Encapsulation and stability of clofazimine liposomes

Drug Delivery Systems on Leprosy Therapy: Moving Towards Eradication?

Leprosy disease remains an important public health issue as it is still endemic in several countries. Mycobacterium leprae, the causative agent of leprosy, presents tropism for cells of the reticuloendothelial and peripheral nervous system. Current multidrug therapy consists of clofazimine, dapsone and rifampicin. Despite significant improvements in leprosy treatment, in most programs, successful completion of the therapy is still sub-optimal. Drug resistance has emerged in some countries. This review discusses the status of leprosy disease worldwide, providing information regarding infectious agents, clinical manifestations, diagnosis, actual treatment and future perspectives and strategies on targets for an efficient targeted delivery therapy.

Modulating the release of pharmaceuticals from lipid cubic phases using a lipase inhibitor

Lipid cubic phase formulations have gained recognition as potential controlled delivery systems for a range of active pharmaceutical and biological agents on account of their desirable physiochemical properties and ability to encapsulate both hydrophobic and hydrophilic molecules. The most widely studied lipid cubic systems are those of the monoacylglycerol lipid family. These formulations are susceptible to lipolysis by a variety of enzymes, including lipases and esterases, which attack the ester bond present on the lipid chain bridging the oleic acid component to the glycerol backbone. The release of poorly soluble molecules residing in the lipid membrane portions of the phase is limited by the breakdown of the matrix; thus, presenting a potential means for further controlling and sustaining the release of therapeutic agents by targeting the matrix stability and its rate of degradation. The aims of the present study were twofold: to evaluate an approach to regulate the rate of degradation of lipid cubic phase drug delivery systems by targeting the enzyme interactions responsible for their demise; and to study the subsequent drug release profiles from bulk lipid cubic gels using model drugs of contrasting hydrophobicity. Here, hybrid materials consisting of cubic phases with monoacylglycerol lipids of different chain lengths formulated with a potent lipase inhibitor tetrahydrolipstatin were designed. Modulation of the release of a hydrophobic model pharmaceutical, a clofazimine salt, was obtained by exploiting the matrices' enzyme-driven digestion. A stable cubic phase is described, displaying controlled degradation with at least a 4-fold improvement compared to the blank systems shown in inhibitor-containing cubic systems. Sustained release of the model hydrophobic pharmaceutical was studied over 30 days to highlight the advantage of incorporating an inhibitor into the cubic network to achieve tunable lipid release systems. This is done without negatively affecting the structure of the matrix itself, as shown by comprehensive small-angle x-ray scattering experiments.

Overcoming clofazimine intrinsic toxicity: statistical modelling and characterization of solid lipid nanoparticles

The aim of this work was to develop solid lipid nanoparticles (SLNs) loaded with clofazimine (CLZ) (SLNs-CLZ) to overcome its intrinsic toxicity and low water solubility, for oral drug delivery. A Box-Behnken design was constructed to unravel the relations between the independent variables in the selected responses. The optimized SLNs-CLZ exhibited the following properties: particle size ca 230 nm, zeta potential of -34.28 mV, association efficiency of 72% and drug loading of 2.4%, which are suitable for oral delivery. Further characterization included Fourier transformed infrared spectroscopy that confirmed the presence of the drug and the absence of chemical interactions. By differential scanning calorimetry was verified the amorphous state of CLZ. The storage stability studies ensured the stability of the systems over a period of 12 weeks at 4°C. In vitro cytotoxicity studies evidenced no effect of both drug-loaded and unloaded SLNs on MKN-28 gastric cells and on intestinal cells, namely Caco-2 and HT29-MTX cells up to 25 µg ml^-1 in CLZ. Free CLZ solutions exhibited IC₅₀ values of 16 and 20 µg ml^-1 for Caco-2 and HT29-MTX cells, respectively. It can be concluded that the optimized system, designed considering important variables for the formulation of poorly soluble drugs, represents a promising platform for oral CLZ delivery.

