Preparation and in vitro/in vivo evaluation of luteinizing hormone releasing hormone (LHRH)-loaded polyhedral and spherical/tubular niosomes

Strategies to improve ellagic acid bioavailability: from natural or semisynthetic derivatives to nanotechnological approaches based on innovative carriers

Ellagic acid (EA) is a polyphenolic compound whose dietary consumption is mainly associated with the intake of red fruits, including pomegranates, strawberries, blackberries, blackcurrants, raspberries, grapes or dried fruits, like walnuts and almonds. A number of studies indicate that EA exerts health-beneficial effects against several chronic pathologies associated with oxidative damage, including different kinds of cancer, cardiovascular and neurodegenerative diseases. Furthermore, EA possesses wound-healing properties, antibacterial and antiviral effects, and acts as a systemic antioxidant. However, clinical applications of this polyphenol have been hampered and prevented by its poor water solubility (9.7 ± 3.2 μg ml^-1 in water) and pharmacokinetic profile (limited absorption rate and plasma half-life <1 h after ingestion of pomegranate juice), properties due to the chemical nature of the organic heterotetracyclic compound. Little has been reported on efficient strategies to enhance EA poor oral bioavailability, including chemical structure modifications, encapsulation within nano-microspheres to be used as carriers, and molecular dispersion in polymer matrices. In this review we summarize the experimental approaches investigated so far in order to improve EA pharmacokinetics, supporting the hypothesis that enhancement in EA solubility is a feasible route for increasing its oral absorption.

Niosomes of active Fumaria officinalis phytochemicals: antidiabetic, antineuropathic, anti-inflammatory, and possible mechanisms of action

Background

Fumaria officinalis (F. officinalis, FO) has been used in many inflammatory and painful-ailments. The main aim of this work is to perform an in-depth bio-guided phytochemical investigation of F. officinalis by identifying its main-active ingredients. Optimizing pharmacokinetics via niosomal-preparation will also be done to enhance their in vivo antineuropathic and anti-inflammatory potentials, and to explore their possible-mechanism of actions.

Methods

Bio-guided phytochemical-investigations including fractionation, isolation, chromatographic-standardization, and identification of the most active compound(s) were done. Optimized niosomal formulations of F. officinalis most active compound(s) were prepared and characterized. An in vivo biological-evaluation was done exploring acute, subchronic, and chronic alloxan-induced diabetes and diabetic-neuropathy, and carrageenan-induced acute inflammatory-pain and chronic-inflammatory edema.

Results

In-vivo bio-guided fractionation and chromatographic phytochemical-analysis showed that the alkaloid-rich fraction (ARF) is the most-active fraction. ARF contained two major alkaloids; Stylopine 48.3%, and Sanguinarine 51.6%. In-vitro optimization, analytical, and in vivo biological-investigations showed that the optimized-niosome, Nio-2, was the most optimized niosomal formulation. Nio-2 had particle size 96.56 ± 1.87 nm and worked by improving the pharmacokinetic-properties of ARF developing adequate entrapment-efficiency, rapid-degradation, and acceptable stability in simulated GI conditions. FO, ARF, and Nio 2 were the most potent antidiabetic and anti-inflammatory compounds. The reduction of the pro-inflammatory tumor necrosis factor-alpha (TNF-alpha) and Interleukin 6 (IL-6), and elevation the anti-inflammatory factor IL-10 levels and amelioration of the in vivo oxidative-stress might be the main-mechanism responsible for their antinociceptive and anti-inflammatory activities.

Conclusions

Fumaria officinalis most-active fraction was identified as ARF. This study offers an efficient and novel practical oral formulation ameliorating various inflammatory conditions and diabetic complications especially neuropathic-pain.

