The influence of hydroxypropyl-β-cyclodextrin on the solubility, dissolution, cytotoxicity, and binding of riluzole with human serum albumin

Controlling the Solubility, Release Rate and Permeation of Riluzole with Cyclodextrins

Riluzole (RLZ), a sodium channel-blocking benzothiazole anticonvulsant BCS class II drug, is very slightly soluble in aqueous medium. To improve aqueous solubility and modulate dissolution rate and membrane permeability, complex formation of RLZ with two cyclodextrin, α-cyclodextrin (α-CD) and sulfobutylether-β-cyclodextrin (SBE-β-CD), was studied. The stability constants demonstrated a greater affinity of SBE-β-CD towards RLZ compared to α-CD. A solubility growth of 1.7-fold and 3.7-fold with α-CD and SBE-β-CD, respectively, was detected in the solutions of 1% cyclodextrins and accompanied by the permeability reduction. For 1% CD solutions, several biopolymers (1% w/v) were tested for the membrane permeability under static conditions. The synergistic positive effect of α-CD and polymer on the solubility accompanied by unchanged permeability was revealed in RLZ/α-CD/PG, RLZ/α-CD/PEG400, and RLZ/α-CD/PEG1000 systems. Solid RLZ/CD complexes were prepared. Dynamic dissolution/permeation experiments for the solid samples disclosed the characteristic features of the release processes and permeation rate through different artificial membranes. The maximal permeation rate was determined across the hydrophilic semi-permeable cellulose membrane followed by the lipophilic PermeaPad barrier (model of intestinal and buccal absorption) and polydimethylsiloxane-polycarbonate membrane (simulating transdermal delivery way). Different mode of the permeation between the membranes was estimated and discussed.

Cyclodextrin inclusion complexes improving antibacterial drug profiles: an update systematic review

Aim: The study aimed to review experimental models using cyclodextrins to improve antibacterial drugs' physicochemical characteristics and biological activities. Methods: The following terms and their combinations were used: cyclodextrins and antibacterial agents in title or abstract, and the total study search was conducted over a period up to October 2022. The review was carried out using PubMed, Scopus and Embase databases. A total of 1580 studies were identified, of which 27 articles were selected for discussion in this review. Results: The biological results revealed that the antibacterial effect of the inclusion complexes was extensively improved. Cyclodextrins can enhance the therapeutic effects of antibiotics already existing on the market, natural products and synthetic molecules. Conclusion: Overall, CDs as drug-delivery vehicles have been shown to improve antibiotics solubility, stability, and bioavailability, leading to enhanced antibacterial activity.

Cyclodextrins and Their Polymers Affect Human Serum Albumin's Interaction with Drugs Used in the Treatment of Pulmonary Infections

Respiratory infectious diseases have challenged medical communities and researchers. Ceftriaxone, meropenem and levofloxacin are widely used for bacterial infection treatment, although they possess severe side effects. To overcome this, we propose cyclodextrin (CD) and CD-based polymers as a drug delivery system for the drugs under consideration. CD polymers demonstrate higher binding affinity for levofloxacin (Ka ≈ 10⁵ M) compared to drug-CD complexes. CDs slightly alter the drugs' affinity for human serum albumin (HSA), whereas CD polymers increase the drugs' binding affinity up to 100 times. The most significant effect was observed for more the hydrophilic drugs ceftriaxone and meropenem. The drug's encapsulation in CD carriers leads to a decrease in the degree of change in the protein's secondary structure. The drug-CD carrier-HSA complexes demonstrate satisfying antibacterial activity in vitro, and even a high binding affinity does not decrease the drug's microbiological properties after 24 h. The proposed carriers are promising for a drug form with a prolonged drug release.

The Solubility Studies and the Complexation Mechanism Investigations of Biologically Active Spiro[cyclopropane-1,3'-oxindoles] with β-Cyclodextrins

In this work, we first improved the aqueous solubility of biologically active spiro[cyclopropane-1,3′-oxindoles] (SCOs) via their complexation with different β-cyclodextrins (β-CDs) and proposed a possible mechanism of the complex formation. β-CDs significantly increased the water solubility of SCOs (up to fourfold). Moreover, the nature of the substituents in the β-CDs influenced the solubility of the guest molecule (MβCD > SBEβCD > HPβCD). Complexation preferably occurred via the inclusion of aromatic moieties of SCOs into the hydrophobic cavity of β-CDs by the numerous van der Waals contacts and formed stable supramolecular systems. The phase solubility technique and optical microscopy were used to determine the dissociation constants of the complexes (Kc~102 M−1) and reveal a significant decrease in the size of the formed crystals. FTIR-ATR microscopy, PXRD, and 1H-1H ROESY NMR measurements, as well as molecular modeling studies, were carried out to elucidate the host−guest interaction mechanism of the complexation. Additionally, in vitro experiments were carried out and revealed enhancements in the antibacterial activity of SCOs due to their complexation with β-CDs.

