Structural and Spectroscopic Characterization of TPGS Micelles: Disruptive Role of Cyclodextrins and Kinetic Pathways

Cyclosporine A micellar nasal spray characterization and antiviral action against SARS-CoV-2

The upper airways represent the point of entrance from where Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection spreads to the lungs. In the present work, α-tocopheryl-polyethylene-glycol succinate (TPGS) micelles loaded with cyclosporine A (CSA) were developed for nasal administration to prevent or treat the viral infection in the very first phases. The behavior of the micelles in presence of simulated nasal mucus was investigated in terms of stability and mucopenetration rate, evidencing long-term stability and fast diffusion across the glycoproteins matrix. Moreover, the spray characteristics of the micellar formulation and deposition profile in a silicon nasal model were studied using three nasal spray devices. Results allowed to identify the nasal spray pump (BiVax, Aptar) able to provide the wider and uniform deposition of the nasal cavity. The cyclosporine A micelles antiviral activity against SARS-CoV-2 was tested on the Omicron BA.1 variant using Vero E6 cells with protocols simulating treatment before, during and after the infection of the upper airways. Complete viral inactivation was observed for the cyclosporine-loaded micelles while a very low activity was evidenced for the non-formulated drug, suggesting a synergistic activity of the drug and the formulation. In conclusion, this work showed that the developed cyclosporine A-loaded micellar formulations have the potential to be clinically effective against a wide spectrum of coronavirus variants.

New opportunities for cyclodextrins in supramolecular assembly: metal organic frameworks, crystalline self-assembly, and catalyzed assembly

Cyclodextrins (CDs) are widely used macrocycles in supramolecular assembly due to their easy availability, versatile functionality and excellent biocompatibility. Although they are well-known for forming host-guest complexes with a wide range of guests and this host-guest chemistry has long been utilized in industry and academia, new opportunities have arisen in recent years, particularly in supramolecular assembly. In the present review, we will first provide a basic introduction to CDs and then summarize their emerging roles in the fields of supramolecular chemistry and materials. This includes their involvement in hybrid frameworks with inorganic components such as metal ions and polyoxometalates, crystalline self-assembly with amphiphilic molecules, and their new possibility of "catassembly" and induced chiral supramolecular structures that have previously been overlooked. Finally, we will comment on the future perspectives of CDs to inspire more ideas and efforts, with the aim of promoting diverse applications of CDs in supramolecular materials.

Small Angle X-Ray Scattering Data Analysis and Theoretical Modelling for the Size and Shape Characterization of Drug Delivery Systems Based on Vitamin E TPGS Micelles

We developed a simple two-dimensional/two-components theoretical model that describes the structure and functionality of a VitE-TPGS system of micelles assuming a hydrophobic inner core and an outer hydrated hydrophilic shell. We then conceptually applied the developed methodology to a simple system of VitE-TPGS micelles unloaded and loaded with an active pharmaceutical ingredient, eltrombopag, to verify if the model could reliably monitor the size change of the micelle upon loading. The fit of laboratory Small Angle X-Ray Scattering data against such model allows us to extract absolute values of the micelles size under a spherical shape hypothesis as well as the distribution within the system between components and level of hydration. The intensity scale of the SAXS experimental data needs to be normalized to a reference standard (pure water) to get absolute scattered intensities. The mathematical model which has been developed under a general hypothesis of ellipsoidal micelles, is applied to our experimental data under the simplified spherical assumption, which suitably fits our experimental data.

Synergistic effect of doxorubicin lauroyl hydrazone derivative delivered by α-tocopherol succinate micelles for the treatment of glioblastoma

We hypothesized that tocopherol succinate (TOS) and D-α-tocopherol polyethylene2000 succinate (TPGS₂₀₀₀) micelles could work as a drug delivery system while enhancing the anti-cancer efficacy of doxorubicin lauryl hydrazone derivative (DOXC₁₂) for the treatment of glioblastoma. The DOXC₁₂-TOS-TPGS₂₀₀₀ micelles were formulated with synthesized DOXC₁₂ and TPGS₂₀₀₀. They showed a high drug loading of hydrophobic DOXC₁₂ (29%), a size of <100 nm and a pH sensitive drug release behaviour. In vitro, fast uptake of DOXC₁₂-TOS-TPGS₂₀₀₀ micelles by GL261 cells was observed. For cytotoxicity, DOXC₁₂-TOS-TPGS₂₀₀₀ micelles were evaluated on two glioblastoma cell lines and showed synergism between DOXC₁₂ and TOS-TPGS_2000. The higher cytotoxicity of DOXC₁₂-TOS-TPGS₂₀₀₀ micelles was mainly caused by necrosis. The DOXC₁₂-TOS-TPGS₂₀₀₀ micelles seem to be a promising delivery system for enhancing the anticancer efficacy of doxorubicin in glioblastoma (GBM).

