Betamethasone-in-cyclodextrin-in-liposome: The effect of cyclodextrins on encapsulation efficiency and release kinetics

Heat-Triggered Release of Dexamethasone from Thermosensitive Liposomes Using Prodrugs or Excipients

Dexamethasone (DXM) is a potent glucocorticoid with an anti-inflammatory and anti-angiogenic activity which is widely clinically used. Systemic side effects limit the long-term use of DXM in patients requiring formulations which deliver and selectively release the drug to the diseased tissues. This in vitro study compares the suitability of DXM and commonly used prodrugs dexamethasone-21-phosphate (DXMP) and dexamethasone-21-palmitate (DP) as well as DXM complexed by 2-hydroxypropyl-γ-cyclodextrin (HP-γ-CD) for the use in thermosensitive liposomes (TSL). DXM showed a poor retention and a low final drug:lipid ratio in a 1,2-dipalmitoyl-sn‑glycero-3-phosphodiglycerol-based TSL (DPPG2-TSL) and a low-temperature sensitive liposome (LTSL). In contrast to DXM, DXMP and DP were stably retained at 37 °C in TSL in serum and could be encapsulated with high drug:lipid ratios in DPPG2-TSL and LTSL. DXMP showed a rapid release at mild hyperthermia (HT) from both TSL in serum, whereas DP remained incorporated in the TSL bilayer. According to release experiments with carboxyfluorescein (CF), HP-γ-CD and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) are suitable vehicles for the loading of DXM into DPPG2-TSL and LTSL. Complexation of DXM with HP-γ-CD increased the aqueous solubility of the drug leading to approx. ten times higher DXM:lipid ratio in DPPG2-TSL and LTSL in comparison to un-complexed DXM. Both DXM and HP-γ-CD showed increased release at HT in comparison to 37 °C in serum. In conclusion, DXMP and DXM complexed by HP-γ-CD represent promising candidates for TSL delivery.

Hispolon Cyclodextrin Complexes and Their Inclusion in Liposomes for Enhanced Delivery in Melanoma Cell Lines

Hispolon, a phenolic pigment isolated from the mushroom species Phellinus linteus, has been investigated for anti-inflammatory, antioxidant, and anticancer properties; however, low solubility and poor bioavailability have limited its potential clinical translation. In this study, the inclusion complex of hispolon with Sulfobutylether-β-cyclodextrin (SBEβCD) was characterized, and the Hispolon-SBEβCD Complex (HSC) was included within the sterically stabilized liposomes (SL) to further investigate its anticancer activity against melanoma cell lines. The HSC-trapped-Liposome (HSC-SL) formulation was investigated for its sustained drug delivery and enhanced cytotoxicity. The inclusion complex in the solid=state was confirmed by a Job’s plot analysis, molecular modeling, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), Proton nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy (SEM). The HSC-SL showed no appreciable deviation in size (<150 nm) and polydispersity index (<0.2) and improved drug encapsulation efficiency (>90%) as compared to control hispolon liposomes. Individually incorporated hispolon and SBEβCD in the liposomes (H-CD-SL) was not significant in loading the drug in the liposomes, compared to HSC-SL, as a substantial amount of free drug was separated during dialysis. The HSC-SL formulation showed a sustained release compared to hispolon liposomes (H-SLs) and Hispolon-SBEβCD liposomes (H-CD-SLs). The anticancer activity on melanoma cell lines (B16BL6) of HSC and HSC-SL was higher than in H-CD-SL and hispolon solution. These findings suggest that HSC inclusion in the HSC-SL liposomes stands out as a potential formulation approach for enhancing drug loading, encapsulation, and chemotherapeutic efficiency of hispolon and similar water insoluble drug molecules.

Liposome-Polymer Complex for Drug Delivery System and Vaccine Stabilization

Liposomes have been used extensively as micro- and nanocarriers for hydrophobic or hydrophilic molecules. However, conventional liposomes are biodegradable and quickly eliminated, making it difficult to be used for delivery in specific routes, such as the oral and systemic routes. One way to overcome this problem is through complexation with polymers, which is referred to as a liposome complex. The use of polymers can increase the stability of liposome with regard to pH, chemicals, enzymes, and the immune system. In some cases, specific polymers can condition the properties of liposomes to be explicitly used in drug delivery, such as targeted delivery and controlled release. These properties are influenced by the type of polymer, crosslinker, interaction, and bond in the complexation process. Therefore, it is crucial to study and review these parameters for the development of more optimal forms and properties of the liposome complex. This article discusses the use of natural and synthetic polymers, ways of interaction between polymers and liposomes (on the surface, incorporation in lamellar chains, and within liposomes), types of bonds, evaluation standards, and their effects on the stability and pharmacokinetic profile of the liposome complex, drugs, and vaccines. This article concludes that both natural and synthetic polymers can be used in modifying the structure and physicochemical properties of liposomes to specify their use in targeted delivery, controlled release, and stabilizing drugs and vaccines.

