Synthese neuartiger Ketoheptose-Analoga für Anwendungen in Medizin und Diagnostik

Ketoheptosen besitzen diabetogene Eigenschaften, sind also in der Lage die Insulinsekretion zu senken. Über GLUT2 werden sie von den β-Zellen bzw. Hepatocyten aufgenommen, und aufgrund eines eingeschränkten Stoffwechsels in den Zellen angereichert. Dieser Umstand macht die entsprechend markierten Heptulose-Derivate interessant für die Diagnostik von Krebserkrankungen und Diabetes. Die 19F-Gluco-heptulose-Analoga wurden ausgehend von der entsprechenden Aldohexose über Oxidation zum Lacton, Kettenverlängerung um eine C-1 Einheit und Funktionalisierung erhalten. Die Einführung des Fluor-Atoms erfolgte entweder durch elektrophile Addition mit Selectfluor oder durch nucleophile Substitution mit DAST. Außerdem wurden 1-Amino- und 3-Amino-Derivate der D-Gluco-heptulose dargestellt, die für die Synthese von STZ-Analoga verwendet werden konnten.Ketoheptoses display diabetogenic properties and therefore can reduce insulin release. They are transported into β-cells or hepytocytes via GLUT2. Decreased metabolism leads to their accumulation in the cells. This circumstance makes the correspondingly labeled heptulose derivatives interesting in the diagnosis of cancer and diabetes. The 19F-heptuloses were synthesized starting with the corresponding aldohexose via oxidation to the lactone, followed by C-1 elongation and functionalization. The introduction of fluorine was carried out either by electrophilic addition with Selectfluor or by nucleophilic substitution with DAST. Additionally, 1-amino and 3-amino derivatives of D-gluco-heptulose were obtained, which could be employed for the synthesis of STZ analogues

Expedient and Versatile Formation of Novel Amino-deoxy-ketoheptuloses

Novel monoketoheptuloses have been synthesized employing an amination step in a <i>pre</i>- and/or <i>post</i>-<b>C1</b> chain elongation using a Petasis reagent by starting from aldohexoses or aldohexosamines. A series of <i>gluco</i> and <i>manno</i> configured 1-/3-deoxy-1-/3-amino-ketohept-2-uloses could be obtained

Immunocytochemistry of GLUT2, uptake of fluorescent desnitroso- streptozotocin analogs and phosphorylation of D-glucose in INS-1E cells

The non-invasive imaging of GLUT2-expressing cells remains a challenge. As streptozotocin, and similarly alloxan, may be transported into cells by GLUT2, the major aim of the present study was to assess the possible use of fluorescent desnitroso-streptozotocin analogs for in vitro labeling of GLUT2-expressing cells. INS-1E cells, human embryonic kidney (HEK) cells, rat isolated pancreatic islets, rat hepatic cells, rat exocrine pancreatic cells and tumoral insulin-producing BRIN-BD11 cells were incubated in the presence of two distinct fluorescent desnitroso-streptozotocin analogs, probes A and B. The immunocytochemistry of GLUT2 in INS-1E cells and the phosphorylation of D-glucose by INS-1E cell homogenates were also examined. The uptake of probes A and B (12.0 μM) by INS-1E cells yielded apparent intracellular concentrations approximately one order of magnitude higher than the extracellular concentration. The two probes differed from one another by the absolute values for their respective uptake and time course, but not so by the pattern of their concentration dependency. Comparable results were recorded in HEK cells, rat isolated pancreatic islets and hepatocytes. Vastly different findings were recorded, however, in rat exocrine pancreatic cells, which do not express GLUT2. Moreover, an unusual concentration dependency for the uptake of each probe was observed in tumoral BRIN-BD11 cells. It is proposed that suitable fluorescent desnitroso-streptozotocin analogs may be used to label GLUT2-expressing cells.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