Water-soluble tocopherol derivatives inhibit SARS-CoV-2 RNA-dependent RNA polymerase

The recent emergence of a novel coronavirus, SARS-CoV-2, has led to the global pandemic of the severe disease COVID-19 in humans. While efforts to quickly identify effective antiviral therapies have focused largely on repurposing existing drugs ^1-4 , the current standard of care, remdesivir, remains the only authorized antiviral intervention of COVID-19 and provides only modest clinical benefits ⁵ . Here we show that water-soluble derivatives of α-tocopherol have potent antiviral activity and synergize with remdesivir as inhibitors of the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp). Through an artificial-intelligence-driven in silico screen and in vitro viral inhibition assay, we identified D-α-tocopherol polyethylene glycol succinate (TPGS) as an effective antiviral against SARS-CoV-2 and β-coronaviruses more broadly that also displays strong synergy with remdesivir. We subsequently determined that TPGS and other water-soluble derivatives of α-tocopherol inhibit the transcriptional activity of purified SARS-CoV-2 RdRp and identified affinity binding sites for these compounds within a conserved, hydrophobic interface between SARS-CoV-2 nonstructural protein 7 and nonstructural protein 8 that is functionally implicated in the assembly of the SARS-CoV-2 RdRp ⁶ . In summary, we conclude that solubilizing modifications to α-tocopherol allow it to interact with the SARS-CoV-2 RdRp, making it an effective antiviral molecule alone and even more so in combination with remdesivir. These findings are significant given that many tocopherol derivatives, including TPGS, are considered safe for humans, orally bioavailable, and dramatically enhance the activity of the only approved antiviral for SARS-CoV-2 infection ^7-9 .

Linking In Vitro Intrinsic Dissolution Rate and Thermodynamic Solubility with Pharmacokinetic Profiles of Bedaquiline Long-Acting Aqueous Microsuspensions in Rats

Pharmacokinetic (PK) profiles of a range of bedaquiline (BDQ) long-acting injectable (LAI) microsuspensions in rats after parenteral (i.e., intramuscular and subcutaneous) administration were correlated with the in vitro intrinsic dissolution rate (IDR) and thermodynamic solubility of BDQ in media varying in surfactant type and concentration to better understand the impact of different nonionic surfactants on the in vivo performance of BDQ LAI microsuspensions. All LAI formulations had a similar particle size distribution. The investigated surfactants were d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), poloxamer 338, and poloxamer 188. Furthermore, the relevance of medium complexity by using a biorelevant setup to perform in vitro measurements was assessed by comparing IDR and thermodynamic solubility results obtained in biorelevant media and formulation vehicle containing different surfactants in varying concentrations. In the presence of a surfactant, both media could be applied to obtain in vivo representative dissolution and solubility data because the difference between the biorelevant medium and formulation vehicle was predominantly nonsignificant. Therefore, a more simplistic medium in the presence of a surfactant was preferred to obtain in vitro measurements to predict the in vivo PK performance of LAI aqueous suspensions. The type of surfactant influenced the PK profiles of BDQ microsuspensions in rats, which could be the result of a surfactant effect on the IDR and/or thermodynamic solubility of BDQ. Overall, two surfactant groups could be differentiated: TPGS and poloxamers. Most differences between the PK profiles (i.e., maximum concentration observed, time of maximum concentration observed, and area under the curve) were observed during the first 21 days postdose, the time period during which particles in the aqueous suspension are expected to dissolve.

