Biocompatibility of a Magnetic Tunnel Junction Sensor Array for the Detection of Neuronal Signals in Culture

Magnetoencephalography has been established nowadays as a crucial in vivo technique for clinical and diagnostic applications due to its unprecedented spatial and temporal resolution and its non-invasive methods. However, the innate nature of the biomagnetic signals derived from active biological tissue is still largely unknown. One alternative possibility for in vitro analysis is the use of magnetic sensor arrays based on Magnetoresistance. However, these sensors have never been used to perform long-term in vitro studies mainly due to critical biocompatibility issues with neurons in culture. In this study, we present the first biomagnetic chip based on magnetic tunnel junction (MTJ) technology for cell culture studies and show the biocompatibility of these sensors. We obtained a full biocompatibility of the system through the planarization of the sensors and the use of a three-layer capping of SiO2/Si3N4/SiO2. We grew primary neurons up to 20 days on the top of our devices and obtained proper functionality and viability of the overlying neuronal networks. At the same time, MTJ sensors kept their performances unchanged for several weeks in contact with neurons and neuronal medium. These results pave the way to the development of high performing biomagnetic sensing technology for the electrophysiology of in vitro systems, in analogy with Multi Electrode Arrays

Biocompatibility of a Magnetic Tunnel Junction Sensor Array for the Detection of Neuronal Signals in Culture

Magnetoencephalography has been established nowadays as a crucial in vivo technique for clinical and diagnostic applications due to its unprecedented spatial and temporal resolution and its non-invasive methods. However, the innate nature of the biomagnetic signals derived from active biological tissue is still largely unknown. One alternative possibility for in vitro analysis is the use of magnetic sensor arrays based on Magnetoresistance. However, these sensors have never been used to perform long-term in vitro studies mainly due to critical biocompatibility issues with neurons in culture. In this study, we present the first biomagnetic chip based on magnetic tunnel junction (MTJ) technology for cell culture studies and show the biocompatibility of these sensors. We obtained a full biocompatibility of the system through the planarization of the sensors and the use of a three-layer capping of SiO2/Si3N4/SiO2. We grew primary neurons up to 20 days on the top of our devices and obtained proper functionality and viability of the overlying neuronal networks. At the same time, MTJ sensors kept their performances unchanged for several weeks in contact with neurons and neuronal medium. These results pave the way to the development of high performing biomagnetic sensing technology for the electrophysiology of in vitro systems, in analogy with Multi Electrode Arrays

OPTO-MAGNETIC SENSOR DEVICE AND MOLECULAR RECOGNITION SYSTEM

It is described an opto-magnetic device sensible to the presence of an analyte in a sample, comprising: an integrated optical circuit (101) having an input (IN) for an input optical radiation and at least one output (OU) for an output optical radiation; said optical circuit defining an area (102) sensible to the variations of a local refraction index probed by the optical radiation, destined to come in contact with the sample; a plurality of probe molecules (105) such to anchor to at least said sensible area (102); a plurality of magnetic particles (107) such to anchor to molecules (106) of the analyte, bound to the probe molecules (105) upon a molecular recognition; a magnetic actuator (108) configured to generate a variable magnetic field and move in an oscillating way said magnetic particles (107) in order to cause a variation of the refraction index probed by the optical radiation in the sensible area (102) of the optical circuit (101), and a variation of at least one characteristic parameter of the output optical radiation correlated to a concentration of the molecules (106) of the analyte in the sample

Exchange Bias Tuning for Magnetoresistive Sensors by Inclusion of Non-Magnetic Impurities

The fine control of the exchange coupling strength and blocking temperature ofexchange bias systems is an important requirement for the development of magnetoresistive sensors with two pinned electrodes. In this paper, we successfully tune these parameters in top- and bottom-pinned systems, comprising 5 nm thick Co40Fe40B20 and 6.5 nm thick Ir22Mn78 films. By inserting Ru impurities at different concentrations in the Ir22Mn78 layer, blocking temperatures ranging from 220 °C to 100 °C and exchange bias fields from 200 Oe to 60 Oe are obtained. This method is then applied to the fabrication of sensors based on magnetic tunneling junctions consisting of a pinned synthetic antiferromagnet reference layer and a top-pinned sensing layer. This work paves the way towards the development of new sensors with finely tuned magnetic anisotropies

Magnetic Tunnel Junction Based Chip to Detect the Magnetic Field of Neuronal Signals: A Platform for In Vitro Studies

Magnetoencephalography (MEG) has revolutionized neuroscience, offering a tool with [...

Reactive Microcontact Printing of DNA Probes on (DMA-NAS-MAPS) Copolymer-Coated Substrates for Efficient Hybridization Platforms

High-performing hybridization platforms fabricated by reactive microcontact printing of DNA probes are presented. Multishaped PDMS molds are used to covalently bind oligonucleotides over a functional copolymer (DMA-NAS-MAPS) surface. Printed structures with minimum width of about 1.5 μm, spaced by 10 μm, are demonstrated, with edge corrugation lower than 300 nm. The quantification of the immobilized surface probes via fluorescence imaging gives a remarkable concentration of 3.3 × 103 oligonucleotides/μm2, almost totally active when used as probes in DNA-DNA hybridization assays. Indeed, fluorescence and atomic force microscopy show a 95% efficiency in target binding and uniform DNA hybridization over printed areas