Extending the Scope of the C-Functionalization of Cyclam via Copper(I)-Catalyzed Alkyne-Azide Cycloaddition to Bifunctional Chelators of Interest

Cyclam, known for its potent chelation properties, is explored for diverse applications through selective N-functionalization, offering versatile ligands for catalysis, medical research, and materials science. The challenges arising from N-alkylation, which could decrease the coordination properties, are addressed by introducing a robust C-functionalization method. The facile two-step synthesis proposed here involves the click chemistry-based C-functionalization of a hydroxyethyl cyclam derivative using Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC). Boc-protecting groups prevent undesired copper coordination, resulting in compounds with a wide range of functionalities. The optimized synthesis conditions enable C-functional cyclams to be obtained easily and advantageously, with high application potential in the previously cited fields. The methodology has been extended to trehalose-based Siamese twin amphiphiles, enabling efficient gene delivery applications.

Cyclodextrin-Based Functional Glyconanomaterials

Cyclodextrins (CDs) have long occupied a prominent position in most pharmaceutical laboratories as "off-the-shelve" tools to manipulate the pharmacokinetics of a broad range of active principles, due to their unique combination of biocompatibility and inclusion abilities. The development of precision chemical methods for their selective functionalization, in combination with "click" multiconjugation procedures, have further leveraged the nanoscaffold nature of these oligosaccharides, creating a direct link between the glyco and the nano worlds. CDs have greatly contributed to understand and exploit the interactions between multivalent glycodisplays and carbohydrate-binding proteins (lectins) and to improve the drug-loading and functional properties of nanomaterials through host-guest strategies. The whole range of capabilities can be enabled through self-assembly, template-assisted assembly or covalent connection of CD/glycan building blocks. This review discusses the advancements made in this field during the last decade and the amazing variety of functional glyconanomaterials empowered by the versatility of the CD component.

Tuning the Topological Landscape of DNA-Cyclodextrin Nanocomplexes by Molecular Design

Original molecular vectors that ensure broad flexibility to tune the shape and surface properties of plasmid DNA (pDNA) condensates are reported herein. The prototypic design involves a cyclodextrin (CD) platform bearing a polycationic cluster at the primary face and a doubly linked aromatic module bridging two consecutive monosaccharide units at the secondary face that behaves as a topology-encoding element. Subtle differences at the molecular level then translate into disparate morphologies at the nanoscale, including rods, worms, toroids, globules, ellipsoids, and spheroids. In vitro evaluation of the transfection capabilities revealed marked selectivity differences as a function of nanocomplex morphology. Remarkably high transfection efficiencies were associated with ellipsoidal or spherical shapes with a lamellar internal arrangement of pDNA chains and CD bilayers. Computational studies support that the stability of such supramolecular edifices is directly related to the tendency of the molecular vector to form noncovalent dimers upon DNA templating. Because the stability of the dimers depends on the protonation state of the polycationic clusters, the coaggregates display pH responsiveness, which facilitates endosomal escape and timely DNA release, a key step in successful transfection. The results provide a versatile strategy for the construction of fully synthetic and perfectly monodisperse nonviral gene delivery systems uniquely suited for optimization schemes.

Trehalose-based Siamese twin amphiphiles with tunable self-assembling, DNA nanocomplexing and gene delivery properties

Trehalose Siamese twin vectors, encompassing gemini and facial amphiphilicity, promote pDNA compaction into core–shell nanocomplexes and selective delivery in the lungs.

Design of cyclodextrin-based systems for intervention execution

Technologies for nucleic acid delivery have displayed high practical potential in mediating genetic manipulation to modulate metabolic pathways to combat aging. In the previous chapter, we have delineated a series of techniques for designing and developing polymeric vectors as nonviral carriers. Based on what we have discussed, this chapter will introduce how the delivery performance and versatility of polymeric vectors can be further enhanced by using cyclodextrins (CDs). Over the years, CDs have shown promising application potential in different areas, ranging from controlled drug release to chiral separation of basic drugs. These applications are largely mediated by the ability of CDs to undergo host–guest inclusion complexation. Upon incorporation of CDs into the design of a polymeric vector, not only can the flexibility of the design be increased, but the development of a multifunctional carrier for genetic manipulation can also be facilitated.

Plasmid-Templated Control of DNA-Cyclodextrin Nanoparticle Morphology through Molecular Vector Design for Effective Gene Delivery

Engineering self-assembled superstructures through complexation of plasmid DNA (pDNA) and single-isomer nanometric size macromolecules (molecular nanoparticles) is a promising strategy for gene delivery. Notably, the functionality and overall architecture of the vector can be precisely molded at the atomic level by chemical tailoring, thereby enabling unprecedented opportunities for structure/self-assembling/pDNA delivery relationship studies. Beyond this notion, by judiciously preorganizing the functional elements in cyclodextrin (CD)-based molecular nanoparticles through covalent dimerization, here we demonstrate that the morphology of the resulting nanocomplexes (CDplexes) can be tuned, from spherical to ellipsoidal, rod-type, or worm-like nanoparticles, which makes it possible to gain understanding of their shape-dependent transfection properties. The experimental findings are in agreement with a shift from chelate to cross-linking interactions on going from primary-face- to secondary-face-linked CD dimers, the pDNA partner acting as an active payload and as a template. Most interestingly, the transfection efficiency in different cells was shown to be differently impacted by modifications of the CDplex morphology, which has led to the identification of an optimal prototype for tissue-selective DNA delivery to the spleen in vivo.

