Development of a low toxicity, effective pDNA vector based on noncovalent assembly of bioresponsive amino-β-cyclodextrin:adamantane-poly(vinyl alcohol)-poly(ethylene glycol) transfection complexes

Cyclodextrin-Based Polymeric Drug Delivery Systems for Cancer Therapy

Cyclodextrins (CDs) are one of the most extensively studied cyclic-oligosaccharides due to their low toxicity, good biodegradability and biocompatibility, facile chemical modification, and unique inclusion capacity. However, problems such as poor pharmacokinetics, plasma membrane disruption, hemolytic effects and a lack of target specificity still exist for their applications as drug carriers. Recently, polymers have been introduced into CDs to combine the advantages of both biomaterials for the superior delivery of anticancer agents in cancer treatment. In this review, we summarize four types of CD-based polymeric carriers for the delivery of chemotherapeutics or gene agents for cancer therapy. These CD-based polymers were classified based on their structural properties. Most of the CD-based polymers were amphiphilic with the introduction of hydrophobic/hydrophilic segments and were able to form nanoassemblies. Anticancer drugs could be included in the cavity of CDs, encapsulated in the nanoparticles or conjugated on the CD-based polymers. In addition, the unique structures of CDs enable the functionalization of targeting agents and stimuli-responsive materials to realize the targeting and precise release of anticancer agents. In summary, CD-based polymers are attractive carriers for anticancer agents.

Construction of a water-soluble and photostable rubropunctatin/β-cyclodextrin drug carrier

The purpose of the current study was to construct a β-cyclodextrin drug carrier for rubropunctatin to improve its water solubility and light stability for future cytotoxicity studies. The inclusion complexation behavior of rubropunctatin with β-cyclodextrin was investigated using FESEM, FT-IR and XRD. A molecular docking study was performed to elucidate the most probable inclusion structure. The inclusion complex could be completely dispersed in water and had a small size of 121.87 ± 2.13 nm (n = 3), a good PDI (0.320 ± 0.017), and an acceptable potential value of -27.7 ± 0.32 mV (n = 3). Furthermore, the stability of the rubropunctatin in water under light irradiation was found to be greatly enhanced after being encapsulated in cyclodextrin, and it exhibited a retention rate of over 70% vs. 10.17%. In addition, the cytotoxicity of the inclusion complex was evaluated by MTT assay and Annexin V-FITC/PI detection using cervical adenocarcinoma HeLa cells. The results showed that the inclusion complex had comparable toxicity compared to rubropunctatin solubilized with 0.4% DMSO. More importantly, the formation of the inclusion complex contributed greatly to the intensification of the bioavailability of rubropunctatin because the use of organic solvent was avoided.

Carbohydrate-based amphiphilic nano delivery systems for cancer therapy

Nanoparticles (NPs) are novel drug delivery systems that have been attracting more and more attention in recent years, and have been used for the treatment of cancer, infection, inflammation and other diseases. Among the numerous classes of materials employed for constructing NPs, organic polymers are outstanding due to the flexibility of design and synthesis and the ease of modification and functionalization. In particular, NP based amphiphilic polymers make a great contribution to the delivery of poorly-water soluble drugs. For example, natural, biocompatible and biodegradable products like polysaccharides are widely used as building blocks for the preparation of such drug delivery vehicles. This review will detail carbohydrate based amphiphilic polymeric systems for cancer therapy. Specifically, it focuses on the nature of the polymer employed for the preparation of targeted nanocarriers, the synthetic methods, as well as strategies for the application and evaluation of biological activity. Applications of the amphiphilic polymer systems include drug delivery, gene delivery, photosensitizer delivery, diagnostic imaging and specific ligand-assisted cellular uptake. As a result, a thorough understanding of the relationship between chemical structure and biological properties facilitate the optimal design and rational clinical application of the resulting carbohydrate based nano delivery systems for cancer therapy.

Recent progress in gene therapy to deliver nucleic acids with multivalent cationic vectors

Due to the potential use as transfecting agents of nucleic acids (DNA or RNA), multivalent cationic non-viral vectors have received special attention in the last decade. Much effort has been addressed to synthesize more efficient and biocompatible gene vectors able to transport nucleic acids into the cells without provoking an immune response. Among them, the mostly explored to compact and transfect nucleic acids are: (a) gemini and multivalent cationic lipids, mixed with a helper lipid, by forming lipoplexes; and (b) cationic polymers, polycations, and polyrotaxanes, by forming polyplexes. This review is focused on the progress and recent advances experimented in this area, mainly during the present decade, devoting special attention to the lipoplexes and polyplexes, as follows: (a) to its biophysical characterization (mainly electrostatics, structure, size and morphology) using a wide variety of experimental methods; and (b) to its biological activity (transfection efficacy and cytotoxicity) addressed to confirm the optimum formulations and viability of these complexes as very promising gene vectors of nucleic acids in nanomedicine.

