It iswellknownthatthemetabolicactivityofsomemicroorganismsresultsinchangesofpHofthe culture medium,aphenomenonthatcanbeusedfordetectionandquantification ofbacteria.However, conventionalglasselectrodesthatarecommonlyusedforpHmeasurementsarebulky,fragileandex- pensive,whichhinderstheirapplicationinminiaturizedsystemsandencouragedtothesearchforal- ternatives. In thiswork,twotypesofmetaloxidepHsensorshavebeentestedtodetectthemetabolicactivityof the bacterium Escherichiacoli (E. coli). ThesepHsensorswereproducedonsiliconchipswithplatinum metal contacts,ontowhichthinlayersofIrOx or Ta2O5 wereincorporatedbytwodifferentmethods (electrodeposition ande-beamsputtering,respectively).Inordertofacilitatemeasurementinsmall sample volumes,anAg/AgClpseudo-referencewasalsoscreen-printedinthechipandwasassayedin parallel toanexternalAg/AgClreferenceelectrode.Asitisshown,thedevelopedsensorsgenerated results indistinguishablefromthoseprovidedbyaconventionalglasspH-electrodebutcouldbeoperated in significantly smallersamplevolumes.Afteroptimizationofthedetectionconditions,themetaloxide sensors aresuccessfullyappliedfordetectionofincreasingconcentrationsofviable E. coli, with detection of lessthan103 cfu mL
1 in undilutedculturemediuminjust5h.