Development and pharmacological evaluation of ropivacaine-2-hydroxypropyl-β-cyclodextrin inclusion complex

Preparation, characterisation and antitumour activity of β-, γ- and HP-β-cyclodextrin inclusion complexes of oxaliplatin

Three water-soluble oxaliplatin complexes were prepared by inclusion complexation with β-cyclodextrin (β-CD), γ-CD and HP-β-CD. The structures of oxaliplatin/CDs were confirmed by NMR, FTIR, TGA, XRD as well as SEM analysis. The results show that the water solubility of oxaliplatin was increased in the complex with CDs in 1:1 stoichiometry inclusion modes, and the cyclohexane ring of oxaliplatin molecule was deeply inserted into the cavity of CDs. Moreover, the stoichiometry was established by a Job plot and the water stability constant (Kc) of oxaliplatin/CDs was calculated by phase solubility studies, all results show that the oxaliplatin/β-CD complex is more stable than free oxaliplatin, oxaliplatin/HP-β-CD and oxaliplatin/γ-CD. Meanwhile, the inclusion complexes displayed almost twice as high cytotoxicity compared to free oxaliplatin against HCT116 and MCF-7 cells. This satisfactory water solubility and higher cytotoxic activity of the oxaliplatin/CD complexes will potentially be useful for their application in anti-tumour therapy.

Preparation, characterization, and pharmacokinetics study of capsaicin via hydroxypropyl-beta-cyclodextrin encapsulation

CONTEXT

Capsaicin (CAP) is an effective drug in the treatment of pain and cancer. However, its practical administration has been limited due to poor aqueous solubility and bioavailability, as well as strong gastrointestinal irritation.

OBJECTIVE

The objective of this study is to improve the solubility and oral bioavailability of CAP by reducing irritation via hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complex formulation, in vitro and in vivo analysis.

MATERIALS AND METHODS

The complex (CAP-HP-β-CD) was developed via the magnetic stirring method and characterized using ultraviolet (UV) absorption spectrometry, infrared radiation (IR) spectroscopy, and differential scanning calorimetry (DSC). Rats were treated with CAP (90 mg × kg(-1)) or CAP-HP-β-CD (corresponding to 90 mg × kg(-1) CAP) by gavage, and all the plasma samples were analyzed with high performance liquid chromatography (HPLC).

RESULTS

The results of UV, IR, and DSC showed that an acceptable CAP-HP-β-CD (encapsulation efficiency, 75.83%; drug loading, 7.44%) was formulated. In vitro release study of CAP-HP-β-CD revealed that the cumulative release of CAP from HP-β-CD encapsulation was obviously enhanced (above 80% increases). Similarly, the in vivo pharmacokinetics parameters also increased, Cmax (from 737.94 to 1117.57 ng × mL(-1)), AUC0- (from 5285.9 to 7409.8 ng × h × mL(-1)) or relative bioavailability (139.38%). The gastric irritation bioassay further showed that the CAP-HP-β-CD was far better than free CAP.

DISCUSSION AND CONCLUSION

CAP exhibited significant aqueous solubility and oral bioavailability, as well as minimal irritation effect after forming inclusion complex with HP-β-CD. Therefore, these findings could provide an equally important alternative option for the clinical use of CAP.

Masking the bitter taste of injectable lidocaine HCl formulation for dental procedures

Several attempts have been made to mask the bitter taste of oral formulations, but none have been made for injectable formulations. This study aims to mask the bitter taste of dental lidocaine HCl (LID) injection using hydroxypropyl-β-cyclodextrin (HP-β-CD) and sodium saccharin. Inclusion complexes of LID and HP-β-CD were prepared by the solution method in 1:1 and 1:2 M ratios. Inclusion complexes in solution were studied using phase solubility in phosphate buffer solutions (pH 8, 9, and 10). Freeze-dried inclusion complexes were characterized using differential scanning calorimetry (DSC), X-ray, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and in vitro release. Injectable formulations were prepared using inclusion complexes and characterized for stability and for taste using an Alpha MOS ASTREE electronic tongue (ETongue). The association constants of HP-β-CD with lidocaine-free base and its ionized form were found to be 26.23 ± 0.00025 and 0.8694 ± 0.00045 M(-1), respectively. Characterization studies confirmed the formation of stable inclusion complexes of LID and HP-β-CD. Injectable formulations were found to be stable for up to 6 months at 4°C, 25°C, and 40°C. The taste evaluation study indicated that HP-β-CD (1:1 and 1:2 M ratios) significantly improved the bitter taste of LID injectable formulation. In conclusion, inclusion complex in the 1:1 M ratio with 0.09% sodium saccharin was considered to be optimum in masking the bitter taste of LID.

