Supramolecular gels of poly-α-cyclodextrin and PEO-based copolymers for controlled drug release

Celecoxib-hydroxypropyl-β-cyclodextrin inclusion complex in a chitosan/PEO-PPO-PEO block copolymer matrix: Structural effect and drug release

HYPOTHESIS

Triblock copolymers of poly(ethylene oxide) and poly(propylene oxide)-based matrices, such as Poloxamer 407 (P407) or Pluronic® F127, are extensively utilized in drug delivery and permeation systems due to their FDA approval and listing in the US and European Pharmacopoeias. The study hypothesizes that incorporating 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and the celecoxib-HP-β-CD inclusion complex into a 16 wt% P407 and chitosan blend in an aqueous acetic acid solution will affect the system's rheological and structural properties.

EXPERIMENTS

Rheological, small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS) experiments were conducted to assess the impact of acetic acid and chitosan on the 16 wt% P407 and chitosan blend. Additionally, in vitro drug release studies were performed to monitor the drug release profile over time.

FINDINGS

The addition of HP-β-CD was found to inhibit gel formation in the 16 wt% P407 and chitosan blend. However, the presence of the celecoxib-HP-β-CD inclusion complex showed no significant structural effects compared to P407 blended with chitosan alone. Rheological and SAXS analyses demonstrated that acetic acid led to the formation of a lamellar phase due to the lower pH, facilitating injectability. The presence of chitosan in acetic acid resulted in the detection of a hexagonal phase, affecting the release of celecoxib.

Preparation, Characterization and Evaluation of the Anti-Inflammatory Activity of Epichlorohydrin-β-Cyclodextrin/Curcumin Binary Systems Embedded in a Pluronic®/Hyaluronate Hydrogel

Curcumin (Cur) is an anti-inflammatory polyphenol that can be complexed with polymeric cyclodextrin (CD) to improve solubility and bioavailability. The aim of the present work was to prepare a CurCD hydrogel to treat inflammatory skin conditions. Epichlorohydrin-β-CD (EpiβCD) was used as polymeric CD. To characterize the binary system, solid-state and in-solution studies were performed. Afterwards, an experimental design was performed to optimize the hydrogel system. Finally, the CurEpiβCD hydrogel system was tested for anti-inflammatory activity using a HaCat psoriasis cell model. Co-grinded Cur/EpiβCD binary system showed a strong interaction and Curcumin solubility was much improved. Its combination with Pluronic® F-127/hyaluronate hydrogel demonstrated an improvement in release rate and Curcumin permeation. After testing its anti-inflammatory activity, the system showed a significant reduction in IL-6 levels. Hydrogel-containing CurEpiβCD complex is a great alternative to treat topical inflammatory diseases.

Polypseudorotaxanes of Pluronic® F127 with Combinations of α- and β-Cyclodextrins for Topical Formulation of Acyclovir

Acyclovir (ACV) is one of the most used antiviral drugs for the treatment of herpes simplex virus infections and other relevant mucosal infections caused by viruses. Nevertheless, the low water solubility of ACV limits both its bioavailability and antiviral performance. The combination of block copolymer micelles and cyclodextrins (CDs) may result in polypseudorotaxanes with tunable drug solubilizing and gelling properties. However, the simultaneous addition of various CDs has barely been investigated yet. The aim of this work was to design and characterize ternary combinations of Pluronic® F127 (PF127), αCD and βCD in terms of polypseudorotaxane formation, rheological behavior, and ACV solubilization ability and controlled release. The formation of polypseudorotaxanes between PF127 and the CDs was confirmed by FT-IR spectroscopy, X-ray diffraction, and NMR spectroscopy. The effects of αCD/βCD concentration range (0–7% w/w) on copolymer (6.5% w/w) gel features were evaluated at 20 and 37 °C by rheological studies, resulting in changes of the copolymer gelling properties. PF127 with αCD/βCD improved the solubilization of ACV, maintaining the biocompatibility (hen’s egg test on the chorio-allantoic membrane). In addition, the gels were able to sustain acyclovir delivery. The formulation prepared with similar proportions of αCD and βCD provided a slower and more constant release. The results obtained suggest that the combination of Pluronic with αCD/βCD mixtures can be a valuable approach to tune the rheological features and drug release profiles from these supramolecular gels.

