Nanogele als pharmazeutische Trägersysteme: winzige Netzwerke mit großen Möglichkeiten

Self-Assembled Cationic Polypeptide Supramolecular Nanogels for Intracellular DNA Delivery

Supramolecular nanogels are an emerging class of polymer nanocarriers for intracellular delivery, due to their straightforward preparation, biocompatibility, and capability to spontaneously encapsulate biologically active components such as DNA. A completely biodegradable three-component cationic supramolecular nanogel was designed exploiting the multivalent host-guest interaction of cyclodextrin and adamantane attached to a polypeptide backbone. While cyclodextrin was conjugated to linear poly-L-lysine, adamantane was grafted to linear as well as star shaped poly-L-lysine. Size control of nanogels was obtained with the increase in the length of the host and guest polymer. Moreover, smaller nanogels were obtained using the star shaped polymers because of the compact nature of star polymers compared to linear polymers. Nanogels were loaded with anionic model cargoes, pyranine and carboxyfluorescein, and their enzyme responsive release was studied using protease trypsin. Confocal microscopy revealed successful transfection of mammalian HeLa cells and intracellular release of pyranine and plasmid DNA, as quantified using a luciferase assay, showing that supramolecular polypeptide nanogels have significant potential in gene therapy applications.

Understanding the Interaction of Polyelectrolyte Architectures with Proteins and Biosystems

The counterions neutralizing the charges on polyelectrolytes such as DNA or heparin may dissociate in water and greatly influence the interaction of such polyelectrolytes with biomolecules, particularly proteins. In this Review we give an overview of studies on the interaction of proteins with polyelectrolytes and how this knowledge can be used for medical applications. Counterion release was identified as the main driving force for the binding of proteins to polyelectrolytes: Patches of positive charge become multivalent counterions of the polyelectrolyte and lead to the release of counterions from the polyelectrolyte and a concomitant increase in entropy. This is shown from investigations on the interaction of proteins with natural and synthetic polyelectrolytes. Special emphasis is paid to sulfated dendritic polyglycerols (dPGS). The Review demonstrates that we are moving to a better understanding of charge-charge interactions in systems of biological relevance. Research along these lines will aid and promote the design of synthetic polyelectrolytes for medical applications.

Polymer Nanocontainers for Intracellular Delivery

Carriers for intracellular delivery are required to overcome limitations of therapeutic agents such as low specificity, systemic toxicity, high clearance rate, and low therapeutic index. Nanocontainers comprised of an aqueous core and a polymer shell have received increasing attention because they readily combine stimuli response to improve intracellular payload release and surface modification to enhance selectivity towards the desired region of action. This Minireview summarizes the design and properties of polymer nanocontainers for intracellular delivery, classified according to the polymer architecture.

Amphiphilic Carbazole-Containing Compounds with Lower Critical Solution Temperature Behavior for Supramolecular Self-Assembly and Solution-Processable Resistive Memories

The self-organization and resistive memory performances of a series of newly synthesized water-soluble amphiphilic carbazole derivatives have been explored. Temperature-dependent UV/Vis absorption spectroscopy has been conducted to study the isodesmic self-assembly mechanism of the carbazole-containing compounds. This class of compounds also exhibits interesting lower critical solution temperature properties, which are sensitive to concentration and ionic additives. One of the compounds has been solution-processed and utilized as an active material in the engineering of resistive memory devices, exhibiting a switching voltage of about 3.9 V, a constant ON/OFF current ratio of 10⁶ , and a long retention time of 10⁴  s. The present work demonstrates the versatile potential applications of water-soluble amphiphilic carbazole-containing compounds in supramolecular chemistry and resistive memory devices.

Stimuli-Responsive Metallogels for Synthesizing Ag Nanoparticles and Sensing Hazardous Gases

A newly synthesized bis-pyridyl ligand having a diphenyl ether backbone (LP6) displayed the ability to form crystalline coordination polymers (CP1-CP6) which were fully characterized by single crystal X-ray diffraction. Most of the resulting polymers were lattice-occluded crystalline solids-a structural characteristic reminiscent to gels. The reactants of the coordination polymers produced metallogels in DMSO/water confirming the validity of the design principles with which the coordination polymers were synthesized. Some of the metallogels displayed material properties like in situ synthesis of Ag nanoparticles and stimuli-responsive gel-sol transition including sensing hazardous gases like ammonia and hydrogen sulfide.

