Tuning structural parameters for the optimization of drug delivery performance of cyclodextrin-based nanosponges

Comparative evaluation of dithranol-loaded nanosponges fabricated by solvent evaporation technique and melt method

Background

Dithranol, a standard drug for psoriasis, has lured keen attention by virtue of its antioxidant, anti-proliferative and anti-inflammatory activities. However, its poor stability and solubility critically impair the formulation design, evaluation and administration. To improve these issues, dithranol was encased in β-cyclodextrin nanosponges using solvent evaporation technique. Previously, nanosponges containing dithranol were developed in our laboratory using melt technique. Herein, a comparison of nanosponges prepared by both techniques was also included.

Results

Different nanosponge batches were engineered using diphenyl carbonate as cross-linker with β-cyclodextrin as polymer employing solvent evaporation technique. Dithranol was loaded in nanosponges via lyophilization. Fourier transform infrared spectroscopy, differential scanning colorimeter and powdered X-ray diffraction studies confirmed successful encapsulation and complexation of this drug in β-cyclodextrin nanosponges. The effect of a variable amount of cross-linker on the solubility, encapsulation efficiency, zeta potential, particle size and polydispersity index was evaluated in fabricated nanocarriers. Further, β-cyclodextrin nanosponge batches were subjected to solubility studies, photostability examination and antioxidant activity analysis and compared with previously prepared dithranol-loaded nanosponges. From the present studies results, it was concluded that dithranol-loaded nanosponges using solvent evaporation technique not only improved solubility and photostability but also preserved the antioxidant efficacy of the chosen drug.

Conclusion

The overall results emphasized moral guidance concerning encapsulation, evaluation and characterization and accredited dithranol solubilization, photostability and antioxidant potential. However, solvent evaporation and melt method are easy and promising methods to fabricate nanosponges for dithranol. This comparative study demonstrated the parameters which were affected by chosen techniques. Further, from the results of present studies, it was concluded that the formulation scientists should select the preparation technique based on the objective of their research work and requirement of desired features.

Graphical abstract

Quercitrin loaded cyclodextrin based nanosponge as a promising approach for management of lung cancer and COVID-19

Lung cancer and pandemic acute respiratory disease, COVID-19, are examples of the most worldwide widespread diseases. The aim of the current study is to develop cyclodextrin based nanosponge (CD-NS) for loading the flavonoid drug, quercitrin (QCT). This is to improve its solubility in an attempt to enhance its activity against lung cancer as well as SARS-CoV-2 virus responsible for COVID-19. Preparation of CD-NS was performed by ultrasound-assisted synthesis method. Two CDs were employed, namely, β cyclodextrin (βCD) and 2-hydroxy propyl-β-cyclodextrin (2-HPβCD) that were crosslinked with diphenyl carbonate, one at a time. QCT loaded CD-NS revealed entrapment efficiency and particle size ranged between 94.17 and 99.03% and 97.10–325.90 nm, respectively. QCT loaded 2-HPβCD-NS revealed smaller particle size compared with that of QCT loaded βCD-NS. Zeta potential absolute values of the prepared formulations were >20 mV, indicating physically stable nanosystems. The selected formulations were investigated by Fourier transform infrared spectroscopy, X-ray powder diffraction and scanning electron microscopy which proved the formation of QCT loaded CD-NS exhibiting porous structure. QCT exhibited partial and complete amorphization in βCD-NS and 2-HPβCD-NS, respectively. In vitro release revealed an improved release of QCT from CD-NS formulations. The biological activity of free QCT and QCT loaded CD-NS was investigated against lung cancer cell line A549 as well as SARS-CoV-2 virus. The results revealed that IC₅₀ values of free QCT against lung cancer cell line A549 and SARS-CoV-2 were higher than those exhibited by QCT loaded CD-NS by 1.57–5.35 and 5.95–26.95 folds, respectively. QCT loaded 2-HPβCD-NS revealed enhanced in vitro release and superior biological activity compared with QCT loaded βCD-NS.

