Sweet Nano

 

Introduction

 

Unraveling the sugar code by investigating the role of the carbohydrate-mediated molecular recognitions is the main focus of the Nano group. In order to achieve our work, we combine our knowledge in sugar science and expertise in organic synthesis with the increasing relevancy and high potential of the nanotechnology. This helps us to build novel and useful systems – based on fullerenes or nanotubes, quantum dots, Fe₃O₄ or Au nanoparticles – that show great potential for studying the sugar-mediated interactions (carbohydrate–lectin and carbohydrate–carbohydrate interactions) but also for in vivo diagnostics and imaging, targeted therapeutics and biosensing.

 

Besides this, we developed the synthesis of fluorescent and radioactive glycodendrimers that impact the comprehension of fundamental weak carbohydrate–protein interactions. Those dendrimers have been also synthesized on conductive polymers or nanoparticles and showed ability to be used as carbohydrate-mediated biosensors, imaging agents and targeted drug delivery systems.

 

We designed a novel platform onto we can study carbohydrate−protein interactions based on Ruthenium(II) glycodendrimers as optical and electrochemical probes. Using the prototypical Concanavalin A−mannose lectin−carbohydrate interaction as an example, oligosaccharide concentrations were electrochemically monitored. The displacement of the Ru(II) complex from lectin-functionalized gold surfaces was repeatedly regenerated. This new platform presents a method to monitor many different complex sugars in parallel.

–Kikkeri, R.; Kamena, F.; Gupta, T.; Hossain, L. H.; Boonyarattanakalin, S.; Gorodyska, G.; Beurer, E.; Textor, M.; Seeberger, P. H. Langmuir 2010, 26, 1520

 

A novel, digital, single-operation analytical method to study glycodendrimer−lectin interactions was investigated in our group. Robust, highly fluorescent derivatives of tris(bipyridine)ruthenieum(II) ([Ru(bipy)₃]²⁺) bearing 2, 4, 6, or 18 mannose or galactose units were designed to perform molecular logic operations. Inputs for these systems were pH, N,N′-4,4′-bis(benzyl-2-boronic acid)bipyridinium dibromide, and different lectins (Concanavalin A, Galantus nivalis agglutinin, and Asialoglycoprotein). The relative change in fluorescence quantum yield of the Ru(II)-glycodendrimers served as output. Together, the fluorescent emission readout, the logic analysis of the photoinduced electron transfer, and the optical behavior provide a single-step method to quickly screen a glycodendrimer library and select the best dendrimer model for studying carbohydrate−lectin interactions.

–Kikkeri, R.; Grünstein, D.; Seeberger, P. H. J. Am. Chem. Soc. 2010, 132, 10230

 

We developed a series of multivalent sensors that self-assemble via hydrophobic supramolecular interactions. The multivalent sensors are comprised of the a fluorescent Ruthenium(II) core surrounded by a heptamannosylated b-cyclodextrin scaffold. Two additional series of sensors were synthesized as proof-of-principle for supramolecular self-assembly, the fluorescent core alone, and the core plus b-cyclodextrin. Photophysical and spectroscopic analyses confirmed that the three mannosylated sensors displayed 14, 28, and 42 sugar units respectively. Each complex adopted original and unique spatial arrangements. The sensors were used to investigate the influence of carbohydrate spatial arrangement and clustering on the mechanistic and qualitative properties of lectin binding. Simple visualization of binding between a fluorescent, multivalent mannose complex and the E. coli strain ORN178 that possesses mannose-specific receptor sites, illustrates the potential for these complexes as biosensors.

–Grünstein, D.; Kikkeri, R.; Maglinao, M.; Collot, M.; Barylyuk, K.; Lepenies, B.; Kamena, F.; Zenobi, R.; Seeberger, P. H. Submitted

–Barylyuk, K.; Balabin, R. M.; Grünstein, D.; Kikkeri, R.; Frankevich, V.; Seeberger,P. H.; Zenobi R. J. Am. Soc. Mass Spectrom. 2011, 22, 1167

 

A process has been developed for the mild, continuous-flow microreactor synthesis of carbohydrate-coated CdSe/ZnS and CdTe/ZnS quantum dots of narrow size distribution (see scheme; NP: nanoparticle, QD: quantum dot, Prec.: precursor). The products can be prepared efficiently and reproducibly in larger amounts. The surface of the QDs can be modified with biologically relevant molecules.

