Mass transport of lipopolysaccharide induced H2O2 detected by an intracellular carbon nanoelectrode sensor.

Hydrogen peroxide is a key component of the innate immune response, regulating how a cell responds to a bacterial threat; however, being transient in nature makes it extremely difficult to detect. We show the development of an improved biosensor capable of the rapid detection of the hydrogen peroxide produced intracellularly in response to both smooth and rough lipopolysaccharides (LPS) structures. The arising signal and mass transport behaviour to the electrodes were characterised. This response was detected utilising a single walled carbon nanotube-based sensor that has been functionalised with an osmium complex for specificity and detecting the change in intracellular concentrations of hydrogen peroxide through chronoamperometry. This was conducted within murine macrophage (RAW264.7) cells and using ultra-pure LPS extracted from two different serotypes of bacteria (0111:B4 and Re495). This allowed the comparison of the immune response when infected with different structures of LPS. We demonstrate that the hydrogen peroxide signal can be electrochemically detected within 3 seconds post injection. Combining the nature of the mass transport of hydrogen peroxide and concentration characteristics, a bacterial 'fingerprint' was identified. The impact of this work will be demonstrated in allowing us to develop a rapid diagnostic for bacterial detection.