Dendrimersomes: Biomedical applications

In recent years, dendrimer-based vesicles, known as dendrimersomes, have garnered significant attention as highly promising alternatives to lipid vesicles in a variety of biomedical applications. Dendrimersomes offer several advantages, including relatively straightforward synthesis, non-immunogenic properties, stability in circulation, and minimal size variability. These vesicles are composed of Janus dendrimers, which are polymers characterized by two dendritic wedges with different terminal groups - hydrophilic and hydrophobic. This dendrimer structure enables the self-assembly of dendrimersomes. The purpose of this highlight is to provide an overview of recent advancements achieved through the utilization of biomimetic dendrimersomes in various biomedical applications such as drug and nucleic acid delivery.

Properties and Bioapplications of Amphiphilic Janus Dendrimers: A Review

Amphiphilic Janus dendrimers are arrangements containing both hydrophilic and hydrophobic units, capable of forming ordered aggregates by intermolecular noncovalent interactions between the dendrimer units. Compared to conventional dendrimers, these molecular self-assemblies possess particular and effective attributes i.e., the presence of different terminal groups, essential to design new elaborated materials. The present review will focus on the pharmaceutical and biomedical application of amphiphilic Janus dendrimers. Important information for the development of novel optimized pharmaceutical formulations, such as structural classification, synthetic pathways, properties and applications, will offer the complete characterization of this type of Janus dendrimers. This work will constitute an up-to-date background for dendrimer specialists involved in designing amphiphilic Janus dendrimer-based nanomaterials for future innovations in this promising field.

Synthesis of Fluorescent, Dumbbell-Shaped Polyurethane Homo- and Heterodendrimers and Their Photophysical Properties

Fluorescent dendrimers have wide applications in biomedical and materials science. Here, we report the synthesis of fluorescent polyurethane homodendrimers and Janus dendrimers, which often pose challenges due to the inherent reactivity of isocyanates. Polyurethane dendrons (G1-G3) were synthesized via a convergent method using a one-pot multicomponent Curtius reaction as a crucial step to establish urethane linkages. The alkyne periphery of the G1-G3 dendrons was modified by a copper catalyzed azide-alkyne click reaction (CuAAC) to form fluorescent dendrons. In the reaction of the surfaces functionalized two different dendrons with a difunctional core, a mixture of three dendrimers consisting of two homodendrimers and a Janus dendrimer were obtained. The Janus dendrimer accounted for a higher proportion in the products' distribution, being as high as 93% for G3. The photophysical properties of Janus dendrimers showed the fluorescence resonance energy transfer (FRET) from one to the other fluorophore of the dendrimer. The FRET observation accompanied by a large Stokes shift make these dendrimers potential candidates for the detection and tracking of interactions between the biomolecules, as well as potential candidates for fluorescence imaging.

Janus Dendrimers to Assess the Anti-HCV Activity of Molecules in Cell-Assays

The use of nanocarriers has been revealed as a valid strategy to facilitate drug bioavailability, and this allows for expanding the drug libraries for the treatment of certain diseases such as viral diseases. In the case of Hepatitis C, the compounds iopanoic acid and 3,3',5-triiodothyroacetic acid (or tiratricol) were identified in a primary screening as bioactive allosteric inhibitors of viral NS3 protease, but they did not exhibit accurate activity inhibiting viral replication in cell-based assays. In this work, dendritic nanocarriers are proposed due to their unique properties as drug delivery systems to rescue the bioactivity of these two drugs. Specifically, four different amphiphilic Janus dendrimers synthesized by combining 2,2'-bis(hydroxymethyl)propionic acid (bis-MPA) and 2,2'-bis(glyciloxy)propionic acid (bis-GMPA) functionalized with either hydrophilic or lipophilic moieties at their periphery were used to entrap iopanoic acid and tiratricol. Interestingly, differences were found in the loading efficiencies depending on the dendrimer design, which also led to morphological changes of the resulting dendrimer aggregates. The most remarkable results consist of the increased water solubility of the bioactive compounds within the dendrimers and the improved antiviral activity of some of the dendrimer/drug aggregates, considerably improving antiviral activity in comparison to the free drugs. Moreover, imaging studies have been developed in order to elucidate the mechanism of cellular internalization.