Encapsulation of α-Pinene in Delivery Systems Based on Liposomes and Cyclodextrins

The essential oil component α-pinene has multiple biological activities. However, its application is limited owing to its volatility, low aqueous solubility, and chemical instability. For the aim of improving its physicochemical properties, α-pinene was encapsulated in conventional liposomes (CLs) and drug-in-cyclodextrin-in-liposomes (DCLs). Hydroxypropyl-β-cyclodextrin/α-pinene (HP-β-CD/α-pinene) inclusion complexes were prepared in aqueous solution, and the optimal solubilization of α-pinene occurred at HP-β-CD:α-pinene molar ratio of 7.5:1. The ethanol-injection method was applied to produce different formulations using saturated (Phospholipon 90H) or unsaturated (Lipoid S100) phospholipids in combination with cholesterol. The size, the phospholipid and cholesterol incorporation rates, the encapsulation efficiency (EE), and the loading rate (LR) of α-pinene were determined, and the storage stability of liposomes was assessed. The results showed that α-pinene was efficiently entrapped in CLs and DCLs with high EE values. Moreover, Lipoid S100 CLs displayed the highest LR (22.9 ± 2.2%) of α-pinene compared to the other formulations. Both carrier systems HP-β-CD/α-pinene inclusion complex and Lipoid S100 CLs presented a gradual release of α-pinene. Furthermore, the DPPH radical scavenging activity of α-pinene was maintained upon encapsulation in Lipoid S100 CLs. Finally, it was found that all formulations were stable after three months of storage at 4 °C.

Ocular Application of Oleuropein in Dry Eye Treatment: Formulation Studies and Biological Evaluation

Background. Oleuropein is already known for its numerous pharmacological properties, but its activity in the ocular field has not yet been investigated. The study aims to verify a possible use of oleuropein (OLE)-based eye drops both in terms of efficacy in dry eye syndrome and stability in aqueous solution. Methods. OLE was co-precipitated with HP-β-cyclodextrin, and the obtained complex was encapsulated into liposomes prepared by hydration of a lipid film composed of Lipoid S100 and cholesterol with different pH buffer solutions. The hydrated vesicles were shrunk by ultrasonication or extrusion. The preparations were characterized from the physicochemical point of view by subjecting them to differential scanning calorimetry, ATR-FTIR, dynamic light scattering analysis, and microscopy. Subsequently, OLE protective activity against hyperosmotic and oxidative stress on rabbit corneal epithelial cells (RCE) was evaluated. Results. The liposomal vesicles obtained after extrusion showed a tendency towards greater encapsulation efficiency (up to 80.77%) compared to that obtained by sonication, and the liposomes hydrated in pH 5.5 solution tended to incapsulate more than the neutral ones. Ultrasonication produced two-dimensional populations of liposomes, the largest of which reached 2149 nm. On the contrary, the extruded liposomes showed homogeneous diameters of about 250 nm. Complexation with cyclodextrin and subsequent encapsulation in liposomes greatly increased the OLE stability in aqueous solution, especially at 4 °C and for the extruded formulations. OLE aqueous solution (OLE7.4-sol, reference) and neutral extruded liposomes (F7.4-e) were well tolerated on RCE cells. Moreover, OLE was able to control the effects of hyperosmolarity on ocular surface cells and to prevent oxidative stress-induced loss of cell viability.

Improvement of Butamben Anesthetic Efficacy by the Development of Deformable Liposomes Bearing the Drug as Cyclodextrin Complex

This work was aimed at enhancing butamben (BTB) anesthetic efficacy by the "drug-in cyclodextrin (CD)-in deformable liposomes" strategy. In the study, phase-solubility studies with natural (α-, β-, γ-) and derivative (hydroxypropyl-α-and β-, sulfobutylether-β, methyl-β) CDs evidenced the highest BTB affinity for βCD and its derivatives and indicated methyl-βCD (RAMEB) as the best carrier. Drug-RAMEB complexes were prepared by different techniques and were characterized for solid-state and dissolution properties. The best BTB-RAMEB product was chosen for entrapment in the aqueous core of deformable liposomes containing stearylamine, either alone or with sodium cholate, as edge activators. Double-loaded (DL) liposomes, bearing the lipophilic drug (0.5% w/v) in the bilayer and its hydrophilic RAMEB complex (0.5% w/v) in the aqueous core, were compared to single-loaded (SL) liposomes bearing 1% w/v plain drug in the bilayer. All vesicles showed homogeneous dimensions (i.e., below 300 nm), high deformability, and excellent entrapment efficiency. DL-liposomes were more effective than SL ones in limiting drug leakage (<5% vs. >10% after a 3 months storage at 4 °C). In vivo experiments in rabbits proved that all liposomal formulations significantly (p < 0.05) increased the intensity and duration of drug anesthetic action compared to its hydroalcoholic solution; however, DL liposomes were significantly (p < 0.05) more effective than SL ones in prolonging BTB anesthetic effect, owing to the presence of the drug-RAMEB complex in the vesicle core, acting as a reservoir. DL liposomes containing both edge activators were found to have the best performance.