A new formulation of hydrophobin-coated niosome as a drug carrier to cancer cells

Hydrophobin-1 (HFB-1) found on the surface of fungal spores, plays a role in the lack of antigen recognition by the host immune system. The present study aimed to evaluate the potential application of HFB-1 for the delivery of doxorubicin (Dox) into different cell lines. Coating the surface of niosomes (Nio) with HFB-1 leads to the hypothesis that this protein can confer protection against in vivo immune-system recognition and prevent the immune response. Thus, HFB-1 could become a promising alternative to polyethylene glycol (PEG). Here, HFB-1-coated niosome loaded with doxorubicin (Dox) based on Span 40, Tween 40 and cholesterol was prepared and compared with the PEG-coated niosome. Physicochemical characteristics of the prepared formulations in terms of size, zeta potential, polydispersity index (PDI), morphology, entrapment efficiency (EE), and release rate were evaluated at different pH levels (2, 5.2, and 7.4). In the end, the in vitro cytotoxicity assay was performed on four different cancer cell lines namely A549, MDA-MB-231, C6 and PC12 in addition to one control cell line (3 T3) to ensure the formulation's selectivity against cancer cells. Results showed that the niosomes coated with HFB-1 presented better size distribution, higher EE, more sustained release profile, enhanced biocompatibility and improved anticancer effects as compared to the PEG-coated niosomes. Interestingly, the viability percentage of the control cell line was higher than different cancer cells when treated with the formulations, which indicates the higher selectivity of the formulation against cancer cells. In conclusion, loading the niosomes with Dox and coating them with HFB-1 enhanced their efficacy and selectivity toward cancer cells, presenting a promising drug delivery system for sustained drug release in cancer treatment.

Niosomes of active Fumaria officinalis phytochemicals: antidiabetic, antineuropathic, anti-inflammatory, and possible mechanisms of action

BACKGROUND

Fumaria officinalis (F. officinalis, FO) has been used in many inflammatory and painful-ailments. The main aim of this work is to perform an in-depth bio-guided phytochemical investigation of F. officinalis by identifying its main-active ingredients. Optimizing pharmacokinetics via niosomal-preparation will also be done to enhance their in vivo antineuropathic and anti-inflammatory potentials, and to explore their possible-mechanism of actions.

METHODS

Bio-guided phytochemical-investigations including fractionation, isolation, chromatographic-standardization, and identification of the most active compound(s) were done. Optimized niosomal formulations of F. officinalis most active compound(s) were prepared and characterized. An in vivo biological-evaluation was done exploring acute, subchronic, and chronic alloxan-induced diabetes and diabetic-neuropathy, and carrageenan-induced acute inflammatory-pain and chronic-inflammatory edema.

RESULTS

In-vivo bio-guided fractionation and chromatographic phytochemical-analysis showed that the alkaloid-rich fraction (ARF) is the most-active fraction. ARF contained two major alkaloids; Stylopine 48.3%, and Sanguinarine 51.6%. In-vitro optimization, analytical, and in vivo biological-investigations showed that the optimized-niosome, Nio-2, was the most optimized niosomal formulation. Nio-2 had particle size 96.56 ± 1.87 nm and worked by improving the pharmacokinetic-properties of ARF developing adequate entrapment-efficiency, rapid-degradation, and acceptable stability in simulated GI conditions. FO, ARF, and Nio 2 were the most potent antidiabetic and anti-inflammatory compounds. The reduction of the pro-inflammatory tumor necrosis factor-alpha (TNF-alpha) and Interleukin 6 (IL-6), and elevation the anti-inflammatory factor IL-10 levels and amelioration of the in vivo oxidative-stress might be the main-mechanism responsible for their antinociceptive and anti-inflammatory activities.

CONCLUSIONS

Fumaria officinalis most-active fraction was identified as ARF. This study offers an efficient and novel practical oral formulation ameliorating various inflammatory conditions and diabetic complications especially neuropathic-pain.

