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Enzyme-targeted fluorescent imaging probes on a multiple antigenic peptide core
Amit K Galande1, Scott A Hilderbrand, Ralph Weissleder
1Center for Molecular Imaging Research, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA.
Journal of Medicinal Chemistry
|July 21, 2006
Summary
Researchers developed novel fluorescent molecular probes using a peptide dendrimer scaffold. These probes activate and emit near-infrared fluorescence specifically after enzymatic cleavage by cathepsin S, enabling targeted imaging.
Area of Science:
- Bioconjugate Chemistry
- Molecular Imaging
- Biochemistry
Background:
- Peptide dendrimers, like the multiple antigenic peptide (MAP) system, are versatile scaffolds with applications in drug delivery, diagnostics, and vaccine development.
- Fluorescent probes are crucial tools in molecular imaging, but developing probes with high specificity and signal-to-noise ratio remains a challenge.
Purpose of the Study:
- To design and synthesize novel, activatable fluorescent molecular probes utilizing a MAP-based scaffold.
- To investigate the enzymatic activation mechanism and optimize probe properties for imaging applications.
Main Methods:
- Synthesis of tetravalent MAP scaffolds incorporating a cathepsin S substrate (Leu-Arg) and poly(ethylene glycol) (PEG) chains.
- Attachment of near-infrared fluorochromes, leading to quenched fluorescence due to H-type dye aggregation.
- Varying PEG chain length to synthesize three probes (CyPEG-1, CyPEG-2, CyPEG-3) and evaluating their aqueous solubility and quenching efficiency.
- Assessing the fluorescence recovery and fold-increase upon proteolytic activation with cathepsin S.
Main Results:
- Three novel fluorescent probes (CyPEG-1, CyPEG-2, CyPEG-3) were successfully synthesized on a MAP scaffold.
- CyPEG-2, with an optimized PEG chain length, exhibited superior aqueous solubility and fluorescence quenching.
- Proteolytic activation of CyPEG-2 with cathepsin S resulted in a >70-fold increase in fluorescence emission and >95% recovery.
Conclusions:
- The developed MAP-based probes offer a novel platform for enzyme-activated molecular imaging.
- CyPEG-2 demonstrates significant potential as a specific and sensitive imaging agent for cathepsin S activity.
- This approach provides a robust method for designing activatable fluorescent probes for biological applications.