Review: Biosensors for the detection of Escherichia coli

The supply of safe potable water, free from pathogens and chemicals, requires routine  analyses and the application of several diagnostic techniques. Apart from being  expensive, many of the detection methods require trained personnel and are often time-consuming. With drastic climate changes, severe droughts, increases in  population and pollution of natural water systems, the need to develop ultrasensitive, low-cost and hand-held, point-of-use detection kits to monitor water quality is critical. Although Escherichia coli is still considered the best indicator of water quality, cell numbers may be below detection limits, or the cells may be non-culturable and thus only detected by DNA amplification. A number of different biosensors have been developed to detect viable, dead or non-culturable microbial cells and chemicals in water. This review discusses the differences in these biosensors and evaluates the application of microfluidics in the design of ultra-sensitive nano-biosensors.Keywords: Biosensors, microfluidics, nano-biosensors, E. coli detectio

Point-of-Care Detection Devices for Healthcare

With recent technological advances in multiple research fields such as materials science, micro-/nano-technology, cellular and molecular biology, bioengineering and the environment, much attention is shifting toward the development of new detection tools that not only address needs for high sensitivity and specificity but fulfil economic, environmental, and rapid point-of-care needs for groups and individuals with constrained resources and, possibly, limited training. Miniaturized fluidics-based platforms that precisely manipulate tiny body fluid volumes can be used for medical, healthcare or even environmental (e.g., heavy metal detection) diagnosis in a rapid and accurate manner. These new detection technologies are potentially applicable to different healthcare or environmental issues, since they are disposable, inexpensive, portable, and easy to use for the detection of human diseases or environmental issues—especially when they are manufactured based on low-cost materials, such as paper. The topics in this book (original and review articles) would cover point-of-care detection devices, microfluidic or paper-based detection devices, new materials for making detection devices, and others

Microscale biosensors for HIV detection and viral load determination

The HIV/AIDS pandemic has killed 39 million people worldwide, and nearly as many people are living with HIV infection today. The global response to this disease has come a long way since the emergence of HIV in the early 1980s, including more than 64 billion USD in international spending between 2002 and 2013 alone [1]. Due to the worldwide effort, HIV infection has been transformed from a death sentence into a manageable, chronic illness that can have limited impact on lifespan when treated properly [2]. Antiretroviral therapy, public health campaigns, and other education and prevention efforts have facilitated an age in which no one, regardless of age, gender, sexual orientation, nationality, or socioeconomic status should face despair on account of this infection. However, barriers persist to bringing proper care to millions of people worldwide, including access to testing and the diagnostic tools necessary for proper administration of therapy. Following serological testing to establish HIV-positive status, the current standard of care requires monitoring of CD4+ T lymphocyte counts and plasma HIV viral load to guide administration of antiretroviral therapy. For many individuals living with HIV worldwide, the expensive and sophisticated laboratory instruments necessary for these measurements are extremely difficult to access due to poor healthcare infrastructure and lack of technical personnel. For those who are capable of bearing the expense and inconvenience of traveling to facilities that can provide one or both of these measurements, continuing care can be hindered by difficulties in patient follow-up. A point-of-care technology capable of performing these essential measurements to HIV therapy, therefore, is a critical need worldwide. Here we explore solutions rooted in micro- and nanotechnology principles to address this immense challenge in global health. Point-of-care diagnostics which meet the following criteria could improve the way that HIV/AIDS is treated, particularly in remote and resource-limited settings: low-cost assays (approximately $10 or less), small sample volumes (approximately 10 μL or less), rapid measurements (approximately 10 minutes or less), as well as technologies that are easy to use and portable. Our expertise in this area began with the development of a lab-on-a-chip micro-cytometer for CD4+ T lymphocyte enumeration from a drop of whole blood, which was tested on HIV-positive patients in the Champaign-Urbana, IL area and matched results from clinical flow cytometry at Carle Foundation Hospital in Urbana, IL [3]. This thesis describes work on the complementary measurement, viral load detection, aimed at meeting the ideal criteria described above for a point-of-care diagnostic technology. Our approaches to viral load measurements follow two broad themes. First, we describe an antigen-based approach which leverages immuno-affinity recognition for whole virus particle detection. In this method, the novel component of our sensing system is an ion-filled liposome which, upon stimulation (in this case, by heating), releases ions into low-conductivity media in a microchannel and can be quantitatively measured by a simple impedance measurement. We have termed this technique “ion-release impedance spectroscopy.” Employing the liposome in an immunoassay involving a primary capture antibody to HIV surface proteins and a secondary, identical antibody anchored to the exterior of the liposome, we are able to show qualitative detection of HIV virions in a microchannel [4]. We have improved aspects of this approach by performing ion-release impedance spectroscopy with liposomes exhibiting a higher melting temperature, and explored immuno-affinity capture of viruses on magnetic beads in an attempt to perform a concentration or separation step from a whole blood sample. Our second approach is detection of viral RNA in whole blood. In this technique, we employ loop-mediated isothermal amplification (LAMP) in the detection of viral RNA following a reverse-transcription test. One novel aspect of this approach is in performing the test from unprocessed whole blood, which we introduce into a microfluidic channel, mix with cell lysis buffer, add to RT-LAMP reagents, and distribute into nanoliter-scale droplets on a silicon microchip. Another novel step is to image this reaction with a consumer mobile smartphone device, which we integrate with the microchip setup using a 3-D printed platform. Results from our smartphone-imaged RT-LAMP technique show amplification in reactions containing as few as 3 virus particles per droplet, corresponding to 670 viruses per microliter of whole blood [5]. The true power of this approach, however, can be realized in a quantitative digital detection approach for which we describe a framework and preliminary designs, providing a basis for a highly-practical viral load test based on the proof-of-concept demonstrated in our lab. These micro- and nanotechnology approaches to HIV viral load measurements give hope for a portable diagnostics platform which could bring the standard of life-saving HIV/AIDS care to people in all parts of the world, no matter how remote or resource-limited