In recent years, the development of portable platforms for performing fast and point-of-care analyses has drawn considerable attention for their wide variety of applications in life science. In this framework, tools combining magnetoresistive biosensors with magnetic markers have been widely studied in order to detect concentrations of specific molecules, demonstrating high sensitivity and ease of integration with conventional electronics. In this work, first, we develop a protocol for efficient hybridization of natural DNA; then, we show the detection of hybridization events involving natural DNA, namely genomic DNA extracted from the pathogenic bacterium Listeria monocytogenes, via a compact magnetic tunneling junction (MTJ)-based biosensing apparatus. The platform comprises dedicated portable electronic and microfluidic setups, enabling point-of-care biological assays. A sensitivity below the nM range is demonstrated. This work constitutes a step forward towards the development of portable lab-on-chip platforms, for the multiplexed detection of pathogenic health threats in food and food processing environment

Methods for the manipulation of single magnetic particles have become very interesting, in particular for in vitro biological studies. Most of these studies require an external microscope to provide the operator with feedback for controlling the particle motion, thus preventing the use of magnetic particles in high-throughput experiments. In this paper, a simple and compact system with integrated electrical feedback is presented, implementing in the very same device both the manipulation and detection of the transit of single particles. The proposed platform is based on zig-zag shaped magnetic nanostructures, where transverse magnetic domain walls are pinned at the corners and attract magnetic particles in suspension. By applying suitable external magnetic fields, the domain walls move to the nearest corner, thus causing the step by step displacement of the particles along the nanostructure. The very same structure is also employed for detecting the bead transit. Indeed, the presence of the magnetic particle in suspension over the domain wall affects the depinning field required for its displacement. This characteristic field can be monitored through anisotropic magnetoresistance measurements, thus implementing an integrated electrical feedback of the bead transit. In particular, the individual manipulation and detection of single 1-μm sized beads is demonstrated.

The resolution of digital lock-in amplifiers working with a narrow bandwidth (<100 Hz) is limited by slow fluctuations, which can be two orders of magnitude larger (μV range) than the noise of the input amplifier (tens of nV). In order to tackle this issue, affecting state-of-the-art laboratory instrumentation and here systematically quantified, three differential sensing configurations are presented. They adapt to different setup conditions and are based on manual and automatic tuning of dummy references, allowing a 25-fold resolution improvement for enhanced long-term tracking of impedance sensors.

A promising strategy to get deeper insight on brain functionalities relies on the investigation of neural activities at the cellular and sub-cellular level. In this framework, methods for recording neuron electrical activity have gained interest over the years. Main technological challenges are associated to finding highly sensitive detection schemes, providing considerable spatial and temporal resolution. Moreover, the possibility to perform non-invasive assays would constitute a noteworthy benefit. In this work, we present a magnetoresistive platform for the detection of the action potential propagation in neural cells. Such platform allows, in perspective, the in vitro recording of neural signals arising from single neurons, neural networks and brain slices.

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