Development and optimization of Riluzole-loaded biodegradable nanoparticles incorporated in a mucoadhesive in situ gel for the posterior eye segment

Riluzole-loaded PLGA nanoparticles (RLZ-NPs) were developed to improve the biopharmaceutical profile of RLZ after ocular administration. Moreover, RLZ-NPs were dispersed in an in situ gelling system (RLZ-NPs-Gel) for topical administration as a potential neuroprotective strategy against glaucoma. Formulations were optimized using the design of experiments approach. Characterization of the physicochemical and rheological properties, as well as interaction studies were carried out. To ensure RLZ-NPs-Gel ocular safety, the irritant potential was also evaluated in vitro and in vivo. Moreover, in vivo ocular biodistribution was also undertaken. Optimized RLZ-NPs showed an average size below 200 nm, an encapsulation efficiency greater than 90% and a negative surface charge. Interaction studies of RLZ-NPs showed that RLZ was dispersed in the polymeric matrix. RLZ-NPs-Gel possess a pseudoplastic behavior and a medium-low post-gelling viscosity to avoid discomfort after ocular application. Simultaneously, RLZ-NPs-Gel were able to increase RLZ-NPs contact with the ocular surface. Both formulations demonstrated the ability to be distributed in the posterior eye segment after 24 h of their application obtaining a more delayed distribution for RLZ-NPs-Gel. Therefore, a novel in situ gelling system able to disperse RLZ-NPs has been successfully developed as innovative neuroprotective strategy for potential topical treatment of glaucoma.

PEG-Modified tert-Octylcalix[8]arenes as Drug Delivery Nanocarriers of Silibinin

The hepatoprotective properties of silibinin, as well its therapeutic potential as an anticancer and chemo-preventive agent, have failed to progress towards clinical development and commercialization due to this material’s unfavorable pharmacokinetics and physicochemical properties, low aqueous solubility, and chemical instability. The present contribution is focused on the feasibility of using PEGylated calixarene, in particular polyoxyethylene-derivatized tert-octylcalix[8]arene, to prepare various platforms for the delivery of silibinin, such as inclusion complexes and supramolecular aggregates thereof. The inclusion complex is characterized by various instrumental methods. At concentrations exceeding the critical micellization concentration of PEGylated calixarene, the tremendous solubility increment of silibinin is attributed to the additional solubilization and hydrophobic non-covalent interactions of the drug with supramolecular aggregates. PEG-modified tert-octylcalix[8]arenes, used as drug delivery carriers for silibinin, were additionally investigated for cytotoxicity against human tumor cell lines.

A LSER-based model to predict the solubilizing effect of drugs by inclusion with cucurbit[7]uril

A LSER model was built for predicting the solubility of inclusion complexes.

Interaction of repaglinide with bovine serum albumin: Spectroscopic and molecular docking approaches

Repaglinide (RPG) regulates the amount of glucose by stimulating the pancreas to release insulin in the blood. In view of its biological importance, we have examined the interaction between RPG and a model protein, bovine serum albumin (BSA) employing various spectroscopic, electrochemical and molecular docking methods. Fluorescence spectra of BSA were recorded in the presence and absence of RPG in phosphate buffer of pH 7.4. Fluorescence intensity of BSA was decreased upon the addition of increased concentrations of RPG, indicating the interaction between RPG and BSA. Stern-Volmer quenching analysis results revealed that RPG quenched the intensity of BSA through dynamic quenching mechanism. This was further confirmed from the time-resolved fluorescence measurements. The binding constant as calculated from the spectroscopic and voltammetric results was observed to be in the order of 10⁴ M⁻¹ at 298 K, suggesting the moderate binding affinity between RPG and BSA. Competitive experimental results revealed that the primary binding site for RPG on BSA was site II. Absorption and circular dichroism studies indicated the changes in the secondary structure of BSA upon its interaction with RPG. Molecular simulation studies pointed out that RPG was bound to BSA in the hydrophobic pocket of site II.

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Dynamic mode of quenching mechanism was noticed in RPG-BSA interaction.

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RPG was bound to BSA at the Sudlow’s site II and the resultant RPG-BSA complex was mainly stabilized by hydrophobic forces.

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The binding constant of RPG-BSA of the order of 10⁴ M⁻¹ at 298 K indicated the non-covalent interactions.

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Secondary structural changes in BSA upon binding to RPG were evident from absorption and circular dichroism studies.

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The influence of β-cyclodextrin and metal ions on RPG-BSA binding affinity was examined.

Paclitaxel/hydroxypropyl-β-cyclodextrin complex-loaded liposomes for overcoming multidrug resistance in cancer chemotherapy

Multidrug resistance (MDR) is the largest obstacle to the success of chemotherapy. The development of innovative strategies and safe sensitizers is required to overcome MDR. Paclitaxel (PTX) is a widely used chemotherapeutic drug, the application of which has been learn to understand MDR. However, the application and use are severely restricted because of this MDR. Cyclodextrins (CDs) of many carriers, additionally have shown anti-cancer capability in MDR cancer cells. In this study, novel paclitaxel/hydroxypropyl-β-cyclodextrin complex-loaded liposomes (PTXCDL) have been developed in an attempt to overcome MDR in a PTX-resistant human lung adenocarcinoma (A549/T) cell line. The in vitro application of PTXCDL exhibited pH-sensitive PTX release, potent cytotoxicity, and enhanced intracellular accumulation. In comparison to in vivo, PTXCDL also show a stronger inhibition of tumor growth. In comparison, these findings suggest that the PTXCDL provide a novel strategy for effective therapy of resistant cancers by overcoming the drug resistance.

