Self-Assembly of Glycerol-Amphiphilic Janus Dendrimers Amplifies and Indicates Principles for the Selection of Stereochemistry by Biological Membranes

One-Component Ionizable Amphiphilic Janus Dendrimers for Targeted mRNA Delivery

mRNA nanomedicine represents a new generation of therapeutics. However, how to deliver mRNA to the desired organs and cells effectively remains challenging. Common mRNA delivery vectors include viral and nonviral types such as four-component lipid nanoparticles (LNPs), polymer-based nanoparticles, lipid-polymer hybrid nanoparticles, and so on. One-component ionizable amphiphilic Janus dendrimers (IAJDs), are an emerging type of mRNA delivery vehicle displaying good stability and high delivery efficiency. In this review, we comprehensively present the design, synthesis, and mRNA delivery properties of IAJDs, with particular focus on the relationship between their molecular structures and organ targeted delivery properties. Other representative types of dendrimers for RNA delivery are also reviewed. Overall, this review summarizes the recent research progress on IAJDs systematically, aiming to guide the development of more efficient mRNA delivery platforms and next-generation mRNA nanomedicines.

Pepticombisomes: Biomimetic Vesicles Crafted From Recombinant Supercharged Polypeptides with Uniformly Distributed Side-Chains

Cell membranes play a key role in bottom-up synthetic biology, as they enable interaction control, transport, and other essential functions. These ultra-thin, flexible, yet stable structures form through the self-assembly of lipids and proteins. While liposomes are common mimics, their synthetic membranes often fail to replicate natural properties due to poor structural control. To address this, pepticombs are introduced, a new family of supramolecular building blocks. They are synthesized by regularly appending anionic surfactants with lipid-long alkyl tails to cationic amino acid residues of recombinant elastin-like supercharged unfolded polypeptides (SUPs). Using microscopy techniques and molecular dynamics simulations, the formation of giant unilamellar vesicles, termed pepticombisomes, is demonstrated and their membrane properties are characterized. The molecular topology of pepticombs allows for precise mimicry of membrane thickness and flexibility, beyond classic polymersomes. Unlike the previously introduced ionically-linked comb polymers, all pepticombs exhibit a uniform degree of polymerization, composition, sequence, and spontaneous curvature. This uniformity ensures consistent hydrophobic tail distribution, facilitating intermolecular hydrogen bonding within the backbone. This generates elastic heterogeneities and the concomitant formation of non-icosahedral faceted vesicles, as previously predicted. Additionally, pepticombisomes can incorporate functional lipids, enhancing design flexibility.

Toward a Complete Elucidation of the Primary Structure-Activity in Pentaerythritol-Based One-Component Ionizable Amphiphilic Janus Dendrimers for In Vivo Delivery of Luc-mRNA

Four-component lipid nanoparticles (LNPs) and viral vectors are key for mRNA vaccine and therapeutics delivery. LNPs contain ionizable lipids, phospholipids, cholesterol, and polyethylene glycol (PEG)-conjugated lipids and deliver mRNA for COVID-19 vaccines to liver when injected intravenously or intramuscularly. In 2021, we elaborated one-component ionizable amphiphilic Janus dendrimers (IAJDs) accessing targeted delivery of mRNA. Simplified synthesis and assembly processes allow for rapid IAJD screening for discovery. The role of the primary structure of IAJDs in activity indicated, with preliminary investigations, that ionizable amine (IA), sequence, and architecture of hydrophilic and hydrophobic domains are important for in vivo targeted delivery. Here, we study the role of the interconnecting linker length between the IA and the hydrophobic domain of pentaerythritol-based IAJDs. The linker length determines, through inductive effects, the position of the IA and the pKa of the IAJDs and through flexibility, the stability of the DNPs, highlighting their extraordinarily important role in effective targeted delivery.

Nano onions based on an amphiphilic Au3(pyrazolate)3 complex

Multilayer vesicles with an onion-like architecture can form by self-assembly of organic amphiphiles such as dendrimers, small-molecule surfactants, and block copolymers. Thus far, there are limited reports about multilayer vesicles based on coordination compounds. Herein, we show that nano onions are obtained by aggregation of an amphiphilic Au3(pyrazolate)3 complex in aqueous solution. The nanostructures were characterized by cryogenic and transition electron microscopy, dynamic light scattering, and energy-dispersive X-ray analysis. Control experiments with analogous Ag(I) and Cu(I) complexes revealed the importance of Au(I) for the formation of well-defined nano onions. A structurally related Au(I) complex without solubilizing polyethylene glycol side chains was analyzed by single-crystal X-ray diffraction. In the solid state, columns of offset, π-stacked Au3(pyrazolate)3 complexes are observed, but short intermolecular Au⋯Au contacts were not found. Molecular dynamics simulations provided further insights into the aggregation process in aqueous solution, supporting the formation of nano-onion structures through lateral interactions between stacked complexes.

