Encapsulation of hydrophobic components in dendrimersomes and decoration of their surface with proteins and nucleic acids.

Reconstructing the functions of living cells using nonnatural components is one of the great challenges of natural sciences. Compartmentalization, encapsulation, and surface decoration of globular assemblies, known as vesicles, represent key early steps in the reconstitution of synthetic cells. Here we report that vesicles self-assembled from amphiphilic Janus dendrimers, called dendrimersomes, encapsulate high concentrations of hydrophobic components and do so more efficiently than commercially available stealth liposomes assembled from phospholipid components. Multilayer onion-like dendrimersomes demonstrate a particularly high capacity for loading low-molecular weight compounds and even folded proteins. Coassembly of amphiphilic Janus dendrimers with metal-chelating ligands conjugated to amphiphilic Janus dendrimers generates dendrimersomes that selectively display folded proteins on their periphery in an oriented manner. A modular strategy for tethering nucleic acids to the surface of dendrimersomes is also demonstrated. These findings augment the functional capabilities of dendrimersomes to serve as versatile biological membrane mimics.

Dual-Degradable Biohybrid Microgels by Direct Cross-Linking of Chitosan and Dextran Using Azide-Alkyne Cycloaddition.

In this work, biocompatible and degradable biohybrid microgels based on chitosan and dextran were synthesized for drug delivery applications. Two kinds of bio-based building blocks, alkyne-modified chitosan and azide-modified dextran, were used to fabricate microgels via single-step cross-linking in water-in-oil emulsions. The cross-linking was initiated in the presence of copper(II) without the use of any extra cross-linkers. A series of pH-responsive and degradable microgels were successfully synthesized by varying the degree of cross-links. The microgels were characterized using 1H NMR and FTIR spectroscopy which proved the successful cross-linking of alkyne-modified chitosan and azide-modified dextran by copper(II)-mediated click reaction. The obtained microgels exhibit polyampholyte character and can carry positive or negative charges in aqueous solutions at different pH values. Biodegradability of microgels was shown at pH 9 or in the presence of Dextranase due to the hydrolysis of carbonate esters in the microgels or 1,6-α-glucosidic linkages in dextran structure, respectively. Furthermore, the microgels could encapsulate vancomycin hydrochloride (VM), an antibiotic, with a high loading of approximately 93.67% via electrostatic interactions. The payload could be released in the presence of Dextranase or under an alkaline environment, making the microgels potential candidates for drug delivery, such as colon-specific drug release.

Membrane-Mimetic Dendrimersomes Engulf Living Bacteria via Endocytosis.

There is much interest in developing vesicular microcompartments from natural and synthetic amphiphiles, enabling programmable interactions with living matter. Of particular interest is the development of vesicles capable of endocytosis of living bacteria. Despite the complexity of this process, theoretical studies predict that the endocytosis of prolate micro-objects is possible without the need of active cell machinery if the energy released upon bacterial adhesion to the membrane surpasses the energy required to bend the membrane. Nonetheless, natural liposomes and synthetic polymersomes fail to sufficiently recapitulate membrane properties to perform this advanced function. Here we report the engulfment of living bacteria into endosomes by cell-like dendrimersomes assembled from Janus dendrimers. Full engulfment occurred in less than a minute after contact. The process is driven by the adhesion of the bacterium to the dendrimersome's membrane by ultraweak interactions, comparable to those utilized by nature. The key to success relies on the combination of high flexibility and stability of the dendrimersomes. The key properties of the dendrimersomes are programmed into the molecular structures of their building blocks. The ability to support endocytosis highlights opportunities for the design and programming of dendrimersomes in biomedical research.

Antifouling Microparticles To Scavenge Lipopolysaccharide from Human Blood Plasma.

