Optical Smartprobes to diagnose pulmonary bacterial infections and lung cancer

Abstract

The work in this thesis describes the approaches taken to advance the field of pulmonary optical molecular imaging for the diagnosis of unexplained pulmonary opacities in the critically ill patient where bacterial causes are suspected and the investigation of pulmonary nodules and masses where lung cancer is suspected. The bacterial work includes the development and assessment of a multivalent fluorescently labelled antimicrobial peptide fragment that allows for the in vivo in situ detection of bacteria in the distal lung. This Smartprobe (chapter 3), called NBD-UBIdend remains specific for bacteria and pathogenic pulmonary fungi (Aspergillus fumigatus) over mammalian cells, and has a clinically relevant limit of detection when it is imaged in an ex vivo whole lung ovine ventilated model using fibered confocal fluorescence microscopy (FCFM). Furthermore, NBD-UBIdend detects all bacteria assessed, including a panel that accounts for 70% of ventilator associated pneumonia causing organisms. Chapter 4, develops this further and describes the in vitro and ex vivo evaluation of another Smartprobe utilising a fluorescently labelled modified polymyxin B moiety, called NBD-PMX. This compound detects gram-negative but not gram-positive bacteria and is compatible with pulmonary FCFM. This combination of Smartprobes and FCFM could allow the immediate stratification of patient therapy in the assessment of pulmonary opacities where bacterial causes are suspected. The lung cancer work includes the use of label free FCFM in a clinical cohort to determine if autofluorescence patterns can differentiate benign and malignant pulmonary nodules. This work (chapter 5) demonstrates here there is no differentiation using FCFM alone and therefore, for this technology to be used in lung cancer diagnostics a Smartprobe strategy may be beneficial. Finally, chapter 6 demonstrates a Smartprobe based approach for interrogating lung cancer and discusses a matrix metalloproteinase (MMP) compound that detects MMPs in a whole ventilated lung utilising a modified spontaneous ovine pulmonary adenocarcinoma model.