Electrode fouling is a major challenge for the long term use of sensors in real samples as it leads to the decay of the electroanalytical signal and is often caused by the formation of an inhibiting layer formed by biomolecules. We demonstrate here that ordered and vertically aligned mesoporous silica generated at the surface of an indium tin oxide electrode by electrochemically assisted self-assembly act as a molecular sieve and a protective layer for the electrode surface. They indeed prevent the adsorption of size excluded large undesired molecules (e.g. haemoglobin) while allowing the detection of small redox active molecules likely to reach the electrode surface through the film (e.g. propranolol) with almost no loss of sensitivity. At a bare electrode, the oxidation of propranolol is completely inhibited in the presence of 5 mu M haemoglobin. At a modified electrode, the sensitivity for propranolol in the absence of haemoglobin is (72.8 +/- 2.9) mA mol(-1) (R-2= 0.992, N= 7) and it remains similar in the presence of 5 mu M haemoglobin with a value of (67.4 +/- 7.2) mA mol(-1) (R-2= 0.992, N= 7).