Currently, one of the most promising treatments of lipopolysaccharides (LPS)-induced sepsis is based on hemofiltration. Nevertheless, proteins rapidly adsorbed on the artificial surface of membranes which leads to activation of coagulation impairing effective scavenging of the endotoxins. To overcome this challenge, we designed polymer-brush-coated microparticles displaying antifouling properties and functionalized them with polymyxin B (PMB) to specifically scavenge LPS the most common endotoxin. Poly[( N-(2-hydroxypropyl) methacrylamide)- co-(carboxybetaine methacrylamide)] brushes were grafted from poly(glycidyl methacrylate) microparticles using photoinduced single-electron transfer living radical polymerization (SET-LRP). Notably, only parts-per-million of copper catalyst were necessary to achieve brushes able to repel adsorption of proteins from blood plasma. The open porosity of the particles, accessible to polymerization, enabled us to immobilize sufficient PMB to selectively scavenge LPS from blood plasma.

Screening Libraries of Amphiphilic Janus Dendrimers Based on Natural Phenolic Acids to Discover Monodisperse Unilamellar Dendrimersomes.

Natural, including plant, and synthetic phenolic acids are employed as building blocks for the synthesis of constitutional isomeric libraries of self-assembling dendrons and dendrimers that are the simplest examples of programmed synthetic macromolecules. Amphiphilic Janus dendrimers are synthesized from a diversity of building blocks including natural phenolic acids. They self-assemble in water or buffer into vesicular dendrimersomes employed as biological membrane mimics, hybrid and synthetic cells. These dendrimersomes are predominantly uni- or multilamellar vesicles with size and polydispersity that is predicted by their primary structure. However, in numerous cases, unilamellar dendrimersomes completely free of multilamellar assemblies are desirable. Here, we report the synthesis and structural analysis of a library containing 13 amphiphilic Janus dendrimers containing linear and branched alkyl chains on their hydrophobic part. They were prepared by an optimized iterative modular synthesis starting from natural phenolic acids. Monodisperse dendrimersomes were prepared by injection and giant polydisperse by hydration. Both were structurally characterized to select the molecular design principles that provide unilamellar dendrimersomes in higher yields and shorter reaction times than under previously used reaction conditions. These dendrimersomes are expected to provide important tools for synthetic cell biology, encapsulation, and delivery.

Electroactive and degradable supramolecular microgels.

In this work, we synthesized electroactive and degradable microgels based on biomacromolecular building blocks, which enable the controlled release of therapeutic drugs. Functional chitosan-poly(hydroquinone) (Ch:PHQ) microgels exhibiting redox-active and pH-sensitive properties were synthesized by an oxidative polymerization in an inverse miniemulsion system. Physically crosslinked microgels were formed by polymerization of hydroquinone in the presence of chitosan through the formation of hydrogen bonds between PHQ and Ch. A series of microgel samples with variable Ch : PHQ ratios were synthesized. These obtained microgels exhibit pH-responsive properties due to the protonation/deprotonation of amino-groups of chitosan in the microgel system. Poly(hydroquinone) is a redox-active polymer exhibiting a two-electron/proton-transfer behavior and conveys this property to the microgels as confirmed by cyclic voltammetry. In addition, the microgels can be switched by electrochemical means: they swell in the oxidized state or shrink in the reduced state. In the presence of urea or lysozyme, the microgels undergo a fast degradation due to the disruption of hydrogen bonds acting as physical crosslinks in the microgel networks or due to the cleavage of glucosidic linkages of the incorporated chitosan scaffold, respectively. Doxorubicin (DOX), an anticancer drug, could be effectively encapsulated into the microgels and released in the presence of an enzyme, indicating that these biodegradable microgels could be used as drug delivery vehicles for tumor cells.

Nerve Cells Decide to Orient inside an Injectable Hydrogel with Minimal Structural Guidance.

Injectable biomaterials provide the advantage of a minimally invasive application but mostly lack the required structural complexity to regenerate aligned tissues. Here, we report a new class of tissue regenerative materials that can be injected and form an anisotropic matrix with controlled dimensions using rod-shaped, magnetoceptive microgel objects. Microgels are doped with small quantities of superparamagnetic iron oxide nanoparticles (0.0046 vol %), allowing alignment by external magnetic fields in the millitesla order. The microgels are dispersed in a biocompatible gel precursor and after injection and orientation are fixed inside the matrix hydrogel. Regardless of the low volume concentration of the microgels below 3%, at which the geometrical constrain for orientation is still minimum, the generated macroscopic unidirectional orientation is strongly sensed by the cells resulting in parallel nerve extension. This finding opens a new, minimal invasive route for therapy after spinal cord injury.

