Enzyme-Targeted Fluorescent Imaging Probes on a Multiple Antigenic Peptide Core

Abstract

Peptide dendrimers have a variety of applications in biology such as the vehicles for drug and gene delivery, molecular inhibitors, protein mimics, and synthetic vaccines. The multiple antigenic peptide (MAP) system is a well-known example of a discrete, dendrimeric scaffold. We explored a novel application of the MAP-based scaffold by designing molecular probes that fluoresce only after enzymatic treatment. The probes, which were synthesized on solid support, incorporate a cathepsin S dipeptide substrate (Leu-Arg), and a poly(ethylene glycol) (PEG) chain in their dendritic arms. The fluorescence emission of the near-infrared fluorochromes attached to the N-termini of the dendritic arms was quenched. Mechanistic studies revealed formation of H-type dye aggregates within the tetravalent MAP system. By varying the length of the PEG chain, three probes were synthesized, CyPEG-1, CyPEG-2, and CyPEG-3 with 4, 8, and 12 ethylene oxide units, respectively. CyPEG-2 showed optimum aqueous solubility and quenching efficiency for imaging applications. Upon proteolytic activation with cathepsin S (EC 3.4.22.27), CyPEG-2 showed greater than 70-fold increase and more than 95% recovery in fluorescence emission.

Activatable Optical Probes for Cancer Imaging

“…42,43 Alternatively, a self-quenched activatable probe was developed based on a multiple antigenic peptide (MAP) core. 44 The probe consisted of a tetravalent branched lysine core with extended dendritic arms into which a cathepsin S dipeptide substrate (LR) was incorporated. The N-terminus of the peptide was conjugated to the NIR fluorophore, CyTE-777, 45 via different lengths of PEG linkers.…”

Dendritic Molecules on Solid Support: Solid‐Phase Synthesis and Applications

“…16d MAP-like systems can also be used as biomineralization templates, 88 metal ion complexants, 89 protein mimics, 90 and molecular probes for enzymatic activity. 20,91 Argininebearing polylysine dendrons demonstrated strong antiangiogenic activity. 92 Similar arginine-decorated MAP-like polylysines, as well as loligomers, MAP-like dendrons decorated with cytoplasmic translocation signal, and nuclear localization signal peptides, were studied as cell and nucleus membrane translocation agents and vehicles for delivery of exogenous molecules into cells and particular cell compartments.…”

New-generation biomedical materials: Peptide dendrimers and their application in biomedicine

“…Multiple antigenic peptides (MAP) were conjugated to the surface of the dendrimers to yield a special peptide dendrimer by Galande et al [61].…”