The π-π stacking-guided supramolecular self-assembly of nanomedicine for effective delivery of antineoplastic therapies

In traditional nano drug-delivery systems, the complex chemical bonds between drug and carrier often complicate the preparation process and are less prone to rupture upon entry into the target, which is detrimental to the timely release of the drug. The π-π stacking provides us with a promising alternative as it is a weak interaction between the aromatic rings. Since most antitumor drugs are hydrophobic molecules with complex aromatic π-π-conjugated structures, the construction of self-assembly based on π-π stacking between drugs and carriers has the advantage of improving the stability and drug loading capacity as well as the improvement of hydrophilicity and biosafety. This article introduces the recent advances in π-π stacking-guided nano self-assembly for antineoplastic delivery.

Self-Assembled Hydrogels Based on Poly-Cyclodextrin and Poly-Azobenzene Compounds and Applications for Highly Efficient Removal of Bisphenol A and Methylene Blue

The excellent physical and chemical properties of cyclodextrin polymer (poly-CD)/azobenzene-modified polyacrylic acid (PAA-Azo) binary composite hydrogels have been designed and prepared. The prepared hydrogels were subjected to a variety of characterizations, including scanning electron microscopy, ultraviolet spectroscopy, circular dichroism spectroscopy, infrared spectroscopy, rheological properties, and specific surface area tests. It was found that the obtained hydrogels have the cross-linked three-dimensional porous network nanostructures, and the formed composite poly-CD/PAA-Azo hydrogel can basically be shear thinned and have good recovery performance. A process of gel-sol transition can occur when the gel has a stimulatory response under UV light irradiation. In addition, such excellent properties of hydrogels exhibit different mechanisms in the adsorption of organic molecules that are harmful to the environment, such as bisphenol A (BPA) and methylene blue (MB). The polymeric hydrogel serves as novel adsorbent agents to adsorb BPA via host-guest interaction and anchor MB via electrostatic interaction and hydrogen bonding.

Precise Molecular Sieving Architectures with Janus Pathways for Both Polar and Nonpolar Molecules

Precise molecular sieving architectures with Janus superhighways are constructed via a molecularly engineered interfacial reaction between cyclodextrin (CD) and trimesoyl chloride (TMC). Interestingly, the CD/TMC nanofilms constructed with both hydrophobic inner cavities and hydrophilic channels exhibit exceptionally high permeances for both polar and nonpolar solvents. The precise molecular sieving functions are determined by the type of CD building blocks and the inner cavities of intrinsic 3D hollow bowls. Positron annihilation spectroscopy (PAS) confirms that a larger inner CD cavity tends to generate a larger free volume and higher microporosity. Based on the rejection ratio of various dyes, the estimated molecular weight cutoff of CD/TMC nanofilms follows the trend of α-CD/TMC (320 Da) <β-CD/TMC (400 Da) <γ-CD/TMC (550 Da), which is in strict accordance with the orders of their free volumes measured by PAS and inner cavity sizes of α-CD <β-CD <γ-CD. This kind of novel CD/TMC molecular sieving membrane with intrinsic microporosity containing tunable pore size and sharp pore-size distribution can effectively discriminate molecules with different 3D sizes.