Environmental Scanning Electron Microscope Imaging of Vesicle Systems

The structural characteristics of liposomes have been widely investigated and there is certainly a strong understanding of their morphological characteristics. Imaging of these systems, using techniques such as freeze-fracturing methods, transmission electron microscopy, and cryo-electron imaging, has allowed us to appreciate their bilayer structures and factors which can influence this. However, there are few methods which all us to study these systems in their natural hydrated state; commonly the liposomes are visualized after drying, staining, and/or fixation of the vesicles. Environmental Scanning Electron Microscopy (ESEM) offers the ability to image a liposome in its hydrated state without the need for prior sample preparation. Within our studies we were the first to use ESEM to study liposomes and niosomes and we have been able to dynamically follow the hydration of lipid films and changes in liposome suspensions as water condenses on to, or evaporates from, the sample in real time. This provides insight into the resistance of liposomes to coalescence during dehydration, thereby providing an alternative assay of liposome formulation and stability.

Formulation, characterization and evaluation of morusin loaded niosomes for potentiation of anticancer therapy

Morusin, a water-insoluble prenylated flavonoid is known for its numerous medicinal properties. It manifests its anticancer potential by suppression of genes involved in tumor progression. However, poor solubility of the drug results in low bioavailability and rapid degradation thus hindering its clinical utilization. In order to overcome this, we have synthesized a niosome system composed of non-ionic surfactant span 60 and cholesterol using a thin-layer evaporation technique to improve the aqueous-phase solubility of the drug. Highly cytocompatible niosomes of 479 nm average size with smooth and uniform spherical morphology were synthesized in a facile manner. Unlike free morusin, nanomorusin was found to be freely dispersible in aqueous media. Having an extremely high drug entrapment efficiency (97%), controlled and sustained release of morusin resulting in enhanced therapeutic efficacy was observed in cancer cell lines of 4 different lineages. The results demonstrate that the morusin-niosome system is a promising strategy for enhanced anti-cancer activity against multiple cancer types and could be an indispensable tool for future targeted chemotherapeutic strategies.

Highly cytocompatible morusin-loaded niosomes were synthesized showing high drug loading and encapsulation efficiencies with sustained release of the drug. Enhanced therapeutic efficacy was observed against 4 different cancer cell lines.

In vitro and in vivo investigation for optimization of niosomal ability for sustainment and bioavailability enhancement of diltiazem after nasal administration

Diltiazem hydrochloride (DTZ) is a calcium channel antagonist depicted by extensive first pass metabolism and low oral bioavailability. The aim of this work was to develop niosomes for potential nasal delivery of DTZ. Niosomes protect hydrophilic drugs inside their core while nasal route offers both rapid onset and evasion of first-pass metabolism. Niosomes were prepared using a combination of Span 60 or Brij-52 with cholesterol (CHOL) in different molar ratios followed by determination of entrapment efficiency, particle size and in vitro drug release. A parallel design was adopted to evaluate the pharmacokinetic performance of DTZ-loaded niosomes in male Wistar rats. Non-compartmental analysis was performed where Cmax, Tmax, t1/2, MRT, area under the release curve (AUC) and Ke were assessed. The prepared niosomes were spherical with mean particle size 0.82-1.59 μm. Span 60-cholesterol niosomes (1:1 molar ratio) showed the highest entrapment and release efficiencies. In vivo study revealed an increase in MRT, t1/2 and AUC with a decrease in Ke. In conclusion, nasal niosomal formulation of DTZ expressed suitable pharmacokinetic parameters and bioavailability through prolonged duration of action inside the body as well as low rate of elimination depicting a promising alternate to the conventional oral route.

