The method includes binding living cells to magnetic particles, adding them to a sensor array, uniformly distributing over the sensor array, magnetically fixing the magnetic particles having the bound cells over the sensor array, and adding substances to maintain and/or improve the cell vitality to the sensory array, and/or adding substances to worsen the cell vitality to the sensor array. The assembly includes a sensor array composed of sensors, which are designed to be in direct fluidic contact with a fluid, and a device for generating a magnetic field over the sensor array. A layer that comprises magnetic particles and living cells is formed on the sensor array.