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Introduction: Fluorescence-guided surgery could potentially reduce local recurrence after pancreatic cancer resection. However, the ideal contrast agent for this purpose is not yet determined. The monoclonal antibody cetuximab targets the EGFR receptor, which is overexpressed in 64% of pancreatic cancers. We investigated the efficacy of near-infrared emitting silver sulphide Quantum Dot (QD)-cetuximab nanoconjugates for targeting EGFR-positive pancreatic cancer. Methods: 2-Mercaptopropionic acid-coated QDs were prepared from AgNO3 and Na2S. Pancreatic cancer cell lines PANC-1 and CFPAC-1 were confirmed EGFR-positive using a commercial AlexaFluor488-cetuximab probe. Nonconjugated QD and cetuximab-conjugated QD (QD-cetuximab) toxicity was assessed after 24 and 48 hours using MTT assay. Fluorescence microscopy was performed following a) formaldehyde-fixed immunofluorescence and b) live staining with QD-cetuximab for four hours at concentrations corresponding to 0, 10, 50, 100, 200, 400 and 600μg ml-1 of silver. Results: Untargeted QDs were non-toxic in both cell lines after 48 hours at all investigated concentrations, whereas QDcetuximab was toxic at 100µg ml-1 after 24 hours in PANC-1 and at 10µg ml-1 in CFPAC-1. Fixed immunofluorescence demonstrated EGFR targeting by QD-cetuximab at concentrations of 50μg ml-1 upwards in both cell lines. Live staining demonstrated similar efficacy of EGFR targeting up to 50μg ml-1 , although a reduction of fluorescence at higher concentrations was observed when compared to fixed immunofluorescence. Conclusion: Silver sulphide QD-cetuximab nanoconjugates have the potential to target live EGFR-positive pancreatic cancer cells at doses of up to 50 μg ml-1 . The reduction in QD fluorescence observed at higher concentrations is likely to be secondary to cetuximab toxicity.
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