Developing point-of-care (PoC) diagnostic platforms for carcinoembryonic antigen detection is essential. However, thefew implementations of transferring the signal amplification strategies in electrochemical sensing on paper-based platforms are not satisfactory in terms of detection limit (LOD). In the quest for pushing down LOD, majority of the research has been targeted towards development of improved nanostructured substrates for entrapping more analyte molecules and augmenting the electron transfer rate to the working electrode. But, such approaches have reached saturation. This paper focuses on enhancing the mass transport of the analyte towards the sensor surface through the application of an electric field, in graphene-ZnO nanorods heterostructure. These hybrid nanostructures have been deposited on flexible polyethylene terephthalate substrates with screen printed electrodes for PoC application. The ZnO nanorods have been functionalized with aptamers and the working sensor has been integrated with smartphone interfaced indigenously developed low cost potentiostat. The performance of the system, requiring only 50 µl analyte has been evaluated using electrochemical impedance spectroscopy and validated against commercially available ELISA kit. Limit of detection of 1 fg/ml in human serum with 6.5% coefficient of variation has been demonstrated, which is more than three orders of magnitude lower than the existing attempts on PoC device.
Most of the existing systems for elderly health monitoring deploy a large number of cognitive sensors including wearable sensors for physiological parameter measurement. Increasing number of sensors not only make the system power consuming and expensive but also intrusive in nature. However, there exists very limited research on power saving algorithms in such systems incorporating customer friendly features. In this paper, we report a modified health monitoring system which addresses both these issues. The central controller unit has an in-built algorithm based on two level adaptive branch prediction techniques to detect the period of inactivity of sensor nodes. Further, only one wearable heart rate sensor node is included in the system which measures the heart rate and detects abnormality. The central controller signals an alarm to the user to wear this predicting the sleeping time. This makes the system minimally intrusive and user friendly. Thus the multi-sensor network consists of motion sensor, current sensor and a wearable heart rate sensor along with a central controller unit. The prototype of the whole system has been installed in the house of elderly person and it has been observed that the time of prediction was close to the actual time for more than 90% of the days for a test period of one month. An average of 68% power saving has been achieved in the modified system.Index terms : health monitoring, elderly people, multi-sensor system, power saving, minimally intrusive.
Reduced graphene oxide, in various configurations has been extensively researched as field effect transistor (FET) biosensor, but they usually exhibit low signal to noise ratio. In this paper, we report the fabrication of low noise FET biosensors with electrochemically reduced graphene oxide(ERGO) on fluorine doped tin oxide(FTO) glass, directly by electrochemical reduction of GO in solution. It has been observed that the sensor is capable of detecting down to1 fM concentration of Hep-B in serum with a dynamic range from 1 fM to 20 pM, linearity of around 95% and current sensitivity of 1.21 mA. Moreover, the signal to noise ratio is around 80 in serum, which is enhanced by more than one order of magnitude compared to the most sensitive reports. Further, the presence of Hep-B can be confirmed by the Lorentzian nature of noise spectra, which makes the detection more precise. The combined advantages of low cost and clean fabrication coupled with sensitive and reliable performance renders the device suitable for point of care diagnostics.
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