β-Cyclodextrin-Based Nanosponges Inclusion Compounds Associated with Gold Nanorods for Potential NIR-II Drug Delivery

This article describes the synthesis and characterization of two nanocarriers consisting of β-cyclodextrin-based nanosponges (NSs) inclusion compounds (ICs) and gold nanorods (AuNRs) for potential near-infrared II (NIR-II) drug-delivery systems. These nanosystems sought to improve the stability of two drugs, namely melphalan (MPH) and curcumin (CUR), and to trigger their photothermal release after a laser irradiation stimulus (1064 nm). The inclusion of MPH and CUR inside each NS was confirmed by field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, Fourier transform infrared spectroscopy, (FT-IR) differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and proton nuclear magnetic resonance (1H-NMR). Furthermore, the association of AuNRs with both ICs was confirmed by FE-SEM, energy-dispersive spectroscopy (EDS), TEM, dynamic light scattering (DLS), ζ-potential, and UV–Vis. Moreover, the irradiation assays demonstrated the feasibility of the controlled-photothermal drug release of both MPH and CUR in the second biological window (1000–1300 nm). Finally, MTS assays depicted that the inclusion of MPH and CUR inside the cavities of NSs reduces the effects on mitochondrial activity, as compared to that observed in the free drugs. Overall, these results suggest the use of NSs associated with AuNRs as a potential technology of controlled drug delivery in tumor therapy, since they are efficient and non-toxic materials.

Recent Updates on Supramolecular-Based Drug Delivery - Macrocycles and Supramolecular Gels

Supramolecules-based drug delivery has attracted significant recent research attention as it could enhance drug solubility, retention time, targeting, and stimuli responsiveness. Among the different supramolecules and assemblies, the macrocycles and the supramolecular hydrogels are the two important categories investigated to a greater extent. Here, we provide the most recent advancements in these categories. Under macrocycles, reports on drug delivery by cyclodextrins, cucurbiturils, calixarenes/pillararenes, crown ethers and porphyrins are detailed. The second category discusses the supramolecular hydrogels of macrocycles/polymers and low molecular weight gelators. The updated information provided could be helpful to advance R & D in this vital area.

Cyclodextrin-Based Nanosponges: Overview and Opportunities

Nanosponges are solid cross-linked polymeric nano-sized porous structures. This broad concept involves, among others, metal organic frameworks and hydrogels. The focus of this manuscript is on cyclodextrin-based nanosponges. Cyclodextrins are cyclic oligomers of glucose derived from starch. The combined external hydrophilicity with the internal hydrophobic surface constitute a unique "microenvironment", that confers cyclodextrins the peculiar ability to form inclusion host‒guest complexes with many hydrophobic substances. These complexes may impart beneficial modifications of the properties of guest molecules such as solubility enhancement and stabilization of labile guests. These properties complemented with the possibility of using different crosslinkers and high polymeric surface, make these sponges highly suitable for a large range of applications. Despite that, in the last 2 decades, cyclodextrin-based nanosponges have been developed for pharmaceutical and biomedical applications, taking advantage of the nontoxicity of cyclodextrins towards humans. This paper provides a critical and timely compilation of the contributions involving cyclodextrins nanosponges for those areas, but also paves the way for other important applications, including water and soil remediation and catalysis.

Nanosponge Approach -A Plethora of Opportunities as a Promising Nanocarrier for Novel Drug Delivery

BACKGROUND

Nanotechnology is the need of the hour! The design of nanotechnologyaided carriers as a tool for the delivery of low solubility molecules offers a potential platform to overcome the issues of current clinical treatment and achieve good targeted release and bioaccessibility.

OBJECTIVE

Nanosponges (NS) encapsulate types of nanocarriers capable of carrying both lipophilic and hydrophilic substances. They are synthesized by mixing a solution of polyester, which is biodegradable, with cross-linkers. These tiny, porous structures are round-shaped, having multiple cavities wherein drugs can be housed to offer programmable release.

METHODS

The detailed literature review and patent search summarize the ongoing research on NS. Substances such as poorly soluble drugs, nutraceuticals, gases, proteins and peptides, volatile oils, genetic material, etc., can be loaded on these novel carriers, which are characterized using various analytical techniques. Target-specific drug delivery and controlled drug release are the advantages offered by NS, along with a myriad of other promising applications.

RESULTS

This review stresses the development of cyclodextrin-based NS, the synthetic methods and characterization of NS, along with factors affecting NS formation, their applications and information on the patented work in this area. NS are solid in character and can be formulated in various dosage forms, such as parenteral, topical, oral or inhalation.

CONCLUSION

Therefore, owing to their promising benefits over other nanocarriers in terms of drug loading, adaptability, sustainability, solubility and tailored release profile, NS is an immediate technological revolution for drug entrapment and as novel drug carriers.The authors expect that these fundamental applications of NS could help the researchers to develop and gain insight about NS in novel drug delivery applications.