Advantages of the combined use of cyclodextrins and nanocarriers in drug delivery: A review

Complexation with cyclodextrins (CDs) has been widely and successfully used in pharmaceutical field, mainly for enhancing solubility, stability and bioavailability of a variety of drugs. However, some important drawbacks, including rapid removal from the bloodstream after in vivo administration, or possible replacement, in biological media, of the entrapped drug moieties by other molecules with higher affinity for the CD cavity, can limit the CDs effectiveness as drug carriers. This review is focused on combined strategies simultaneously exploiting CD complexation, and loading of the complexed drug into various colloidal carriers (liposomes, niosomes, polymeric nanoparticles, lipid nanoparticles, nanoemulsions, micelles) which have been investigated as a possible means for circumventing the problems associated with both such carriers, when used separately, and join their relative benefits in a unique delivery system. Several examples of applications have been reported, to illustrate the possible advantages achievable by such a dual strategy, depending on the CD-nanocarrier combination, and mainly resulting in enhanced performance of the delivery system and improved biopharmaceutical properties and therapeutic efficacy of drugs. The major problems and/or drawbacks found in the development of such systems, as well as the (rare) case of failures in achieving the expected improvements have also been highlighted.

Anaesthetic benefits of a ternary drug delivery system (Ropivacaine-in-Cyclodextrin-in-Liposomes): in-vitro and in-vivo evaluation

OBJECTIVES

To evaluate whether a ternary system composed of hydroxypropyl-β-cyclodextrin (HP-βCD) further encapsulated into egg phosphatidylcholine liposomes (LUV) could prolong the action and reduce the toxicity of ropivacaine (RVC).

METHODS

Dynamic light scattering and NMR were used to characterize the inclusion complex (RVC : HP-βCD), liposomal (RVC : LUV) and ternary (LUV : RVC : HP-βCD) systems containing 0.25% RVC. Their encapsulation efficiency, release kinetics, in-vitro cytotoxicity and in-vivo anaesthetic effect (paw-withdraw tests in mice) were also evaluated.

KEY FINDINGS

1 : 1 RVC : HP-βCD inclusion complex was encapsulated in liposomes (220.2 ± 20.3 nm size, polydispersity <0.25, zeta potentials = -31.7 ± 1.4 mV). NMR (diffusion-ordered spectroscopy (DOSY)) revealed stronger anaesthetic binding to LUV : RVC : HP-βCD (K_a  = 342 m^-1 ) than to RVC : HP-βCD (K_a  = 128 m^-1 ) or liposomal formulation (K_a  = 22 m^-1 ). The formulations promoted in-vitro sustained drug release and partially reverted the cytotoxicity of RVC against 3T3 fibroblasts in the profile: LUV : RVC : HP-βCD ≥ RVC : HP-βCD > RVC : LUV. Accordingly, in-vivo sensory block of free RVC (180 min) was prolonged ca. 1.7 times with the ternary system and RVC : HP-βCD (300 min) and 1.3 times with RVC : LUV (240 min).

CONCLUSIONS

These results confirm the suitability of this double-carrier system in clinical practice, to decrease the toxicity and prolong the anaesthesia time evoked by RVC.

Liposomes and drug-in-cyclodextrin-in-liposomes formulations encapsulating 17β-estradiol: An innovative drug delivery system that prevents the activation of the membrane-initiated steroid signaling (MISS) of estrogen receptor α

The encapsulation into liposomes of several types of molecules presents the advantages to protect the activity of these molecules and to target specific tissues. Nevertheless, a major obstacle remains the incomplete understanding of nano-bio interactions. Specifically, the impact that inclusion of drug into liposomes or of drug-in-cyclodextrin-in liposomes (DCL) could have on the molecular and cellular mechanism of drug action is largely unknown. As a proof of concept, we evaluated the impact of 17β-estradiol (E2) included into liposomes or DCL on estrogen receptor (ER)α signaling pathways. Indeed, ERα relays the pleiotropic actions of E2 in physiology and pathophysiology through two major pathways: (1) the genomic/nuclear effects associated to the transcriptional activity of the ERα and (2) the rapid/nongenomic/membrane-initiated steroid signaling (MISS) effects related to the induction of fast signaling pathways occurring when ERα is anchored to the plasma membrane. We evidenced that the inclusion of E2 into liposomes (Lipo-E2) or into DCL (DCL-E2) prevented the activation of the rapid/nongenomic/extranuclear/MISS pathway of ERα, while the activation of the genomic/nuclear pathway was maintained. These results support that Lipo-E2 and DCL-E2 could be a useful tool to delineate the complex molecular mechanisms associated to ERα. In conclusion, this study supports the notion that inclusion of drugs into liposomes or DCL could modify some specific pathways of their molecular and cellular mechanisms of action. These results emphasized that attention should be paid to nano-bio interactions induced by the use of nanovectors in medicine.

