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The completeness of tumor removal during surgery is dependent on the surgeon's ability to differentiate tumor from normal tissue using subjective criteria that are not easily quantifiable. A way to objectively assess tumor margins during surgery in patients would be of great value. We have developed a method to visualize tumors during surgery using activatable cell-penetrating peptides (ACPPs), in which the fluorescently labeled, polycationic cell-penetrating peptide (CPP) is coupled via a cleavable linker to a neutralizing peptide. Upon exposure to proteases characteristic of tumor tissue, the linker is cleaved, dissociating the inhibitory peptide and allowing the CPP to bind to and enter tumor cells. In mice, xenografts stably transfected with green fluorescent protein show colocalization with the Cy5-labeled ACPPs. In the same mouse models, Cy5-labeled free ACPPs and ACPPs conjugated to dendrimers (ACPPDs) delineate the margin between tumor and adjacent tissue, resulting in improved precision of tumor resection. Surgery guided by ACPPD resulted in fewer residual cancer cells left in the animal after surgery as measured by Alu PCR. A single injection of ACPPD dually labeled with Cy5 and gadolinium chelates enabled preoperative whole-body tumor detection by MRI, intraoperative guidance by real-time fluorescence, intraoperative histological analysis of margin status by fluorescence, and postoperative MRI tumor quantification. Animals whose tumors were resected with ACPPD guidance had better long-term tumor-free survival and overall survival than animals whose tumors were resected with traditional bright-field illumination only.

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The scientific world is noting with sadness the unexpected passing of Roger Tsien at the untimely age of 64. It's not clear what led to his demise but it seems to have happened on a bike trail in Oregon.Tsien is of course one of the fathers of Green Fluorescent...
I always get excited when I see an unexpected glowing spot on a TLC plate. Fluorescence! Ive sent many a graduate student on a wild goose chase to try to identify the source of that glow.My curiosity about these compounds blossomed during my time in industry,...
I always get excited when I see an unexpected glowing spot on a TLC plate. Fluorescence! Ive sent many a graduate student on a wild goose chase to try to identify the source of that glow.My curiosity about these compounds blossomed during my time in industry,...
If you’ve contracted one of the common, nasty cancers of the large organs (lung, colon, breast, etc.), and it hasnt spread yet, the best course is to cut it out. Surgeons do this pretty well if the tumor is clearly defined and easily discerned from normal...