Modeling and development of screen-printed impedance biosensor for cytotoxicity studies of lung carcinoma cells

Electrical cell-substrate impedance sensing (ECIS) is a powerful technique to monitor real-time cell behavior. In this study, an ECIS biosensor formed using two interdigitated electrode structures (IDEs) was used to monitor cell behavior and its response to toxicants. Three different sensors with varied electrode spacing were first modeled using COMSOL Multiphysics and then fabricated and tested. The silver/silver chloride IDEs were fabricated using a screenprinting technique and incorporated with polydimethylsiloxane (PDMS) cell culture wells. To study the effectiveness of the biosensor, A549 lung carcinoma cells were seeded in the culture wells together with collagen as an extracellular matrix (ECM) to promote cell attachment on electrodes. A549 cells were cultured in the chambers and impedance measurements were taken at 12-h intervals for 120 h. Cell index (CI) for both designs were calculated from the impedance measurement and plotted in comparison with the growth profile of the cells in T-flasks. To verify that the ECIS biosensor can also be used to study cell response to toxicants, the A549 cells were also treated with anti-cancer drug, paclitaxel, and its responses were monitored over 5 days. Both simulation and experimental results show better sensitivity for smaller spacing between electrodes

RECENT TRENDS IN DENGUE DETECTION METHODS USING BIOSENSORS

ABSTRACT: Dengue illness is an infectious tropical disease, transmitted by Aedes mosquitos, that poses a serious health threat to the tropical world. This disease causes widespread infection worldwide, with about 50 million cases of dengue occurring per annum out of which 500,000 recorded cases of dengue hemorrhagic fever and 22,000 deaths.  Currently, there are no effective vaccines available to prevent the spread of the infection. Accurate and rapid laboratory diagnostic tests are required for early detection to reduce patient mortality rate. In this paper,  common laboratory diagnosis methods for detecting dengue virus infection are discussed. Currently, virus isolation, RT-PCR and serology methods provide the most direct and accurate response for detection of dengue. However, these methods require tedious steps, expensive requirements and expert staffs. Recent research have proposed the usage of biosensors as an alternative new technology for detection of dengue. In this work, various types of biosensors such as electrochemical, piezoelectric, and optical biosensor have been described and compared to evaluate their effectiveness in dengue detection.  It is observed that the optical biosensor offers the best detection due to its high sensitivity as compared to others, although it is popularly known as an expensive method. Alternatively, the use of electrochemical and piezoelectric biosensors (QCM) is highly recommended for detection of dengue due to their ease-of-use, low cost, low reagent consumption, disposability, and minimal sample preparation. These approaches have the potential to improve the rate of survival, particularly in resource-limited countries. ABSTRAK: Virus denggi adalah penyakit berjangkit tropika bawaan nyamuk Aedes yang menimbulkan ancaman serius kepada kesihatan global. Penyakit ini menyebabkan jangkitan yang meluas di seluruh dunia, dengan kira-kira 50 juta kes denggi yang berlaku setiap tahun di mana 500,000 kes demam denggi berdarah dan 22,000 kematian direkodkan. Buat masa ini, tiada vaksin yang berkesan untuk mencegah penyebaran jangkitan ini. Ujian diagnostik makmal yang cepat dan tepat diperlukan untuk pengesanan denggi awal untuk mengurangkan kadar kematian pesakit. Dalam artikel ini, kaedah diagnosis makmal yang biasa dilakukan untuk mengesahkan jangkitan virus denggi akan dibincangkan. Pada masa kini, kaedah pengasingan virus, RT-PCR dan serologi adalah tindak balas yang paling cepat dan tepat untuk mengesan denggi. Walau bagaimanapun, kaedah-kaedah ini memerlukan langkah-langkah yang melecehkan, kos penyelenggaraan yang tinggi dan kakitangan  yang terlatih.  Penyelidikan terkini telah mencadangkan penggunaan biosensor sebagai teknologi baru alternatif untuk mengesan denggi.  Dalam artikel  ini juga pelbagai jenis biosensor seperti biosensor elektrokimia, piezoelektrik, dan biosensor optik telah dijelaskan dan dibandingkan untuk menilai keberkesanannya dalam pengesanan denggi. Difahamkan bahawa biosensor optik menawarkan pengesanan terbaik kerana kepekaannya yang tinggi berbanding dengan yang lain, walaupun ia dikenali sebagai kaedah berkos tinggi. Sebaliknya, biosensor elektrokimia dan piezoelektrik (QCM) sangat disyorkan untuk mengesan denggi kerana ia mudah digunakan, berkos rendah, penggunaan bahan uji yang terhad, boleh dipakai buang, dan mempunyai penyediaan sampel yang minima. Pendekatan-pendekatan ini berpotensi untuk meningkatkan kadar kemandirian di kawasan-kawasan sumber terhad