A novel potential nanophototherapeutic based on the assembly of an amphiphilic cationic β-cyclodextrin and an anionic porphyrin

The development of cyclodextrin nanoassemblies as useful carriers for photosensitizer drugs (PS) delivery in biological environment is a topic of increasing interest. In this paper, we present a spectroscopic investigation on a nanosystem based on an amphiphilic cationic β-cyclodextrin derivative (CD-N) and an anionic porphyrin (TPPS). Nanoassemblies were prepared by hydration of an organic film containing the two species. The system was characterized by complementary techniques such as UV-vis, stationary and time-resolved fluorescence, and Dynamic Light Scattering (DLS) at different TPPS/CD-N molar ratios. Time-resolved fluorescence data showed that, at all the investigated molar ratios, TPPS is present both as self-aggregated species and monomers forming supramolecular adducts with CD-N. Moreover, DLS measurements evidenced families of aggregates having hydrodynamic radii ranging between 50 and 350 nm and the size distribution profile depending on the TPPS/CD-N molar ratio. At the highest CD-N concentration, the hydrodynamic radii of the aggregates were nearly the same as those of neat CD-N in the absence of TPPS (50 nm). No aging phenomena were registered, pointing out the high stability of these nanoassemblies in aqueous solution for at least a month. Preliminary studies on the internalization in tumoral cells and subsequent irradiation for PDT application were carried out. The results support the feasibility of these nanoaggregates to promote PS internalization in HeLa cells, inducing cell death upon visible light irradiation.

Transfection-capable polycationic nanovectors which include PEGylated-cyclodextrin structural units: a new synthesis pathway

Polycationic nanoentities with low variability are able to act as cooperating carriers for dsDNA complexation and transport.

Cyclodextrin- and calixarene-based polycationic amphiphiles as gene delivery systems: a structure-activity relationship study

Multi-head/multi-tail facial amphiphiles built on cyclodextrin (CD) and calixarene (CA) scaffolds are paradigmatic examples of monodisperse gene delivery systems. The possibility to precisely control the architectural features at the molecular level offers unprecedented opportunities for conducting structure-activity relationship studies. A major requirement for those channels is the design of a sufficiently diverse ensemble of compounds for parallel evaluation of their capabilities to condense DNA into transfection nanoparticles where the gene material is protected from the environment. Here we have undertaken the preparation of an oriented library of β-cyclodextrin (βCD) and calix[4]arene (CA4) vectors with facial amphiphilic character designed to ascertain the effect of the cationic head nature (aminothiourea-, arginine- or guanidine-type groups) and the macrocyclic platform on the abilities to complex plasmid DNA (pDNA) and in the efficiency of the resulting nanocomplexes to transfect cells in vitro. The hydrophobic domain, formed by hexanoyl or hexyl chains, remains constant in each series, matching the overall structure found to be optimal in previous studies. DLS, TEM and AFM data support that all the compounds self-assemble in the presence of pDNA through a process that involves initially electrostatic interactions followed by formation of βCD or CA4 bilayers between the oligonucleotide filaments. Spherical transfectious nanoparticles that are monomolecular in DNA are thus obtained. Evaluation in epithelial COS-7 and human rhabdomyosarcoma RD-4 cells evidenced the importance of having primary amino groups in the vector to warrant high levels of transfection, probably because of their buffering capacity. The results indicate that the optimal cationic head depends on the macrocyclic core, aminothiourea groups being preferred in the βCD series and arginine groups in the CA4 series. Whereas the transfection efficiency relationships remain essentially unchanged within each series, irrespective of the cell type, the optimal platform (βD or CA4) strongly depends on the cell type. The results illustrate the potential of monodisperse vector prototypes and diversity-oriented strategies on identifying the optimal candidates for gene therapy applications.

Cyclodextrin-scaffolded amphiphilic aminoglucoside clusters: self-assembling and gene delivery capabilities

The self-assembling and gene transfer capabilities of monodisperse amphiphilic aminoglucoside–cyclodextrin conjugates depend on the amino disposition at the glycationic head.

Cyclodextrins in non-viral gene delivery

Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides. They consist of (α-1,4)-linked glucose units, and possess a basket-shaped topology with an "inner-outer" amphiphilic character. Over the years, substantial efforts have been undertaken to investigate the possible use of CDs in drug delivery and controlled drug release, yet the potential of CDs in gene delivery has received comparatively less discussion in the literature. In this article, we will first discuss the properties of CDs for gene delivery, followed by a synopsis of the use of CDs in development and modification of non-viral gene carriers. Finally, areas that are noteworthy in CD-based gene delivery will be highlighted for future research. Due to the application prospects of CDs, it is anticipated that CDs will continue to emerge as an important tool for vector development, and will play significant roles in facilitating non-viral gene delivery in the forthcoming decades.