Emerging Supramolecular Therapeutic Carriers Based on Host-Guest Interactions

Recent advances in host-guest chemistry have significantly influenced the construction of supramolecular soft biomaterials. The highly selective and non-covalent interactions provide vast possibilities of manipulating supramolecular self-assemblies at the molecular level, allowing a rational design to control the sizes and morphologies of the resultant objects as carrier vehicles in a delivery system. In this Focus Review, the most recent developments of supramolecular self-assemblies through host-guest inclusion, including nanoparticles, micelles, vesicles, hydrogels, and various stimuli-responsive morphology transition materials are presented. These sophisticated materials with diverse functions, oriented towards therapeutic agent delivery, are further summarized into several active domains in the areas of drug delivery, gene delivery, co-delivery and site-specific targeting deliveries. Finally, the possible strategies for future design of multifunctional delivery carriers by combining host-guest chemistry with biological interface science are proposed.

Soft Supramolecular Nanoparticles by Noncovalent and Host-Guest Interactions

Supramolecular chemistry provides a tool for the formation of highly ordered structures by means of noncovalent interactions. Soft supramolecular nanoparticles are self-assembled nanoassemblies based on small building blocks and stabilized by basic noncovalent interactions, selective host-guest interactions, or a combination of different interaction types. This review provides an overview of the existing approaches for the formation of supramolecular nanoparticles by various types of noncovalent interactions, with a strong focus on host-guest-mediated assemblies. The approaches are ordered based on the nature of the stabilizing supramolecular interaction, while focusing on the aspects that determine the particle structure. Where applicable, the use of these self-assembled nanostructures as vectors in molecular diagnostics and therapeutics is described as well. The stable yet reversible nature of supramolecular interactions and their chemical flexibility offer great prospects for the development of highly engineered nanoparticles which are compatible with the complexity of living systems.

Acid-Labile Poly(glycidyl methacrylate)-Based Star Gene Vectors

It was recently reported that ethanolamine-functionalized poly(glycidyl methacrylate) (PGEA) possesses great potential applications in gene therapy due to its good biocompatibility and high transfection efficiency. Importing responsivity into PGEA vectors would further improve their performances. Herein, a series of responsive star-shaped vectors, acetaled β-cyclodextrin-PGEAs (A-CD-PGEAs) consisting of a β-CD core and five PGEA arms linked by acid-labile acetal groups, were proposed and characterized as therapeutic pDNA vectors. The A-CD-PGEAs owned abundant hydroxyl groups to shield extra positive charges of A-CD-PGEAs/pDNA complexes, and the star structure could decrease charge density. The incorporation of acetal linkers endowed A-CD-PGEAs with pH responsivity and degradation. In weakly acidic endosome, the broken acetal linkers resulted in decomposition of A-CD-PGEAs and morphological transformation of A-CD-PGEAs/pDNA complexes, lowering cytotoxicity and accelerating release of pDNA. In comparison with control CD-PGEAs without acetal linkers, A-CD-PGEAs exhibited significantly better transfection performances.

Polysaccharides for the Delivery of Antitumor Drugs

Among the several delivery materials available so far, polysaccharides represent very attractive molecules as they can undergo a wide range of chemical modifications, are biocompatible, biodegradable, and have low immunogenic properties. Thus, polysaccharides can contribute to significantly overcome the limitation in the use of many types of drugs, including anti-cancer drugs. The use of conventional anti-cancer drugs is hampered by their high toxicity, mostly depending on the indiscriminate targeting of both cancer and normal cells. Additionally, for nucleic acid based drugs (NABDs), an emerging class of drugs with potential anti-cancer value, the practical use is problematic. This mostly depends on their fast degradation in biological fluids and the difficulties to cross cell membranes. Thus, for both classes of drugs, the development of optimal delivery materials is crucial. Here we discuss the possibility of using different kinds of polysaccharides, such as chitosan, hyaluronic acid, dextran, and pullulan, as smart drug delivery materials. We first describe the main features of polysaccharides, then a general overview about the aspects ruling drug release mechanisms and the pharmacokinetic are reported. Finally, notable examples of polysaccharide-based delivery of conventional anti-cancer drugs and NABDs are reported. Whereas additional research is required, the promising results obtained so far, fully justify further efforts, both in terms of economic support and investigations in the field of polysaccharides as drug delivery materials.

Polycations with excellent gene transfection ability based on PVP-g-PDMAEMA with random coil and micelle structures as non-viral gene vectors

PVP-g-PDMAEMA formed random coils in water and PVP-g-PDMAEMA-b-PMMA self-assembled into spherical core–shell micelles. Both displayed excellent pDNA compacting abilities at an extremely low N/P ratio, with PVP-g-PDMAEMA-b-PMMA also showing excellent gear transfection efficiency.

