RESUMEN
During infectious disease outbreaks, the centers for disease control need to monitor particular areas. Considerable effort has been invested in the development of portable, user-friendly, and cost-effective systems for point-of-care (POC) diagnostics, which could also create an Internet of Things (IoT) for healthcare via a global network. However, at present IoT based on a functional POC instrument is not available. Here we show a fast, user-friendly, and affordable IoT system based on a miniaturized polymerase chain reaction device. We demonstrated the system's capability by amplification of complementary deoxyribonucleic acid (cDNA) of the dengue fever virus. The resulting data were then automatically uploaded via a Bluetooth interface to an Android-based smartphone and then wirelessly sent to a global network, instantly making the test results available anywhere in the world. The IoT system presented here could become an essential tool for healthcare centers to tackle infectious disease outbreaks identified either by DNA or ribonucleic acid.
RESUMEN
Optofluidic devices combining optics and microfluidics have recently attracted attention for biomolecular analysis due to their high detection sensitivity. Here, we show a silicon chip with tubular microchannels buried inside the substrate featuring temperature gradient (∇T) along the microchannel. We set up an optical fluorescence system consisting of a power-modulated laser light source of 470 nm coupled to the microchannel serving as a light guide via optical fiber. Fluorescence was detected on the other side of the microchannel using a photomultiplier tube connected to an optical fiber via a fluorescein isothiocyanate filter. The PMT output was connected to a lock-in amplifier for signal processing. We performed a melting curve analysis of a short dsDNA - SYBR Green I complex with a known melting temperature (TM) in a flow-through configuration without gradient to verify the functionality of the proposed detection system. We then used the segmented flow configuration and measured the fluorescence amplitude of a droplet exposed to ∇T of ≈ 2.31 °C mm-1, determining the heat transfer time as ≈ 554 ms. The proposed platform can be used as a fast and cost-effective system for performing either MCA of dsDNAs or for measuring protein unfolding for drug-screening applications.
RESUMEN
Availability of potable water is a problem especially in developing countries as their water sources are often contaminated biologically as well as by heavy metals. Electrochemical methods are suitable for field application to monitor heavy metal contents. Noble metal electrodes with large surface areas are the subject of intensive development as they can yield an improved signal-to-noise ratio, enhanced sensitivity, and lower limits of detection (LOD). Here, we present a nanostructured Au microelectrode array subsequently modified by selective electrodeposition in lithographically defined circles within a partially cross-linked gelatin layer. This method increased its surface area by a factor of ≈1440 in comparison with an original lithography-based prepared array. The Au surface properties can be tailored by a degree of gelatin layer cross-linking. We used this array for an ultrasensitive detection of the As3+ ions content by stripping voltammetry achieving LOD of ≈0.0212 parts per billion (signal-to-noise ratio = 3.3), 470× below the content limit recommended by the World Health Organization for potable water. These nanostructured arrays were used to detect ions of other metals such as Cr, Cd, Hg, Cu, and Sb. In combination with a portable electrochemical device, we can envision an ultrasensitive heavy metal detection system for field application to monitor heavy metal contamination.
RESUMEN
In this work, we present a study on reusable thin metal film resistivity-based sensor for direct measurement of binding of thiol containing molecules in liquid samples. While in bulk conductors the DC current is not influenced by the surface events to a measureable degree in a thin metal layer the electrons close to the surface conduct a significant part of electricity and are influenced by the surface interactions. In this study, the thickness of the gold layer was kept below 100 nm resulting in easily measureable resistivity changes of the metal element upon a surface SH-groups binding. No further surface modifications were necessary. Thin film gold layers deposited on a glass substrate by vacuum sputtering were photolithographically structured into four sensing elements arranged in a Wheatstone bridge to compensate for resistance fluctuations due to the temperature changes. Concentrations as low 100 pM provided measureable signals. The surface after the measurement could be electrolytically regenerated for next measurements.
