Kondrat'eva ligation: Diels-Alder-based irreversible reaction for bioconjugation.

Diversification of existing chemoselective ligations is required to efficiently access complex and well-defined biomolecular assemblies with unique and valuable properties. The development and bioconjugation applications of a novel Diels-Alder-based irreversible site-specific ligation are reported. The strategy is based on a Kondrat'eva cycloaddition between bioinert and readily functionalizable 5-alkoxyoxazoles and maleimides that readily react together under mild and easily tunable reaction conditions to afford a fully stable pyridine scaffold. The potential of this novel bioconjugation is demonstrated through the preparation of fluorescent conjugates of biomolecules and a novel Förster resonance energy transfer (FRET)-based probe suitable for the in vivo detection and imaging of urokinase-like plasminogen activator (uPA), which is a key protease involved in cancer invasion and metastasis.

Selective photodetection and photodynamic therapy for prostate cancer through targeting of proteolytic activity.

Frequent side effects of radical treatment modalities and the availability of novel diagnostics have raised the interest in focal therapies for localized prostate cancer. To improve the selectivity and therapeutic efficacy of such therapies, we developed a minimally invasive procedure based on a novel polymeric photosensitizer prodrug sensitive to urokinase-type plasminogen activator (uPA). The compound is inactive in its prodrug form and accumulates passively at the tumor site by the enhanced permeability and retention effect. There, the prodrug is selectively converted to its photoactive form by uPA, which is overexpressed by prostate cancer cells. Irradiation of the activated photosensitizer exerts a tumor-selective phototoxic effect. The prodrug alone (8 µmol/L) showed no toxic effect on PC-3 cells, but upon irradiation the cell viability was reduced by 90%. In vivo, after systemic administration of the prodrug, PC-3 xenografts became selectively fluorescent. This is indicative of the prodrug accumulation in the tumor and selective local enzymatic activation. Qualitative analysis of the activated compound confirmed that the enzymatic cleavage occurred selectively in the tumor, with only trace amounts in the neighboring skin or muscle. Subsequent photodynamic therapy studies showed complete tumor eradication of animals treated with light (150 J/cm(2) at 665 nm) 16 hours after the injection of the prodrug (7.5 mg/kg). These promising results evidence the excellent selectivity of our prodrug with the potential to be used for both imaging and therapy for localized prostate cancer.

Like a bolt from the blue: phthalocyanines in biomedical optics.

The purpose of this review is to compile preclinical and clinical results on phthalocyanines (Pcs) as photosensitizers (PS) for Photodynamic Therapy (PDT) and contrast agents for fluorescence imaging. Indeed, Pcs are excellent candidates in these fields due to their strong absorbance in the NIR region and high chemical and photo-stability. In particular, this is mostly relevant for their in vivo activation in deeper tissular regions. However, most Pcs present two major limitations, i.e., a strong tendency to aggregate and a low water-solubility. In order to overcome these issues, both chemical tuning and pharmaceutical formulation combined with tumor targeting strategies were applied. These aspects will be developed in this review for the most extensively studied Pcs during the last 25 years, i.e., aluminium-, zinc- and silicon-based Pcs.