Visceral mesh modified with cyclodextrin for the local sustained delivery of ropivacaine

The aim of the study was to develop a polyester visceral implant modified with a cyclodextrin polymer for the local and prolonged delivery of ropivacaine to reduce post operatory pain. Therefore, we applied a coating of an inguinal mesh with a crosslinked polymer of hydroxypropyl-β-cyclodextrin (HPβCD) whose specific host-guest complex forming properties were expected to improve the adsorption capacity of the implant toward anesthetic, and then to release it within a sustained period. The modification reaction of the textile with cyclodextrin was explored through the study of the influence of the pad/dry/cure process parameters and the resulting implant (PET-CD) was characterized by solid state NMR and SEM. Besides, the inclusion complex between ropivacaine and CD was studied by NMR and capillary electrophoresis in PBS medium. Finally, ropivacaine sorption test showed that a maximum of 30 mg/g of ropivacaine could be adsorbed on the functionalized samples. In dynamic batch tests in PBS at pH 7.4, the release could be observed up to 6h. The cytocompatibility of the PET-CD loaded with ropivacaine was also studied and reached 65% cell vitality after 6 days.

Anaesthetic efficacy of bupivacaine 2-hydroxypropyl-β-cyclodextrin for dental anaesthesia after inferior alveolar nerve block in rats

Bupivacaine is a long-acting local anaesthetic that is widely used in medicine and dentistry. The duration and intensity of its sensory blockade in animal models is increased by its inclusion in complexes with cyclodextrins. The aim of the present study was to evaluate the anaesthetic efficacy of bupivacaine 2-hydroxypropyl-β-cyclodextrin (HPβCD) inclusion complex for dental anaesthesia after inferior alveolar nerve block in rats. Thirty rats were each given an injection close to the mandibular foramen of 0.2ml of one of the following formulations: 0.5% bupivacaine alone; 0.5% bupivacaine with 1:200,000 epinephrine; and 0.5% bupivacaine-HPβCD inclusion complex (bupivacaine-HPβCD). The other sides were used as controls, with either 0.9% saline or anaesthetic-free HPβCD solution being injected. The onset, success, and duration of pulpal anaesthesia were assessed by electrical stimulation ("pulp tester") on inferior molars. Results were analysed using ANOVA (Tukey), log rank, and chi square tests (α=5%). There were no differences among the formulations in onset of anaesthesia (p=0.59) or between the bupivacaine plus epinephrine and bupivacaine plus HPβCD in duration of anaesthesia, but bupivacaine plus epinephrine gave significantly higher values than bupivacaine alone (p=0.007). Bupivacaine plus epinephrine was a better anaesthetic than bupivacaine alone (p=0.02), while Bupi-HPβCD gave intermediate results, and therefore did not differ significantly from the other 2 groups (p=0.18 with bupivacaine alone; and p=0.44 with bupivacaine plus epinephrine). The bupivacaine-HPβCD complex showed similar anaesthetic properties to those of bupivacaine with epinephrine.

Benzocaine complexation with p-sulfonic acid calix[n]arene: experimental ((1) H-NMR) and theoretical approaches

The aim of this work was to study the interaction between the local anesthetic benzocaine and p-sulfonic acid calix[n]arenes using NMR and theoretical calculations and to assess the effects of complexation on cytotoxicity of benzocaine. The architectures of the complexes were proposed according to (1) H NMR data (Job plot, binding constants, and ROESY) indicating details on the insertion of benzocaine in the cavity of the calix[n]arenes. The proposed inclusion compounds were optimized using the PM3 semiempirical method, and the electronic plus nuclear repulsion energy contributions were performed at the DFT level using the PBE exchange/correlation functional and the 6-311G(d) basis set. The remarkable agreement between experimental and theoretical approaches adds support to their use in the structural characterization of the inclusion complexes. In vitro cytotoxic tests showed that complexation intensifies the intrinsic toxicity of benzocaine, possibly by increasing the water solubility of the anesthetic and favoring its partitioning inside of biomembranes.

L-diphenylalanine microtubes as a potential drug-delivery system: characterization, release kinetics, and cytotoxicity

Microtubes obtained from the self-assembly of L-diphenylalanine (FF-MTs) were evaluated as potential vehicles for drug delivery. The biological marker Rhodamine B (RhB) was chosen as a model drug and conjugated to the peptide arrays during self-organization in the liquid phase. Microscopy and X-ray studies were performed to provide morphological and structural information. The data revealed that the cargo was distributed either in small aggregates at the hydrophobic surface of the FF-MTs or homogeneously embedded in the structure, presumably anchored at polar sites in the matrix. Raman spectroscopy revealed notable shifts of the characteristic RhB resonance peaks, demonstrating the successful conjugation of the fluorophore and peptide assemblies. In vitro assays were conducted in erythrocytes and fibroblast cells. Interestingly, FF-MTs were found to modulate the release of the load. The release of RhB from the FF-MTs followed first-order kinetics with a steady-state profile, demonstrating the potential of these carriers to deliver drugs at constant rates in the body. Cytotoxicity investigations revealed high cell viability up to concentrations of 5 mg mL(-1), demonstrating the low toxicity of the FF-MTs.