Wheat germ agglutinin liposomes with surface grafted cyclodextrins as bioadhesive dual-drug delivery nanocarriers to treat oral cells

Topical management of oral infection requires combined use of multiple classes of drugs and frequent dosing due to low drug retention rates. The sustained, co-delivery of drugs with different solubilities to cells using nanoparticle drug delivery systems remains a challenge. Here, we developed wheat germ agglutinin (WGA) conjugated liposomes with surface grafted cyclodextrin (WGA-liposome-CD) as bioadhesive dual-drug nanocarriers. We effectively encapsulated two physiochemically different drugs (ciprofloxacin and betamethasone) and demonstrated sustained co-drug release in saliva over a 24 h period in vitro. As proof of therapeutic utility in oral cells, we infected oral keratinocytes with Aggregatibacter actinomycetemcomitans, a bacterial pathogen responsible for chronic periodontal disease. Drug release, resulting from nanocarrier cell binding, produced a significant increase in oral cell survival and synergistically reduced inflammation. These results suggest that WGA-liposome-CD nanocarriers are novel cyto-adhesive candidates for delivering multiple drugs with sustained therapeutic activity for localized drug delivery to oral cells.

Encapsulation of Isoniazid-conjugated Phthalocyanine-In-Cyclodextrin-In-Liposomes Using Heating Method

Liposomes are reputed colloidal vehicles that hold the promise for targeted delivery of anti-tubercular drugs (ATBDs) to alveolar macrophages that host Mycobacterium tuberculosis. However, the costly status of liposome technology, particularly due to the use of special manufacture equipment and expensive lipid materials, may preclude wider developments of therapeutic liposomes. In this study, we report efficient encapsulation of a complex system, consisting of isoniazid-hydrazone-phthalocyanine conjugate (Pc-INH) in gamma-cyclodextrin (γ-CD), in liposomes using crude soybean lecithin by means of a simple organic solvent-free method, heating method (HM). Inclusion complexation was performed in solution and solid-state, and evaluated using UV-Vis, magnetic circular dichroism, ¹H NMR, diffusion ordered spectroscopy and FT-IR. The HM-liposomes afforded good encapsulation efficiency (71%) for such a large Pc-INH/γ-CD complex (PCD) system. The stability and properties of the PCD-HM-liposomes look encouraging; with particle size 240 nm and Zeta potential −57 mV that remained unchanged upon storage at 4 °C for 5 weeks. The release study performed in different pH media revealed controlled release profiles that went up to 100% at pH 4.4, from about 40% at pH 7.4. This makes PCD-liposomes a promising system for site-specific ATBD delivery, and a good example of simple liposomal encapsulation of large hydrophobic compounds.

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.

Advances of nanosystems containing cyclodextrins and their applications in pharmaceuticals

For many years, researchers have worked with supramolecular structures involving inclusion complexes with cyclodextrins. These studies have resulted in new commercially available drugs which have been of great benefit. More recently, studies using nanoparticles, including nanosystems containing cyclodextrins, have become a focus of academic research due to the versatility of the systems and their remarkable therapeutic potential. This review focuses on studies published between 2002 and 2018 involving nanosystems containing cyclodextrins. We consider the type of nanosystems, their importance in a health context, the physicochemical techniques used to show the quality of these systems and their potential for the development of novel pharmaceutical formulations. These have been developed in recent studies which have mainly been focusing on basic science with no clinical trials as yet being performed. This is important to note because it means that the studies do not include any toxicity tests. Despite this limitation, the characterization assays performed suggest that these new formulations may have therapeutic potential. However, more research is required to assess the efficacy and safety of these nanosystems.

Novel Findings about Double-Loaded Curcumin-in-HPβcyclodextrin-in Liposomes: Effects on the Lipid Bilayer and Drug Release

In this study, the encapsulation of curcumin (Cur) in “drug-in-cyclodextrin-in-liposomes (DCL)” by following the double-loading technique (DL) was proposed, giving rise to DCL–DL. The aim was to analyze the effect of cyclodextrin (CD) on the physicochemical, stability, and drug-release properties of liposomes. After selecting didodecyldimethylammonium bromide (DDAB) as the cationic lipid, DCL–DL was formulated by adding 2-hydroxypropyl-α/β/γ-CD (HPβCD)–Cur complexes into the aqueous phase. A competitive effect of cholesterol (Cho) for the CD cavity was found, so cholesteryl hemisuccinate (Chems) was used. The optimal composition of the DCL–DL bilayer was obtained by applying Taguchi methodology and regression analysis. Vesicles showed a lower drug encapsulation efficiency compared to conventional liposomes (CL) and CL containing HPβCD in the aqueous phase. However, the presence of HPβCD significantly increased vesicle deformability and Cur antioxidant activity over time. In addition, drug release profiles showed a sustained release after an initial burst effect, fitting to the Korsmeyer-Peppas kinetic model. Moreover, a direct correlation between the area under the curve (AUC) of dissolution profiles and flexibility of liposomes was obtained. It can be concluded that these “drug-in-cyclodextrin-in-deformable” liposomes in the presence of HPβCD may be a promising carrier for increasing the entrapment efficiency and stability of Cur without compromising the integrity of the liposome bilayer.