19F-heptuloses as tools for the non-invasive imaging of GLUT-2 expressing cells

Suitable analogs of d-mannoheptulose are currently considered as possible tools for the non-invasive imaging of pancreatic islet insulin-producing cells. Here, we examined whether 19F-heptuloses could be used for non-invasive imaging of GLUT2-expressing cells. After 20 min incubation, the uptake of 19F-heptuloses (25 mM) by rat hepatocytes, as assessed by 19F NMR spectroscopy, ranged from 0.50 (1-deoxy-1-fluoro-d- mannoheptulose and 3-deoxy-3-fluoro-d-mannoheptulose) to 0.25 (1,3-dideoxy-1,3-difluoro-d-mannoheptulose) and 0.13 (1-deoxy-1-fluoro-d- glucoheptulose, 3-deoxy-3-fluoro-d-glucoheptulose and 1,3-dideoxy-1,3-difluoro- d-glucoheptulose) μmol per 3 × 10 6 cells. 19F MRI experiments also allowed the detection of 1-deoxy-1-fluoro-d-mannoheptulose in rat hepatocytes. All three 19F-mannoheptuloses cited above, as well as 7-deoxy-7-fluoro-d-mannoheptulose and 1-deoxy-1-fluoro-d-glucoheptulose inhibited insulin release evoked in rat isolated pancreatic islets by 10 mM d-glucose to the same extent as that observed with an equivalent concentration (10 mM) of d-mannoheptulose, while 3-deoxy-3-fluoro-d-glucoheptulose and 1,3-dideoxy-1,3-difluoro-d-glucoheptulose (also 10 mM) were less potent than d-mannoheptulose in inhibiting insulin release. The 1-deoxy-1-fluoro-d- mannoheptulose and 3-deoxy-3-fluoro-d-mannoheptulose only marginally affected INS-1 cell viability. These findings are compatible with the view that selected 19F-heptuloses may represent suitable tools for the non-invasive imaging of hepatocytes and insulin-producing cells by 19F MRI. © 2011 Elsevier Inc. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Immunocytochemistry of GLUT2, uptake of fluorescent desnitroso-streptozotocin analogs and phosphorylation of D-glucose in INS-1E cells

The non-invasive imaging of GLUT2-expressing cells remains a challenge. As streptozotocin, and similarly alloxan, may be transported into cells by GLUT2, the major aim of the present study was to assess the possible use of fluorescent desnitroso-streptozotocin analogs for in vitro labeling of GLUT2-expressing cells. INS-1E cells, human embryonic kidney (HEK) cells, rat isolated pancreatic islets, rat hepatic cells, rat exocrine pancreatic cells and tumoral insulin-producing BRIN-BD11 cells were incubated in the presence of two distinct fluorescent desnitroso-streptozotocin analogs, probes A and B. The immunocytochemistry of GLUT2 in INS-1E cells and the phosphorylation of D-glucose by INS-1E cell homogenates were also examined. The uptake of probes A and B (12.0 μM) by INS-1E cells yielded apparent intracellular concentrations approximately one order of magnitude higher than the extracellular concentration. The two probes differed from one another by the absolute values for their respective uptake and time course, but not so by the pattern of their concentration dependency. Comparable results were recorded in HEK cells, rat isolated pancreatic islets and hepatocytes. Vastly different findings were recorded, however, in rat exocrine pancreatic cells, which do not express GLUT2. Moreover, an unusual concentration dependency for the uptake of each probe was observed in tumoral BRIN-BD11 cells. It is proposed that suitable fluorescent desnitroso-streptozotocin analogs may be used to label GLUT2-expressing cells.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Glycoconjugated Amphiphilic Polymers via Click-Chemistry for the Encapsulation of Quantum Dots

Herein, we present a strategy for the glycoconjugation of nanoparticles (NPs), with a special focus on fluorescent quantum dots (QDs), recently described by us as “preassembly” approach. Therein, prior to the encapsulation of diverse nanoparticles by an amphiphilic poly­(isoprene)-<i>b</i>-poly­(ethylene glycol) diblock copolymer (PI-<i>b</i>-PEG), the terminal PEG appendage was modified by covalently attaching a carbohydrate moiety using Huisgen-type click-chemistry. Successful functionalization was proven by NMR spectroscopy. The terminally glycoconjugated polymers were subsequently used for the encapsulation of QDs in a phase transfer process, which fully preserved fluorescence properties. Binding of these nanoconstructs to the lectin Concanavalin A (Con A) was studied via surface plasmon resonance (SPR). Depending on the carbohydrate moiety, namely, d-<i>manno</i>-heptulose, d-glucose, d-galactose, 2-deoxy-2-{[methylamino)­carbonyl]­amino}-d-glucopyranose (“des­(nitroso)-streptozotocin”), or d-maltose, the glycoconjugated QDs showed enhanced affinity constants due to multivalent binding effects. None of the constructs showed toxicity from 0.001 to 1 μM (particle concentration) using standard WST and LDH assays on A549 cells