Evaluation of proniosomes as an alternative strategy to optimize piroxicam transdermal delivery

The current investigation aims to evaluate the transdermal potential of niosomes bearing a potent non-steroidal anti-inflammatory, piroxicam. Piroxicam-loaded niosomes were prepared and characterized for surface morphology, entrapment efficiency and in vitro permeation across excised rat skin from various proniosome gel formulations using Franz diffusion cells. Various non-ionic surfactants were used to achieve optimum encapsulation efficiency. The prepared proniosomes significantly improved drug permeation and reduced the lag time (p < 0.05). Proniosomes prepared with Span 60 provided a higher piroxicam flux across the skin than did those prepared with Tween 80. Niosomes prepared using Span 60 showed a higher release rate than those prepared using non-ionic surfactants, Span 20 and Span 80, while those prepared from Tween showed higher release rate than formula prepared with Span. This indicates that lipophilicity and hydrophilicity of surfactant has a main role in release rates of piroxicam. Particle size of piroxicam niosomal vesicles formed by proniosome was determined by scanning electron microscopy. The encapsulation efficiency was evaluated by a specific high performance liquid chromatography method. Niosomes formed from using Spans and Tweens exhibited very high encapsulation efficiency. The results are very encouraging and suggest that niosomes can act as promising carriers offering an alternative approach for transdermal delivery of piroxicam.     

Effects of surfactant type and cholesterol level on niosomes physical properties and in vivo ocular performance using timolol maleate as a model drug

This study aimed at investigating the roles of both Span^® surfactant type (having a gel/liquid transition temperature range from <10 to 55 °C), and cholesterol level on in vitro characteristics and in vivo performance of timolol maleate niosomes. Span 20, Span 40 and Span 60 niosomes were prepared using the thin film hydration method. Span:cholesterol levels employed were 7:3 mol/mol (a minimum concentration for stable niosomes) and 1:1 mol/mol (a maximum concentration accommodated by niosomes). Niosomes were characterized for size, percentage entrapment efficiency, morphology, in vitro release and intra-ocular pressure (IOP) lowering activity in rabbits. The order of the area under IOP-time curve (AUC) was ranked as follows: Span 40 > Span 20 > Span 60. The AUC and IOP_max values for Span 40:cholesterol (7:3) niosomes were superior due to having a good compromise between thermo-responsiveness and efficient capacity for loading a significant drug cargo, compared with Span 20 and Span 60.     

Evaluation of proniosomes as an alternative strategy to optimize piroxicam transdermal delivery

The current investigation aims to evaluate the transdermal potential of niosomes bearing a potent non-steroidal anti-inflammatory, piroxicam. Piroxicam-loaded niosomes were prepared and characterized for surface morphology, entrapment efficiency and in vitro permeation across excised rat skin from various proniosome gel formulations using Franz diffusion cells. Various non-ionic surfactants were used to achieve optimum encapsulation efficiency. The prepared proniosomes significantly improved drug permeation and reduced the lag time (p < 0.05). Proniosomes prepared with Span 60 provided a higher piroxicam flux across the skin than did those prepared with Tween 80. Niosomes prepared using Span 60 showed a higher release rate than those prepared using non-ionic surfactants, Span 20 and Span 80, while those prepared from Tween showed higher release rate than formula prepared with Span. This indicates that lipophilicity and hydrophilicity of surfactant has a main role in release rates of piroxicam. Particle size of piroxicam niosomal vesicles formed by proniosome was determined by scanning electron microscopy. The encapsulation efficiency was evaluated by a specific high performance liquid chromatography method. Niosomes formed from using Spans and Tweens exhibited very high encapsulation efficiency. The results are very encouraging and suggest that niosomes can act as promising carriers offering an alternative approach for transdermal delivery of piroxicam.     

