that two processes are superimposed there: First, diffusion-limited chemical reactions at interfaces that undermine the layer adhesion. The second process is the influx of ions and body fluid components that leave the aqueous phase and migrate through the rubber to internal interfaces. The latter observation is new for active implants. Our mathematical description with a Stefan-model coupled to volume diffusion reproduces the experimental data in good agreement and lends itself to further generalisation.

Methodological foundations for substantiating safe levels of exposure to artificial nanomaterials (for example, carbon nanotubes) (literature review)

Introduction. The unique physicochemical properties of carbon nanotubes allow them to be used in many fields. The global nanomaterials market is growing every year. An important step in introducing products to the domestic and world markets is to determine the safe exposure levels of CNTs. Establishing a corporate standard can serve as a preliminary stage before the approval of a state hygiene standard. Material and methods. The material for the analysis was the sources of information on the available standards for the content of CNTs in the air of the working area using information from regulatory agencies, research centers, CNT manufacturers, bibliographic and abstract databases Web of Science, Scopus, PubMed, RSCI. Results. A scheme for justifying safe levels of exposure to CNTs (corporate standard) has been developed, consisting of several stages: characterization of CNTs in the air at workplaces, selection of experimental doses of CNTs, preparation of CNT dispersions, and conducting toxicological and hygienic experiments. Justification of the corporate standard is carried out in in vitro and in vivo experiments. The planning of experiments should be carried out taking into account the target organ under the influence of CNT - the respiratory system. The recommended dose / concentration range for experiments should include doses / concentrations derived from calculated and literature data. A necessary step is to obtain homogeneous dispersions in which CNTs become bioavailable for biological systems. In vitro and in vivo experiments determine the level of exposure at which no harmful effect is observed and / or the lowest level of exposure at which there is a harmful effect on the cell culture / respiratory tract of animals. After the stage of substantiating the corporate standard, the enterprise should take measures for several years to adjust the corporate standard based on data from clinical and hygienic studies, during which the working conditions and health status of workers are monitored, and extended toxicological and hygienic studies. Conclusion. The presence of a corporate standard will allow the manufacturer of CNTs to carry out activities for the development and implementation of a production control program with the introduction of monitoring the air condition in the working area. The development of a corporate regulation can be seen as a preparatory stage before the establishment of a government regulation.

Shock Hugoniot Data for Water up to 5 Mbar Obtained with Quartz Standard at High-Energy Laser Facilities

In this work, we present experimental results on the behavior of liquid water at megabar pressure. The experiment was performed using the HIPER (High-Intensity Plasma Experimental Research) laser facility, a uniaxial irradiation chamber of GEKKO XII (GXII) at the Institute of Laser Engineering (ILE), and the PHELIX at GSI (GSI Helmholtz Centre for Heavy Ion Research), a single-beam high-power laser facility, to launch a planar shock into solid multilayered water samples. Equation-of-state data of water H 2 O are obtained in the pressure range 0.50–4.6 Mbar by tuning the laser-drive parameters. The Hugoniot parameters (pressure, density, etc.) and the shock temperature were simultaneously determined by using VISAR and SOP as diagnostic tools and quartz as the standard material for impedance mismatch experiments. Finally, our experimental results are compared with hydrodynamic simulations tested with different equations of state, showing good compatibility with tabulated SESAME tables for water.

Diagnostic Accuracy of MRC in Benign and ML in Obstructive Jaundice Patients, Taking Histopathology as Gold Standard

Objectives: To find out the diagnostic accuracy of magnetic resonance cholangiopancreatography in benign and malignant lesions in patients of obstructive jaundice, taking histopathology as gold standard. Material and methods: This cross sectional study was conducted at Department of Radiology, Bahawal Victoria Hospital, Bahawalpur October 2019 to April 2020. A total of 164 patients with suspected cases of obstructive jaundice and age 25-65 years of either gender were included. Then magnetic resonance cholangiopancreatography (MRCP) was performed in every patient by 1.5 Tesla MR System using a torso phased-array coil. After this, each patient was undergone operation in the concerned ward. Findings of MRCP were compared with the findings of histopathology. Results: In MRCP positive patients, 78 were true positive (TP) and 13 were false positive (FP). Among 73, MRCP negative patients, 08 were false negative (FN) whereas 65 were True Negative (TN). Overall specificity, sensitivity, NPV, PPV and diagnostic accuracy of magnetic resonance cholangiopancreatography in benign and malignant lesions in patients of obstructive jaundice, taking histopathology as gold standard was 90.70%, 83.33%, 85.71%, 89.04% and 87.20% respectively. Conclusion: This study concluded that magnetic resonance cholangiopancreatography (MRCP) is the non-invasive modality of choice with diagnostic accuracy in diagnosing in benign and malignant lesions in obstructive jaundice patients. Keywords: obstructive jaundice, sensitivity, magnetic resonance imaging.