Formulation and Evaluation of Supramolecular Food-Grade Piperine HP β CD and TPGS Complex: Dissolution, Physicochemical Characterization, Molecular Docking, In Vitro Antioxidant Activity, and Antimicrobial Assessment

The purpose of the present study was to improve the aqueous solubility, dissolution, and antioxidant activity of the water-insoluble drug piperine (PIP). The study was performed by preparing PIP binary inclusion complex (PIP BIC) and piperine ternary inclusion complex (PIP TIC) by different methods. The effect of a hydrophilic auxiliary substance (TPGS) was assessed with addition to PIP and hydroxypropyl beta cyclodextrin (HP β CD) complex. The phase solubility study was performed to evaluate the complexation efficiency and stability constant. The aqueous solubility, dissolution, physicochemical assessment, antioxidant activity, antimicrobial activity, and molecular docking were further evaluated to check the effect of the complexation of PIP. The stability constant (Ks) value was found to be 238 and 461 M⁻¹ for the binary and ternary inclusion complex. The dissolution study results showed a marked enhancement of release in comparison to pure drug. XRD and SEM studies revealed the presence of more agglomerated and amorphous structures of PIP, which confirmed the formation of complexes. The results of DPPH radical scavenging and antimicrobial activity showed a significant (p < 0.05) enhancement in scavenging activity for PIP TIC (microwave irradiation (MI)). The docking studies have revealed that the binding affinity of TPGS at the PIP-HP β CD complex was −5.2 kcal/mol.

Morphology, gelation and cytotoxicity evaluation of D-α-Tocopheryl polyethylene glycol succinate (TPGS) - Tetronic mixed micelles

HYPOTHESIS

The combination of polymeric surfactants into mixed micelles is expected to improve properties relevant to their use in drug delivery, such as micellar size, gelation, and toxicity. We investigated synergistic effects in mixtures of D-α-Tocopheryl polyethylene glycol succinate (TPGS), an FDA-approved PEGylated derivative of vitamin E, and Tetronic surfactants, pH-responsive and thermogelling polyethylene oxide (PEO)-polypropylene oxide (PPO) 4-arm block copolymers. We hypothesized that mixed micelles would form under specific conditions and provide a handle to tune formulation characteristics.

EXPERIMENTS

We examined the morphology of the self-assembled structures in mixtures of TPGS with two Tetronic: T1107 and T908, using a combination of dynamic light scattering (DLS), small-angle neutron scattering (SANS), NMR spectroscopy (NOESY and diffusion NMR) and oscillatory rheology, over a range of compositions, temperatures and pH. Cell viability was assessed in NIH/3T3 fibroblasts.

FINDINGS

The combination of TPGS with either of the two Tetronic produces spherical core-shell micelles that comprise both surfactants in their structure (mixed micelles). T1107 unimers incorporate into TPGS aggregates below the critical micelle temperature of the poloxamine, while mixed micelles only form under limited conditions with T908. At high concentration/temperature, small proportions of TPGS extend the gel phase, more markedly with T1107, with similar elastic moduli (30-50 kPa) and a BCC crystalline structure. Cell viability of NIH/3T3 fibroblasts grown in the hydrogels increases significantly when the poloxamine gels are doped with TPGS, making the combination of poloxamines and TPGS a promising platform for drug delivery.

Structural characterization by scattering and spectroscopic methods and biological evaluation of polymeric micelles of poloxamines and TPGS as nanocarriers for miltefosine delivery

Miltefosine (MF), an alkylphospholipid originally developed for breast cancer treatment, is a highly active drug for the treatment against leishmaniasis, a neglected tropical disease considered the world's second leading cause of death by a parasitic agent after malaria. MF exhibits dose-limiting gastrointestinal side effects in patients and its penetration through lipophilic barriers is reduced. In this work we propose a reformulation of MF by incorporating the drug to poly(ethylene)oxide (PEO)-based polymeric micelles, specifically, D-α-tocopheryl polyethylene glycol succinate (TPGS) and Tetronic block copolymers (T904 and T1107). A full structural characterization of the aggregates has been carried out by SANS (small-angle neutron scattering) and dynamic light scattering (DLS), in combination with proton 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, to determine the precise location of the drug. The structure of MF micelles has been characterized as a function of the temperature and concentration. In the presence of the block-copolymers, MF forms mixed micelles in a wide range of temperatures, TPGS being the co-surfactant that incorporates more MF unimers. The hydrophobic tail of MF and those of the block copolymers are in close contact within the micelles, which present a core-shell structure with a hydrophilic corona formed by the PEG blocks of the TPGS and the zwitterion head group of the MF. In order to identify the best carrier, the antileishmanicidal activity of MF in the different formulations has been tested on macrophages, promastigotes and intracellular amastigotes. The combination of the three vehicles with MF makes the formulated drug more active than MF alone against L. major promastigotes, however, only the combination with T904 increases the MF activity against intracellular amastigotes. With the aim of exploring gel-based formulations of the drug, the combination of MF and T1107 under gelation conditions has also been investigated.