Molecular Patchy Clusters with Controllable Symmetry Breaking for Structural Engineering

Anisotropic patchy particles with molecular precision are exquisite building blocks for constructing diverse meso-structures of high complexity. In this research, a library of molecular patchy clusters consisting of a collection of functional polyhedral oligomeric silsesquioxane cages with exact regio-configuration and composition were prepared through a robust and modular approach. By meticulously tuning the composition, molecular symmetry, and other parameters, these patchy clusters could assemble into diverse nanostructures, including unconventional complex spherical phases (i.e., Frank-Kasper σ phase and dodecagonal quasicrystalline phase). As the size of the hydrophilic patch expands, a transition sequence from disorder to hexagonally packed cylinders and then to double gyroids was recorded, corresponding to a progressive decrease of interfacial curvature. On the other hand, regioisomers with the same composition but different regio-configuration adopt similar molecular packing but varied phase stability, as a result of the local self-sorting process to alleviate excess unfavorable interfacial contact. These precisely defined molecular patchy clusters provide a model system for a general understanding of the hierarchical structure formation and evolution based on anisotropic spherical building blocks at the nanoscale.

Advances in drug delivery, gene delivery and therapeutic agents based on dendritic materials

Dendrimers are synthetic polymers that grow in three dimensions into well-defined structures. Their morphological appearance resembles a number of trees connected by a common point. Dendritic nanoparticles have been studied for a large number of pharmaceutical and biomedical applications including gene and drug delivery, clinical diagnosis and MRI. Despite the application of dendrimers, research is still in its childhood in comparison with liposomes and other nanomaterials. They are now playing a key role in several therapeutic strategies, with dendrimer-based products in clinical trials. The aim of this review is to describe the state-of-the-art of biomedical applications of dendrimers – and dendrimer conjugates – such as drug and gene delivery and antiviral activity.

Self-Assembling Hybrid Linear-Dendritic Block Copolymers: The Design of Nano-Carriers for Lipophilic Antitumoral Drugs

Two series of amphiphilic block copolymers with a hybrid linear-dendritic structure are presented. The compounds consisted of a hydrophilic poly (ethylene glycol) (PEG) block and a 2,2'-bis(hydroxymethyl)propionic acid (bis-MPA) dendron functionalized with stearic acid chains that impart a hydrophobic nature to the block. Different self-assembled nanostructures with a hydrophobic interior and a hydrophilic external part were obtained depending on the length of the PEG chain (Mn = 2000 and Mn = 5000) and the generation of the bis-MPA dendron. The materials were characterized by transmission electron microscopy (TEM). The shapes of the aggregates ranged from spherical or cylindrical micelles to flexible bilayers. The hydrophobic core enabled these nanostructures to encapsulate the water-insoluble drug plitidepsin. The efficacy of these new plitidepsin-containing carriers was evaluated in four cancer cell-lines and they showed similar anticancer activity to the current standard drug formulation.

Synthesis of amphiphilic, Janus diblock hyperbranched copolyamides and their self-assembly in water

An amphiphilic, Janus diblock hyperbranched copolyamide was synthesized by the condensation reaction, and the morphologies of aggregates in water were changed from spherical to dendritic-like structures via cylindrical-like structures in response to increasing temperature.

Cationic poly(ester amide) dendrimers: alluring materials for biomedical applications

Novel cationic poly(ester amide) dendrimers have been synthesized by copper(i) azide-alkyne cycloaddition (CuAAC) of a tripropargylamine core and azide-terminated dendrons, in turn prepared by iterative amide coupling of the new monomer 2,2'-bis(glycyloxymethyl)propionic acid (bis-GMPA). The alternation of ester and amide groups provided a dendritic scaffold that was totally biocompatible and degradable in aqueous media at physiological and acidic pH. The tripodal dendrimers naturally formed rounded aggregates with a drug that exhibited low water solubility, camptothecin, thus improving its cell viability and anti-Hepatitis C virus (anti-HCV) activity. The presence of numerous peripheral cationic groups enabled these dendrimers to form dendriplexes with both pDNA and siRNA and they showed effective in vitro siRNA transfection in tumoral and non-tumoral cell lines.