In Vivo Polymer Mechanochemistry with Polynucleotides.

Polymer mechanochemistry utilizes mechanical force to activate latent functionalities in macromolecules and widely relies on ultrasonication techniques. Fundamental constraints of frequency and power intensity have prohibited the application of the polymer mechanochemistry principles in a biomedical context up to now, although medical ultrasound is a clinically established modality. Here, a universal polynucleotide framework is presented that allows the binding and release of therapeutic oligonucleotides, both DNA- and RNA-based, as cargo by biocompatible medical imaging ultrasound. It is shown that the high molar mass, colloidal assembly, and a distinct mechanochemical mechanism enable the force-induced release of cargo and subsequent activation of biological function in vitro and in vivo. Thereby, this work introduces a platform for the exploration of biological questions and therapeutics development steered by mechanical force.

Assessing the NLRP3 Inflammasome Activating Potential of a Large Panel of Micro- and Nanoplastics in THP-1 Cells.

Due to the ubiquity of environmental micro- and nanoplastics (MNPs), inhalation and ingestion by humans is very likely, but human health effects remain largely unknown. The NLRP3 inflammasome is a key player of the innate immune system and is involved in responses towards foreign particulate matter and the development of chronic intestinal and respiratory inflammatory diseases. We established NLRP3-proficient and -deficient THP-1 cells as an alternative in vitro screening tool to assess the potential of MNPs to activate the NLRP3 inflammasome. By investigating cytokine release (IL-1ß and IL-8) and cytotoxicity after treatment with engineered nanomaterials, this in vitro approach was compared to earlier published ex vivo murine bone marrow-derived macrophages and in vivo data. This approach showed a strong correlation with previously published data, verifying that THP-1 cells are a suitable model to investigate NLRP3 inflammasome activation. We then investigated the proinflammatory potential of eight MNPs of different size, shape, and chemical composition. Only amine-modified polystyrene (PS-NH2) acted as a direct NLRP3 activator. However, polyethylene terephthalate (PET), polyacrylonitrile (PAN), and nylon (PA6) induced a significant increase in IL-8 release in NLRP3-/- cells. Our results suggest that most MNPs are not direct activators of the NLRP3 inflammasome, but specific MNP types might still possess pro-inflammatory potential via other pathways.

Unraveling the Mechanism and Kinetics of Binding of an LCI-eGFP-Polymer for Antifouling Coatings.

The ability of proteins to adsorb irreversibly onto surfaces opens new possibilities to functionalize biological interfaces. Herein, the mechanism and kinetics of adsorption of protein-polymer macromolecules with the ability to equip surfaces with antifouling properties are investigated. These macromolecules consist of the liquid chromatography peak I peptide from which antifouling polymer brushes are grafted using single electron transfer-living radical polymerization. Surface plasmon resonance spectroscopy reveals an adsorption mechanism that follows a Langmuir-type of binding with a strong binding affinity to gold. X-ray reflectivity supports this by proving that the binding occurs exclusively by the peptide. However, the lateral organization at the surface is directed by the cylindrical eGFP. The antifouling functionality of the unimolecular coatings is confirmed by contact with blood plasma. All coatings reduce the fouling from blood plasma by 8894% with only minor effect of the degree of polymerization for the studied range (DP between 101 and 932). The excellent antifouling properties, combined with the ease of polymerization and the straightforward coating procedure make this a very promising antifouling concept for a multiplicity of applications.

Bioactive gyroid scaffolds formed by sacrificial templating of nanocellulose and nanochitin hydrogels as instructive platforms for biomimetic tissue engineering.

A sacrificial templating process using lithographically printed minimal surface structures allows complex de novo geo-metries of delicate hydrogel materials. The hydrogel scaffolds based on cellulose and chitin nanofibrils show differences in terms of attachment of human mesenchymal stem cells, and allow their differentiation into osteogenic outcomes. The approach here serves as a first example toward designer hydrogel scaffolds viable for biomimetic tissue engineering.