Памяти Александра Евгеньевича Будникова

In photodynamic therapy (PDT), photosensitizers and light are used to cause photochemically induced cell death. The selectivity and the effectiveness of the phototoxicity in cancer can be increased by a specific uptake of the photosensitizer into tumor cells. A promising target for this goal is the folic acid receptor α (FRα), which is overexpressed on the surface of many tumor cells and mediates an endocytotic uptake. Here, we describe a polysaccharide-based nanoparticle system suitable for targeted uptake and its photochemical and photobiological characterization. The photosensitizer 5, 10, 15, 20-tetraphenyl-21H, 23H-porphyrine (TPP) was encapsulated in spermine- and acetal-modified dextran (SpAcDex) nanoparticles and conjugated with folic acid (FA) on the surface [SpAcDex(TPP)-FA]. The particles are successfully taken up by human HeLa-KB cells, and a light-induced cytotoxicity is observable. An excess of free folate as the competitor for the FRα-mediated uptake inhibits the phototoxicity. In conclusion, folate-modified SpAcDex particles are a promising drug delivery system for a tumor cell targeted photodynamic therapy

Responsive Polysaccharide Macrosurfactants from Dextran Building Blocks

Stimuli-responsive macromolecular drug delivery systems and smart nanomaterials from oligo- and polysaccharide block copolymers with amphiphilic character are emerging classes of compounds in nanomedicine. Combining a non-toxic character with controllable degradability, high biocompatibility and excellent solubility in aqueous solvents, they can serve as precisely tunable and robust nanomaterials and represent a green and sustainable alternative to artificial polymeric materials. With their inherent capacity to self-organize into micelles, rods or polymersomes they can protect and significantly improve the bioavailability of sensitive and pharmaceutically active cargo that would not be otherwise applicable in biological systems. This thesis reports several synthetic approaches towards end group functionalized dextrans and their application in the construction of amphiphilic responsive block copolymers and starlike polysaccharide brush architectures. Key steps of the synthesis include a versatile reductive amination by a modified microwave-assisted procedure, involving a co-solvent system, and the introduction of p-substituted aniline derivatives. Hereby it was possible to install useful functionalities at the chain end in an effective, facile and time saving manner. This approach led us to azide- and alkyne- end-modified dextrans, which were used for the Cu-promoted synthesis of the first-ever reported amphiphilic, pH-responsive block copolymer consisting solely of polysaccharide blocks. The material has surface-activity and self-assembles in water into spherical micellar nanoparticles. This Cu-mediated transformation was then further developed to a metal-free thiol-based approach. Hereby it was possible to gain access to single- and double-stimuli-responsive polysaccharide macrosurfactants from a single starting material. Their amphiphilic nature and degradation behavior were studied in detail with a focus on drug loading capacities and triggered release. A highly potent, near-infrared (NIR) absorbing photosensitizer was encapsulated and successfully delivered into the cytosol of HeLa cells, where a phototoxic effect was triggered with controlled NIR light exposure. The broad potential of end-on functionalized dextrans was then shown by developing dextran macromonomers for the ring-opening metathesis polymerization (ROMP) of polysaccharide brush polymers. Materials, that might become valuable intermediates in the synthesis of artificial proteoglycans for tissue engineering applications. In summary, with our established method we can synthesize biocompatible and responsive amphiphiles from sustainable resources by metal-free polysaccharide macromonomer ligation. More generalized, the synthetic procedure should be applicable to all polysaccharide systems with an inherent reducing end, giving access to a plethora of applications at the interface of biochemistry, polymer synthesis and material science (e.g. coatings, surfactants, surfmers, block copolymers and hydrogels).Stimulus-responsive makromolekulare Drug Delivery Systeme und intelligente Nanomaterialien aus amphiphilen Oligo-, und Polysaccharid Block