Journal: Bioactive Materials

Article Title: Development of an implantable sensor system for in vivo strain, temperature, and pH monitoring: comparative evaluation of titanium and resorbable magnesium plates

doi: 10.1016/j.bioactmat.2024.09.015

Figure Lengend Snippet: Simplified circuit diagram. Components are shown in the 3D rendering (top) of the printed circuit board (PCB) and labeled by number corresponding to the schematic (bottom). Their voltage requirements and communication protocols are also shown. Blue boxes indicate components attached to the stretchable cables as shown in the top 3D rendering. Strain gauges (SG) were glued to the magnesium and titanium plates as two Wheatstone half-bridges, with bridge completion resistors (R) soldered to the PCB inside the titanium case. One bridge was used to measure axial loading and the other for measuring in-plane bending, by gluing the gauges appropriately. They were sampled with a 24-bit analog-to-digital converter (ADC, 3) that was converted to the correct voltage level (using the level shifter, 2) and communicated with the microcontroller (1) using the serial peripheral interface (SPI). The temperature sensors at two locations (osteotomy and reference) and the accelerometer (4) were read using the inter-integrated circuit (IIC) bus. The pH sensor (ISFET), whose gate-source voltage ( V GS ) was conditioned to linearly depend on pH (5), was amplified with a gain of 3.6 and read using a 12-bit ADC internal to the microcontroller. Data was stored in nonvolatile memory (6) using the quad serial peripheral interface (QSPI).

Article Snippet: The pH sensor consists of an ion-sensitive field effect transistor (ISFET) that has a sensing area of 1.2 × 3 mm 2 with a 2 mm diameter Ag/AgCl reference electrode combined in a 10 mm diameter package (MSFET3351, Microsens SA, Switzerland).

Techniques: Labeling, Amplification

Journal: bioRxiv

Article Title: Wireless in vivo Recording of Cortical Activity by an Ion-Sensitive Field Effect Transistor

doi: 10.1101/2023.01.19.524785

Figure Lengend Snippet: a Source and drain of ISFET device are connected to top and bottom plates of capacitor, linking in parallel to circuit. b Q of resonator is dependent on ionic concentrations local to ISFET gate electrode. c Active site of ISFET is embedded through cranial window on surface of somatosensory cortex. d Ion fluctuations detected wirelessly represented in time domain by S11 minima between resonator and antenna over 60 s window.

Article Snippet: For both in vitro and in vivo experiments, the drain and source terminals of a MSFET 3351 ion sensitive field effect transistor (ISFET) (Microsens SA, Lausanne, Switzerland) were bonded in parallel to a standard printed-circuit resonator comprising gold-plated copper (thickness of 36 μm) ten-turn square inductors (W/L: 3.5 × 3.5 mm, turn width: 75 μm, turn spacing: 75 μm) and a 30 × 50 mm parallel plate capacitor.

Techniques:

Journal: bioRxiv

Article Title: Wireless in vivo Recording of Cortical Activity by an Ion-Sensitive Field Effect Transistor

doi: 10.1101/2023.01.19.524785

Figure Lengend Snippet: a Simulation arena of RLC resonator coupled to ISFET model. S-parameter frequency response is evaluated at a near field receiver. b E-field is maximized at resonance. c Changes in ionic concentrations at ISFET gate decrease impedance, Q, and e-field. d Left - representative ISFET model connected to resonator. Right - current field density at 0.5 V overdrive voltage ( V ov ). e Drain-source current ( I ds ) as a function of V ov . f Small signal transconductance ( g m ) as a function of V ov . g Frequency response modulation at physiological pH range. Inset - closeup surrounding resonance.

Article Snippet: For both in vitro and in vivo experiments, the drain and source terminals of a MSFET 3351 ion sensitive field effect transistor (ISFET) (Microsens SA, Lausanne, Switzerland) were bonded in parallel to a standard printed-circuit resonator comprising gold-plated copper (thickness of 36 μm) ten-turn square inductors (W/L: 3.5 × 3.5 mm, turn width: 75 μm, turn spacing: 75 μm) and a 30 × 50 mm parallel plate capacitor.