Co-Encapsulation of EGCG and Quercetin in Liposomes for Optimum Antioxidant Activity

Although different delivery systems have been developed to overcome the limits of Epigallocatechin-3-gallate (EGCG) and quercetin in food application, none have referred to their simultaneous encapsulation. In this study, these two polyphenols were successfully co-loaded into liposomes. Under the optimal conditions (lecithin-total polyphenols ratio 25:1, lecithin-cholesterol ratio 6:1, lecithin-Tween 80 ratio 8:1 and ultrasonic time 2 min), the mean size, polydispersity index (PDI) and zeta potential of liposomes were 111.10 ± 0.52 nm, 0.259 ± 0.006 and -19.83 ± 0.45 mV, with an encapsulation efficiency of 64.05 ± 1.56% and 61.73 ± 2.55% for EGCG and quercetin, respectively. After 30-day storage, an increase of 4.05% was observed in the mean size with no significant change (P ≥ 0.05) in the PDI and zeta potential. Moreover, 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay revealed a synergistic antioxidant effect of the two compounds in liposomal system. These results demonstrated that co-encapsulation of EGCG and quercetin enhances their effectiveness. PRACTICAL APPLICATION: EGCG and quercetin are natural polyphenols abound in the human diet with diverse biological activities. These two polyphenols were successfully co-encapsulated into a homogeneous and stable liposomal system. Interestingly, a synergistic antioxidant effect of the two polyphenols was observed due to co-encapsulation. This indicated that the simultaneous delivery of EGCG and quercetin was an attractive approach to improve their functionality for expanding their application in food, cosmetic and pharmaceutical industries.

Role of Biorelevant Dissolution Media in the Selection of Optimal Salt Forms of Oral Drugs: Maximizing the Gastrointestinal Solubility and in Vitro Activity of the Antimicrobial Molecule, Clofazimine

Clofazimine is an antimycobacterial agent that is routinely used for the treatment of leprosy. Clofazimine has also been shown to have high clinical potential for the treatment of many Gram-positive pathogens, including those that exhibit high levels of antibiotic resistance in the medical community. The use of clofazimine against these pathogens has largely been limited by the inherently poor water solubility of the drug substance. In this work, the possibility of repurposing and reformulating clofazimine to maximize its clinical potential is investigated. To achieve this, the potential of novel salt forms of clofazimine as supersaturating drug-delivery vehicles to enhance the aqueous solubility and gastrointestinal solubility of the drug substance was explored. The solution properties of seven novel salt forms, identified during an initial screening process, were examined in water and in a gastrointestinal-like media and were compared and contrasted with those of the free base, clofazimine, and the commercial formulation of the drug, Lamprene. The stability of the most promising solid forms was tested, and their bioactivity against Staphylococcus aureus was also compared with that of the clofazimine free base and Lamprene. Salts forms which showed superior stability as well as solubility and activity to the commercial drug formulation were fully characterized using a combination of spectroscopic techniques, including X-ray diffraction, solid-state NMR, and Fourier transform infrared spectroscopy.

Nanopharmaceuticals as a solution to neglected diseases: Is it possible?

The study of neglected diseases has not received much attention, especially from public and private institutions over the last years, in terms of strong support for developing treatment for these diseases. Support in the form of substantial amounts of private and public investment is greatly needed in this area. Due to the lack of novel drugs for these diseases, nanobiotechnology has appeared as an important new breakthrough for the treatment of neglected diseases. Recently, very few reviews focusing on filiarasis, leishmaniasis, leprosy, malaria, onchocerciasis, schistosomiasis, trypanosomiasis, and tuberculosis, and dengue virus have been published. New developments in nanocarriers have made promising advances in the treatment of several kinds of diseases with less toxicity, high efficacy and improved bioavailability of drugs with extended release and fewer applications. This review deals with the current status of nanobiotechnology in the treatment of neglected diseases and highlights how it provides key tools for exploring new perspectives in the treatment of a wide range of diseases.

Complexation of clofazimine by macrocyclic cucurbit[7]uril reduced its cardiotoxicity without affecting the antimycobacterial efficacy

Cucurbit[7]uril (CB[7]) has recently attracted increasing attention in pharmaceutical sciences due to its great potential in improving the physicochemical properties and bioactivity of drug molecules. Herein, we have investigated the influence of CB[7]'s complexation on the solubility, antimycobacterial activity, and cardiotoxicity of a model anti-tuberculosis drug, clofazimine (CFZ), that has poor water-solubility and inherent cardiotoxicity. In our study, CFZ was found to be complexed by CB[7], in a 1 : 1 binding mode with a relatively strong binding affinity (in the order of magnitude of 10(4)-10(5) M(-1)), as determined by the phase solubility method via HPLC-UV analysis and (1)H NMR titration, as well as UV-visible spectroscopic titration, and further confirmed by electrospray ionization mass spectrometry (ESI-MS). Upon complexation, the solubility of virtually insoluble CFZ was significantly increased, reaching a concentration of up to approximately 0.53-fold of the maximum solubility of CB[7]. The inherent cardiotoxicity of CFZ was dramatically reduced to almost nil in the presence of CB[7]. Importantly, on the other hand, such a supramolecular complexation of the drug did not compromise its therapeutic efficacy, as shown by the antimycobacterial activities examined against Mycobacterium smegmatis, demonstrating the significant potential of CB[7] as a functional pharmaceutical excipient.