Ultra-High-Molecular-Weight-Polyethylene (UHMWPE) as Desired Polymer Material for Biomedical

It is very important that any materials used as implant material work in harmony with the body. There will be drawback with every material. No matter how good, as nothing can be 100% identical as the natural human tissue. The body operates in an environment at a constant temperature of 37°C and pH of 7.25, so choice of materials will have to withstand these conditions. Incorrect use of material can cause rejection by the body, infection and even cancer, leading to more pain and discomfort by the patient. In turn the possibility of even further damage to the joint. The implant must work in the same way as the body part it is replacing- clear understanding of how the joint works is needed. Ultrahigh molecular weight polyethylene is considered as the standard material for Artificial joints to decrease the total weight and the wear rate to make it more flexible. This is what makes Ultra-High-Molecular-Weight-Polyethylene (UHMWPE) such an appropriate polymer. It is very widely used in total hip and knee joint replacements having the highest known impact strength of any thermoplastic presently made, can highly withstand abrasion, and has a very low coefficient of friction. Therefore, these properties, connected with extremely low moisture absorption, make UHMWPE especial material for the medical industry due to good industrial impact and wear resistance sliding applications. For moving joints, the friction would be damaging without the natural lubrication. In implant components this does not exist, however UHMWPE is self-lubricating, making it ideal for component such as an acetabular cup, which would wrap around a metallic femoral head in a hip joint. Also, UHMWPE has high impact strength, high toughness, and low elastic modulus, but it has disadvantages such as low tensile, transverse and compressive strengths with high creep rate. This review article deals with the history of UHMWPE, its material properties that make it an ideal candidate for total joints, implant-component fabrication procedures and provides insights as to why some of the implants eventually fail.

Influence of Menisci on Tibiofemoral Contact Mechanics in Human Knees: A Systematic Review

Purpose: Menisci transfer axial loads, while increasing the load-bearing tibiofemoral contact area and decreasing tibiofemoral contact pressure (CP). Numerous clinical and experimental studies agree that an increased CP is one predominant indicator for post-traumatic osteoarthritis (PTOA) of the knee joint. However, due to the immense variability in experimental test setups and wide range of treatment possibilities in meniscus surgery, it is difficult to objectively assess their impact on the CP determination, which is clearly crucial for knee joint health. Therefore, the aim of this systematic review is to investigate the influence of different meniscal injuries and their associated surgical treatments on the CP. Secondly, the influence of different test setups on CP measurements is assessed. On the basis of these results, we established the basis for recommendations for future investigations with the aim to determine CPs under different meniscal states.Methods: This review was conducted in accordance with the PRISMA guidelines. Studies were identified through a systematic literature search in Cochrane, PubMed and Web of Science databases. Literature was searched through pre-defined keywords and medical subject headings.Results: This review indicates a significant increase of up to 235% in peak CP when comparing healthy joints and intact menisci with impaired knee joints, injured or resected menisci. In addition, different test setups were indicated to have major influences on CP: The variety of test setups ranged from standard material testing machines, including customized setups via horizontal and vertical knee joint simulators, through to robotic systems. Differences in applied axial knee joint loads ranged from 0 N up to 2,700 N and resulted unsurprisingly in significantly different peak CPs of between 0.1 and 12.06 MPa.Conclusion: It was shown that untreated traumatic meniscal tears result in an increased CP. Surgical repair intervention were able to restore the CP comparable to the healthy, native condition. Test setup differences and particularly axial joint loading variability also led to major CP differences. In conclusion, when focusing on CP measurements in the knee joint, transparent and traceable in vitro testing conditions are essential to allow researchers to make a direct comparison between future biomechanical investigations.