Accelerated Ten-Gram-Scale Synthesis of One-Component Multifunctional Sequence-Defined Ionizable Amphiphilic Janus Dendrimer 97

One-component multifunctional sequence-defined ionizable amphiphilic Janus dendrimers (IAJDs) were discovered in our laboratories in 2021 to represent a new class of synthetic vectors for the targeted delivery of messenger RNA (mRNA). They coassemble with mRNA by simple injection of their ethanol solution into a pH 4 acetate buffer containing the nucleic acid into monodisperse dendrimersome nanoparticles (DNPs) with predictable dimensions. DNPs are competitive with 4-component lipid nanoparticles (LNPs), which are used in commercial COVID-19 vaccines, except that IAJDs are prepared in fewer reaction steps than each individual component of the LNPs. This simple methodology for the synthesis of IAJDs and their coassembly with mRNA into DNPs, together with the precise placement of their individual components and indefinite stability at room temperature in air, make them attractive candidates for the development of nanomedicine-based targeted mRNA delivery. Access to the large-scale synthesis of IAJDs without the need for sophisticated technologies, instrumentation, and synthetic skills is expected to open numerous new opportunities worldwide in nanomedicine. The goal of this publication is to report an accelerated ten-gram-scale synthesis of IAJD97 from inexpensive food additives obtained from renewable plant phenolic acid starting materials by methodologies accessible to any laboratory. This accelerated synthesis can be accomplished in 4 days. We expect that the work reported here will impact the field of nanomedicine in both developed and less developed countries.

Supramolecular assembly of dendronized diacetylenes into thermoresponsive chiral fibers and their covalent fixation through topochemical polymerization

By combination of dendritic topological structures with photopolymerizable diacetylene, here we report on supramolecular chiral assembly of the dendronized diacetylenes in water. These dendronized diacetylenes are constituted with three-fold dendritic oligoethylene glycols (OEGs), bridged with a dipeptide from phenylalanine and glycine. These dendronized amphiphiles exhibit intensive propensity to aggregate in water and form helical fibers, which show characteristic thermoresponsive behavior with phase transition temperatures dominated by hydrophilicity of the dendritic OEGs. Topochemical polymerization of these supramolecular fibers through UV irradiation transfers them into the covalent helical dendronized polydiacetylenes. Chirality of these dendronized polydiacetylenes can be mediated through the thermally-induced phase transitions, but is also intriguingly dependent on vortex via stirring. Through stirring the solutions, chiralities of the dendronized polydiacetylenes are inverted, which can be reversibly recovered after keeping still the solution. Hydrogels are formed from these dendronized diacetylenes through concentration-enhanced interactions between the supramolecular fibers. Their mechanical properties can be greatly increased through thermally-enhanced interactions between the fibers with storage moduli increased from 20 Pa to a few hundred Pa. In addition, through photo-polymerization, the supramolecular fibers are transferred into covalent dendronized polydiacetylenes, and the corresponding hydrogels show much improved mechanical properties with storage moduli about 10 kPa.

Diverse Approaches for the Difunctionalization of PPH Dendrimers, Precise Versus Stochastic: How Does this Influence Catalytic Performance?

Random difunctionalization of dendrimer surfaces, frequently employed in biological applications, provides the advantage of dual functional groups through a synthetic pathway that is simpler compared to precise difunctionalization. However, is the random difunctionalization as efficient as the precise difunctionalization on the surface of dendrimers? This question is unanswered to date because most dendrimer families face challenges in achieving precise functionalization. Polyphosphorhydrazone (PPH) dendrimers present a unique opportunity to obtain precise difunctionalization at each terminal branching point. The work concerning catalysis we report with PPH dendrimers, whether precisely or randomly functionalized, addresses this question. Across PPH dendrimers, from generations 1 to 3, precise functionalization consistently outperforms random functionalization in terms of efficiency. This finding introduces a novel concept in dendrimer science, emphasizing the superiority of precise over random functionalization methodologies. Introducing a groundbreaking concept in the field of dendrimers.

