Synthesis, Photophysical, and Biological Evaluation of Sulfated Polyglycerol Dendronized Perylenebisimides (PBIs)--A Promising Platform for Anti-Inflammatory Theranostic Agents?

1,7,9,10-Tetrasubstituted PMIs Accessible through Decarboxylative Bromination: Synthesis, Characterization, Photophysical Studies, and Hydrogen Evolution Catalysis

In this work, we present a new synthetic strategy for fourfold-substituted perylene monoimides via tetrabrominated perylene monoanhydrides. X-ray diffraction analysis unveiled the intramolecular stacking orientation between the substituents and semicircular packing behavior. We observed the remarkable influence of the substituent on the longevity and nature of the excited state upon visible light excitation. In the presence of poly(dehydroalanine)-graft-poly(ethylene glycol) graft copolymers as solubilizing template, the chromophores are capable of sensitizing [Mo3 S13 ]2- clusters in aqueous solution for stable visible light driven hydrogen evolution over three days.

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.

Cells Undergo Major Changes in the Quantity of Cytoplasmic Organelles after Uptake of Gold Nanoparticles with Biologically Relevant Surface Coatings

Here, we use cryo soft X-ray tomography (cryo-SXT), which delivers 3D ultrastructural volumes of intact cells without chemical fixation or staining, to gain insight about nanoparticle uptake for nanomedicine. We initially used dendritic polyglycerol sulfate (dPGS) with potential diagnostic and therapeutic applications in inflammation. Although dPGS-coated gold nanoparticle (dPGS-AuNP) uptake followed a conventional endocytic/degradative pathway in human lung epithelial cell lines (A549), with cryo-SXT, we detected ∼5% of dPGS-AuNPs in the cytoplasm, a level undetectable by confocal light microscopy. We also observed ∼5% of dPGS-AuNPs in a rarely identified subcellular site, namely, lipid droplets, which are important for cellular energy metabolism. Finally, we also found substantial changes in the quantity of cytoplasmic organelles upon dPGS-AuNP uptake over the 1-6 h incubation period; the number of small vesicles and mitochondria significantly increased, and the number of multivesicular bodies and the number and volume of lipid droplets significantly decreased. Although nearly all organelle numbers at 6 h were still significantly different from controls, most appeared to be returning to normal levels. To test for generality, we also examined cells after uptake of gold nanoparticles coated with a different agent, polyethylenimine (PEI), used for nucleic acid delivery. PEI nanoparticles did not enter lipid droplets, but they induced similar, albeit less pronounced, changes in the quantity of cytoplasmic organelles. We confirmed these changes in organelle quantities for both nanoparticle coatings by confocal fluorescence microscopy. We suggest this cytoplasmic remodeling could reflect a more common cellular response to coated gold nanoparticle uptake.

Investigations of Anti-Inflammatory Activity of a Peptide-Based Hydrogel Using Rat Air Pouch Model

The growing area of biomaterial sciences has attracted broad attention in recent years in the development of peptide-based biocompatible materials with inherent therapeutic potentials. Here, we developed an Amoc (9-anthracenemethoxycarbonyl)-capped dipeptide-based biocompatible, injectable, thixotropic, and self-healable hydrogel. In vitro cytotoxicity of the hydrogel was investigated with the human embryonic kidney cell (HEK293) line. We observed that the synthesized peptide is noncytotoxic. The hydrogel showed an antibacterial efficacy against Gram-positive and Gram-negative bacteria. In vivo anti-inflammatory activity of the hydrogel was investigated using the rat air pouch model of acute inflammation. The major parameters considered for the anti-inflammatory study were exudate volume, total and differential white blood cell count, tissue histology, and lipid peroxidation assay. These experimental data suggest biocompatibility and potential therapeutic applications of peptide hydrogel in inflammation.

Fluorescent Polymer-Single-Walled Carbon Nanotube Complexes with Charged and Noncharged Dendronized Perylene Bisimides for Bioimaging Studies

Fluorescent nanomaterials are expected to revolutionize medical diagnostic, imaging, and therapeutic tools due to their superior optical and structural properties. Their inefficient water solubility, cell permeability, biodistribution, and high toxicity, however, limit the full potential of their application. To overcome these obstacles, a water-soluble, fluorescent, cytocompatible polymer-single-walled carbon nanotube (SWNT) complex is introduced for bioimaging applications. The supramolecular complex consists of an alkylated polymer conjugated with neutral hydroxylated or charged sulfated dendronized perylene bisimides (PBIs) and SWNTs as a general immobilization platform. The polymer backbone solubilizes the SWNTs, decorates them with fluorescent PBIs, and strongly improves their cytocompatibility by wrapping around the SWNT scaffold. In photophysical measurements and biological in vitro studies, sulfated complexes exhibit superior optical properties, cellular uptake, and intracellular staining over their hydroxylated analogs. A toxicity assay confirms the highly improved cytocompatibility of the polymer-wrapped SWNTs toward surfactant-solubilized SWNTs. In microscopy studies the complexes allow for the direct imaging of the SWNTs' cellular uptake via the PBI and SWNT emission using the 1st and 2nd optical window for bioimaging. These findings render the polymer-SWNT complexes with nanometer size, dual fluorescence, multiple charges, and high cytocompatibility as valuable systems for a broad range of fluorescence bioimaging studies.

Synthesis and Self-Assembly of Bay-Substituted Perylene Diimide Gemini-Type Surfactants as Off-On Fluorescent Probes for Lipid Bilayers

Interest in bay-substituted perylene-3,4:9,10-tetracarboxylic diimides (PDIs) for solution-based applications is growing due to their improved solubility and altered optical and electronic properties compared to unsubstituted PDIs. Synthetic routes to 1,12-bay-substituted PDIs have been very demanding due to issues with steric hindrance and poor regioselectivity. Here we report a simple one-step regioselective and high yielding synthesis of a 1,12-dihydroxylated PDI derivative that can subsequently be alkylated in a straightforward fashion to produce nonplanar 1,12-dialkoxy PDIs. These PDIs show a large Stokes shift, which is specifically useful for bioimaging applications. A particular cationic PDI gemini-type surfactant has been developed that forms nonfluorescent self-assembled particles in water ("off state"), which exerts a high fluorescence upon incorporation into lipophilic bilayers ("on state"). Therefore, this probe is appealing as a highly sensitive fluorescent labelling marker with a low background signal for imaging artificial and cellular membranes.

Linear dendronized polyols as a multifunctional platform for a versatile and efficient fluorophore design

Linear dendronized polyols (LDPs)as a modular platform for bright, stable, and biocompatible polymeric fluorophores applicable for fluorescent bioimaging studies.

Nutritional and Nanotechnological Modulators of Microglia

Microglia are the essential responders to alimentary, pharmacological, and nanotechnological immunomodulators. These neural cells play multiple roles as surveyors, sculptors, and guardians of essential parts of complex neural circuitries. Microglia can play dual roles in the central nervous system; they can be deleterious and/or protective. The immunomodulatory effects of alimentary components, gut microbiota, and nanotechnological products have been investigated in microglia at the single-cell level and in vivo using intravital imaging approaches, and different biochemical assays. This review highlights some of the emerging questions and topics from studies involving alimentation, microbiota, nanotechnological products, and associated problems in this area of research. Some of the advantages and limitations of in vitro and in vivo models used to study the neuromodulatory effects of these factors, as well as the merits and pitfalls of intravital imaging modalities employed are presented.