Self-Assembly Behavior of Amphiphilic Janus Dendrimers in Water: A Combined Experimental and Coarse-Grained Molecular Dynamics Simulation Approach

Amphiphilic Janus dendrimers (JDs) are repetitively branched molecules with hydrophilic and hydrophobic components that self-assemble in water to form a variety of morphologies, including vesicles analogous to liposomes with potential pharmaceutical and medical application. To date, the self-assembly of JDs has not been fully investigated thus it is important to gain insight into its mechanism and dependence on JDs’ molecular structure. In this study, the aggregation behavior in water of a second-generation bis-MPA JD was evaluated using experimental and computational methods. Dispersions of JDs in water were carried out using the thin-film hydration and ethanol injection methods. Resulting assemblies were characterized by dynamic light scattering, confocal microscopy, and atomic force microscopy. Furthermore, a coarse-grained molecular dynamics (CG-MD) simulation was performed to study the mechanism of JDs aggregation. The obtaining of assemblies in water with no interdigitated bilayers was confirmed by the experimental characterization and CG-MD simulation. Assemblies with dendrimersome characteristics were obtained using the ethanol injection method. The results of this study establish a relationship between the molecular structure of the JD and the properties of its aggregates in water. Thus, our findings could be relevant for the design of novel JDs with tailored assemblies suitable for drug delivery systems.

Photoswitchable Janus glycodendrimer micelles as multivalent inhibitors of LecA and LecB from Pseudomonas aeruginosa

The first example of the self-assembly and lectin binding properties of photoswitchable glycodendrimer micelles is reported. Light-addressable micelles were assembled from a library of 12 amphiphilic Janus glycodendrimers composed of variable carbohydrate head groups and hydrophobic tail groups linked to an azobenzene core. Spontaneous association in water gave cylindrical micelles with uniform size distribution as determined by dynamic light scattering (DLS) and small angle neutron scattering (SANS). Trans-cis photoisomerization of the azobenzene dendrimer core was used to probe the self-assembly behaviour and lectin binding properties of cylindrical micelles, revealing moderate-to-potent inhibition of lectins LecA and LecB from Pseudomonas aeruginosa.

Vesicles from Amphiphilic Dumbbells and Janus Dendrimers: Bioinspired Self-Assembled Structures for Biomedical Applications

The current review focuses on vesicles obtained from the self-assembly of two types of dendritic macromolecules, namely amphiphilic Janus dendrimers (forming dendrimersomes) and amphiphilic dumbbells. In the first part, we will present some synthetic strategies and the various building blocks that can be used to obtain dendritic-based macromolecules, thereby showing their structural versatility. We put our focus on amphiphilic Janus dendrimers and amphiphilic dumbbells that form vesicles in water but we also encompass vesicles formed thereof in organic solvents. The second part of this review deals with the production methods of these vesicles at the nanoscale but also at the microscale. Furthermore, the influence of various parameters (intrinsic to the amphiphilic JD and extrinsic-from the environment) on the type of vesicle formed will be discussed. In the third part, we will review the numerous biomedical applications of these vesicles of nano- or micron-size.

Modular synthesis of self-assembling Janus-dendrimers and facile preparation of drug-loaded dendrimersomes

Materials and methods aimed at the next generation of nanoscale carriers for drugs and other therapeutics are currently in great demand. Yet, creating these precise molecular arrangements in a feasible and straightforward manner represents a remarkable challenge. Herein we report a modular synthetic route for amphiphilic Janus-dendrimers via a copper-catalyzed click reaction (CuAAC) and a facile procedure, using simple injection, to obtain highly uniform dendrimersomes with efficient loading of the model drug compound propranolol. The resulting assemblies were analyzed by dynamic light scattering and cryogenic transmission electron microscopy revealing the formation of unilamellar and multilamellar dendrimersomes. The formation of a bilayer structure was confirmed using cryo-TEM and confocal microscopy visualization of an encapsulated solvatochromic dye (Nile Red). The dendrimersomes reported here are tunable in size, stable over time and display robust thermal stability in aqueous media. Our results expand the scope of dendrimer-based supramolecular colloidal systems and offer the means for one-step fabrication of drug-loaded dendrimersomes in the size range of 90-200 nm, ideal for biomedical applications.