Preparation and evaluation of reverse-phase evaporation and multilamellar niosomes as ophthalmic carriers of acetazolamide

Niosomes have been reported as a possible approach to improve the low corneal penetration and bioavailability characteristics shown by conventional ophthalmic vehicles. Niosomes formed from Span 40 or Span 60 and cholesterol in the molar ratios of 7:4, 7:6 and 7:7 were prepared using reverse-phase evaporation and thin film hydration methods. The prepared systems were characterized for entrapment efficiency, size, shape and in vitro drug release. Stability studies were carried out to investigate the leaching of drug from niosomes during storage. The intraocular pressure (IOP) lowering activity of acetazolamide niosomal formulations in rabbits was measured using Shi?tz tonometer. Histological examination for the corneal tissues of rabbits receiving niosomal formulations was carried out for assessment of the ocular irritancy of niosomes. The results showed that the type of surfactant, cholesterol content and the method of preparation altered the entrapment efficiency and drug release rate from niosomes. Higher entrapment efficiency was obtained with multilamellar niosomes prepared from Span 60 and cholesterol in a 7:6 molar ratio. Niosomal formulations have shown a fairly high retention of acetazolamide inside the vesicles (approximately 75%) at a refrigerated temperature up to a period of 3 months. Each of the tested acetazolamide niosomes prepared by either method produced a significant decrease in IOP compared to the solution of free drug and plain niosomes. Multilamellar acetazolamide niosomes formulated with Span 60 and cholesterol in a 7:4 molar ratio were found to be the most effective and showed prolonged decrease in IOP. Histological examination of corneal tissues after instillation of niosomal formulation for 40 days showed slight irritation in the substantia propria of the eye which is reversible and no major changes in tissues were observed.     

Niosomal delivery of 5-fluorouracil

Non-ionic surfactant vesicles (niosomes) have shown promise as cheap, chemically stable alternatives to liposomes. Niosomes of spans (Sorbitan monoesters) have shown promise of commercial exploitation. Hence, niosomes were prepared of 5-fluorouracil (FU) using different spans. Niomsomes were prepared by the hand shaking method (HSM), reverse phase evaporation (REV) and ether injection method (EIM) using a series of Spans, i.e. Span 20, 40, 60 and 80. HSM giving least permeable vesicles were used to study the effect of variables like type of Span, composition of lipid and total lipid concentration on entrapment efficiency (EE) and release rate. Span 40 and 60 released 40.9 and 37.1% drug in 6 h while Span 20 and 80 displayed 52.2 and 57.1% release, respectively in the same time. Niosomes of Span 40 showed a mean vesicle size of 8.1 microns, EE of 15.3 +/- 1.3% and released 78.6% drug in 6 h; inclusion of cholesterol reduced the vesicle size to 4.8 microns, EE to 12.3 +/- 0.9% and the release to 50.5% (in 6 h), while incorporation of dicetyphosphate further reduced the vesicle size to 3.87 microns, EE to 10.9 +/- 1.1% and reduced release to 40.9% (in 6 h). Increase in the amount of lipid used translated into an almost linear increase in EE. Biodistribution of drug in rats was modified on encapsulation. The concentration of niosomal drug in liver, lung and kidney was increased while it decreased in intestine compared to free drug solution following intravenous administration. The niosomal formulation displayed higher and sustained plasma drug level profile compared to free drug solution. Pharmacokinetic calculations revealed an increase in half-life, area under the curve and decrease in volume of distribution of the drug on encapsulation. Thus, the study suggests that niosomes can act as promising carriers for 5-Fluorouracil.     