A Janus carbaporphyrin pseudo-dimer

Carbaporphyrin dimers, investigated for their distinctive electronic structures and exceptional properties, have predominantly consisted of systems containing identical subunits. This study addresses the associated knowledge gap by focusing on asymmetric carbaporphyrin dimers with Janus-like characteristics. The synthesis of a Janus-type carbaporphyrin pseudo-dimer 5 is presented. It displays antiaromatic characteristics on the fused side and nonaromatic behavior on the unfused side. A newly synthesized tetraphenylene (TPE) linked bis-dibenzihomoporphyrin 8 and a previously reported dibenzo[g,p]chrysene (DBC) linked bis-dicarbacorrole 9 were prepared as controls. Comprehensive analyses, including 1H NMR spectral studies, single crystal X-ray diffraction analyses, and DFT calculations, validate the mixed character of 5. A further feature of the Janus pseudo-dimer 5 is that it may be transformed into a heterometallic complex, with one side coordinating a Cu(III) center and the other stabilizing a BODIPY complex. This disparate regiochemical reactivity underscores the potential of carbaporphyrin dimers as versatile frameworks, with electronic features and site-specific coordination chemistry controlled through asymmetry. These findings position carbaporphyrin dimers as promising candidates for advances in electronic structure studies, coordination chemistry, materials science, and beyond.

Aptamer-Targeted Dendrimersomes Assembled from Azido-Modified Janus Dendrimers "Clicked" to DNA

Amphiphilic Janus dendrimers (JDs), synthetic alternatives to lipids, have the potential to expand the scope of nanocarrier delivery systems. JDs self-assemble into vesicles called dendrimersomes, encapsulate both hydrophobic cargo and nucleic acids, and demonstrate enhanced stability in comparison to lipid nanoparticles (LNPs). Here, we report the ability to enhance the cellular uptake of Janus dendrimersomes using DNA aptamers. Azido-modified JDs were synthesized and conjugated to alkyne-modified DNAs using copper-catalyzed azide alkyne cycloaddition. DNA-functionalized JDs form nanometer-sized dendrimersomes in aqueous solution via thin film hydration. These vesicles, now displaying short DNAs, are then hybridized to transferrin receptor binding DNA aptamers. Aptamer-targeted dendrimersomes show improved cellular uptake as compared to control vesicles via fluorescence microscopy and flow cytometry. This work demonstrates the versatility of using click chemistry to conjugate functionalized JDs with biologically relevant molecules and the feasibility of targeting DNA-modified dendrimersomes for drug delivery applications.

A Sequence-Defined ABC Dendritic Macromolecule with Amino Acid Peripheral Functionality via Iterative Chemoselective Reactions

Chemoselective reactions allow near-precision control over the polymer composition and topology to create sequence-controlled polymers with similar secondary and tertiary structures to those found in proteins. Dendrimers are recognized as well-defined macromolecules with the potential to mimic protein surface functionality due to the large number of functional groups available at its periphery with the internal structure acting as the support scaffold. Transitioning from using small-molecule dendrimers to dendritic macromolecules will not only allow retention of the high peripheral functionality but also provide an internal scaffold with a desired polymer composition within each generational layer. Here, we exemplify a systematic approach to creating a dendritic macromolecule with the placement of different polymer building blocks in precise locations within the internal structure and the placement of three different amino acid moieties clustered at the periphery. The synthesis of this ABC dendritic macromolecule was accomplished through iterative chemoselective reactions.

The Constitutional Isomerism of One-Component Ionizable Amphiphilic Janus Dendrimers Orchestrates the Total and Targeted Activities of mRNA Delivery

Constitutional isomerism has been previously demonstrated by one of our laboratories to represent a powerful design strategy for the elaboration of complex functional self-organizations. Here we report the design, synthesis, and characterization of 14 positional, skeletal, and functional constitutional isomeric one-component, multifunctional, sequence-defined, amphiphilic ionizable Janus dendrimers (IAJDs). Their coassembly by simple injection with luciferase mRNA (Luc-mRNA) to form dendrimersome nanoparticles (DNPs) was studied. Subsequently, the resulting DNPs were employed to investigate, with screening experiments, the delivery of Luc-mRNA in vivo. Constitutional isomerism was shown to produce changes of up to two orders of magnitude of the total-body luciferase activity and targeted luciferase activity to the spleen and liver, of up to three orders of magnitude difference in targeted luciferase activity to the lungs and up to six orders of magnitude to lymph nodes. These results indicate that constitutional isomerism may represent not only a simple but also an important synthetic strategy that most probably may impact the activity of all components of synthetic vectors used in RNA-based nanomedicine, including in mRNA vaccines and therapeutics.

Epichlorohydrin-based CuAAC dendrimers with a calix[4]arene core and polar hydroxyl/oxyethyl terminal groups: synthesis, aggregation and use in catalysis

1st and 2nd generation amphiphilic dendrimers were obtained. Spherical palladium nanodendrites stabilized by amphiphilic dendrimers show excellent catalytic activities in coupling and reduction of aromatics in water.