RADIOLOGICAL TESTS VERSUS PATHOLOGICAL DIAGNOSTICS: COMPLIMENTARY OR ANTAGONISTIC RELATIONSHIP- AN INSTITUTIONAL EXPERIENCE

Aims & Objective: To determine the yield, reliability and diagnostic accuracy of Breast Imaging Reporting and Data System in evaluation of breast lesions taking histopathology as gold standard. Material and Methods: This cross-sectional, analytical study was conducted at Pathology dept. Of SMSMC Jaipur from June 2019 to June 2020. The data of the core needle biopsies of breast lesions received at the Pathology department which had been also categorized on mammogram, according to the Breast Imaging Reporting and Data System (BI-RADS), were selected for the study. All clinical parameters, the site of the biopsy, the radiological findings, the pathological diagnoses were studied. The concordance between the radiological and pathological results was studied . According to BI-RADS, categories II and III were classified as benign and BI-RADs IV and V as malignant. The breast core biopsies were classified as benign and malignant, according to the diagnosis. Results: A total of 115 patients were included in the study. BI-RADS system for reporting whencompared with histopathology had sensitivity of 93.55%, specificity 68.18%, positive predictive value92.55%, negative predictive value 71.43% and diagnostic accuracy 88.70%. Conclusion: The findings of this study report a high diagnostic accuracy of BI-RADS in the diagnosis ofbreast carcinoma.

Alumina, Zirconia and Their Composite Ceramics with Properties Tailored for Medical Applications

Although in 1977 the first ceramic composite material had been introduced into the market, it was a long time before composite materials were qualified for medical applications. For a long period high purity alumina ceramics have been used as ball-heads and cups. Because of their brittleness, in 1986 yttria stabilized zirconia has been introduced into this application, because of higher strength and fracture toughness. However, due to its hydrothermal instability this material disappeared in orthopaedic applications in 2000. Meanwhile a composite materials based on an alumina matrix with dispersed metastable tetragonal zirconia particles and in-situ formed hexagonal platelets became the standard material for ceramic ball-heads, because of their excellent mechanical strength, hardness and improved fracture toughness. Especially fracture toughness can be improved further by special material formulations and tailored microstructure. It has been shown that a mixed stabilisation of zirconia by yttria and ceria with dispersed alumina and hexagonal platelets overcomes the hydrothermal instability and excellent materials properties can be achieved. Such materials do have big potential to be used in dental applications. Furthermore, these materials also can be seen as a new generation for ball-heads, because of their enhanced fracture toughness. All materials are described within these articles. In order to achieve the required properties of the materials, special raw materials are required. Therefore, it is quite important to understand and know the raw material manufacturing procedures.

A New Reference Plasmid “pGMT27” Provides an Efficient Transgenic Detection Method for Flue-Cured Tobacco

Owing to the economic value of its foliage, tobacco (Nicotiana tabacum) is cultivated all across the world. For the detection of genetically modified (GM) tobacco, there is a lack of universal standard material which ultimately limits the detection methods because the accuracy and comparability of the results cannot be ensured. Here, we prepared a reference plasmid “pGMT27” for the detection of GM tobacco, which was 18,296 bp in length harboring two of the tobacco endogenous and seven exogenous genes. By using qualitative PCR test for the nine genes, 10 copies were used for plasmid sensitivity. In the quantitative real-time PCR (qPCR) assays with pGMT27 as a calibrator, the reaction efficiencies for P-35S and NR were 101.427% and 98.036%, respectively, whereas the limit of detection (LOD) and limit of quantification (LOQ) were 5 copies and 10 copies per reaction. For standard deviation (SD) and relative standard deviation (RSD) of the Ct values, the repeatability values were from 0.04 to 0.42 and from 0.18% to 1.29%, respectively; and the reproducibility values were from 0.04 to 0.39 and from 0.18% to 1.14%, respectively. For the unknown sample test, the average conversion factor (Cf) was 0.39, and the accuracy bias was from −15.55% to 1.93%; for precision, the SD values ranged from 0.02 to 0.62, while RSD values were from 1.34% to 10.6%. We concluded that using the pGMT27 plasmid as a calibrator provided a highly efficient transgenic detection method for flue-cured tobacco.