Liposomal flucytosine capped with gold nanoparticle formulations for improved ocular delivery

Nanoliposomes have an organized architecture that provides versatile functions. In this study, liposomes were used as an ocular carrier for nanogold capped with flucytosine antifungal drug. Gold nanoparticles were used as a contrasting agent that provides tracking of the drug to the posterior segment of the eye for treating fungal intraocular endophthalmitis. The nanoliposomes were prepared with varying molar ratios of lecithin, cholesterol, Span 60, a positive charge inducer (stearylamine), and a negative charge inducer (dicetyl phosphate). Formulation F6 (phosphatidylcholine, cholesterol, Span 60, and stearylamine at a molar ratio of 1:1:1:0.15) demonstrated the highest extent of drug released, which reached 7.043 mg/h. It had a zeta potential value of 42.5±2.12 mV and an average particle size approaching 135.1±12.0 nm. The ocular penetration of the selected nanoliposomes was evaluated in vivo using a computed tomography imaging technique. It was found that F6 had both the highest intraocular penetration depth (10.22±0.11 mm) as measured by the computed tomography and the highest antifungal efficacy when evaluated in vivo using 32 infected rabbits' eyes. The results showed a strong correlation between the average intraocular penetration of the nanoparticles capped with flucytosine and the percentage of the eyes healed. After 4 weeks, all the infected eyes (n=8) were significantly healed (P<0.01) when treated with liposomal formulation F6. Overall, the nanoliposomes encapsulating flucytosine have been proven efficient in treating the infected rabbits' eyes, which proves the efficiency of the nanoliposomes in delivering both the drug and the contrasting agent to the posterior segment of the eye.

Targeting brain cells with glutathione-modulated nanoliposomes: in vitro and in vivo study

Background

The blood–brain barrier prevents many drug moieties from reaching the central nervous system. Therefore, glutathione-modulated nanoliposomes have been engineered to enhance the targeting of flucytosine to the brain.

Methods

Glutathione-modulated nanoliposomes were prepared by thin-film hydration technique and evaluated in the primary brain cells of rats. Lecithin, cholesterol, and span 65 were mixed at 1:1:1 molar ratio. The molar percentage of PEGylated glutathione varied from 0 mol% to 0.75 mol%. The cellular binding and the uptake of the targeted liposomes were both monitored by epifluorescent microscope and flow cytometry techniques. A biodistribution and a pharmacokinetic study of flucytosine and flucytosine-loaded glutathione–modulated liposomes was carried out to evaluate the in vivo brain-targeting efficiency.

Results

The size of glutathione-modulated nanoliposomes was <100 nm and the zeta potential was more than −65 mV. The cumulative release reached 70% for certain formulations. The cellular uptake increased as molar percent of glutathione increased to reach the maximum at 0.75 mol%. The uptake of the targeted liposomes by brain cells of the rats was three times greater than that of the nontargeted liposomes. An in vivo study showed that the relative efficiency was 2.632±0.089 and the concentration efficiency was 1.590±0.049, and also, the drug-targeting index was 3.670±0.824.

Conclusion

Overall, these results revealed that glutathione-PEGylated nanoliposomes enhance the effective delivery of flucytosine to brain and could become a promising new therapeutic option for the treatment of the brain infections.

Effect of formulation design and freeze-drying on properties of fluconazole multilamellar liposomes

Fluconazole-entrapped multilamellar liposomes were prepared using the thin-film hydration method. The effects of cholesterol molar ratio, charge-inducing agents, and α-tocopherol acetate on encapsulation efficiency values and in vitro drug release of multilamellar liposomes were studied. Freeze-dried liposomal products were prepared with or without cryoprotectants. Results showed that incorporation of stearylamine resulted in an increased entrapment of fluconazole, whereas incorporation of dicetyl phosphate decreased the drug entrapment efficiency. The incorporation of α-tocopherol acetate into fluconazole multilamellar liposomes resulted in the increase of entrapment efficiency of fluconazole liposomes. In vitro release studies revealed that incorporation of cholesterol into multilamellar liposomal formulations decreased drug permeability from formulations. Positively charged fluconazole multilamellar liposomes gave rise to a slow release rate compared to neutral liposomes whereas negatively charged fluconazole liposomes showed a rapid release rate. Physical stability studies showed that lyophilized cake of liposomes without cryoprotectants was compact and difficult to reconstitute compared to fluffy easily reconstituted cakes upon using cryoprotectants. Fluconazole retained in freeze-dried liposomes without cryoprotectants was 63.452% compared to 91.877% using three grams of trehalose as a cryoprotectant per gram lipid in positively charged multilamellar liposomes. Physical stability studies showed superior potentials of the lyophilized product after reconstitution in comparison with those of a solution product.