Temoporfin-in-Cyclodextrin-in-Liposome-A New Approach for Anticancer Drug Delivery: The Optimization of Composition

The main goal of this study was to use hybrid delivery system for effective transportation of temoporfin (meta-tetrakis(3-hydroxyphenyl)chlorin, mTHPC) to target tissue. We suggested to couple two independent delivery systems (liposomes and inclusion complexes) to achieve drug-in-cyclodextrin-in-liposome (DCL) nanoconstructs. We further optimized the composition of DCLs, aiming to alter in a more favorable way a distribution of temoporfin in tumor tissue. We have prepared DCLs with different compositions varying the concentration of mTHPC and the type of β-cyclodextrin (β-CD) derivatives (Hydroxypropyl-, Methyl- and Trimethyl-β-CD). DCLs were prepared by thin-hydration technique and mTHPC/β-CD complexes were added at hydration step. The size was about 135 nm with the surface charge of (−38 mV). We have demonstrated that DCLs are stable and almost all mTHPC is bound to β-CDs in the inner aqueous liposome core. Among all tested DCLs, trimethyl-β-CD-based DCL demonstrated a homogenous accumulation of mTHPC across tumor spheroid volume, thus supposing optimal mTHPC distribution.

Amisulpride-CD-Loaded Liposomes: Optimization and In Vivo Evaluation

Amisulpride (AMS) is an atypical antipsychotic agent used for the treatment of schizophrenia. The effect of different variables, i.e., the type of cyclodextrins (CDs), ratio of drug/CDs, and type of loading on the prepared AMS-CD liposomes (single and double loaded) was studied by applying 2³ full factorial design. Double-loaded liposomes are loaded with AMS-hydroxyl propyl-β-cyclodextrin (HP-β-CD) in the aqueous phase and free drug in the lipophilic bilayer, while single-loaded liposomes are loaded only with AMS-HP-β-CD in the aqueous phase. Entrapment efficiency, particle size, polydespersibility, and zeta potential were selected as dependent variables. Design Expert® software was used to obtain an optimized formulation with high entrapment efficiency (64.55 ± 1.27%), average particle size of 40.1 ± 2.77 nm, polydespersibility of 0.44 ± 0.37, and zeta potential of - 48.8 ± 0.28. Optimized formula was evaluated for in vitro release, surface morphology and stability study was also conducted. AMS-HP-β-CD in double-loaded liposomes exhibited higher drug release than those in the conventional liposomes and in the single-loaded liposomes. The maximum plasma concentration (C_max) of AMS in optimized AMS-HP-β-CD double-loaded liposomal formulation increased by 1.55- and 1.29-fold, as compared to the commercial tablets and conventional liposomes, respectively. However, the relative bioavailability of AMS double-loaded liposomes was 1.94- and 1.28-folds of commercial tablet and conventional liposomes, respectively.

Nanoliposome-Encapsulated Brinzolamide-hydropropyl-β-cyclodextrin Inclusion Complex: A Potential Therapeutic Ocular Drug-Delivery System

Novel ocular drug delivery systems (NODDSs) remain to be explored to overcome the anatomical and physiological barriers of the eyes. This study was to encapsulate brinzolamide (BRZ)-hydropropyl-β-cyclodextrin (HP-β-CD) inclusion complex (HP-β-CD/BRZ) into nanoliposomes and investigate its potential as one of NODDS to improve BRZ local glaucomatous therapeutic effect. HP-β-CD/BRZ was firstly prepared to enhance the solubility of poorly water-soluble BRZ. The HP-β-CD/BRZ loaded nanoliposomes (BCL) were subsequently constructed by thin-film dispersion method. After the optimization of the ratio of BRZ to HP-β-CD, the optimal BCL showed an average size of 82.29 ± 6.20 nm, ζ potential of -3.57 ± 0.46 mV and entrapment efficiency (EE) of 92.50 ± 2.10% with nearly spherical in shape. The X-ray diffraction (XRD) confirmed the formation of HP-β-CD/BRZ and BCL. The in vitro release study of BCL was evaluated using the dialysis technique, and BCL showed moderate sustained release. BCL (1 mg/mL BRZ) showed a 9.36-fold increase in the apparent permeability coefficient and had a sustained and enhanced intraocular pressure reduction efficacy when compared with the commercially available formulation (BRZ-Sus) (10 mg/mL BRZ). In conclusion, BCL might have a promising future as a NODDS for glaucoma treatment.

A comparison between conventional liposome and drug-cyclodextrin complex in liposome system

A drug-cyclodextrin complex in liposome system was prepared in order to make a comparison with conventional risperidone-loaded liposome. Thin film hydration, reverse phase evaporation and ethanol injection methods were taken as preparation means to obtain the two types of liposome. Differential thermal analysis (DTA) and transmission electron microscopy (TEM) were used to investigate the thermal characters of inclusion complexes and morphology of liposome, respectively. Particle size, zeta potential and encapsulation efficiency were studied by light scattering analysis and ultrafiltration. In vitro release was carried out in the pH 7.4 phosphate buffer solution and samples were collected at the certain time. As a result, drug-cyclodextrin complex in liposome prepared by various methods displayed lower encapsulation efficiency than conventional liposome. However, size was larger and its stability was better than the latter. The second release phase of novel delivery system was slightly slower after initial burst release at the first phase, while the conventional liposome displayed a more regular trait. Thus, the novel liposome have potential to be developed as co-administration formulation with long-acting injection.