Integrated multichannel electrochemical–quartz crystal microbalance sensors for liquid sensing

This paper highlights the design, simulation and fabrication of an array of twelve integrated electrochemical – quartz crystal microbalance (IEQCM) sensors on a single substrate for liquid sensing. Integration of both measurement techniques is made possible by combining the three electrode electrochemical device with the top and bottom electrodes for the microbalance. Important design parameters such as the working electrode radius and gap spacing, were studied using both theoretical calculations and COMSOL Multiphysics R finite element simulations. The sensor’s working electrode radius affects the magnitude of the frequency response while the gap affects the capacitance and current density which are important for electrochemical measurements. It was found that the best values for the working electrode radius was 2 mm and gap spacing was 0.5 mm. The sensors were fabricated using microfabrication techniques for the gold electrode and screen printing techniques for the reference electrode. Water contact angle, atomic force microscopy, and scanning electron microscope were utilized to study the surface roughness of the IEQCM sensor. IEQCM has a low contact angle of 53.0 ± 1 ◦ and low surface roughness of 1.92nm. For liquid sensing, an array of circular chambers were fabricated using polydimethylsiloxane (PDMS) and placed on top of the quartz substrate for liquid testing. Electrochemical measurements and cyclic voltammetry were performed using the sensor in ferri-ferrocyanide and phosphate buffered saline solution to study the function of scan rates on the peak current with respect to the potential difference. For mass sensing measurements, liquid water droplets of 1uL – 10 uL were placed onto the sensing surface and the change in resonance frequencies of the sensors were measured. These resonance frequency changes can be converted in mass change/area in accordance to the advanced Sauerbrey equation. The multichannel IEQCM sensor shows good potential as a parallel sensor for both biosensing and environmental applications

Piezoelectric characteristics of CMOS compatible AIN SAW resonators

In this work, we predict the surface acoustic wave characteristics by 2D COMSOL finite element modeling. The dispersion of simulated acoustic mode shapes, acoustic phase velocity and coupling coefficient were performed on a CMOS-compatible 1.4 GHz SAW resonator. C-axis oriented Aluminium Nitride (AIN) was chosen as the piezoelectric material due to its compatibility with CMOS technology and higher phase velocity. The influences of AIN thickness on electromechanical coupling coefficient and phase velocity are discussed. High acoustic velocities (v∼5220 m/s) and coupling factors (k2∼0.19%) can be observed for SAW resonator with khAIN∼ 3.9. The measurement results are found to be consistent with FEM results with deviation less than 6% for resonance frequency and phase velocity

A new crescent moon visibility criteria using circular regression model: a case study of Teluk Kemang, Malaysia

Many astronomers have studied lunar crescent visibility throughout history. Its importance is unquestionable, especially in determining the local Islamic calendar and the dates of important Islamic events. Different criteria have been used to predict the possible visibility of the crescent moon during the sighting process. However, so far, the visibility models used are based on linear statistical theory, whereas the useful variables in this study are in the circular unit. Hence, in this paper, we propose new visibility tests using the circular regression model, which will split the data into three visibility categories; visible to the unaided eye, may need optical aid and not visible. We formulate the procedure to separate the categories using the residuals of the fitted circular regression model. We apply the model on 254 observations collected at Baitul Hilal Teluk Kemang Malaysia, starting from March 2000 to date. We show that the visibility test developed based on elongation of the moon (dependent variable) and altitude of the moon (independent variable) gives the smallest misclassification rate. From the statistical analysis, we propose the elongation of the moon 7.28°, altitude of the moon of 3.33° and arc of vision of 3.74 at sunset as the new crescent visibility criteria. The new criteria have a significant impact on improving the chance of observing the crescent moon and in producing a more accurate Islamic calendar in Malaysia