The study on the entrapment efficiency and in vitro release of puerarin submicron emulsion

The entrapment efficiency (EE) and release in vitro are very important physicochemical characteristics of puerarin submicron emulsion (SME). In this paper, the performance of ultrafiltration (UF), ultracentrifugation (UC), and microdialysis (MD) for determining the EE of SME were evaluated, respectively. The release study in vitro of puerarin from SME was studied by using MD and pressure UF technology. The EE of SME was 86.5%, 72.8%, and 55.8% as determined by MD, UF, and UC, respectively. MD was not suitable for EE measurements of puerarin submicron oil droplet, which could only determine the total EE of submicron oil droplet and liposomes micelles, but it could be applied to determine the amount of free drug in SMEs. Although UC was the fastest and simplest to use, its results were the least reliable. UF was still the relatively accurate method for EE determination of puerarin SME. The release of puerarin SME could be evaluated by using MD and pressure UF, but MD seemed to be more suitable for the release study of puerarin emulsion. The drug release from puerarin SME at three drug concentrations was initially rapid, but reached a plateau value within 30 min. Drug release of puerarin from the SME occurred via burst release.

Determination of entrapment efficiency and drug phase distribution of submicron emulsions loaded silybin

This paper compared the performance of ultrafiltration (UF), ultracentrifugation (UC) and microdialysis (MD) for determining the entrapment efficiency (EE) of submicron emulsions (SE) loaded with a model drug, silybin (SB). Also, a novel way was created to evaluate the drug phase distribution of SE. The EE of SEI, SEII and SEIII with a range of particle sizes (109.8, 171.7 and 213.2 nm) and the drug phase distribution of SEII and SEIII were separately determined by the three methods. The EEs of SEI were 99.8%, 91.1%, 84.4% determined by MD, UF, UC, respectively, and the EEs of SEII and SEIII were 99.5%, 86.4%, 72.1% and 99.4%, 84.3%, 66.3%, separately. The accuracy of MD to determine EE of SE is much less than that of UF. Although UC is the fastest and most simple to use, its results are the least reliable. The sequence of the amount of drug in SE is as follows: O/W interface, aqueous phase and oil phase. Over 80% of SB was in the O/W interface of SEII and SEIII individually. The method created is reliable for quantifying the phase distribution of drug in submicron emulsions.

Hydroxyzine- and Cetirizine-Loaded Liposomes: Effect of Duration of Thin Film Hydration, Freeze-Thawing, and Changing Buffer pH on Encapsulation and Stability

PURPOSE

To assess the effect of the duration of film hydration, freeze-thawing, and changing buffer pH on the extent of entrapment of hydroxyzine and cetirizine, H1-antihistamines with different polarity, into liposomes, and the stability of these liposomes.

METHODS

Multilamellar vesicles (MLV) were prepared by thin-lipid film hydration using L-alpha-phosphatidylcholine (PC) and buffer containing 80 mg hydroxyzine at pH 7. For MLV containing hydroxyzine, the liposomes were subjected to 1) hydration for 1 h, 24 h, or 48 h for the control batch, batch B, or batch D respectively; and 2) hydration for 1 h, 24 h, or 48 h with freeze-thawing for 5-cycles for batch A, batch C, or batch E, respectively. These formulations were stored at 10 +/- 2 degrees C and 37 +/- 0.1 degrees C. Small unilamellar vesicles (SUV) and MLV were prepared using L-alpha-phosphatidylcholine (PC), and buffer at pH 5.0, 5.5, 6.0, 6.5, and 7.0, containing 80 mg hydroxyzine or 82 mg cetirizine by the ethanol injection and thin-lipid film hydration methods, respectively. These formulations were stored at 10 +/- 2 degrees C. Liposomes were evaluated immediately after preparation and after storage by determining percent entrapment of hydroxyzine (PETH) or of cetirizine (PEC) and by observing changes in the physical appearance (PA). Particle size (PSA) of the liposomes freshly prepared at pH=6.5 was measured from transmission electron micrographs (TEM).