Copolymeren stellen eine Stoffklasse dar, die mehr und mehr Bedeutung in der Nanomedizin bekommt. Diese repräsentieren im Vergleich zu künstlichen Polymer Materialien eine grüne, nachhaltige und vielversprechende Alternative. Aufgrund ihrer geringen Toxizität, kontrollierbarer Abbaubarkeit, hoher Bioverträglichkeit und exzellenter Löslichkeit in wässrigen Lösemitteln können sie als präzise steuerbare und robuste Nanomaterialien dienen. Durch ihre charakteristische Fähigkeit zur Selbstorganisation zu Mizellen, Stäbchen oder Polymersomen ist es möglich die Bioverfügbarkeit von sensiblen, pharmazeutisch aktiven Substanzen, welche sonst nicht in biologischen Systemen anwendbar wären, durch Verkapselung zu bewahren und signifikant zu verbessern. Die vorliegende Dissertation präsentiert verschiedene synthetische Verfahren zur Endgruppen Funktionalisierung von Dextranen und deren Verwendung zum Aufbau von amphiphilen, responsiven Block Copolymeren und sternartiger Polysaccharid Bürsten. Wir haben ein Mikrowellen-unterstütztes Verfahren abgewandelt und eine vielseitig einsetzbare Synthesestrategie entwickelt. Basierend auf reduktiver Aminierung in einem Co-Lösemittelsystem konnten p-substituierte Aniline am reduzierenden Ende von Dextran eingeführt werden. Dadurch wurde es möglich verschiedene nützliche Funktionalitäten am Polymer Kettenende auf eine effiziente, einfache und zeitsparende Art anzubringen. Azid- und Alkin- endgruppen modifizierte Dextrane wurden anschließend verwendet um Kupfer katalysiert, bis dahin nicht bekannte, pH-responsive Block Copolymere herzustellen, welche ausschließlich aus Polysaccharid Bausteinen aufgebaut sind. Das Material zeigte oberflächenaktive Eigenschaften und ordnete sich spontan in Wasser zu kugelartigen micellaren Nanopartikeln. Dieses Konzept wurde schließlich weiterentwickelt zu einem metallfreien, auf Thiolen basierenden Verfahren. Dadurch wurde, ausgehend von einem einzigen Edukt, der Zugang zu einfach- und doppel-stimulus-responsiven Polysaccharid Makrotensiden ermöglicht. Deren amphiphile Natur und Zersetzungsverhalten wurde im Detail untersucht, mit Fokus auf Wirkstoff Einschlusskapazität und induzierbarer Freisetzung. Ein hoch wirksamer Photo-sensibilitsator mit Absorption im Nahinfrarot Bereich konnte eingeschlossen und erfolgreich in das Cytosol von HeLa Zellen transportiert werden. Dort konnte ein photo-toxischer Effekt durch kontrollierte Bestrahlung mit NIR-Licht ausgelöst werden. Die breite Anwendbarkeit von endgruppen funktionalisierten Dextranen wurde anschließend durch die Entwicklung von Makromonomeren für die Ring-öffnende-Metathese-Polymerisation (ROMP) von molekularen Bürstenpolymeren aus Polysacchariden gezeigt. Diese Materialien könnten wertvolle Zwischenstufen in der Synthese von künstlichen Proteoglykanen für die Erzeugung von künstlichem biologischen Gewebe werden. Zusammenfassend, lassen sich mit unserer etablierten Methode biokompatible und responsive Amphiphile durch übergangsmetalfreie Ligation synthetisieren, basierend auf polysaccharid Makromonomeren aus nachhaltigen Ressourcen. Im breiteren Kontext sollte das Verfahren auf alle Polysaccharide mit einem reduzierenden Ende anwendbar sein. Hiermit ergibt sich der Zugang zu einer Vielzahl an Anwendungen an der Schnittstelle zwischen Biochemie, Polymer Synthese und Materialwissenschaften (z. B. Beschichtungen, Surfactants, Surfmers, Block Copolymere und Hydrogele)

Amphiphilic Polysaccharide Block Copolymers for pH-Responsive Micellar Nanoparticles

A full polysaccharide amphiphilic block copolymer was prepared from end group-functionalized dextrans using copper-mediated azide–alkyne click chemistry. Sufficient modification of the reducing end in both blocks was achieved by microwave-enhanced reductive amination in a borate-buffer/methanol solvent system. The combination of a hydrophilic dextran block with a hydrophobic acetalated dextran block results in an amphiphilic structure that turns water-soluble upon acid treatment. The material has a low critical micelle concentration and self-assembles in water to spherical micellar nanoparticles. The formed nanoparticles have a narrow size distribution below 70 nm in diameter and disassemble in slightly acidic conditions. The amphiphilic polysaccharide system shows low toxicity and can stabilize the hydrophobic model drug curcumin in aqueous solutions over extended time periods