Analysis data of the 22 years of observations on the young crescent moon at Telok Kemang observatory in relation to the Imkanur Rukyah criteria 1995

The main challenge in the young crescent moon (YCM) observation is the ability to detect the appearance of the YCM, which has varying contrast due to the phenomenon of twilight. The advancement of technology in digital imaging helps the faint and thin image of the YCM to be detected and taken during observation. The techniques used in the observations of the YCM were naked eyes, telescope, and telescope with cameras. A digital imaging technique is also being used in the observations to assist in detecting and recording the image of the YCM more effectively. This paper presents the analysis of the YCM observation data recorded at Telok Kemang Observatory from 2000 to the present. A total of 275 observation sessions were conducted during this study, with 87 positive sightings successfully recorded. The studies found that the smallest elongation and the minimum altitude at sunset of the YCM successfully recorded were 6.81° and 5.40°, respectively. The moon was recorded at an altitude of 3.37°, while the sky is still bright with the sun at an altitude of –2.64° using the digital imaging technique. Based on the records, the YCM which has the minimum criteria of Imkanur Rukyah, i.e., altitude of 2° and elongation of 3° at sunset was never detected or recorded during the 22 years of observations. Therefore, this work suggests the need to change the visibility of Imkanur Rukyah criteria used since 1995 to a more potentially observable criterion. In other aspects, the lengthy observation activities have contributed to the development of a database system for JAKIM that other researchers can access

Recent Studies of Human Limbs Rehabilitation Using Mechanomyography Signal: A Survey

In rehabilitation and medical offices, mechanomyography (MMG) is a noninvasive, painless technology that can be applied for a number of goals. The goal of this study is to present a thorough overview of recent studies on mechanomyography-based human limb rehabilitation. The present study illuminates the utilization of distinct transducers, including accelerometers, piezoelectric contact sensors, and condenser microphone sensors. Furthermore, it underscores the diverse results that these investigations have yielded. The main findings of this review, which apply to all of these forms of mechanomyography sensors, are that the ratio of sensor mass to muscle mass under observation is the most crucial factor in sensor selection. Therefore, it is believed that accelerometers are the most trustworthy devices for spotting MMG signals during both voluntary and induced muscular contractions

Study of multichannel QCM prospects in VOC detection

Quartz Crystal Microbalance (QCM) is a mass detection sensor capable of measuring mass sensitivity at nanogram levels when based on a thickness shear mode piezoelectric crystal set at high frequencies. These sensors detect with high accuracy while benefiting from simple geometry, low costs, and ease of fabrication. Researchers prefer piezoelectric crystal sensors to the recent methods of gas chromatography/mass chromatography (GC/MC), high pressure liquid chromatography and nuclear magnetic resonance (NMR), which are time-consuming and not cost-effective. Unlike conventional QCM sensors that are limited to a single-electrode structure—which minimizes their scope of detection—the Multichannel QCM (MQCM) incorporates multiple sensors fabricated on a single crystal wafer. Each sensor is selectively coated with a sensing material that promotes the adsorption of target vapours. One of the widely used application of QCM sensors is in Volatile Organic Compounds (VOC) detection. This paper imparts a critical overview of recent publications on the application of MQCMs with various sensing materials

Contributions of mean and shape of blood pressure distribution to worldwide trends and variations in raised blood pressure: A pooled analysis of 1018 population-based measurement studies with 88.6 million participants