–Kikkeri, R.; Laurino, P.; Odedra A.; Seeberger, P. H. Angew. Chem. Int. Ed. 2010, 122, 2098.

 

PEGylated quantum dots (QDs) capped with Mannose, Galactose, and Galactosamine have been synthesized. The stable, high quantum yield fluorescence of QDs was exploited to study specific carbohydrate−protein interactions in vitro and in vivo.

–Kikkeri, R.; Lepenies, B.; Adibekian, A.; Laurino P.; Seeberger, P. H. J. Am. Chem. Soc. 2009, 131, 2110

 

We developed in cooperation with Prof. Rubinstein (Weizmann Institute, Israel) LSPR transducers based on gold island films that were optimized for monitoring the specific interaction between Concanavalin A and Mannose. The results indicate that carbohydrate-modified Au island films can be used as convenient, effective and sensitive LSPR transducers for studying carbohydrate-protein interactions. Biosensing applications of this system based on sugars relevant to pathogenic viruses, parasites or bacteria is ongoing.

–Bellapadrona, G.; Tesler, A. B.; Grünstein, D.; Hossain, L. H.; Kikkeri, R.; Seeberger, P. H.; Vaskevich, A.; Rubinstein, I. Submitted

 

See also for other work:

–Kikkeri, R.; Hossain, L. H.; Seeberger, P. H. Chem. Commun. 2008, 18, 2127

–Kikkeri, R.; García-Rubio, I.; Seeberger, P. H. Chem. Commun. 2009, 2, 235

–Bernardes, G. J. L.; Kikkeri, R.; Maglinao, M.; Laurino, P.; Collot, M.; Hong, S.-Y.; Lepenies, B.; Seeberger, P. H. Org. Biomol. Chem. 2010, 8, 4987

 

 

RecentWork

 

Radiolabelled carbohydrates have been of growing interest in nuclear medicine during the recent years. An enormous success of ¹⁸F-fluoro-2-deoxy-glucose ([18F]-FDG) as a positron emission tomography imaging agent pioneered the application of simple carbohydrates in radiopharmaceuticals. However, the application of ¹⁸F-isotope is limited to facilities that have a cyclotron in the vicinity of both chemistry laboratories and nuclear medicine departments. Consequently, ^99mTc-labelled Glucose tracers that mimic the biodistribution of FDG can simplify the labeling and imaging procedures and simultaneously decrease the clinical costs. In the course of this project radiolabeling of Glucose, Mannose and Galactose is targeted. The biodistribution and other in vivo tests will be carried out by collaborating with Dr. Ralph Buchert (Charité Hospital, Berlin). In the case of:

§ ^99mTc-glucose, a precise comparison with [18F]-FDG is of our interest.

§ ^99mTc-mannose, imaging of sentinel node and a comparison with existing reports.

The advanced goal of this project is to applying more complicated carbohydrates which are synthesized in our research group and studying their biological behavior, as well as, labeling of different mammalian lectins which might provide selective targeting of different organs.

 

Cell labeling using Fe₃O₄ nanoparticles coupled to near infrared fluorescence (NIRF) tag give the opportunity to exhibit and investigate inflammation and cell migration during ischemic stroke and glioblastoma in a non-invasive form upon combination of MR and NIR imaging. The cells marked with these particles within and outside brain could be tracked, analyzed and characterized using “magnetic activated cell sorting” (MACS), and, “fluorescence activated cell sorting” by mean of histology.

Carbohydrate-functionalized nanoparticles with Sialyl Lewis A, Sialyl Lewix X or Lewis X is also planned to be used for pre-symptomatic in vivo imaging of ischemic stroke using targeted specific markers of the inflammation such as early-activated cerebral endothelium (E-/P-selectin).

Other coating of the iron oxide core with PET- or SPECT- ligands could provide both anatomic and metabolic information using multimodal simultaneous PET-MRI.