Mimicking Complex Biological Membranes and Their Programmable Glycan Ligands with Dendrimersomes and Glycodendrimersomes

Synthetic vesicles have been assembled and coassembled from phospholipids, their modified versions, and other single amphiphiles into liposomes, and from block copolymers into polymersomes. Their time-consuming synthesis and preparation as stable, monodisperse, and biocompatible liposomes and polymersomes called for the elaboration of new synthetic methodologies. Amphiphilic Janus dendrimers (JDs) and glycodendrimers (JGDs) represent the most recent self-assembling amphiphiles capable of forming monodisperse, stable, and multifunctional unilamellar and multilamellar onion-like vesicles denoted dendrimersomes (DSs) and glycodendrimersomes (GDSs), dendrimercubosomes (DCs), glycodendrimercubosomes (GDCs), and other complex architectures. Amphiphilic JDs consist of hydrophobic dendrons connected to hydrophilic dendrons and can be thought of as monodisperse oligomers of a single amphiphile. They can be functionalized with a variety of molecules such as dyes, and, in the case of JGDs, with carbohydrates. Their iterative modular synthesis provides efficient access to sequence control at the molecular level, resulting in topologies with specific epitope sequence and density. DSs, GDSs, and other architectures from JDs and JGDs serve as powerful tools for mimicking biological membranes and for biomedical applications such as targeted drug and gene delivery and theranostics. This Review covers all aspects of the synthesis of JDs and JGDs and their biological activity and applications after assembly in aqueous media.

Polyurethane based organic macromolecular contrast agents (PU-ORCAs) for magnetic resonance imaging

Combination of its convenience for non-invasive application and high spatial resolution make Magnetic Resonance Imaging (MRI) one of the leading imaging modalities.

An emerging class of amphiphilic dendrimers for pharmaceutical and biomedical applications: Janus amphiphilic dendrimers

In recent years, a new class of dendrimer, known as Janus dendrimers (JDs), has attracted much attention due to their different structures and properties to the conventional symmetric forms. The broken symmetry of JDs offers the opportunity to form complex self-assembled materials, and presents new sets of properties that are presently inconceivable for homogeneous or symmetrical dendrimers. Due to their unique features, JDs have a promising future in pharmaceutical and biomedical fields, as seen from the recent interest in their application in conjugating multiple drugs and targeting moieties, forming supramolecular hydrogels, enabling micellar delivery systems, and preparing nano-vesicles, known as dendrimersomes, for drug encapsulation. The present paper is the first review, with an emphasis on various emerging applications of JDs, in the drug delivery and biomedical field reported so far. In addition, the paper describes different synthetic methods for producing JDs that can guide the design of new biocompatible forms with pharmacological activities, and that have the potential to be nano drug delivery vehicles. Furthermore, future studies to optimize the applications of JDs in drug delivery sciences and biomedical field to realize their potential to treat various disease conditions are identified and highlighted. Overall, this review identifies the current status of JDs in terms of their synthesis and applications, as well as the future research for their translation into macromolecules for clinical applications to solve health problems. It highlights the future combined efforts needed to be taken by dendrimer chemists, formulation scientist and microbiologists to develop novel antibacterials and nanomedicines from JDs.

Nanoobjects formed by ionic PAMAM dendrimers: hydrophilic/lipophilic modulation and encapsulation properties

In this paper, we present the preparation and properties of some ionic PAMAM derivatives, which combine hydrophilic and lipophilic carboxylic acid chains as counter-ions for all protonable inner and outer amino groups. The amphiphilic nature of the final ionic codendrimers and, hence, their self-assembling features can be modulated by using different ratios between hydrophilic and lipophilic chains. In the bulk, these new materials self-organize into smectic A liquid crystal phases. In water, they self-assemble into different types of nano-objects depending on the molecular composition. The study of the morphology of these nano-structures, their cytotoxicity and their capability to encapsulate a lipophilic anticancer drug are reported herein. Some of these nanoobjects are non-cytotoxic and present good drug trapping ability, which make them interesting nanocarriers for applications in nanotechnology and biomedicine.

Recent advances in click chemistry applied to dendrimer synthesis

Dendrimers are monodisperse polymers grown in a fractal manner from a central point. They are poised to become the cornerstone of nanoscale devices in several fields, ranging from biomedicine to light-harvesting. Technical difficulties in obtaining these molecules has slowed their transfer from academia to industry. In 2001, the arrival of the "click chemistry" concept gave the field a major boost. The flagship reaction, a modified Hüisgen cycloaddition, allowed researchers greater freedom in designing and building dendrimers. In the last five years, advances in click chemistry saw a wider use of other click reactions and a notable increase in the complexity of the reported structures. This review covers key developments in the click chemistry field applied to dendrimer synthesis from 2010 to 2015. Even though this is an expert review, basic notions and references have been included to help newcomers to the field.