Near-Infrared BODIPY Photosensitizer for Modulating Mitochondrial Fusion Proteins and Inhibiting Choroidal Neovascularization

Photosensitizers have emerged as cytotoxic reactive oxygen species (ROS) activators in photodynamic therapy (PDT), which induced cell apoptosis. As the major contributors to ROS and oxidative stress, mitochondria play an important role in cell apoptosis. Although there are many reports about near-infrared 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) as photosensitizers (PSs) for PDT, this kind of PS has rarely been used for treating mitochondrial function and choroidal neovascularization application at the same time. Herein, a novel near-infrared PS (BDP2) characterized by good water solubility, long wavelength excitation, and high ROS quantum yield has been made. Under near-infrared light irradiation, BDP2 would generate ROS with high yield, induce a mitochondrial morphology change, and trigger cell apoptosis by changing the fusion protein level. Deep investigation revealed that BDP2 can cause oxidative stress, break the balance between fusion and fission of mitochondrial dynamics protein through decreasing fusion protein MFN2 and OPA1 expression, and finally cause cell apoptosis. Due to these characteristics, the BDP2 PS was used to treat choroidal neovascularization in animal models and can inhibit neovascularization.

Targeted and Equally Distributed Delivery of mRNA to Organs with Pentaerythritol-Based One-Component Ionizable Amphiphilic Janus Dendrimers

Delivery of nucleic acids with viral and synthetic vectors has pioneered genetic nanomedicine. Four-component lipid nanoparticles (LNPs) consisting of ionizable lipids, phospholipids, cholesterol, and PEG-conjugated lipids, assembled by microfluidic or T-tube, are the benchmark synthetic vector for delivery of mRNA. One-component multifunctional sequence-defined ionizable amphiphilic Janus dendrimer (IAJD) delivery systems for mRNA were developed by us to complement LNPs. IAJDs consist of multifunctional hydrophilic low-generation dendrons or minidendrons conjugated to hydrophobic dendrons. They were inspired by amphiphilic Janus dendrimers and glycodendrimers. IAJDs coassemble with mRNA into predictable-size vesicles, named dendrimersome nanoparticles (DNPs), by simple injection in acetate buffer, rather than by the complex technology required by LNPs. Assembly of DNPs by simple injection together with sequence design in the hydrophilic and hydrophobic modules of IAJDs endowed rapid screening to access discovery. Molecular design principles for targeted delivery were elaborated when the branching points of IAJDs were constructed from symmetrically and nonsymmetrically substituted plant phenolic acids interconnected by pentaerythritol (PE). Here, we report the first library containing simplified IAJDs constructed in only three steps from symmetrically trialkylated PE in the hydrophobic domain and four different piperazine-based ionizable amines in the hydrophilic part. Rapid coassembly with mRNA and in vivo screening led to the discovery of the two most active IAJDs targeting the spleen, liver, and lymph nodes, one predominantly to the spleen and liver and six delivering equally to the spleen, liver, lung, and lymph nodes. These IAJDs represent the simplest synthetic vectors and the first viral or synthetic system delivering equally to multiple organs.

Screening Libraries to Discover Molecular Design Principles for the Targeted Delivery of mRNA with One-Component Ionizable Amphiphilic Janus Dendrimers Derived from Plant Phenolic Acids

Viral and synthetic vectors to deliver nucleic acids were key to the rapid development of extraordinarily efficient COVID-19 vaccines. The four-component lipid nanoparticles (LNPs), containing phospholipids, PEG-conjugated lipids, cholesterol, and ionizable lipids, co-assembled with mRNA via a microfluidic technology, are the leading nonviral delivery vector used by BioNTech/Pfizer and Moderna to access COVID-19 mRNA vaccines. LNPs exhibit a statistical distribution of their four components when delivering mRNA. Here, we report a methodology that involves screening libraries to discover the molecular design principles required to realize organ-targeted mRNA delivery and mediate activity with a one-component ionizable multifunctional amphiphilic Janus dendrimer (IAJD) derived from plant phenolic acids. IAJDs co-assemble with mRNA into monodisperse dendrimersome nanoparticles (DNPs) with predictable dimensions, via the simple injection of their ethanol solution in a buffer. The precise location of the functional groups in one-component IAJDs demonstrated that the targeted organs, including the liver, spleen, lymph nodes, and lung, are selected based on the hydrophilic region, while activity is associated with the hydrophobic domain of IAJDs. These principles, and a mechanistic hypothesis to explain activity, simplify the synthesis of IAJDs, the assembly of DNPs, handling, and storage of vaccines, and reduce price, despite employing renewable plant starting materials. Using simple molecular design principles will lead to increased accessibility to a large diversity of mRNA-based vaccines and nanotherapeutics.