The Impact of Hydration and Dehydration on the Mobility and Location of Ibuprofen Molecules in the Voids of Ultra-Stable Zeolite Y

Mesoporous dealuminated zeolites are used as hosts for ibuprofen. This drug experiences high mobility when confined in mesopores, which is largely dependent on the water content. Zeolites are materials that are naturally hydrated under ambient conditions. Nitrogen adsorption and X-ray diffraction (XRD) show that the samples with the content of ibuprofen up to 38% have the guest phase residing only in mesopores. ¹H and ¹³C MAS NMR studies of samples in ambient conditions, after dehydration, and in hydration prove the impact of water for increased mobility of ibuprofen. Increased mobility of the introduced phase was also detected for samples with no water content. It was ascribed to ibuprofen located outside mesopores, which experiences a prolonged time of cooling to room temperature. This phenomenon is important for all the future uses of the melting method in guest-host systems and the future use of zeolites for biomedical applications.

The role of water in the confinement of ibuprofen in SBA-15

The introduction of ibuprofen into mesopores of SBA-15 has been accomplished using the melting method. Samples exhibit from 9 to 33% of the hydrophobic drug. They are not toxic to mouse monocyte-macrophage cells and do not stimulate a pro-inflammatory response. The sample with 25% of the drug showed no crystalline ibuprofen and almost filled the mesopores, while the sample with 33% showed a total filling of the mesopores with some crystalline ibuprofen present. By means of 1D (¹H, ¹³C HPDEC, ¹³C CP MAS) and 2D (¹H-¹H NOESY) MAS NMR spectroscopy, it has been shown that water coexists with ibuprofen in mesopores and has an impact on the mobility of ibuprofen molecules and their location within the sample (outside or inside mesopores). Studies in the dehydrated state show for the first time that the high mobility of ibuprofen in mesopores is directly connected to the presence of water. Dehydrated samples show slightly slower release rates in comparison to their hydrated counterparts.

β-Cyclodextrin-Based Nanosponges Functionalized with Drugs and Gold Nanoparticles

Drugs are widely used as therapeutic agents; however, they may present some limitations. To overcome some of the therapeutic disadvantages of drugs, the use of β-cyclodextrin-based nanosponges (βCDNS) constitutes a promising strategy. βCDNS are matrices that contain multiple hydrophobic cavities, increasing the loading capacity, association, and stability of the included drugs. On the other hand, gold nanoparticles (AuNPs) are also used as therapeutic and diagnostic agents due to their unique properties and high chemical reactivity. In this work, we developed a new nanomaterial based on βCDNS and two therapeutic agents, drugs and AuNPs. First, the drugs phenylethylamine (PhEA) and 2-amino-4-(4-chlorophenyl)-thiazole (AT) were loaded on βCDNS. Later, the βCDNS-drug supramolecular complexes were functionalized with AuNPs, forming the βCDNS-PhEA-AuNP and βCDNS-AT-AuNP systems. The success of the formation of βCDNS and the loading of PhEA, AT, and AuNPs was demonstrated using different characterization techniques. The loading capacities of PhEA and AT in βCDNS were 90% and 150%, respectively, which is eight times higher than that with native βCD. The functional groups SH and NH2 of the drugs remained exposed and allowed the stabilization of the AuNPs, 85% of which were immobilized. These unique systems can be versatile materials with an efficient loading capacity for potential applications in the transport of therapeutic agents.

Production and Mechanical Characterisation of TEMPO-Oxidised Cellulose Nanofibrils/β-Cyclodextrin Films and Cryogels

Wood-based TEMPO-oxidised cellulose nanofibrils (toCNF) are promising materials for biomedical applications. Cyclodextrins have ability to form inclusion complexes with hydrophobic molecules and are considered as a method to bring new functionalities to these materials. Water sorption and mechanical properties are also key properties for biomedical applications such as drug delivery and tissue engineering. In this work, we report the modification with β-cyclodextrin (βCD) of toCNF samples with different carboxyl contents viz. 756 ± 4 µmol/g and 1048 ± 32 µmol/g. The modification was carried out at neutral and acidic pH (2.5) to study the effect of dissociation of the carboxylic acid group. Films processed by casting/evaporation at 40 °C and cryogels processed by freeze-drying were prepared from βCD modified toCNF suspensions and compared with reference samples of unmodified toCNF. The impact of modification on water sorption and mechanical properties was assessed. It was shown that the water sorption behaviour for films is driven by adsorption, with a clear impact of the chemical makeup of the fibres (charge content, pH, and adsorption of cyclodextrin). Modified toCNF cryogels (acidic pH and addition of cyclodextrins) displayed lower mechanical properties linked to the modification of the cell wall porosity structure. Esterification between βCD and toCNF under acidic conditions was performed by freeze-drying, and such cryogels exhibited a lower decrease in mechanical properties in the swollen state. These results are promising for the development of scaffold and films with controlled mechanical properties and added value due to the ability of cyclodextrin to form an inclusion complex with active principle ingredient (API) or growth factor (GF) for biomedical applications.

