Enzymatically Activatable Diagnostic Probes
ABSTRACT Molecular imaging of disease development, progression and treatment is seen as key to further advancement in the understanding and triumph over illness. The role of enzymes is to catalyze the biochemical reactions that help regulate health, and when dysregulated in complex organisms lead to or indicate disease. The ability to image the action of these proteins for diagnostic purposes opens a window for the researcher and clinician to witness specifc molecular events in vitro and in vivo. Such probes have been developed and deployed for the optical, radionuclide and magnetic resonance modalities and offer significant benefits over conventional agents. The signal of enzymatically-activated probes is regulated by the specific activity of the desired enzyme. This allows for a higher signal to background ratio over non-specific and targeted agents. It also enables the modulation of contrast agent distribution (and even cellular accumulation) following enzymatic activity. This review summarizes the strategies and probes in development and use in this emergent field of molecular imaging, with a particular focus on the research and medical relevance of these advances.
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ABSTRACT: Anthracycline cytostatics can be observed at the level of organelles, cells and whole organisms due to their fluorescent properties. Imaging techniques based on detection of fluorescence can be used not only for observation of drug interaction with tumor cells, but also for targeting therapy of tumors with nanoparticles containing anthracycline cytostatics. Doxorubicin and daunorubicin, enclosed in liposomes, as representatives of nanoparticles suitable for targeted therapy, are used in clinical practice. The main advantage of liposomal drugs is to reduce the side effects due to differences in pharmacokinetics and distribution of the drug in the body. Due to the fact that all biological mechanisms of action of anthracycline drugs are not still fully understood, modern imaging techniques offer tool for in vivo studies of these mechanisms. Key words: nanomedicine - cytostatic agents - drug delivery systems - doxorubicin - liposomes.Klinická onkologie: casopis Ceské a Slovenské onkologické spolecnosti 08/2013; 26(4):239-44. DOI:10.14735/amko2013239
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ABSTRACT: In the era of personalized medicine, there is an urgent need for in vivo techniques able to sensitively detect and quantify molecular activities. Sensitive imaging of gamma rays is widely used; however, radioactive decay is a physical constant, and its signal is independent of biological interactions. Here, we introduce a framework of previously uncharacterized targeted and activatable probes that are excited by a nuclear decay-derived signal to identify and measure molecular signatures of disease. We accomplished this by using Cerenkov luminescence, the light produced by β-particle-emitting radionuclides such as clinical positron emission tomography (PET) tracers. Disease markers were detected using nanoparticles to produce secondary Cerenkov-induced fluorescence. This approach reduces background signal compared to conventional fluorescence imaging. In addition to tumor identification from a conventional PET scan, we demonstrate the medical utility of our approach by quantitatively determining prognostically relevant enzymatic activity. This technique can be applied to monitor other markers and represents a shift toward activatable nuclear medicine agents.Nature medicine 09/2013; 19(10). DOI:10.1038/nm.3323 · 28.05 Impact Factor
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ABSTRACT: The epidemiology of prostate cancer has dramatically changed since the introduction of prostate-specific antigen (PSA) screening in the 1980's. Most prostate cancers today are detected at early stages of the disease and are considered 'indolent'; however, some patients' prostate cancers demonstrate a more aggressive behaviour which leads to rapid progression and death. Increasing understanding of the biology underlying the heterogeneity that characterises this disease has led to a continuously evolving role of imaging in the management of prostate cancer. Functional and metabolic imaging techniques are gaining importance as the impact on the therapeutic paradigm has shifted from structural tumour detection alone to distinguishing patients with indolent tumours that can be managed conservatively (e.g., by active surveillance) from patients with more aggressive tumours that may require definitive treatment with surgery or radiation. In this review, we discuss advanced imaging techniques that allow direct visualisation of molecular interactions relevant to prostate cancer and their potential for translation to the clinical setting in the near future. The potential use of imaging to follow molecular events during drug therapy as well as the use of imaging agents for therapeutic purposes will also be discussed. • Advanced imaging techniques allow direct visualisation of molecular interactions in prostate cancer. • MRI/PET, optical and Cerenkov imaging facilitate the translation of molecular biology. • Multiple compounds targeting PSMA expression are currently undergoing clinical translation. • Other targets (e.g., PSA, prostate-stem cell antigen, GRPR) are in development.European Radiology 02/2015; 25(5). DOI:10.1007/s00330-014-3539-5 · 4.34 Impact Factor