In the last years, it has been a growing interest in the development of biosensors for different applications in medicine, environmental sensing, food testing, etc. [1] Bridging the gap between the laboratory status of the biosensors to applications is expensive and time-consuming. Besides their design, manufacture and biofunctionalization, an extensive experimental testing work is required. One way to reduce the testing time is reusing the biosensors. With this aim, different regeneration strategies have been explored by different groups [2-4]. However, most of the protocols for regeneration require to remove the transducers from the experimental system and to reassemble the system again.

In this work, we pursue a strategy to reuse silicon-based photonic biosensors functionalized with molecular beacon (MB) probes immobilized for multiple detection of target microRNAs. This strategy aims at performing a so-called online regeneration, which not only allows saving time, but also reducing the sensor-to-sensor variance in the experimental sensing results, what is specially useful when testing similar levels of analyte. Chemical regeneration based on formamide (FA) was the strategy explored in this study. FA is a denaturing agent for nucleic acids, it is commonly used in DNA solutions [5]. However, little is known about FA as denaturing agent for microRNA bounded to MB probes immobilized on silicon surfaces as in the case we are interested in [6]. Our study consisted of, after running a typical microRNA sensing experiment, flowing FA in water to dehybridize the probes and regenerate the sensor for performing further experiments. Several tests were carried out and finally a regeneration protocol based on FA was successfully developed.

References:

[1] P. J. Conroy, S. Hearty, P. Leonard, and R. J. O’Kennedy, Seminars in Cell&Development Biology, 2009, 20, 10-26.

[2] Stephane Leahy, and Yongjun Lai, Sensing and Bio-Sensing Research, 2015, 6, 24-27.

[3] J. A. Goode, J. V. Rushworth, and P. A. Millner, Langmuir, 2015, 31, 6267-6276.

[4] Saumya Joshi, Vijay Deep Bhatt, Andreas Märtl, Markus Becherer, and Paolo Lugli, Biosenors, 2018, 8, 9.

[5] Julia Fuchs, Daniel Dell’Atti, Arnaud Buhot, Roberto Calemczuk, Marco Macini, Thierry Livache, Anal. Biochem, 2010, 397, 132-134

[6] Ángela Ruiz-Tórtola, Francisco Prats-Quílez, Daniel González-Lucas, María-José Bañuls, Ángel Maquieira, Guy Wheeler, Tamas Dalmay, Amadeu Griol, Juan Hurtado, and Jaime García-Rupérez. Biomed. Opt. Express 2018, 9(4), 1717-1727.

The energy consumption in wireless sensor networks is the critical concern of different studies, especially because of the great effort, or even the impossibility, to replace the battery of their motes. Consequently, it is fundamental to investigate and evaluate the energy spent by every individual task executed by the motes in order to provide an efficient use of their batteries. In this work, we employ different metrics to present a thorough study of how the use of multiple transmission power levels affects multihop wireless sensor networks. This work is motivated by the current employment of the multiple transmission power levels, on both academic works and commercial solutions, which is a novel feature of some radio transceivers commonly used in wireless sensor network motes. Aiming reliable and extensive analysis, this study employs simulations in different scenarios and models of commonly employed electronic components. The contribution of this works is a detailed investigation of the impact caused by the use of different transmission power levels employing different metrics, offering a wide perspective on the subject. In general, the results of this study indicate that the use of multiple power levels grants both positive and negative results, according to the scenario and metrics analyzed. Consequently, the analysis, results and remarks are presented in a didactic manner in order to provide valuable information and to support other works regarding this topic.