Cyclodextrin Inclusion of Medicinal Compounds for Enhancement of their Physicochemical and Biopharmaceutical Properties

Owing to their wide structural diversity and unique complexing properties, cyclodextrins (CDs) find manifold applications in drug discovery and development. The focus of this mini-review is on their uses as 'enabling excipients' both in the context of early drug discovery and in subsequent optimisation of drug performance. Features highlighted here include descriptions of the structures of CDs, synthetic derivatisation to fine-tune their properties, the nature of inclusion complexation of drugs within the CD cavity, methodology for the study of free and complexed hosts in the solid state and in solution, the inherent pharmacological activity of several CDs and its utility, novel CD-based drug delivery systems, and the role of CDs in drug discovery and optimisation. Illustrative examples are generally based on research reported during the last two decades. Application of CDs to the optimisation of the performance of established drugs is commonplace, but there are many opportunities for the intervention of CDs during the early stages of drug discovery, which could guide the selection of suitable candidates for development, thereby contributing to reducing the attrition rate of new molecular entities.

Facile preparation of self-assembled hydrogels constructed from poly-cyclodextrin and poly-adamantane as highly selective adsorbents for wastewater treatment

Self-assembled hydrogel materials constructed from cyclodextrin polymer (P-CD)/adamantane-modified poly acrylic acid (PAA-Ad) were designed and prepared via host-guest interactions. It was observed that the prepared supramolecular hydrogels had an interconnected three-dimensional porous network. In addition, the obtained hydrogels showed a recovery performance and it was confirmed that the host-guest interactions between β-cyclodextrin and adamantane were the main driving force for the formation of the hydrogels. The mechanical properties of the hydrogels could be adjusted by varying the concentrations of PAA-Ad. In particular, the prepared supramolecular hydrogels exhibited superior performances in water purification. The results demonstrated that the hydrogels possessed different mechanisms in the adsorption of the four typical poisonous organic dye molecules used, including bisphenol A (BPA), 4-aminoazobenzene (N-Azo), methylene blue (MB), and rhodamine B (RhB). The hydrogels mainly adsorbed N-Azo by host-guest interaction and adsorbed BPA by host-guest interaction and hydrogen bond synergy. They also adsorbed MB and RhB by hydrogen bonding and electrostatic interaction.

Evaluation of solubility enhancement, antioxidant activity, and cytotoxicity studies of kynurenic acid loaded cyclodextrin nanosponge

Kynurenic acid demonstrates antioxidant, neuroprotective and free radical scavenging properties. However, low aqueous solubility of kynurenic acid limits its therapeutic activity. In the present study, cyclodextrin nanosponges were used to improve the solubility and therapeutic activity of kynurenic acid. The formation of kynurenic acid loaded nanosponge was confirmed by different characterization techniques. The solubility of kynurenic acid was significantly increased with nanosponge (111.1 μg/ml) compared to free kynurenic acid (16.4 μg/ml) and β-cyclodextrin (28.6 μg/ml). High drug loading (19.06%) and encapsulation efficiency (95.31%) were achieved with NS. The particle size and zeta potential of kynurenic acid loaded nanosponge was around 255.8 nm and -23 mV respectively. Moreover, higher solubilization of kynurenic acid loaded nanosponge produced better antioxidant activity compared to free kynurenic acid. The kynurenic acid loaded nanosponge and blank nanosponge were found nontoxic in the cytotoxicity assay. Thus, these studies demonstrated that nanosponges can be used as a carrier for the delivery of kynurenic acid.