Dual-responsive TPGS crosslinked nanocarriers to overcome multidrug resistance

Efficient delivery of chemotherapeutic agents into tumor cells and reversal of chemoresistance are crucially important to enhance cancer therapy.

PEGylated mucus-penetrating nanocrystals for lung delivery of a new FtsZ inhibitor against Burkholderia cenocepacia infection

C109 is a potent but poorly soluble FtsZ inhibitor displaying promising activity against Burkholderia cenocepacia, a high-risk pathogen for cystic fibrosis (CF) sufferers. To harness C109 for inhalation, we developed nanocrystal-embedded dry powders for inhalation suspension consisting in C109 nanocrystals stabilized with D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) embedded in hydroxypropyl-β-cyclodextrin (CD). The powders could be safely re-dispersed in water for in vitro aerosolization. Owing to the presence of a PEG shell, the rod shape and the peculiar aspect ratio, C109 nanocrystals were able to diffuse through artificial CF mucus. The promising technological features were completed by encouraging in vitro/in vivo effects. The formulations displayed no toxicity towards human bronchial epithelial cells and were active against planktonic and sessile B. cenocepacia strains. The efficacy of C109 nanosuspensions in combination with piperacillin was confirmed in a Galleria mellonella infection model, strengthening their potential for combined therapy of B. cenocepacia lung infections.

Ex Vivo Conjunctival Retention and Transconjunctival Transport of Poorly Soluble Drugs Using Polymeric Micelles

This paper addresses the problem of ocular delivery of lipophilic drugs. The aim of the paper is the evaluation of polymeric micelles, prepared using TPGS (d-α-Tocopheryl polyethylene glycol 1000 succinate), a water-soluble derivative of Vitamin E and/or poloxamer 407, as a vehicle for the ocular delivery of dexamethasone, cyclosporine, and econazole nitrate. The research steps were: (1) characterize polymeric micelles by dynamic light scattering (DLS) and X-ray scattering; (2) evaluate the solubility increase of the three drugs; (3) measure the in vitro transport and conjunctiva retention, in comparison to conventional vehicles; (4) investigate the mechanisms of enhancement, by studying drug release from the micelles and transconjunctival permeation of TPGS; and (5) study the effect of micelles application on the histology of conjunctiva. The data obtained demonstrate the application potential of polymeric micelles in ocular delivery, due to their ability to increase the solubility of lipophilic drugs and enhance transport in and across the conjunctival epithelium. The best-performing formulation was the one made of TPGS alone (micelles size ≈ 12 nm), probably because of the higher mobility of these micelles, an enhanced interaction with the conjunctival epithelium, and, possibly, the penetration of intact micelles.

Novel O/W nanoemulsions for nasal administration: Structural hints in the selection of performing vehicles with enhanced mucopenetration

We propose novel oil-in-water nanoemulsions (O/W NEs) including PEGylated surfactants and chitosan, showing good biocompatibility and optimization for nasal administration of drugs or vaccines. The transmucosal route has been shown to be ideal for a fast and efficient absorption and represents a viable alternative when the oral administration is problematic. The critical structural features in view of optimal encapsulation and transmucosal delivery were assessed by characterizing the NEs with complementary scattering techniques, i.e. dynamic light scattering (DLS), small angle X-ray (SAXS) and neutron scattering (SANS). Combined results allowed for selecting the formulations with the best suited structural properties and in addition establishing their propensity to enter the mucus barrier. To this scope, mucin was used as a model system and the effect of adding chitosan to the NEs, as adjuvant, was investigated. Remarkably, the presence of chitosan had a positive impact on the diffusion of the NE particles through the mucin matrix. We can infer that chitosan-mucin interaction induces density inhomogeneity and an increase in the pore size within the gel matrix that enhances the PEGylated NEs mobility. The coupling of mucoadhesive and mucopenetrating agents is shown to be a promising strategy for innovative transmucosal delivery systems.