Increasing solubility of red bell pepper carotenoids by complexation with 2-hydroxypropyl-β-cyclodextrin

Red bell pepper carotenoids were complexed with 2-hydroxypropyl-β-cyclodextrin (2-HPβCD) in different mass ratios (1:4, 1:6, 1:8 and 1:10) through ultrasonic homogenization in order to increase carotenoid solubility and their use as natural pigment in food. Inclusion complexes, red bell pepper extract and physical mixtures were analyzed by DSC, FT-IR, (1)H NMR and DLS. Solubility assay was performed to identify the effect of complexation on the solubility of carotenoids. From characterization assays, results showed that inclusion process occurred for all tested ratios. Results for water solubility assays demonstrated clear differences between solubility index of inclusion complexes (8.06±2.59-16.55±4.40mg/mL) and physical mixtures (3.53±1.44-7.3±1.88mg/mL), while carotenoid extract was no water soluble, as expected. These results indicated that molecular inclusion of carotenoids in 2-HPβCD was efficient to enhance their solubility in water, enabling application of red bell pepper carotenoid as natural pigment and/or bioactive substances in food.

Clove essential oil-in-cyclodextrin-in-liposomes in the aqueous and lyophilized states: From laboratory to large scale using a membrane contactor

This work is dedicated to prepare liposomal dry powder formulations of inclusion complexes of clove essential oil (CEO) and its main component eugenol (Eug). Ethanol injection method and membrane contactor were applied to prepare liposomes at laboratory and large scale, respectively. Various liposomal formulations were tested: (1) free hydroxypropyl-β-cyclodextrin loaded liposomes; (2) drug in hydroxypropyl-β-cyclodextrin in liposomes (DCL); (3) DCL2 obtained by double loading technique, where the drug is added in the organic phase and the inclusion complex in the aqueous phase. Liposomes were characterized for their particle size, polydispersity index, Zeta potential, morphology, encapsulation efficiency of CEO components and Eug loading rate. Reproducible results were obtained with both injection devices. Compared to Eug-loaded liposomes, DCL and DCL2 improved the loading rate of Eug and possessed smaller vesicles size. The DPPH(•) scavenging activity of Eug and CEO was maintained upon incorporation of Eug and CEO into DCL and DCL2. Contrary to DCL2, DCL formulations were stable after 1 month of storage at 4°C and upon reconstitution of the dried lyophilized cakes. Hence, DCL in aqueous and lyophilized forms, are considered as a promising carrier system to preserve volatile and hydrophobic drugs enlarging their application in cosmetic, pharmaceutical and food industries.

Supramolecular cyclodextrin-based drug nanocarriers

Hosting of polymers, lipids and drug conjugates makes cyclodextrins suitable to prepare biocompatible, targetable and stimuli-responsive supramolecular drug nanocarriers.

Controlled-release drug delivery system based on fluocinolone acetonide-cyclodextrin inclusion complex incorporated in multivesicular liposomes

Multivesicular liposomes (MVLs) have been widely studied for encapsulation of hydrophilic drugs due to their structural properties and large aqueous inner cavities. In this study, to investigate MVLs and their potential application for incorporation of hydrophobic drugs, new drug delivery system for fluocinolone acetonide (FA), as a lipophilic model drug, was developed combining the advantages of cyclodextrin inclusion complexes (CD-IC) and multivesicular liposomes. FA was complexed with several CDs to form inclusion complex (FA-CD-IC) and then FA-CD-IC was incorporated into MVLs by reverse-phase evaporation method. Physicochemical characterization of drug-CD-IC, at a molar ratio of 1:1 (drug to CD) was studied using ¹HNMR, FT-IR, DSC and UV spectroscopy. The influence of various types of CDs on the aqueous solubility of FA, encapsulation efficiency and release profile in MVLs was studied. The results revealed the formation of inclusion complexes between the drug and CDs. Both the CD's type and proportion played an important role in the physicochemical properties of the systems. The inclusion complex of the drug with hydroxypropyl-β-cyclodextrin exhibited the most appropriate loading and sustained-release profile over prolonged periods. The results reveal the promising potential of MVLs as a stable drug delivery system to release the drug in a sustained manner for the treatment of ocular inflammatory disease.

Drug-in-cyclodextrin-in-liposomes: a promising delivery system for hydrophobic drugs

INTRODUCTION

Recently, the entrapment of hydrophobic drugs in the form of water-soluble drug-cyclodextrin (CD) complex in liposomes has been investigated as a new strategy to combine the relative advantages of CDs and liposomes into one system, namely drug-in-CD-in-liposome (DCL) systems.

AREAS COVERED

For DCLs preparation, an overall understanding of the interaction between CDs and lipid components of liposomes is necessary and valuable. The present article reviews the preparation, characterization and application of DCLs, especially as antitumor or transdermal carriers. Double-loading technique, an interesting strategy to control release and increase drug-loading capacity, is also discussed.

