Single-cell pathogen detection with a reverse-phase immunoassay on impedimetric transducers

Roberto De La Rica, Antoni Baldi, Cesar Fernandez-Sanchez, Hiroshi Matsui

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)


The risk of infectious diseases has compelled some industries to establish a zero-tolerance standard for the presence of microorganisms in a given sample. Here, we address this issue with a novel reverse-phase immunoassay on impedimetric transducers for the specific detection of extremely low numbers of pathogens (less than 10 cells). After simply spotting the sample onto the electrodes, physisorbed analytes were targeted with urease-labeled antibodies, and the urease on the pathogens hydrolyzed urea to ionic species with a concomitant decrease of the resistivity of the solution. By this methodology, the limit of detection (LOD) based on the 3 sigma criterion was 1 Escherichia coli cell with an assay time under 1 h. However, the precise number of cells present in highly diluted samples is uncertain, making it difficult to assess the final LOD of the sensor. We overcome this problem by using an atomic force microscope to deposit and image in situ the exact number cells on the transducer. After performing the immunoassay, a single E. coli cell was successfully detected without ambiguity in the number of cells even in the presence of a 10(4) excess of a competing microorganism, thus demonstrating the outstanding LOD and selectivity of the proposed reverse-phase immunoassay.
Original languageEnglish
Pages (from-to)7732-7736
Number of pages5
JournalAnalytical Chemistry
Issue number18
Publication statusPublished - 15 Sept 2009


  • reverse-phase
  • immunoassay
  • single-cell
  • pathogen detection
  • impedimetric transducers


Dive into the research topics of 'Single-cell pathogen detection with a reverse-phase immunoassay on impedimetric transducers'. Together they form a unique fingerprint.

Cite this