A biodegradable adamantane polymer with ketal linkages in its backbone for gene therapy

We present a polyketal, termed pADK, which can increase the gene transfection efficiency of PEI1800–cyclodextran conjugates 60 fold and degrade into nontoxic, neutral and excretable compounds.

Polymeric supra-amphiphiles based on terminal group electrostatic interactions: fabrication of micelles with modifiable surfaces

On the basis of terminal group electrostatic interactions (TGEI), a supra-amphiphile is formed between a homopolymer of polylactic acid with carboxyl group at one end (PLA-COOH) and hepta-6-hydrazyl-β-cyclodextrin (HH-CD). The amphiphile can self-assemble into a micellar structure in aqueous solution. The outer surface of the micelle, which is composed of cyclodextrins, can be further modified via host-guest interactions. Considering the biocompatibility of the building blocks, the application of the micelles in a nanocarrier of anticancer drugs is further explored.

Supramolecular copolymers obtained from two-component gels: metal ion-mediated cross-linking, enhanced viscoelasticity and supramolecular yarns

Bolaamphiphilic l-histidine and 2,2′-bipyridine-dicarboxylic acids were assembled into supramolecular polymers, which were further cross-linked by Cu(ii) ions.

Effect of pendant group on pDNA delivery by cationic-β-cyclodextrin:alkyl-PVA-PEG pendant polymer complexes

We have previously shown that cationic-β-cyclodextrin:R-poly(vinyl alcohol)-poly(ethylene glycol) (CD+:R-PVA-PEG) pendant polymer host:guest complexes are safe and efficient vehicles for nucleic acid delivery, where R = benzylidene-linked adamantyl or cholesteryl esters. Herein, we report the synthesis and biological performance of a family of PVA-PEG pendant polymers whose pendant groups have a wide range of different affinities for the β-CD cavity. Cytotoxicity studies revealed that all of the cationic-β-CD:pendant polymer host:guest complexes have 100-1000-fold lower toxicity than branched polyethylenimine (bPEI), with pDNA transfection efficiencies that are comparable to bPEI and Lipofectamine 2000. Complexes formed with pDNA at N/P ratios greater than 5 produced particles with diameters in the 100-170 nm range and ζ-potentials of 15-35 mV. Gel shift and heparin challenge experiments showed that the complexes are most stable at N/P ≥ 10, with adamantyl- and noradamantyl-modified complexes displaying the best resistance toward heparin-induced decomplexation. Disassembly rates of fluoresceinated-pDNA:CD(+):R-PVA-PEG-rhodamine complexes within HeLa cells showed a modest dependence on host:guest binding constant, with adamantyl-, noradamantyl-, and dodecyl-based complexes showing the highest loss in FRET efficiency 9 h after cellular exposure. These findings suggest that the host:guest binding constant has a significant impact on the colloidal stability in the presence of serum and cellular uptake efficiency, whereas endosomal disassembly and transfection performance of cationic-β-CD:R-poly(vinyl alcohol)-poly(ethylene glycol) pendant polymer complexes appears to be controlled by the hydrolysis rates of the acetal grafts onto the PVA main chain.

Microfluidic Assembly of Cationic-β-Cyclodextrin:Hyaluronic Acid-Adamantane Host:Guest pDNA Nanoparticles

Traditionally, transfection complexes are typically formed by bulk mixing, producing particles with high polydispersity and limited control over vector size. Herein, we demonstrate the use of a commercial micro-reactor to assemble pDNA:cationic cyclodextrin:pendant polymer nanoparticles using a layer-by-layer approach. Our studies reveal that the particles formulated via microfluidic assembly have much smaller sizes, lower polydispersity, lower ζ-potentials, and comparable cell viability and transfection profiles in HeLa cells than bulk mixed particles. The complexes also show a flow rate-dependent stability, with particles formed at slower flow rates giving rise to more stable complexes as determined by heparin challenge. Our findings suggest that microfluidic reactors offer an attractive method for assembling reproducible, size-controlled complexes from multi-component transfection complex assemblies.

Polysaccharide-based nucleic acid nanoformulations

Therapeutic application of nucleic acids requires their encapsulation in nanosized carriers that enable safe and efficient intracellular delivery. Before the desired site of action is reached, drug-loaded nanoparticles (nanomedicines) encounter numerous extra- and intracellular barriers. Judicious nanocarrier design is highly needed to stimulate nucleic acid delivery across these barriers and maximize the therapeutic benefit. Natural polysaccharides are widely used for biomedical and pharmaceutical applications due to their inherent biocompatibility. At present, there is a growing interest in applying these biopolymers for the development of nanomedicines. This review highlights various polysaccharides and their derivatives, currently employed in the design of nucleic acid nanocarriers. In particular, recent progress made in polysaccharide-assisted nucleic acid delivery is summarized and the specific benefits that polysaccharides might offer to improve the delivery process are critically discussed.