EXPERT OPINION

DCL approach can be useful in increasing drug solubility and vesicles stability, in controlling the in vivo fate of hydrophobic drugs and in avoiding burst release of drug from the vesicles. To obtain stable DCL, the CDs should have a higher affinity to drug molecules compared with liposomal membrane lipids. DCLs prepared by double-loading technique seem to be a suitable targeted drug delivery system because they have a fast onset action with prolonged drug release process and the significantly enhanced drug-loading capacity. In particular, DCLs are suitable for the delivery of hydrophobic drugs which also possess volatility.

Photostability of barnidipine in combined cyclodextrin-in-liposome matrices

Background: The improvement of barnidipine photostability was investigated in cyclodextrin or liposome matrices and in appropriate combinations of these matrices. These supramolecular systems allowed the preparation of liquid formulations, as an alternative to the current solid commercial specialties. Materials & methods: Photodegradation stressing tests were performed according to the ICH rules and monitored by derivative spectrophotometry. Optimization was evaluated in terms of drug-inclusion efficiency. Results: The photodegradation rate of barnidipine in ethanol proved rapid (residual percentage of 29.81%) after a radiation exposure of 225 kJ/m2. The residual concentrations detected for liposome and cyclodextrin complexes were 42.90 and 72.03%, respectively. The best results were obtained when the drug–cyclodextrin complex was in turn entrapped in liposomes (residual percentage of 90.78%). Conclusion: The stability of the drug-in-cyclodextrin-in-liposome system increased significantly with a value close to that of solid formulations whose residual percentage was 96.03%.

Photoinduced drug release from complexes of liposome and fluorescent silver nanoparticles

Fluorescent silver nanoparticles (AgNPs) were embedded in the bilayer of liposomes and acted as a photothermic switch for photoinduced drug release.

Influence of lecithin-lipid composition on physico-chemical properties of nanoliposomes loaded with a hydrophobic molecule

In this work, we studied the effect of nanoliposome composition based on phospholipids of docosahexaenoic acid (PL-DHA), salmon and soya lecithin, on physico-chemical characterization of vector. Cinnamic acid was encapsulated as a hydrophobic molecule in nanoliposomes made of three different lipid sources. The aim was to evaluate the influence of membrane lipid structure and composition on entrapment efficiency and membrane permeability of cinnamic acid. These properties are important for active molecule delivery. In addition, size, electrophoretic mobility, phase transition temperature, elasticity and membrane fluidity were measured before and after encapsulation. The results showed a correlation between the size of the nanoliposome and the entrapment. The entrapment efficiency of cinnamic acid was found to be the highest in liposomes prepared from salmon lecithin. The nanoliposomes composed of salmon lecithin presented higher capabilities as a carrier for cinnamic acid encapsulation. These vesicles also showed a high stability which in turn increases the membrane rigidity of nanoliposome as evaluated by their elastic properties, membrane fluidity and phase transition temperature.

Spray-dried voriconazole-cyclodextrin complexes: solubility, dissolution rate and chemical stability

The present work investigates the effect of complexation with hydroxypropyl-beta-cyclodextrin (HPBCD) and 2-O-methyl-beta-cyclodextrin (2-O-MBCD), on voriconazole solubility, dissolution rate and chemical stability. Drug-cyclodextrin complexes were prepared as aqueous solutions, which were spray-dried, and their properties were compared to wet ground samples and physical mixtures. DSC analysis revealed absence of crystalline voriconazole from spray-dried complexes. FTIR spectroscopy indicated changes in the H-bonding network of the hydroxyl groups of cyclodextrin following drug inclusion. Dissolution rate of voriconazole was significantly higher from spray-dried complexes with either cyclodextrin in comparison with free drug, physical mixtures, or wet ground mixtures. However, two degradation impurities were found in aged samples, with slightly higher impurity level with HPBCD. Performed solubility studies suggested that 2-O-MBCD is more efficient solubilizer. Molecular docking simulations showed a difference in the 1:1 binding affinities and sites, with HPBCD surprisingly forming complexes of much lower energy, thus suggesting a multiple rather than a 1:1 complexation.

Pluronic F127-modified liposome-containing tacrolimus–cyclodextrin inclusion complexes: improved solubility, cellular uptake and intestinal penetration

Objective

The aim of this study was to investigate Pluronic F127-modified liposome-containing cyclodextrin (CD) inclusion complex (FLIC) for improving the solubility, cellular uptake and intestinal penetration of tacrolimus (FK 506) in the gastrointestinal (GI) tract.

Methods

Molecular modelling was performed to screen the optimal CD for the solubilization of FK 506. FLIC was prepared by thin-lipid film hydration with the inclusion complex solutions followed by membrane extrusion. Dilution tests were conducted in simulated gastric fluids and phosphate-buffered solution of sodium taurocholate to investigate the solubility improvement of FK506. The cellular uptake of nanocarriers was studied in Caco-2 cells, and intestinal mucous membrane penetration in the GI tract was evaluated in Sprague–Dawley rats.