Preparation and characterization of inclusion complexes formed between baicalein and cyclodextrins

This study investigates the solubility of baicalein (Ba) with the addition of modified cyclodextrins using phase solubility method. The solubility of Ba in the presence of natural (α-, β-, and γ-) cyclodextrins and its derivatives, namely, hydroxypropyl-β-cyclodextrin (HP-β-CD) and (2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD), was higher than that of free Ba. In particular, the stability constant of inclusion complex with DM-β-CD was 13672.67l mol(-1), which was the highest among the examined cyclodextrins. The inclusion complexes of Ba and DM-β-CD were prepared via freeze-drying method, which were both characterized in the solution and solid state by UV-vis spectroscopy, differential scanning calorimetry (DSC), proton nuclear magnetic resonance ((1)H NMR), scanning electron microscopy (SEM), and X-ray powder diffractometry (XRPD). The UV-vis, DSC, (1)H NMR, SEM, and XRPD results proved the formation of inclusion complex between Ba and DM-β-CD. Furthermore, the dissolution rate and thermal stability of the inclusion complex were significantly enhanced compared with the pure drug. Therefore, using DM-β-CD can effectively improve the solubility and thermal stability of free Ba, which is a promising approach to promote its clinical application.

Experimental and theoretical NMR determination of isoniazid and sodium p-sulfonatocalix[n]arenes inclusion complexes

In this work the inclusion complex formation of isoniazid with sodium p-sulfonatocalix[n]arenes is reported aiming to improve the physicochemical and biopharmaceutical properties of isoniazid a first line antibuberculosis drug. The architectures of the complexes were proposed according to NMR data Job plot indicating details on the insertion of the isoniazid in the calix[n]arenes cavities. DFT theoretical NMR calculations were also performed for sodium p-sulfonatocalix[4]arene complex with isoniazid, with various modes of complexation being considered, to provide support for the experimental proposal. A comparison between experimental and theoretical ¹H NMR chemical shifts profiles allowed for the inclusion complex characterization confirming the isoniazid inclusion mode which is preferentially through the hydrazide moiety. The remarkable agreement between experimental and theoretical NMR profiles adds support to their use in the structural characterization of inclusion compounds. Antibacterial activity was evaluated and the results indicated the inclusion complexes as a potential strategy for tuberculosis treatment.

Solubilization of haloperidol by acyclic succinoglycan oligosaccharides

The isolated succinoglycan octasaccharide dimers isolated from Sinorhizobium meliloti 1021 have unique acyclic structures, displaying amphipathic properties against water. Thus, their potential usage as solubilizers of various water-insoluble drugs through non-covalent complexation are possible. In this study, we examined the solubility of a poorly water-soluble drug, haloperidol, in the presence of the acyclic form of succinoglycan dimers, and demonstrated that its solubility was increased up to 87 fold, Interestingly, the level of its solubility was even 7-10 fold higher than that achieved with β cyclodextrin or its derivatives that are cyclic forms, which is possibly due to the molecular flexibility of the acyclic structure of the dimers as well as the hydrophobic nature. Analyses of the stoichiometry and the stability constants for each complex were performed using phase solubility method, respectively. Additional analyses were also performed to confirm the formation of succinoglycan-drug complexes. Furthermore hypothetical 3-dimesional conformation of the complex was estimated through molecular docking simulations. Upon cytotoxicity test with a human cell line, the succinoglycan dimers displayed little effect up to 1000 μM, suggesting their potential usage to improve solubility and bioavailability of poorly soluble therapeutic agents.

Non-inclusion complexes between riboflavin and cyclodextrins

Objectives

To investigate the molecular interaction between β-cyclodextrin (βCD) or hydroxypropyl-β-cyclodextrin (HPβCD) and riboflavin (RF), and to test the anticancer potential of these formulations.

Methods

The physicochemical characterization of the association between RF and CDs was performed by UV-vis absorption, fluorescence, differential scanning calorimetry and NMR techniques. Molecular dynamics simulation was used to shed light on the mechanism of interaction of RF and CDs. Additionally, in-vitro cell culture tests were performed to evaluate the cytotoxicity of the RF–CD complexes against prostate cancer cells.

Key findings

Neither βCD nor HPβCD led to substantial changes in the physicochemical properties of RF (with the exception of solubility). Additionally, rotating frame Overhauser effect spectroscopy experiments detected no spatial correlations between hydrogens from the internal cavity of CDs and RF, while molecular dynamics simulations revealed ‘out-of-ring’ RF–CD interactions. Notwithstanding, both RF–βCD and RF–HPβCD complexes were cytotoxic to PC3 prostate cancer cells.

Conclusions

The interaction between RF and either βCD or HPβCD, at low concentrations, seems to be made through hydrogen bonding between the flavonoid and the external rim of both CDs. Regardless of the mechanism of complexation, our findings indicate that RF–CD complexes significantly increase RF solubility and potentiate its antitumour effect.