Complete
tumor removal during surgery has a great impact on patient survival. To that end, the surgeon should detect the
tumor, remove it and validate that there are no
residual cancer cells left behind. Residual cells at the incision margin of the tissue removed during surgery are associated with
tumor recurrence and poor prognosis for the patient. In order to remove the
tumor tissue completely with minimal collateral damage to healthy tissue, there is a need for diagnostic tools that will differentiate between the
tumor and its normal surroundings. Methods: We designed, synthesized and characterized three novel polymeric Turn-ON probes that will be activated at the
tumor site by
cysteine cathepsins that are highly expressed in multiple
tumor types. Utilizing orthotopic
breast cancer and
melanoma models, which spontaneously metastasize to the brain, we studied the kinetics of our polymeric Turn-ON nano-probes. Results: To date, numerous low molecular weight
cathepsin-sensitive substrates have been reported, however, most of them suffer from rapid clearance and reduced signal shortly after administration. Here, we show an improved
tumor-to-background ratio upon activation of our Turn-ON probes by
cathepsins. The signal obtained from the
tumor was stable and delineated the
tumor boundaries during the whole
surgical procedure, enabling accurate resection. Conclusions: Our findings show that the control groups of
tumor-bearing mice, which underwent either standard surgery under white light only or under the fluorescence guidance of the commercially-available imaging agents ProSense® 680 or 5-aminolevulinic
acid (5-ALA), survived for less time and suffered from
tumor recurrence earlier than the group that underwent
image-guided surgery (IGS) using our Turn-ON probes. Our "smart" polymeric probes can potentially assist surgeons' decision in real-time during surgery regarding the
tumor margins needed to be removed, leading to improved patient outcome.