Supramolecular polypseudorotaxane gels for controlled delivery of rAAV vectors in human mesenchymal stem cells for regenerative medicine

The aim of this work was to investigate, for the first time, the possibility of using supramolecular polypseudorotaxane gels as scaffolds that can durably deliver rAAV vectors for applications in cartilage regeneration. Dispersions of Pluronic^® F68 (PF68) or Tetronic^® 908 (T908) containing either hyaluronic acid (HA) or chondroitin sulfate (CS) were prepared in PBS. Then, alpha-cyclodextrin (αCD) was added to some dispersions to form polypseudorotaxane gels. Polysaccharides and αCD reinforced the viscoelasticity of the gels, which could withstand autoclaving without changes. In vitro release of rAAV vectors and subsequent transduction of human mesenchymal stem cells (hMSCs) by rAAV vectors from the release medium and from gels in direct contact with the cells were investigated. Compared with free vectors, the gels provided higher levels of transgene expression. CS (or HA)/PF68/αCD gels rapidly released rAAV vectors while CS (or HA)/T908/αCD gels provided sustained release probably due to different interactions with the viral vectors. Incorporation of αCD into CS (or HA)/PF68 gels resulted on higher rAAV concentrations and sustained levels of transgene expression over time. HA increased the bioactivity and cytocompatibility of the gels, especially those based on T908. Overall, combining rAAV gene transfer with polypseudorotaxane gels may provide new, promising tools for human tissue engineering and regenerative medicine strategies.

Preparation and investigation of temperature-responsive calix[4]arene-based molecular gels

Higher temperature enhances the strength and the toughness of the gel comprised of kerosene and a tetracholesteryl derivative based on calix[4]arene.

HMDSO-plasma coated electrospun fibers of poly(cyclodextrin)s for antifungal dressings

Electrospun mats containing cyclodextrin polymers (poly-αCD or poly-βCD) were developed to act as wound dressings showing tunable release rate of the antifungal agent fluconazole incorporated forming inclusion complexes. Poly-αCD and poly-βCD were prepared via cross-linking with epichlorohydrin (EPI) as water-soluble large molecular weight polymers. Then, polyCDs forming complexes with fluconazole were mixed with poly-(ε-caprolactone) (PCL) or poly(N-vinylpyrrolidone) (PVP) for electrospinning. Obtained bead-free fibers showed a random distribution, diameters in the 350-850nm range, and a variety of physical stability behaviors in aqueous environment. Mats were coated by hexamethyldisiloxane (HMDSO) plasma polymerization to create a hydrophobic layer that prevented rapid drug diffusion. HMDSO coating was evidenced by the Si content of mat surface (EDX analysis) and by the increase in the water contact angle (up to 130°). In physiological-mimicking medium, non-treated mats showed burst release of fluconazole, whereas HMDSO-coated mats sustained the release and delayed disintegration of PVP-based mats. Antifungal tests evidenced that both coated and non-coated mats efficiently inhibited the growth of Candida albicans.

Supramolecular host-guest polycationic gene delivery system based on poly(cyclodextrin) and azobenzene-terminated polycations

This article describes the supramolecular host-guest polycationic gene delivery system based on poly(β-cyclodextrin) (PCD) and azobenzene-terminated polycations. The azobenzene-terminated linear (Az-LPDM) and branched (Az-BPDM) cationic polymers were synthesized by atom transfer radical polymerization (ATRP) of 2-dimethylamino ethyl methacrylate (DMAEMA). The formation and photosensitive behavior of the supramolecular polycations of azobenzene-terminated polycations Az-LPDM and Az-BPDM with PCD were confirmed by UV-vis and NMR analysis. The supramolecular PCD/Az-BPDM/DNA and PCD/Az-LPDM/DNA polyplexes showed smaller size and were less positive than those of their corresponding polyplexes without PCD. Moreover, the UV irradiation may promote release of DNA from the photosensitive supramolecular polyplexes due to dissociation of supramoelcular polyplexes. In vitro experiments revealed that the photosensitive supramolecular polycationic polyplexes (PCD/Az-LPDM/DNA and PCD/Az-BPDM/DNA) exhibited enhancement of cellular uptake, higher transfection efficiency, and lower cytoxicity compared to the azobenzene-terminated polycation/DNA polyplexes in the absence of PCD. Branched polycationic polyplexes showed higher transfection efficiency than its linear polycationic polyplexes. Furthermore, after UV irradiation, the transfection efficiency of photosensitive supramolecular polyplexes was improved resulting from more DNAs delivered and released inside of the cell nuclei. Thus this photoresponsive supramolecular host-guest system containing azobenzene-terminated branched cationic polymers and PCD is a promising gene vector.