The use of accelerometers to obtain information on the state of honeybee colonies has several advantages over sound recorded by microphones, in that (i) accelerometers can reside in a honeybee hive for several years with a negligible effect of propolis coating (ii) they are particularly good at monitoring the low frequency signals which form a large part of the honeybee communication processes, and (iii) they sense a physical property, the vibration, that is probably far more relevant to them than sounds. One example of accelerometers allowing the observation of specific vibrational communication signals has been reported for the ‘whooping signal’ (doi: 10.1371/journal.pone.0171162). The vibrational amplitude is also dependent on the local environment/substrate and this has been demonstrated to be a strong indicator of an active queen (doi:10.1371/journal.pone.0141926). These previous reports have used ultra-high performance accelerometers (Brüel and Kjær, 4507) which also require separate signal conditioning electronics before the vibrational data can be logged; this represents a very expensive arrangement that precludes wide deployment. In this work we demonstrate that the 805M1 single axis analogue output accelerometer, that incorporates a piezo-ceramic crystal with low power electronics in a shielded housing, can be used to monitor honey bee activity and requires only a low cost microcontroller with an audio shield to log the data. We present high quality accelerometer output signals for both individual bee pulses and long term amplitude monitoring using this affordable measurement system. The signals appear of similar quality to those acquired with ten fold more expensive equipment.

Optical integrated sensors, such as Mach-Zehnder Interferometers (MZI), offer remarkable advantages in terms of sensitivity and compactness for label-free bio-sensing applications [1-2], although they need from additional structures and long arms to perform the sensing. In this work, we report a new interferometric sensing method encompassing the benefits of MZIs while reducing the footprint of the integrated device. This new approach is based on the interference between two Bloch modes propagating through a single-channel and one-dimensional photonic crystal, where the slow-wave effect takes place.

The principle of operation is the following: a single-mode waveguide working in TE polarization excites two modes, which interfere with each other by an abrupt discontinuity into the second single-mode waveguide at the output. For a given variation of the cladding refractive index unit (RIU), the propagation constant of the guided modes changes, producing an increase in the phase shift. Due to the slow-wave phenomenon whereby light travels slower than in other structures, good values of sensitivity are obtained for short device lengths in comparison to other interferometers and without the necessity of long modal sections to achieve enough phase shift (dimensions around 35 microns) . In summary, this approach could result in novel interferometric sensing structures for lab-on-a-chip integrated devices and other bio-sensing applications.

[1] Q. Liu, X. Tu, K. W. Kim, J. S. Kee, Y. Shin, K. Han, Y. J. Yoon, G. Q. Lo, and M. K. Park, Sensors Actuators, B Chem. 188, 681 (2013).

[2] Q. Kun, H. Shuren, and S. T., Opt. Lett. 1 (2016).

[3] K. E. Zinoviev, A. B. González-Guerrero, C. Domínguez, and L. M. Lechuga, J. Light. Technol. 29, 1926 (2011).

An individual's cardiovascular state is a crucial aspect of healthy life. However, it is not routinely assessed outside the clinical setting. Smart wearables use photoplethysmography (PPG) to monitor the arterial pulse wave (PW) and estimate heart rate. The PPG PW is strongly influenced by the ejection of blood from the heart, providing opportunity to monitor cardiac parameters using smart wearables. The aim of this study was to investigate the feasibility of monitoring cardiac contractility and left ventricular ejection time (LVET) from a peripheral PPG signal.

PPG PWs were simulated under a range of cardiovascular conditions using a numerical model of PW propagation. PWs were simulated at measurement sites suitable for non-invasive measurements, including the upper arm, wrist, and neck. Indices of cardiac contractility and LVET were extracted from the first and second derivatives of the PPG PWs, and compared to reference values extracted from the blood pressure PW at the aortic root.

There was strong agreement between the estimated and reference values of LVET, indicating that it may be feasible to assess LVET from PPG signals, including those acquired by smart watches. The correlations between the estimated and reference contractility parameters were less strong, indicating that further work is required to assess contractility robustly using smart wearables.

This study demonstrated the feasibility of assessing LVET using smart wearables, which would allow individuals to monitor their cardiovascular state on a daily basis. Further development of techniques to monitor contractility would be particularly for safety monitoring during drug trials.