A Platinum(II) Based Correlative Probe for Bacteria

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. This is especially so for correlative probes, which are proving to be powerful tools for enhancing the imaging of live cells. In this work a platinum(II)-naphthalimide molecule has been developed to extend small molecule correlative probes to bacterial imaging. The probe was designed to exploit the naphthalimide moiety as a luminescent probe for super-resolution microscopy, with the platinum(II) centre enabling visualisation of the complex with ion nanoscopy. Photophysical characterisation and theoretical studies confirmed that the emission properties of the naphthalimide are not altered by the platinum(II) centre. Structured illumination microscopy (SIM) imaging on live Bacillus cereusrevealed that the platinum(II) centre does not change the sub-cellular localisation of the naphthalimide, and confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis of the sample was used to monitor the uptake of the platinum(II) complex within the bacteria and proved the correlative action of the probe. The successful combination of these two probe moieties with no perturbation of their individual detection introduces a platform for a versatile range of new correlative probes for bacteria.