Supramolecular Nanostructures Based on Cyclodextrin and Poly(ethylene oxide): Syntheses, Structural Characterizations and Applications for Drug Delivery

Cyclodextrins (CDs) have been extensively studied as drug delivery carriers through host⁻guest interactions. CD-based poly(pseudo)rotaxanes, which are composed of one or more CD rings threading on the polymer chain with or without bulky groups (or stoppers), have attracted great interest in the development of supramolecular biomaterials. Poly(ethylene oxide) (PEO) is a water-soluble, biocompatible polymer. Depending on the molecular weight, PEO can be used as a plasticizer or as a toughening agent. Moreover, the hydrogels of PEO are also extensively studied because of their outstanding characteristics in biological drug delivery systems. These biomaterials based on CD and PEO for controlled drug delivery have received increasing attention in recent years. In this review, we summarize the recent progress in supramolecular architectures, focusing on poly(pseudo)rotaxanes, vesicles and supramolecular hydrogels based on CDs and PEO for drug delivery. Particular focus will be devoted to the structures and properties of supramolecular copolymers based on these materials as well as their use for the design and synthesis of supramolecular hydrogels. Moreover, the various applications of drug delivery techniques such as drug absorption, controlled release and drug targeting based CD/PEO supramolecular complexes, are also discussed.

PEO-PPO-PEO micelles as effective rAAV-mediated gene delivery systems to target human mesenchymal stem cells without altering their differentiation potency

Recombinant adeno-associated viral (rAAV) vectors are clinically adapted gene transfer vectors for direct human cartilage regenerative medicine. Their appropriate use in patients is still limited by a relatively low efficacy of vector penetration inside the cells, by the pre-existing humoral immune responses against the viral capsid proteins in a large part of the human population, and by possible inhibition of viral uptake by clinical compounds such as heparin. The delivery of rAAV vectors to their targets using optimized vehicles is therefore under active investigation. Here, we evaluated the possibility of providing rAAV to human bone marrow-derived mesenchymal stem cells (hMSCs), a potent source of cartilage regenerative cells, via self-assembled poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymers as linear poloxamers or X-shaped poloxamines. Encapsulation in poloxamer PF68 and poloxamine T908 polymeric micelles allowed for an effective, durable, and safe modification of hMSCs via rAAV to levels similar to or even higher than those noted upon direct vector application. The copolymers were capable of restoring the transduction of hMSCs with rAAV in conditions of gene transfer inhibition, i.e. in the presence of heparin or of a specific antibody directed against the rAAV capsid, enabling effective therapeutic delivery of a chondrogenic sox9 sequence leading to an enhanced chondrocyte differentiation of the cells. The present findings highlight the value of PEO-PPO copolymers as powerful tools for rAAV-based cartilage regenerative medicine.

STATEMENT OF SIGNIFICANCE

While recombinant adeno-associated viral (rAAV) vectors are adapted vectors to treat a variety of human disorders, their clinical use is still restricted by pre-existing antiviral immune responses, by a low efficacy of natural vector entry in the target cells, and by inhibition of viral uptake by clinically used compounds like heparin. The search for alternative routes of rAAV delivery is thus becoming a new field of investigation. In the present study, we describe the strong benefits of providing rAAV to human mesenchymal stem cells, a potent source of cells for regenerative medicine, encapsulated in polymeric micelles based on poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymers as novel, effective and safe delivery systems for human gene therapy.