© The Author(s) 2018. Background: Change in the prevalence of raised blood pressure could be due to both shifts in the entire distribution of blood pressure (representing the combined effects of public health interventions and secular trends) and changes in its high-blood-pressure tail (representing successful clinical interventions to control blood pressure in the hypertensive population). Our aim was to quantify the contributions of these two phenomena to the worldwide trends in the prevalence of raised blood pressure. Methods: We pooled 1018 population-based studies with blood pressure measurements on 88.6 million participants from 1985 to 2016. We first calculated mean systolic blood pressure (SBP), mean diastolic blood pressure (DBP) and prevalence of raised blood pressure by sex and 10-year age group from 20-29 years to 70-79 years in each study, taking into account complex survey design and survey sample weights, where relevant. We used a linear mixed effect model to quantify the association between (probittransformed) prevalence of raised blood pressure and age-group- and sex-specific mean blood pressure. We calculated the contributions of change in mean SBP and DBP, and of change in the prevalence-mean association, to the change in prevalence of raised blood pressure. Results: In 2005-16, at the same level of population mean SBP and DBP, men and women in South Asia and in Central Asia, the Middle East and North Africa would have the highest prevalence of raised blood pressure, and men and women in the highincome Asia Pacific and high-income Western regions would have the lowest. In most region-sex-age groups where the prevalence of raised blood pressure declined, one half or more of the decline was due to the decline in mean blood pressure. Where prevalence of raised blood pressure has increased, the change was entirely driven by increasing mean blood pressure, offset partly by the change in the prevalence-mean association. Conclusions: Change in mean blood pressure is the main driver of the worldwide change in the prevalence of raised blood pressure, but change in the high-blood-pressure tail of the distribution has also contributed to the change in prevalence, especially in older age groups

Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants

Summary Background Comparable global data on health and nutrition of school-aged children and adolescents are scarce. We aimed to estimate age trajectories and time trends in mean height and mean body-mass index (BMI), which measures weight gain beyond what is expected from height gain, for school-aged children and adolescents. Methods For this pooled analysis, we used a database of cardiometabolic risk factors collated by the Non-Communicable Disease Risk Factor Collaboration. We applied a Bayesian hierarchical model to estimate trends from 1985 to 2019 in mean height and mean BMI in 1-year age groups for ages 5–19 years. The model allowed for non-linear changes over time in mean height and mean BMI and for non-linear changes with age of children and adolescents, including periods of rapid growth during adolescence. Findings We pooled data from 2181 population-based studies, with measurements of height and weight in 65 million participants in 200 countries and territories. In 2019, we estimated a difference of 20 cm or higher in mean height of 19-year-old adolescents between countries with the tallest populations (the Netherlands, Montenegro, Estonia, and Bosnia and Herzegovina for boys; and the Netherlands, Montenegro, Denmark, and Iceland for girls) and those with the shortest populations (Timor-Leste, Laos, Solomon Islands, and Papua New Guinea for boys; and Guatemala, Bangladesh, Nepal, and Timor-Leste for girls). In the same year, the difference between the highest mean BMI (in Pacific island countries, Kuwait, Bahrain, The Bahamas, Chile, the USA, and New Zealand for both boys and girls and in South Africa for girls) and lowest mean BMI (in India, Bangladesh, Timor-Leste, Ethiopia, and Chad for boys and girls; and in Japan and Romania for girls) was approximately 9–10 kg/m2. In some countries, children aged 5 years started with healthier height or BMI than the global median and, in some cases, as healthy as the best performing countries, but they became progressively less healthy compared with their comparators as they grew older by not growing as tall (eg, boys in Austria and Barbados, and girls in Belgium and Puerto Rico) or gaining too much weight for their height (eg, girls and boys in Kuwait, Bahrain, Fiji, Jamaica, and Mexico; and girls in South Africa and New Zealand). In other countries, growing children overtook the height of their comparators (eg, Latvia, Czech Republic, Morocco, and Iran) or curbed their weight gain (eg, Italy, France, and Croatia) in late childhood and adolescence. When changes in both height and BMI were considered, girls in South Korea, Vietnam, Saudi Arabia, Turkey, and some central Asian countries (eg, Armenia and Azerbaijan), and boys in central and western Europe (eg, Portugal, Denmark, Poland, and Montenegro) had the healthiest changes in anthropometric status over the past 3·5 decades because, compared with children and adolescents in other countries, they had a much larger gain in height than they did in BMI. The unhealthiest changes—gaining too little height, too much weight for their height compared with children in other countries, or both—occurred in many countries in sub-Saharan Africa, New Zealand, and the USA for boys and girls; in Malaysia and some Pacific island nations for boys; and in Mexico for girls. Interpretation The height and BMI trajectories over age and time of school-aged children and adolescents are highly variable across countries, which indicates heterogeneous nutritional quality and lifelong health advantages and risks