Techniques:

Journal: bioRxiv

Article Title: Wireless in vivo Recording of Cortical Activity by an Ion-Sensitive Field Effect Transistor

doi: 10.1101/2023.01.19.524785

Figure Lengend Snippet: a Experimental configuration: readouts of ISFET-coupled resonator immersed in different pH samples are received by near field antenna. A series of frequency response sweeps is acquired by high-speed vector network analyzer. b Examples of frequency response curves for physiological pH levels. c Current-voltage (IV) characteristic curve. Inset: Change in drain-source voltage ( V ds ) with pH levels. d Arithmetic mean of signal-to-noise ratio per pH level (red: outliers, included in mean, n = 10, all error bars denote s.e.m.).

Article Snippet: For both in vitro and in vivo experiments, the drain and source terminals of a MSFET 3351 ion sensitive field effect transistor (ISFET) (Microsens SA, Lausanne, Switzerland) were bonded in parallel to a standard printed-circuit resonator comprising gold-plated copper (thickness of 36 μm) ten-turn square inductors (W/L: 3.5 × 3.5 mm, turn width: 75 μm, turn spacing: 75 μm) and a 30 × 50 mm parallel plate capacitor.

Techniques: Plasmid Preparation

Journal: bioRxiv

Article Title: Wireless in vivo Recording of Cortical Activity by an Ion-Sensitive Field Effect Transistor

doi: 10.1101/2023.01.19.524785

Figure Lengend Snippet: a Pre-stimulus readouts of spontaneous activity. b Readouts from S1HL somatosensory cortex during a 2 Hz electrical stimulus of contralateral hindpaw. c Representative maximum single pulse responses in wireless ISFET recording. d Peak differential LFP recordings in response to stimulation. c Heatmap depicting maximum peaks of LFP recordings in d. e Average amplitude of response to stimulation normalized to baseline. Asterix denotes t-test p-values < .05, error bars are standard errors, n = 5 for all conditions, error bars denote s.e.m.

Article Snippet: For both in vitro and in vivo experiments, the drain and source terminals of a MSFET 3351 ion sensitive field effect transistor (ISFET) (Microsens SA, Lausanne, Switzerland) were bonded in parallel to a standard printed-circuit resonator comprising gold-plated copper (thickness of 36 μm) ten-turn square inductors (W/L: 3.5 × 3.5 mm, turn width: 75 μm, turn spacing: 75 μm) and a 30 × 50 mm parallel plate capacitor.

Techniques: Activity Assay

Journal: bioRxiv

Article Title: Wireless in vivo Recording of Cortical Activity by an Ion-Sensitive Field Effect Transistor

doi: 10.1101/2023.01.19.524785

Figure Lengend Snippet: a ISFET traces can be sorted by both duration and amplitude of response. b Majority of ISFET fluctuations are of duration < 500 ms, with positive sustained fluctuations displaying durations of up to 2.5 s. Negative phase responses are of duration < 100 ms. c Spectrograms of ISFET wireless response following stimulation onset reveal excitatory response centered around 0.1 – 5 Hz. Duration and intensity of response are inversely proportional to frequency of stimulation. ISFET activity at frequencies greater than the delta wave band was minimal. d Response normalized to baseline for both wireless ISFET and LFP electrode recordings show maximal excitatory response at 2Hz stimulation frequency, and a reduced response at frequencies > 5Hz in the delta wave band. Asterix denotes t-test p-values < .05, error bars are standard errors, n = 5 for all conditions, error bars denote s.e.m..

Article Snippet: For both in vitro and in vivo experiments, the drain and source terminals of a MSFET 3351 ion sensitive field effect transistor (ISFET) (Microsens SA, Lausanne, Switzerland) were bonded in parallel to a standard printed-circuit resonator comprising gold-plated copper (thickness of 36 μm) ten-turn square inductors (W/L: 3.5 × 3.5 mm, turn width: 75 μm, turn spacing: 75 μm) and a 30 × 50 mm parallel plate capacitor.

Techniques: Activity Assay