A pH-independent instantaneous release of flurbiprofen: a study of the preparation of complexes, their characterization and in vitro/in vivo evaluation

In this study, furbiprofen/hydroxypropyl-β-cyclodextrin (HPβCD) inclusion complexes were prepared to improve the drug dissolution and facilitate its application in hydrophilic gels. Inclusion complexes were prepared using a supercritical fluid processing and a conventional optimized co-lypholization method was employed as a reference. The entrapment efficacy and drug loading of both methods were investigated. Evaluation of drug dissolution enhancement was conducted in deionized water as well as buffer solutions of different pH. Carbopol 940 gels of both flurbiprofen and flurbiprofen/HPβCD inclusion complexes, with or without penetration enhancers, were prepared and percutaneous permeation studies were performed using rat abdominal skin samples. Formation of flurbiprofen/HPβCD inclusion complexes was confirmed by Fourier transform-infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. The results obtained showed that SCF processing produced a higher EE (81.91 ± 1.54%) and DL (6.96 ± 0.17%) compared with OCL with values of 69.11 ± 2.23% and 4.00 ± 1.01%, respectively. A marked instantaneous release of flurbiprofen/HPβCD inclusion complexes prepared by SCF processing (103.04 ± 2.66% cumulative release within 5 min, a 10-fold increase in comparison with flurbiprofen alone) was observed. In addition, this improvement in dissolution was shown to be pH-independent (the percentage cumulative release at pH 1.2, 4.5, 6.8 and 7.4 at 5 min was 95.19 ± 1.71, 101.75 ± 1.44, 105.37 ± 4.58 and 96.84 ± 0.56, respectively). Percutaneous permeability of flurbiprofen-in-HPβCD-in-gels could be significantly accelerated by turpentine oil and was related to the water content in the system. An in vivo pharmacokinetic study showed a 2-fold increase in C_max and a shortened T_max as well as a comparable relative bioavailability when compared with the commercial flurbiprofen Cataplasms (Zepolas^®). With their superior dissolution, these flurbiprofen/HPβCD inclusion complexes prepared by SCF processing could provide improved applications for flurbiprofen.

Interaction between the photosensitizer lumichrome and human serum albumin: effect of excipients

Lumichrome (Lc) is a photodegradation product of riboflavin that can be used as a photosensitizer (PS) in antibacterial photodynamic therapy (aPDT). The binding of Lc with plasma proteins such as human serum albumin (HSA) could affect its efficiency as PS. Excipients are necessary to prepare stable formulations to be used in aPDT and they may affect the PS-HSA binding. Hydroxypropyl (HP)-α, β, γ-cyclodextrin (CD), polyethylene glycol 400 (PEG400) and Pluronic^® F-127 (PF127) were selected as model excipients in this study. The intrinsic HSA fluorescence quenching and absorption and fluorescence spectroscopy were used to evaluate the Lc-HSA interaction in the absence and presence of excipients. Nano-differential scanning calorimetry (DSC) was used to determine the effect of excipients on HSA. The photostability of the samples was also evaluated. The combined results showed a modest interaction between Lc and HSA which was reduced mainly by HPβCD. No major alterations of the HSA nano-DSC thermogram were observed after addition of excipients. HSA did enhance Lc photodegradation. The presence of PF127 did also induce photochemical destabilization of Lc independent of HSA. In conclusion, HPαCD, HPγCD and PEG400 seemed to be the excipients more suitable for use in topical preparations containing Lc.

Inhibition of Photodegradation of Highly Dispersed Folic Acid Nanoparticles by the Antioxidant Effect of Transglycosylated Rutin

We developed highly dispersible and photostable nanoparticles of vitamin, folic acid (FA). FA was wet bead milled with milling and dispersing adjuvants and transglycosylated compounds such as α-glucosyl hesperidin (Hesperidin-G) and rutin (Rutin-G), which solubilized FA. The milled slurries of FA particles with transglycosylated compounds consisted of nanosized particles with a median diameter of <100 nm. The lyophilized formulations of these slurries retained their nanometer size after resuspension in water with no aggregation. The apparent solubility of FA in these formulations was 100-fold higher than that of untreated FA. The solubilizing effect of Rutin-G may affect the particle size reduction and dispersibility of FA. The photostability results showed that the strong antioxidant activity of Rutin-G substantially increased the photostability of FA solution. On the basis of these results, bead milling of FA with Rutin-G is a promising technique for developing highly dispersible, photostable nanoparticle FA formulations.

Interactions of cucurbit[6,7]urils with human serum albumin and their effects on zaltoprofen transportation

Interference of CB[6,7]s on a HSA–zaltoprofen binding system was studied for conducting the applications of CB[6,7]s.