This article describes a method for neuromodulation of human iPSC-derived neurons using focused ultrasound (FUS). The process involves recording neuronal activity before and after ultrasound application to assess changes in electrical signaling.
Begin with a microelectrode array or MEA system containing a parafilm-covered multi-well MEA plate and a focused ultrasound transducer above it.
One of the MEA wells contains media with human iPSC-derived neurons over embedded microelectrodes, where the neurons communicate with each other via electrical signals.
Set up the transducer for the emission of ultrasound waves.
Apply degassed coupling gel on the parafilm and lower the transducer to establish contact with the gel without air bubbles for efficient ultrasound transmission.
Next, the MEA system records the electrical signals from the neurons via the microelectrodes to obtain a baseline neuronal activity.
Using the transducer, apply continuous high-frequency ultrasound waves, which pass through the coupling gel and parafilm and reach the neurons.
The ultrasound waves excite the neurons and modulate their electrical activity. Re-record this electrical signal.
An increase in neuronal activity after ultrasound treatment, compared to pre-treatment, confirms the successful neuromodulation.
To begin, aspirate the culture medium to fill a single well in a 24-well neuron culture plate having embedded microelectrode arrays or MEA. After preparing three hundred milliliters of degassed and deionized water, carefully fill it in the focussed ultrasound or FUS transducer cone. Using a customized threaded rod, secure the 3D-printed holder to a frame. Position the frame such that the head of the FUS transducer is over the well that will be stimulated. Use a rubber band to secure parafilm over the well on the 24-well MEA plate containing the medium and the human induced pluripotent stem cells or hIPSCs.
Set the FUS parameters on the transducer power output or TPO control panel. The values of the various parameters are mentioned on the screen. Next, apply coupling gel on top of the parafilm over the well, and lower the FUS transducer into the coupling gel, ensuring contact with the gel with minimal air bubbles. Start the FUS sonication by pressing the bottom right button on the TPO, and wait at least five minutes between each round of sonication to allow the neurons to return to a baseline state.
If the connection is appropriate, the trigger pulse generated by the FUS system will automatically align the FUS stimulation sequence with the MEA recording. Analyze the signal by reading the FUS sonication time with the transfer data based on the change in the firing rate associated with the FUS.
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