Novel nanostructured supramolecular hydrogels for the topical delivery of anionic drugs

A bis-imidazolium-based amphiphilic molecule was used to form novel supramolecular gels in ethanol-water mixtures. The proportion of solvents, the concentration of gellant and the temperature are factors that strongly influence the gelling process. The physical gels that are formed comprise entangled fibers of around 100nm in diameter, able to incorporate anionic drugs, whose morphology varies depending on the drug they incorporate. These hydrogels are soft and therefore optimum for skin application. They show good stability when compared to previously reported gels. Suitable drug release and skin permeation profiles were obtained, and, moreover, they seem to promote the retention of the drug inside the skin. Finally, effective in vivo anti-inflammatory activity was observed, especially with the indomethacin-incorporated gel, which indicates that these supramolecular hydrogels are a good option for the delivery of poor water soluble drugs for the treatment of acute inflammation or other skin diseases.

Supramolecular cyclodextrin-based drug nanocarriers

Supramolecular systems formed by the binding of several cyclodextrins (CDs) to polymers or lipids, either via non-covalent or covalent links, open a wide range of possibilities for the delivery of active substances. CDs can perform as multifunctionalizable cores to which very diverse (macro)molecules and drugs can be conjugated. Grafting with amphiphilic molecules can lead to nanoassemblies exhibiting a variety of architectures. CDs can also polymerize with other CDs or can be used to functionalize preexisting polymers to form polymers/networks with enhanced capability to form inclusion complexes. Alternatively, CDs can be exploited as transient cross-linkers to form poly(pseudo)rotaxane-based networks or zipper-like assemblies. Combination of mutifunctionality and complexation ability of CDs has been shown to be useful to develop depot-like formulations and colloidal nanocarriers with improved performances regarding easiness of administration, protection of the encapsulated substances, control of the delivery rate, and cell interactions. The aim of this review is to provide an overall view of the diversity of designs of CD-based supramolecular nanosystems with a special focus on the advances materialized in the last five years, including clinical trials.

Redox-responsive mesoporous silica as carriers for controlled drug delivery: a comparative study based on silica and PEG gatekeepers

Hybrid mesoporous silica nanoparticles (MSNs) modified with polymer polyethylene glycol (PEG) through the biodegradable disulfide bonds were prepared to achieve 'on demand' drug release. In this system, PEG chains were chosen as the representative gatekeepers that can block drugs within the mesopores of MSNs. After the addition of glutathione (GSH), the gatekeepers were removed from the pore outlets of MSNs, followed by the release of encapsulated drugs. In this research, the effects of grafting density of gatekeepers on the drug release and biocompatibility of silica carriers were also investigated. First, PEG modified MSNs were prepared by the condensation reaction between the carboxyl groups of MSN and the hydroxyl of PEG. The structure of the resultant MSN-SS-PEG was characterized by transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms analysis and Fourier transform infrared spectroscopy (FTIR). Rhodamine B (RhB) as the model drug was loaded into MSNs. The in vitro assay results indicated that RhB was released rapidly after the addition of 10 mM GSH; M1-SS-PEG had the best capping efficiency compared with M0.5 and M1.5 groups. Moreover, hemolysis assay, serum protein adsorption and cell viability test indicated that with the increase of PEG grafting density, the biocompatibility of silica carriers increased.

Inclusion and functionalization of polymers with cyclodextrins: current applications and future prospects

The numerous hydroxyl groups available in cyclodextrins are active sites that can form different types of linkages. They can be crosslinked with one another, or they can be derivatized to produce monomers that can form linear or branched networks. Moreover, they can form inclusion complexes with polymers and different substrates, modifying their physicochemical properties. This review shows the different applications using polymers with cyclodextrins, either by forming inclusion complexes, ternary complexes, networks, or molecularly imprinted polymers (MIPs). On one hand, the use of cyclodextrins enhances the properties of each polymer, and on the other the use of polymers decreases the amount of cyclodextrins required in different formulations. Both cyclodextrins and polymers contribute synergistically in several applications such as pharmacological, nutritional, environmental, and other industrial fields. The use of polymers based on cyclodextrins is a low cost easy to use potential tool with great future prospects.