Non-Ionic Surfactant Vesicles (Niosomes) as New Drug Delivery Systems

Lipid vesicular systems composed of hydrated amphihiles with or without bilayer inducing agents such as cholesterol. On the basis of used amphiphilic molecule different nomenclature are used as liposomes, ufasomes and niosomes. Nonionic surfactants with mono-, di- or trialkyl chains form niosomes which are lipid vesicles with more chemical stability in comparison with phospholipids of liposomes. Both hydrophobic and hydrophilic chemicals can be encapsulated in niosomes as a new drug delivery system. This drug carrier system could have administered via injection, oral, pulmonary, vaginal, rectal, ophthalmic, nasal or transdermal routes with penetration enhancing potential. This chapter presents a detailed explain about niosome forming components, methods of preparation and routes of administration. Many examples for drug delivery potential of niosomes are also available in this review. Vaccine adjuvant and genetic substances vector capabilities are not given here.

Non-Ionic Surfactant Vesicles (Niosomes) as New Drug Delivery Systems

Lipid vesicular systems composed of hydrated amphihiles with or without bilayer inducing agents such as cholesterol. On the basis of used amphiphilic molecule different nomenclature are used as liposomes, ufasomes and niosomes. Nonionic surfactants with mono-, di- or trialkyl chains form niosomes which are lipid vesicles with more chemical stability in comparison with phospholipids of liposomes. Both hydrophobic and hydrophilic chemicals can be encapsulated in niosomes as a new drug delivery system. This drug carrier system could have administered via injection, oral, pulmonary, vaginal, rectal, ophthalmic, nasal or transdermal routes with penetration enhancing potential. This chapter presents a detailed explain about niosome forming components, methods of preparation and routes of administration. Many examples for drug delivery potential of niosomes are also available in this review. Vaccine adjuvant and genetic substances vector capabilities are not given here.

In Vitro and In Vivo Evaluation of Niosomal Formulation for Controlled Delivery of Clarithromycin

The present study was focused on formulating and evaluating clarithromycin (CLR) containing niosomal formulation for in vitro and in vivo pharmacokinetic behavior. Niosomal formulations (empty and drug loaded) were prepared by using different ratio of surfactant (various Span grades 20, 40, 60, and 80) and cholesterol by thin film hydration method and were evaluated for in vitro characteristics, stability studies, and in vivo study. Dicetyl phosphate (DCP) was added to the niosomal formulation. Various pharmacokinetic parameters were determined from plasma of male SD rats. Span 60 containing niosomal formulation NC2 (cholesterol to surfactant ratio 1 : 1) displayed highest entrapment efficiency with desired particle size of 4.67 μm. TEM analyses showed that niosomal formulation was spherical in shape. Niosomes containing Span 60 displayed higher percentage of drug release after 24 h as compared to other formulations. NC2 formulation was found to be stable at the end of the study on storage condition. Various pharmacokinetic parameters, namely, AUC, AUMC, and MRT of niosomal formulation, were found to be 1.5-fold, 4-fold, and 3-fold plain drug, respectively. The present study suggested that niosomal formulations provide sustained and prolonged delivery of drug with enhance bioavailability.

Niosomes of ascorbic acid and α-tocopherol in the cerebral ischemia-reperfusion model in male rats

The objective of the present study was to prepare a stable iv injectable formulation of ascorbic acid and α-tocopherol in preventing the cerebral ischemia. Different niosomal formulations were prepared by Span and Tween mixed with cholesterol. The physicochemical characteristics of niosomal formulations were evaluated in vitro. For in vivo evaluation, the rats were made ischemic by middle cerebral artery occlusion model for 30 min and the selected formulation was used for determining its neuroprotective effect against cerebral ischemia. Neuronal damage was evaluated by optical microscopy and transmission electron microscopy. The encapsulation efficiency of ascorbic acid was increased to more than 84% by remote loading method. The cholesterol content of the niosomes, the hydrophilicity potential of the encapsulated compounds, and the preparation method of niosomes were the main factors affecting the mean volume diameter of the prepared vesicles. High physical stability of the niosomes prepared from Span 40 and Span 60 was demonstrated due to negligible size change of vesicles during 6 months storage at 4-8(°)C. In vivo studies showed that ST60/Chol 35 : 35 : 30 niosomes had more neuroprotective effects against cerebral ischemic injuries in male rats than free ascorbic acid.

