Among the all compounds presented above three of them turned out to be resilient to cell culture medium. Therefore they were subjected to further examination this time in the cell culture. Working electrodes made from pencil graphite modified with syringaldazine and covered with the appropriate protective layer were immobilized in cell culture Petri dishes as shown in Figure . Working electrode was kept in the cell culture during the whole time frame of the experiment, whereas reference and counter electrodes were placed only during the measurements. Cell culture medium and especially metabolites excreted by the cells both have huge impact on the antifouling layer. The experiments showed that the electrodes modified with TMOS layer could endure in cell culture for up to six weeks, PLL-PEG up to 2 weeks and complete loss of syringaldazine signal was observed for PLLA after just 72 hours (Figure ). Comparison of electrodes signal from different layers was based on DPV measurements, the heights of the individual peaks. As a 100% was taken height of DPV peak on the beginning of experiments, which means just after HeLa cells were seeded on the tissue culture dishes and medium culture was added. Plot of loss of signal during prolonged measurements was made by taking averages of the six repeats. As expected major changes are observed during the first hours of contact with the cell culture. After just three hours the peak area was reduced by half in case of TMOS layer or a quarter of case PLLA.