RESULTS

Increasing thin-film hydration time or repeated freeze-thawing did not affect the initial PETH or long-term stability of control, A, B, C, D, and E batches of MLV containing hydroxyzine stored at 10 +/- 2 degrees C. At 37 +/- 0.1 degrees C, PETH of all MLV batches decreased considerably after 1 month. This was more evident in batches B, C, and E exposed to freeze-thawing. The PETH of SUV increased markedly from 53.0% to 84.0% when the pH of the buffer was increased from 5.0 to 5.5. As pH increased from 6.0 to 7.0, PETH continued to increase from 84% to 94%. The initial PETH of MLV increased slightly from 82.0% to 94.0% as the buffer pH values increased from 5.0 to 7.0. There was no effect of pH on initial PEC, and stability of SUV or initial PEC of MLV, which ranged from 92% to 94%, as buffer pH values increased from 5.0 to 6.5. After storage at 10 +/- 2 degrees C PEC in MLV decreased from 94% to 74%.

CONCLUSIONS

The freeze-thawing processes had some effect on the stability of liposomes stored at temperatures higher than ambient temperature, 37 +/- 0.1 degrees C. The effect of changing the buffer pH from 5.5 to 7.0, and from 5.0 to 6.5 on initial PETH and PEC, respectively, was minimal. After 24 months at l0 +/- 2 degrees C, pH had no effects on PETH; however, PEC of MLV decreased.

Liposomal budesonide for dry powder inhaler: preparation and stabilization

The purpose of the study was to prepare stable liposomally entrapped budesonide (BUD) for a dry powder inhaler (DPI) formulation. BUD liposomes composed of egg phosphatidyl choline and cholesterol were prepared by lipid film hydration technique and sonicated to have the desired size (< 5 micro m). A rapid method was used for separation of free drug by centrifugation at a lower centrifugal force (G value). Liposomal dispersion was subjected to lyophilization after blending BUD with cryoprotectant in varying bulk and mass ratios, and percent drug remaining entrapped after lyophilization was optimized. Comparative drug retention studies on storage of DPI formulations were carried out in accordance with International Conference on Harmonization guidelines. Critical relative humidity of the formulations was determined and reported as one of the manufacturing controls. Sucrose was found to be the most effective cryoprotectant when present on both sides of the lamellae of liposomes in a bulk strength of 500 mM and mass ratio of lipid:sugar; 1:10. Blending of sorbolac before lyophilization showed better retention of encapsulated drug (95.59%). The respirable fraction of the product (20.69 +/- 1.50%) was comparable with that of the control (26.49 +/- 1.52%), suggesting that the liposomal BUD can be successfully delivered throughout the broncho-pulmonary tree. The findings demonstrate that liposome of BUD can be prepared with a high entrapment value, stabilized by lyophilization, and delivered as an aerosolized DPI. The stability studies of lyophilized product suggests a shelf-life of one year when stored under refrigeration (2 degrees C-8 degrees C).

Preparation and in vitro evaluation of liposomal/niosomal delivery systems for antipsoriatic drug dithranol

Dithranol is one of the mainstays in the topical treatment of psoriasis. However, the use of dithranol in psoriatic condition is inconvenient and troublesome, as it has irritating, burning, staining and necrotizing effect on the normal as well as the diseased skin. The entrapment of drug in vesicles is viewed to help in the localized delivery of the drug and an improved availability of the drug at the site will reduce the dose and in turn, the dose-dependent side effects like irritation and staining. The investigations deal with critical parameters controlling the formulation and stabilization of dithranol loaded liposomes and niosomes. The entrapment efficiency of dithranol in liposomes was optimized by altering the proportion of phosphatidyl choline and cholesterol, and in case of niosomes it was between Span 60 and cholesterol. Hydration and permeation mediums were also established keeping in view the poor solubility and stability of dithranol. The mean liposome and niosomes sizes were 4+/-1.25 and 5+/-1.5 microm, respectively. The drug-leakage study carried out at different temperatures of 4-8, 25+/-2 and 37 degrees C for a period of two months affirms that the drug leakage increased at a higher temperature. The in vitro permeation study using mouse abdominal skin shows significantly enhanced permeation with vesicles as indicated by flux of dithranol from liposomes (23.13 microg/cm(2)/h) and niosomes (7.78 microg/cm(2)/h) as compared with the cream base (4.10 microg/cm(2)/h).