Formulation and in vitro evaluation of ciprofloxacin containing niosomes for pulmonary delivery

In order to develop a niosome-encapsulated ciprofloxacin (CPFX) HCl formulation for pulmonary delivery, the feasibility of encapsulation of CPFX in niosomes, its stability and nebulization capability was evaluated. Various combinations of nonionic surfactants with cholesterol were used to prepare the formulations. The in vitro deposition data of the niosomal formulations were examined using an Andersen cascade impactor. Formulations composed of Span 60 and Tween 60 in combination with 40 mol% of cholesterol exhibited high encapsulation efficacy and stability and also had fine particle fraction and nebulization efficiency of about 61.9% &#x00B1; 1.0 and 77.9 &#x00B1; 2.8, respectively. Minimal inhibitory concentration of the niosomal CPFX against some pulmonary pathogens were lower than free CPFX. Using the MTT assay in human lung carcinoma cell line (A549), niosome-entrapped CPFX showed significantly lower cytotoxicity in comparison to the free drug. These results indicate that niosome can be used as a carrier for pulmonary delivery of CPFX via nebulization.

Environmental scanning electron microscope imaging of vesicle systems

The structural characteristics of liposomes have been widely investigated and there is certainly a strong understanding of their morphological characteristics. Imaging of these systems, using techniques such as freeze-fracturing methods, transmission electron microscopy, and cryo-electron imaging, has allowed us to appreciate their bilayer structures and factors that influence this. However, there are a few methods that study these systems in their natural hydrated state; commonly, the liposomes are visualized after drying, staining and/or fixation of the vesicles. Environmental scanning electron microscopy (ESEM) offers the ability to image a liposome in its hydrated state without the need for prior sample preparation. We were the first to use ESEM to study the liposomes and niosomes, and have been able to dynamically follow the hydration of lipid films and changes in liposome suspensions as water condenses onto, or evaporates from, the sample in real-time. This provides an insight into the resistance of liposomes to coalescence during dehydration, thereby providing an alternative assay for liposome formulation and stability.

Immuno-targeting of nonionic surfactant vesicles to inflammation

Niosomes composed of sorbitan monostearate (Span 60), polyoxyethylene sorbitan monostearate (Tween 61), cholesterol, and dicetyl phosphate were conjugated with a purified monoclonal antibody to CD44 (IM7) through a cyanuric chloride (CC) linkage on the polyoxyethylene group of the Tween 61 molecule. Inclusion of small amounts of Tween 61 within the surfactant component of niosomes formed using thin film hydration techniques and sonication did not hamper vesicle stability as compared to Span 60 niosomes. Conjugation was verified by UV absorbance of fluorescently tagged IM7 in non-fluorescing niosomes and fluorescent micrographs. The immuno-niosomes were incubated with synovial lining cells expressing CD44. Attachment of niosomes was evident and showed selectivity and specificity compared to controls. These findings suggest that the resulting immuno-niosomes may provide an effective method for targeted drug delivery.

Environmental scanning electron microscopy offers real-time morphological analysis of liposomes and niosomes

Liposomes have been imaged using a plethora of techniques. However, few of these methods offer the ability to study these systems in their natural hydrated state without the requirement of drying, staining, and fixation of the vesicles. However, the ability to image a liposome in its hydrated state is the ideal scenario for visualization of these dynamic lipid structures and environmental scanning electron microscopy (ESEM), with its ability to image wet systems without prior sample preparation, offers potential advantages to the above methods. In our studies, we have used ESEM to not only investigate the morphology of liposomes and niosomes but also to dynamically follow the changes in structure of lipid films and liposome suspensions as water condenses on to or evaporates from the sample. In particular, changes in liposome morphology were studied using ESEM in real time to investigate the resistance of liposomes to coalescence during dehydration thereby providing an alternative assay of liposome formulation and stability. Based on this protocol, we have also studied niosome-based systems and cationic liposome/DNA complexes.

