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

Abstract

Herein we describe a platform technology for the synthesis and characterization of partially aminated, (35)S-labeled, dendritic polyglycerol sulfate (dPG(35)S 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 (Mn ≈ 4.5 kDa) containing 9.4% N-phthalimide protected amine functionalities was prepared on a large scale. Sulfation and simultaneous radio labeling with (35)SO3 pyridine complex, followed by cleavage of the N-phthalimide protecting groups, yielded dPG(35)S 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.

The Effect of Polyglycerol Sulfate Branching On Inflammatory Processes

“…Subsequently, workup was performed by dialysis in saturated EDTA solution, saturated aqueous NaCl solution, and water in succession. The dye loading was determined by UV absorbance at 552 nm based on an excitation coefficient of ϵ = 120 000 L mol −1 cm −1 for the conjugated dye dPG 100 S‐ICC: dye loading = 0.6, DS = 96%, MW calculated = 11.3 kDa hPG 60 S‐ICC: dye loading = 0.6, DS = 95%, MW calculated = 14.5 kDa hPG 42 S‐ICC: dye loading = 0.23, DS = 93%, MW calculated = 13.8 kDa hPG 24 S‐ICC: dye loading = 0.13, DS = 95%, MW calculated = 14.4 kDa hPG 60 ‐ICC: dye loading = 1.25, DS = 0%, MW calculated = 7.2 kDa …”

Dendritic Polyglycerol Sulfate Inhibits Microglial Activation and Reduces Hippocampal CA1 Dendritic Spine Morphology Deficits

“…22 The control triglycerol-Cy5 was prepared by amide coupling of Cy5 NHS-ester to a monoamino glycerol G1 dendron (triglycerol). 53,54 Materials. 2,5-Diphenyltetrazolium bromide (MTT), cytochalasin D, DMSO, filipin III, Griess reagent, Hoechst 33342, lipopolysaccharides from E. coli 055:B5, methyl-β-cyclodextrin, monophosphoryl lipid A from Salmonella enterica serotype minnesota Re 595, rat-tail collagen, and sucrose were purchased from Sigma-Aldrich.…”

“…47,56 Seeing that dPGS was nontoxic in microglia at a concentration of 100 nM (MTT assay, trypan blue exclusion assay and Hoechst 33342 labeling of cell nuclei, see below), we investigated if this lack of toxicity could be explained by their inability to enter the cells and only temporarily bind to plasma membrane putative selectin receptors. 20,53 For this we used dPGS-Cy5 and the control triglycerol-Cy5 (TG-Cy5) and untreated cells (controls for autofluorescence). Imaging of live cells by fluorescence microscopy ( Figure 3A) and z-stack analyses together with the measurements of relative fluorescence intensities by high-throughput imaging (Operetta) and spectrofluorometry provided a clearly time-dependent course of internalization of the fluorescent compounds ( Figure 3B and 3C).…”

Polyglycerol-opioid conjugate produces analgesia devoid of side effects

“…Based on our previous studies on PG-based targeting of inflammation and tumors (Gröger et al, 2013; Calderón et al, 2011), we constructed covalent PG-M conjugates with a size of 5 nm where morphine is immobilized on hyperbranched PG scaffolds by an ester linkage (Figure 1; 2). Hyperbranched PG is a novel class of hydrophilic dendritic macromolecules with multiple hydroxyl functional groups and a polyether backbone, characterized by tunable end group functionalities, defined topological 3D architecture, enhanced stability, and inertness to non-specific interactions with biological environments (Calderón et al, 2010; Wilms et al, 2010).…”