Secondary-Structure-Driven Self-Assembly of Reactive Polypept(o)ides: Controlling Size, Shape, and Function of Core Cross-Linked Nanostructures

Achieving precise control over the morphology and function of polymeric nanostructures during self-assembly remains a challenge in materials as well as biomedical science, especially when independent control over particle properties is desired. Herein, we report on nanostructures derived from amphiphilic block copolypept(o)ides by secondary-structure-directed self-assembly, presenting a strategy to adjust core polarity and function separately from particle preparation in a bioreversible manner. The peptide-inherent process of secondary-structure formation allows for the synthesis of spherical and worm-like core-cross-linked architectures from the same block copolymer, introducing a simple yet powerful approach to versatile peptide-based core-shell nanostructures.

Stimulus-Responsive Short Peptide Nanogels for Controlled Intracellular Drug Release and for Overcoming Tumor Resistance

Multidrug resistance (MDR) poses a major burden to cancer treatment. As one important factor contributing to MDR, overexpression of P-glycoprotein (P-gp) results in a reduced intracellular drug accumulation. Hence, the ability to effectively block the efflux protein and to accumulate the therapeutics in cancer cells is of great significance in clinical practice. In this work, we successfully developed a smart stimulus-responsive short peptide-assembled system, termed as PD/VER nanogels, which synergistically combined the acid-activatable antitumor prodrug doxorubicin (Dox) with the P-gp inhibitor verapamil (VER) for reversing MDR. Systematic studies demonstrated that such an inhibitor-encapsulated nanogel could effectively enhance the accumulation of Dox in resistant cancer cells, thereby revealing significantly higher antitumor activity compared to free Dox molecules. This work showed that the assembly of bioactive agents with a synergistic effect into nano-drugs could provide a useful strategy to overcome cancer drug resistance.

Engineered nanoparticles for drug delivery in cancer therapy

In medicine, nanotechnology has sparked a rapidly growing interest as it promises to solve a number of issues associated with conventional therapeutic agents, including their poor water solubility (at least, for most anticancer drugs), lack of targeting capability, nonspecific distribution, systemic toxicity, and low therapeutic index. Over the past several decades, remarkable progress has been made in the development and application of engineered nanoparticles to treat cancer more effectively. For example, therapeutic agents have been integrated with nanoparticles engineered with optimal sizes, shapes, and surface properties to increase their solubility, prolong their circulation half-life, improve their biodistribution, and reduce their immunogenicity. Nanoparticles and their payloads have also been favorably delivered into tumors by taking advantage of the pathophysiological conditions, such as the enhanced permeability and retention effect, and the spatial variations in the pH value. Additionally, targeting ligands (e.g., small organic molecules, peptides, antibodies, and nucleic acids) have been added to the surface of nanoparticles to specifically target cancerous cells through selective binding to the receptors overexpressed on their surface. Furthermore, it has been demonstrated that multiple types of therapeutic drugs and/or diagnostic agents (e.g., contrast agents) could be delivered through the same carrier to enable combination therapy with a potential to overcome multidrug resistance, and real-time readout on the treatment efficacy. It is anticipated that precisely engineered nanoparticles will emerge as the next-generation platform for cancer therapy and many other biomedical applications.

Ratiometric MRI sensors based on core-shell nanoparticles for quantitative pH imaging

Ratiometric MRI sensors consist of paramagnetic cores and pH-sensitive polymer shells. The core-shell nanostructure enables the coexistence of two incompatible NMR relaxation properties in one particle. The sensors show pH sensitivity in transverse relaxivity (r2 ), but not in longitudinal relaxivity (r1 ). Quantitative pH imaging is achieved by measuring the r2 /r1 value with a clinical 3 T MRI scanner.