In vitro study of polyoxyethylene alkyl ether niosomes for delivery of insulin

In this study, niosomes of polyoxyethylene alkyl ethers (Brij) were prepared for encapsulation of insulin by film hydration method. Without cholesterol, brij 35 and brij 58 did not form niosomes, apparently because of relatively large polar head groups in comparison with their alkyl chains. The size of vesicles depended on the cholesterol content, charge incorporation or hydrophilicity of surfactants. Entrapment of insulin in bilayer structure of niosomes protected it against proteolytic activity of alpha-chymotrypsin, trypsin and pepsin in vitro. The maximum protection activity was seen in brij 92/cholesterol (7:3 molar ratios) in which only 26.3+/-3.98% of entrapped insulin was released during 24h in simulated intestinal fluid (SIF). The kinetic of drug release for most formulations could be best described by Baker and Lonsdale equation indicating diffusion based delivery mechanism. These results indicate that niosomes could be developed as sustained release oral dosage forms for delivery of peptides and proteins such as insulin.

Sample preparation for peptides and proteins in biological matrices prior to liquid chromatography and capillary zone electrophoresis

The determination of peptides and proteins in a biological matrix normally includes a sample-preparation step to obtain a sample that can be injected into a separation system in such a way that peptides and proteins of interest can be determined qualitatively and/or quantitatively. This can be a rather challenging, labourious and/or time-consuming process. The extract obtained after sample preparation is further separated using a compatible separation system. Liquid chromatography (LC) is the generally applied technique for this purpose, but capillary zone electrophoresis (CZE) is an alternative, providing fast, versatile and efficient separations. In this review, the recent developments in the combination of sample-preparation procedures with LC and CZE, for the determination of peptides and proteins, will be discussed. Emphasis will be on purification from and determination in complex biological matrices (plasma, cell lysates, etc.) of these compounds and little attention will be paid to the proteomics area. Additional focus will be put on sample-preparation conditions, which can be 'hard' or 'soft', and on selectivity issues. Selectivity issues will be addressed in combination with the used separation technique and a comparison between LC and CZE will be made.

Development and physical characterization of sorbitan monoester niosomes for insulin oral delivery

Niosomes of sorbitan monoesters (Span 20, 40, 60, and 80) were prepared using the film hydration method without sonication. Unlike the other surfactants, Span 80 did not form niosomes in the absence of a sufficient amount of cholesterol. The size of vesicles depended on the cholesterol molar ratio or charge incorporation. The amount of insulin released in simulated intestinal fluid from Span 40 and 60 was lower than Span 20 and 80 vesicles. Vesicles containing Span 60 showed the highest protection of insulin against proteolytic enzymes and good stability in the presence of sodium desoxycholate and storage temperatures.

Release Studies on Niosomes Containing Fatty Alcohols as Bilayer Stabilizers Instead of Cholesterol