Key findings

The results showed that β-CD had the strongest binding energy with the guest molecule among the CDs. The prepared FLIC has an average diameter of 180.8 ± 8.1 nm with a spherical shape. The solubility and cellular uptake of FK 506 was greatly improved by the incorporation of CD complexes in the Pluronic F127-modified liposomes. Intestinal mucous membrane penetration was also significantly improved by the preparation of FLIC.

Conclusion

With improved drug solubility and intestinal mucous membrane penetration, FLIC shows a promising oral delivery system for FK 506.

Application of response surface methodology in development of sirolimus liposomes prepared by thin film hydration technique

Introduction : The present investigation was aimed to optimize the formulating process of sirolimus liposomes by thin film hydration method. Methods : In this study, a 3(2) factorial design method was used to investigate the influence of two independent variables in the preparation of sirolimus liposomes. The dipalmitoylphosphatidylcholine (DPPC) /Cholesterol (Chol) and dioleoyl phosphoethanolamine(DOPE) /DPPC molar ratios were selected as the independent variables. Particle size (PS) and Encapsulation Efficiency (EE %) were selected as the dependent variables. To separate the un-encapsulated drug, dialysis method was used. Drug analysis was performed with a validated RP-HPLC method. Results : Using response surface methodology and based on the coefficient values obtained for independent variables in the regression equations, it was clear that the DPPC/Chol molar ratio was the major contributing variable in particle size and EE %. The use of a statistical approach allowed us to see individual and/or interaction effects of influencing parameters in order to obtain liposomes with desired properties and to determine the optimum experimental conditions that lead to the enhancement of characteristics. In the prediction of PS and EE % values, the average percent errors are found to be as 3.59 and 4.09%. This value is sufficiently low to confirm the high predictive power of model. Conclusion : Experimental results show that the observed responses were in close agreement with the predicted values and this demonstrates the reliability of the optimization procedure in prediction of PS and EE % in sirolimus liposomes preparation.

The effects of lyophilization on the physico-chemical stability of sirolimus liposomes

PURPOSE

The major limitation in the widespread use of liposome drug delivery system is its instability. Lyophilization is a promising approach to ensure the long-term stability of liposomes. The aim of this study was to prepare sirolimus-loaded liposomes, study their stability and investigate the effect of lyophilization either in the presence or in the absence of lyoprotectant on liposome properties.

METHODS

Two types of multi-lamellar liposomes, conventional and fusogenic, containing sirolimus were prepared by modified thin film hydration method with different ratio of dipalmitoylphosphatidylcholine (DPPC), cholesterol and dioleoylphosphoethanolamine (DOPE), and were lyophilized with or without dextrose as lyoprotectant. Chemical stability investigation was performed at 4°C and 25°C until 6 months using a validated HPLC method. Physical stability was studied with determination of particle size (PS) and encapsulation efficiency (EE %) of formulations through 6 months.

RESULTS

Chemical stability test at 4°C and 25°C until 6 months showed that drug content of liposomes decreased 8.4% and 20.2% respectively. Initial mean EE % and PS were 72.8 % and 582 nm respectively. After 6 months mean EE % for suspended form, lyophilized without lyoprotectant and lyophilized with lyoprotectant were 54.8 %, 62.3% and 67.1 % at 4°C and 48.2%, 60.4 % and 66.8 % at 25°C respectively. Corresponding data for mean PS were 8229 nm, 2397 nm and 688nm at 4°C and 9362 nm, 1944 nm and 737 nm at 25°C respectively.

CONCLUSION

It is concluded that lyophilization with and without dextrose could increase shelf life of liposome and dextrose has lyoprotectant effect that stabilized liposomes in the lyophilization process.

How membrane permeation is affected by donor delivery solvent

We investigate theoretically and experimentally how the rate and extent of membrane permeation is affected by switching the donor delivery solvent from water to squalane for different permeants and membranes. In a model based on rate-limiting membrane diffusion, we derive explicit equations showing how the permeation extent and rate depend mainly on the membrane-donor and membrane-receiver partition coefficients of the permeant. Permeation results for systems containing all combinations of hydrophilic or hydrophobic donor solvents (aqueous solution or squalane), permeants (caffeine or testosterone) and polymer membranes (cellulose or polydimethylsiloxane) have been measured using a cell with stirred donor and re-circulating receiver compartments and continuous monitoring of the permeant concentration in the receiver phase. Relevant partition coefficients are also determined. Quantitative comparison of model and experimental results for the widely-differing permeation systems successfully enables the systematic elucidation of all possible donor solvent effects in membrane permeation. For the experimental conditions used here, most of the permeation systems are in agreement with the model, demonstrating that the model assumptions are valid. In these cases, the dominant donor solvent effects arise from changes in the relative affinities of the permeant for the donor and receiver solvents and the membrane and are quantitatively predicted using the separately measured partition coefficients. We also show how additional donor solvent effects can arise when switching the donor solvent causes one or more of the model assumptions to be invalid. These effects include a change in rate-limiting step, permeant solution non-ideality and others.