A novel targeting probe for fluorescent guided surgery in colorectal cancer resections

Background Tailoring the extent of colorectal cancer surgical resection on an individual basis would improve patient outcomes, but to achieve this goal, staging of the disease, particularly lymph node status, must be improved. Sentinel lymph node mapping has been effective in other tumours types but is ineffective in colorectal cancer. Near infra-red fluorophores are of interest in fluorescent guided surgery, but lack the ability to target the specific tissue of interest. The aim of this research is to develop a targeted near infra-red based probe to identify tumour and lymph node metastases. Methods Immunofluorescence was used to determine appropriate target and control recognition molecules in addition to appropriate target and control cell lines. Semiconducting organic polymer CN-PPV nanoparticles were produced utilising a self-assembly method and characterised over time. The selected target and control recognition molecules were conjugated to non-functionalised (NPs) and maleimide functionalised (MNPs) semiconducting organic polymer CN-PPV nanoparticles and cell binding, as well as cell toxicity, were evaluated in vitro. Results Both the target anti-CEA recognition molecules bound specifically to the target cell lines and not to controls. Characterisation of the NPs and MNPs displayed physical stability over time as well as demonstrating negligible adverse cytotoxic effects. Conjugation of both target and control antibody recognition molecules to the MNP led to non-specific binding of the conjugate to control cell lines. The target affimer recognition molecule NP conjugates demonstrated increased binding to target cell lines (42%, p<0.0001) and little non-specific binding to control cell lines (14%, p=0.3348). Conclusions Fluorescent guided surgery is a promising route for intraoperative stratification of colorectal cancer resections if an accurate probe were to be developed. I have shown that the semiconducting organic polymer nanoparticle used in this research possesses the attributes required of a clinical probe for fluorescent guided surgery. However, it requires modification with an appropriate recognition molecule to accurately target colorectal cancer tissue. The affimer NP conjugate is a more promising candidate for this role than its antibody MNP counterpart.