Monomers of some amphiphiles organize into bilayers to form liposomes and niosomes. Such bilayers are unstable or leaky and hence cholesterol is a common ingredient included to stabilize them. Cholesterol stabilizes bilayers, prevents leakiness, and retards permeation of solutes enclosed in the aqueous core of these vesicles. Other than cholesterol a material with good bilayer-stabilizing properties is yet to be identified. We have substituted cholesterol with fatty alcohols in niosomes containing polyglyceryl-3-di-isostearate (PGDS) and polysorbate-80 (PS-80) to explore their membrane-stabilizing property via permeation studies. Niosomes of polyglyceryl-3-di-isostearate, fatty alcohol/cholesterol, and polysorbate were prepared by ether injection method. Aqueous solution of ketorolac tromethamine (KT) was entrapped in them. The effects of alkyl chain length of fatty alcohols (C(12), C(14), C(16), C(18), and C(16+18)), of acyl chain length of polyoxyethylene sorbitan monoester surfactants, and of the molar ratio of lipid mixture on the release rate of ketorolac from niosomes were assessed by employing modified dissolution-dialysis method. Niosomes with cholesterol or fatty alcohols have exhibited a common release pattern. Niosomes containing fatty alcohol showed a considerably slower release rate of KT than those containing cholesterol. Based on the release rate, fatty alcohols can be ranked as stearyl<myristyl<cetyl<lauryl<cetostearyl. In niosomes containing PGDS, myristyl alcohol (MA), and polysorbate, the fatty acid chain length of polyoxyethylene sorbitan ester-type surfactants has influenced the release rate and encapsulation efficiency. Based on the release rate, polysorbates can be ranked as polysorbate-20 (C(12))<polysorbate-60 (C(18))<polysorbate-80 (C(9=9))<polysorbate-40 (C(16)). In niosome preparation containing polysorbate-20 and dioctyl sodium sulfosuccinate (anionic surfactant), the release rate was slower than niosomes containing polysorbate-20. When MA concentration is kept constant at 50 mole% and the ratio of PGDS and PS-80 was altered, significant changes in entrapment efficiency and the release rate were observed. However, this ratio did not exhibit any relation with encapsulation efficiency or release rate. The release rate and entrapment exhibited an inverse correlation (r(2)=0.8774 at p<0.02 for the data of molar ratios of PGDS:MA:PS80; r(2)=0.975 at p<0.001 for the data of acyl chain length variation of polysorbates). It can be concluded that stable niosomes of polyglyceryl-3-di-isostearate could be prepared with fatty alcohols and polysorbates instead of cholesterol and that the release of solutes from these niosomes can be optimized by altering membrane constituents and their concentrations.

Maltodextrin-based proniosomes

Niosomes are nonionic surfactant vesicles that have potential applications in the delivery of hydrophobic or amphiphilic drugs. Our lab developed proniosomes, a dry formulation using a sorbitol carrier coated with nonionic surfactant, which can be used to produce niosomes within minutes by the addition of hot water followed by agitation. The sorbitol carrier in the original proniosomes was soluble in the solvent used to deposit surfactant, so preparation was tedious and the dissolved sorbitol interfered with the encapsulation of one model drug. A novel method is reported here for rapid preparation of proniosomes with a wide range of surfactant loading. A slurry method has been developed to produce proniosomes using maltodextrin as the carrier. The time required to produce proniosomes by this simple method is independent of the ratio of surfactant solution to carrier material and appears to be scalable. The flexibility of the proniosome preparation method would allow for the optimization of drug encapsulation in the final formulation based on the type and amount of maltodextrin. This formulation of proniosomes is a practical and simple method of producing niosomes at the point of use for drug delivery.

In vitro/in vivo characterisation of polyhedral niosomes

Non-ionic surfactant vesicles (niosomes) formed by a hexadecyl diglycerol ether (C16G2) and a series of polyoxyethylene alkyl ethers exhibit a variety of shapes dependent on their membrane composition. These surfactants form with an equimolar amount of cholesterol a mixture of largely spherical and tubular niosomes. In the absence of cholesterol, they form faceted polyhedral structures. The physicochemical and biological differences between polyhedral and spherical/tubular niosomes were studied. Polyhedral niosomes undergo a reversible shape transformation into spherical structures on heating above their phase transition temperature (Tm). The viscosity of polyhedral niosomes at room temperature is higher than their spherical counterparts due to their faceted and relatively rigid shape, and is more dependent on temperature due to shape transformation. At room temperature, polyhedral niosomes possess more rigid gel phase membranes and are less osmotically sensitive; however, they are more permeable because of a lack of or low levels of cholesterol in their membranes. Polyhedral niosomes loaded with luteinising hormone releasing hormone (LHRH), nonetheless, slow the release of drug compared to solution, albeit to a small extent.