Development of a nanoamorphous exosomal delivery system as an effective biological platform for improved encapsulation of hydrophobic drugs

Despite their great potential, the nano-sized extracellular vesicles are yet to become effective delivery systems for poorly water-soluble drugs. Here, we present a novel platform of exosomes as a drug delivery system by engineering of a poorly water-soluble drug into a poloxamer-based molecular nanostructured dispersion composed of a hydrophilic and a hydrophobic moiety for an enhanced anticancer efficacy. For the first time, aspirin was loaded into exosomes as an anticancer agent via a one-step fabrication combining the nano-matrix formation of the nanostructured dispersion and exosomes loading. Our approach could transform crystalline aspirin to a nanoamorphous form in the nano-matrix structured exosomes, leading to increased drug encapsulation efficiency for exosomes, improved dissolution and strongly enhanced cytotoxicity of aspirin to cancer cells. Interestingly, cytotoxicity of aspirin to both breast and colorectal cancer cells could be strongly enhanced by the nanoamorphous aspirin-loaded exosomes, and this cytotoxic effect was more pronounced to parental cells of the exosomes, reminiscent of homing effect. Hence, this study has pioneered a novel nanoplatform of nanoamorphous exosomal delivery system to transform an anti-inflammatory drug into a potent anti-cancer agent.

Solubilization of Carbamazepine in TPGS Micelles: Effect of Temperature and Electrolyte Addition

D-α-Tocopheryl polyethylene glycol succinate (TPGS), a polyethylene glycol condensate, is a biologically important nonionic amphiphile. In this study, we report on aqueous solution behavior of TPGS with a focus on its clouding, surface activity, micellar characteristics, and solubilization capacity for a model hydrophobic drug, carbamazepine (CBZ). Micelles were characterized by dynamic light and small-angle neutron scattering studies as a function of temperature, salt addition, and CBZ solubilization. TPGS showed a cloud point of 78°C and possessed good surface activity (as observed from surface tension reduction and adsorption parameters). The critical micelle concentration (CMC), obtained from surface tension and fluorescence studies, was 0.02 mM. Scattering studies showed formation of stable micelles (average diameter-12 nm), exhibiting no significant changes in size upon salt addition (up to 1 M NaCl), CBZ incorporation (up to 5 mM), and temperature increase (40°C). Micelles in 5 wt% TPGS showed about twentyfold enhancement in CBZ solubility. Considering the remarkable CBZ solubilization and its positioning in the core, we suggest that the formulation can be exploited as a sustained delivery vehicle.

Complex systems that incorporate cyclodextrins to get materials for some specific applications

Cyclodextrins (CDs) are a family of biodegradable cyclic hydrocarbons composed of α-(1,4) linked glucopyranose subunits, the more common containing 6, 7 or 8 glucose units are named α, β and γ-cyclodextrins respectively. Since the discovery of CDs, they have attracted interest among scientists and the first studies were about the properties of the native compounds and in particular their use as catalysts of organic reactions. Characteristics features of different types of cyclodextrins stimulated investigation in different areas of research, due to its non-toxic and non-inmunogenic properties and also to the development of an improved industrial production. In this way, many materials with important properties have been developed. This mini-review will focus on chemical systems that use cyclodextrins, whatever linked covalently or mediated by the non covalent interactions, to build complex systems developed mainly during the last five years.

In Vivo-Relevant Transwell Dish-Based Dissolution Testing for Orally Inhaled Corticosteroid Products

PURPOSE

To establish an in vivo-relevant Transwell dish-based dissolution test system for the "respirable" aerosols of inhaled corticosteroids (ICSs) using marketed inhaler products.

METHODS

"Respirable" ≤ 5.8 or 6.5 μm aerosols of 7 ICSs from 11 inhaler products were collected onto the filter membranes under the modified assembly of the cascade impactor. Their dissolution in 10 ml of the simulated lung lining fluid (sLLF) was determined over time in the Transwell dish at 37°C and ~100% relative humidity in the presence of subsequent diffusive permeation across the Transwell's supporting membrane.

RESULTS

While three ICSs with high-to-intermediate solubility enabled the first-order "sink" and complete dissolution in 6 h, 4 ICSs with poor solubility including fluticasone propionate (FP) resulted in the pseudo-zero-order "non-sink", slow and limited dissolution. The aerosol dissolution rate constants (k_diss) were derived, well-correlated with the solubility. For FP, but not for highly-soluble flunisolide (FN), dissolution was kinetically aerosol mass-dependent. However, for a given ICS, dissolution profiles were indistinguishable between the formulations and products upon comparable aerosol mass collection.

CONCLUSIONS

The in vivo-relevant Transwell dish-based "respirable" aerosol dissolution test system was developed, kinetically discriminative in accordance with the ICS solubility, but indistinguishable for a given ICS between the marketed products.