Abstract: A method and system for detecting a parameter of a host cell, a cell culture or medium is provided. A host cell is transfected with an expressible DNA sequence which is under expression control of an inducible promoter sequence. The promoter sequence is inducible in correlation with the parameter, the expressible sequence encoding an enzymatically active product which can catalyze a reaction giving rise to an electrical signal which is detectable in an electrochemical measurement. An electrical signal determined in an electrochemical system then serves as an indication for the parameter.