Synthesis and Biological Evaluation of Radio and Dye Labeled Amino Functionalized Dendritic Polyglycerol Sulfates as Multivalent Anti-Inflammatory Compounds

Herein we describe a platform technology for the synthesis and characterization of partially aminated, ³⁵S-labeled, dendritic polyglycerol sulfate (dPG³⁵S amine) and fluorescent dPGS indocarbocyanine (ICC) dye conjugates. These polymer conjugates, based on a biocompatible dendritic polyglycerol scaffold, exhibit a high affinity to inflamed tissue in vivo and represent promising candidates for therapeutic and diagnostic applications. By utilizing a one-step sequential copolymerization approach, dendritic polyglycerol (M_n ≈ 4.5 kDa) containing 9.4% N-phthalimide protected amine functionalities was prepared on a large scale. Sulfation and simultaneous radio labeling with ³⁵SO₃ pyridine complex, followed by cleavage of the N-phthalimide protecting groups, yielded dPG³⁵S amine as a beta emitting, inflammation specific probe with free amino functionalities for conjugation. Furthermore, efficient labeling procedures with ICC via iminothiolane modification and subsequent “Michael” addition of the maleimide functionalized ICC dye, as well as by amide formation via NHS derivatized ICC on a dPGS amine scaffold, are described. The dPGS-ICC conjugates were investigated with respect to their photophysical properties, and both the radiolabeled and fluorescent compounds were comparatively visualized in histological tissue sections (radio detection and fluorescence microscopy) of animals treated with dPGS. Furthermore, cellular uptake of dPGS-ICC was found in endothelial cord blood (HUVEC) and the epithelial lung cells (A549). The presented synthetic routes allow a reproducible, controlled synthesis of dPGS amine on kilogram scale applying a one-pot batch reaction process. dPGS amine can be used for analysis via radioactivity or fluorescence, thereby creating a new platform for inflammation specific, multimodal imaging purposes using other attachable probes or contrast agents.