Discordant evolution of mitochondrial and nuclear yeast genomes at population level

International audienceBackground: Mitochondria are essential organelles partially regulated by their own genomes. The mitochondrial genome maintenance and inheritance differ from the nuclear genome, potentially uncoupling their evolutionary trajectories. Here, we analysed mitochondrial sequences obtained from the 1011 Saccharomyces cerevisiae strain collection and identified pronounced differences with their nuclear genome counterparts. Results: In contrast with pre-whole genome duplication fungal species, S. cerevisiae mitochondrial genomes show higher genetic diversity compared to the nuclear genomes. Strikingly, mitochondrial genomes appear to be highly admixed, resulting in a complex interconnected phylogeny with a weak grouping of isolates, whereas interspecies introgressions are very rare. Complete genome assemblies revealed that structural rearrangements are nearly absent with rare inversions detected. We tracked intron variation in COX1 and COB to infer gain and loss events throughout the species evolutionary history. Mitochondrial genome copy number is connected with the nuclear genome and linearly scale up with ploidy. We observed rare cases of naturally occurring mitochondrial DNA loss, petite, with a subset of them that do not suffer the expected growth defect in fermentable rich media. Conclusions: Overall, our results illustrate how differences in the biology of two genomes coexisting in the same cells can lead to discordant evolutionary histories

Aortic valve replacement with or without myocardial revascularization in octogenarians. Can minimally invasive extracorporeal circuits improve the outcome?

OBJECTIVE: The positive impact of minimally invasive extracorporeal circuits (MiECC) on patient outcome is expected to be most evident in patients with limited physiologic reserves. Nevertheless, most studies have limited their use to low-risk patients undergoing myocardial revascularization. As such, there is little evidence to their benefit outside this patient population. We, therefore, set out to explore their potential benefit in octogenarians undergoing aortic valve replacement (AVR) with or without concomitant myocardial revascularization. METHODS: Based on the type of the utilized ECC, we performed a retrospective propensity score-matched comparison among all octogenarians (n = 218) who received a primary AVR with or without concomitant coronary artery bypass grafting in our institution between 2003 and 2010. RESULTS: A MiECC was utilized in 32% of the patients. The propensity score matching yielded 52 matched pairs. The 30-day postoperative mortality (2% vs. 10%; p=0.2), the incidence of low cardiac output (0% vs. 6%; p=0.2) and the Intensive Care Unit (ICU) stay (2.5 ± 2.6 vs. 3.8 ± 4.7 days; p=0.06) were all in favour of the MiECC group, but failed to reach statistical significance while the 90-day postoperative mortality did (2% vs. 16%; p=0.02). CONCLUSION: MiECCs have a positive influence on the outcome of octogenarians undergoing AVR with or without concomitant coronary artery bypass grafting. Their use should, therefore, be extended beyond isolated coronary artery bypass graft (CABG) surgery

Dual-Responsive Enzyme–Polysaccharide Conjugate as a Nanocarrier System for Enzyme Prodrug Therapy

Biopolymer-based drug delivery systems have gained considerable attention in the field of nanomedicine. In this study, a protein–polysaccharide conjugate was synthesized by covalent conjugation of the enzyme horseradish peroxidase (HRP) with acetalated dextran (AcDex) via a thiol exchange reaction. The resulting bioconjugate shows a dual-responsive behavior in acidic and reductive environments to achieve a controlled release of drugs. The self-assembly of this amphiphilic HRP–AcDex conjugate allows the encapsulation of prodrug indole-3-acetic acid (IAA) into the hydrophobic polysaccharide core. Under slightly acidic conditions, the acetalated polysaccharide reverts to its native hydrophilic form, which triggers the disassembly of micellar nanoparticles and the release of the encapsulated prodrug. The conjugated HRP further activates the prodrug by oxidation of IAA into cytotoxic radicals, which leads to cellular apoptosis. The results indicate that the HRP–AcDex conjugate in combination with IAA has great potential to be used as a novel enzyme prodrug therapy for cancer treatment