Cyclodextrin-Polypyrrole Coatings of Scaffolds for Tissue Engineering

Polypyrrole is one of the most investigated conductive polymers used for tissue engineering applications because of its advantageous properties and the ability to promote different cell types' adhesion and proliferation. Together with β-cyclodextrin, which is capable of accommodating helpful biomolecules in its cavity, it would make a perfect couple for use as a scaffold for tissue engineering. Such scaffolds were prepared by the polymerisation of 6-(pyrrol-3-yl)hexanoic acid on polycaprolactone microfibres with subsequent attachment of β-cyclodextrin on the polypyrrole layer. The materials were deeply characterised by several physical and spectroscopic techniques. Testing of the cyclodextrin enriched composite scaffold revealed its better performance in in vitro experiments compared with pristine polycaprolactone or polypyrrole covered polycaprolactone scaffolds.

Environmentally Sustainable and Ecosafe Polysaccharide-Based Materials for Water Nano-Treatment: An Eco-Design Study

Nanoremediation, which is the use of nanoparticles and nanomaterials for environmental remediation, is widely explored and proposed for preservation of ecosystems that suffer from the increase in human population, pollution, and urbanization. We herein report a critical analysis of nanotechnologies for water remediation by assessing their sustainability in terms of efficient removal of pollutants, appropriate methods for monitoring their effectiveness, and protocols for the evaluation of any potential environmental risks. Our purpose is to furnish fruitful guidelines for sustainable water management, able to promote nanoremediation also at European level. In this context, we describe new nanostructured polysaccharide-based materials obtained from renewable resources as alternative efficient and ecosafe solutions for water nano-treatment. We also provide eco-design indications to improve the sustainability of the production of these materials, based on life-cycle assessment methodology.

Dynamics and interactions of ibuprofen in cyclodextrin nanosponges by solid-state NMR spectroscopy

Two different formulations of cyclodextrin nanosponges (CDNS), obtained by polycondensation of β-cyclodextrin with ethylenediaminetetraacetic acid dianhydride (EDTAn), were treated with aqueous solutions of ibuprofen sodium salt (IbuNa) affording hydrogels that, after lyophilisation, gave two solid CDNS-drug formulations. ¹H fast MAS NMR and ¹³C CP-MAS NMR spectra showed that IbuNa was converted in situ into its acidic and dimeric form (IbuH) after freeze-drying. ¹³C CP-MAS NMR spectra also indicated that the structure of the nanosponge did not undergo changes upon drug loading compared to the unloaded system. However, the ¹³C NMR spectra collected under variable contact time cross-polarization (VCT-CP) conditions showed that the polymeric scaffold CDNS changed significantly its dynamic regime on passing from the empty CDNS to the drug-loaded CDNS, thus showing that the drug encapsulation can be seen as the formation of a real supramolecular aggregate rather than a conglomerate of two solid components. Finally, the structural features obtained from the different solid-state NMR approaches reported matched the information from powder X-ray diffraction profiles.

SANS investigation of water adsorption in tunable cyclodextrin-based polymeric hydrogels

A quantitative law for the hydration-dependence of pore size in cyclodextrin-based hydrogels is provided by SANS experiments.

Correlation between collective and molecular dynamics in pH-responsive cyclodextrin-based hydrogels

The joint use of UV Raman and Brillouin scattering experiments is employed to explore phase evolutions in pH-responsive polysaccharide hydrogels.

Guest-matrix interactions affect the solvation of cyclodextrin-based polymeric hydrogels: a UV Raman scattering study

The focus of the present work is to shed light on possible modifications of the molecular properties of polysaccharide hydrogels induced by the establishment of specific non-covalent interactions during the loading of a guest compound inside the gel phase. With this aim, a case study of the encapsulation of caffeine (Caf) inside cyclodextrin-based hydrogels, namely, cyclodextrin nanosponges (NS), is systematically investigated here by using UV Raman scattering experiments. The UV Raman spectra of the hydrogels, analysed as a function of temperature, concentration of the guest molecule loaded in the gel phase and pH, prove particularly informative both on the structural rearrangements of the hydrophobic/hydrophilic groups of the polymeric network and on the breaking/formation of specific guest-matrix interactions. Analysis of the temperature dependence of dynamical parameters, i.e., the dephasing time associated with specific vibrational modes of the polymer backbone, enables the proposal of a molecular picture in which the loading of Caf in NS hydrogels tends to favour access of the water solvent to the more hydrophobic portions of the polymer matrix, which is in turn reflected in a marked increase in the solvation of the whole system. The achievements of this work appear of interest with respect to the design of new possible strategies for controlling the diffusion/release of bioactive molecules inside hydrogel networks, besides corroborating the potential of UV Raman scattering experiments to give new molecular insights into complex phenomena affecting hydrogel phases.