Niosomal delivery of 5-fluorouracil

Non-ionic surfactant vesicles (niosomes) have shown promise as cheap, chemically stable alternatives to liposomes. Niosomes of spans (Sorbitan monoesters) have shown promise of commercial exploitation. Hence, niosomes were prepared of 5-fluorouracil (FU) using different spans. Niomsomes were prepared bythehand shakingmethod (HSM), reversephaseevaporation(REV) and ether injection method (EIM) using a series of Spans, i.e. Span 20, 40, 60 and 80. HSM giving least permeable vesicles were used to study the effect of variables like type of Span, composition of lipid and total lipid concentration on entrapment efficiency (EE) and release rate. Span 40 and 60 released 40.9 and 37.1%drug in 6h while Span 20 and 80 displayed 52.2 and 57.1%release, respectively in the same time. Niosomes of Span 40 showed amean vesicle size of 8.1mum, EE of 15:3 1:3%and released 78.6% drug in 6h; inclusion of cholesterol reduced the vesicle size to4.8mum, EE to12:3 0:9%and the release to 50.5%(in 6h), while incorporation of dicetyphosphate further reduced the vesicle size to3.87mum, EE to10:9 1:1%and reduced release to40.9%(in 6h). Increase in the amount of lipid used translated intoan almost linear increase in EE. Biodistribution of drug in rats was modified on encapsulation. The concentration of niosomal drug in liver, lung and kidney was increased while it decreased in intestine compared to free drug solution following intravenous administration. The niosomal formulation displayed higher and sustained plasma drug level profile compared to free drug solution. Pharmacokinetic calculations revealed an increase in half-life, area under the curve and decrease in volume of distribution of the drug on encapsulation. Thus, the study suggests that niosomes can act as promising carriers for 5-Fluorouracil.     

PEGylated non-ionic surfactant vesicles as drug delivery systems for Gambogenic acid

Abstract

Gambogenic acid (GNA), a popular Chinese traditional medicine, has its limitations of coming into use due to its low aqueous solubility and poor bioavailability. In this study, therefore, the PEGylated non-ionic surfactant vesicles drug delivery systems were prepared from biocompatible non-ionic surfactant of Span60, cholesterol and dicetyl phosphate (DCP) by the improved ethanol injection method, and were modified with a polyethylene glycol monostearate15 (PEG15-SA). PEG15-SA, as a biocompatible, non-toxic and non-immunogenic hydrophilic segment, was grafted onto the surface of colloidal niosomes carries to reduce the uptake by the reticuloendothelial system (RES), prolonging the circulation time and attaining higher entrapment efficiency. To our knowledge, this work is the first to report that PEG15-SA was applied to coating of niosomes for encapsulation of GNA. The optimized PEG-GNA-NISVs (P-GNA-NISVs) were characterized in terms of mean vesicles size, polydispersity index (PDI), Zeta potential and entrapment efficiency of the P-GNA-NISVs. The results showed that the mean diameter, PDI, Zeta potential, and the entrapment efficiency of the P-GNA-NISVs were 70.1?nm, 0.166, ?44.3?mV and 87.74%, respectively. Furthermore, the release studies of GNA from PEGylated niosomes in vitro and the pharmacokinetics in vivo exhibited a prolonged release profile as studied over 24?h. In conclusion, the result suggests that P-GNA-NISVs prepared in this way not only have higher encapsulation capacity, more colloidal stability but also offer an approach that the PEGylated niosomes is a promising carrier for anticancer GNA.     

Proniosomes as a drug carrier for transdermal delivery of ketorolac.

Niosomes are nonionic surfactant vesicles that have potential applications in the delivery of hydrophobic and hydrophilic drugs. Permeation of a potent nonsteroidal anti-inflammatory, ketorolac, across excised rabbit skin from various proniosome gel formulations was investigated using Franz diffusion cells. Each of the prepared proniosomes significantly improved drug permeation and reduced the lag time (P<0.05). Proniosomes prepared with Span 60 provided a higher ketorolac flux across the skin than did those prepared with Tween 20 (7- and 4-fold the control, respectively). A change in the cholesterol content did not affect the efficiency of the proniosomes, and the reduction in the lecithin content did not significantly decrease the flux (P>0.05). The encapsulation efficiency and size of niosomal vesicles formed by proniosome hydration were also characterized by specific high performance liquid chromatography method and scanning electron microscopy. Each of the prepared niosomes achieved about 99% drug encapsulation. Vesicle size was markedly dependent on the composition of the proniosomal formulations. Proniosomes may be a promising carrier for ketorolac and other drugs, especially due to their simple production and facile up.     

Effect of formulation compositions on niosomal preparations

This study was aimed to investigate the effects of molar ratio of cholesterol to Span 60 and stabilizers (Solutol HS 15 or dicetyl phosphate (DCP)) on the entrapment of methylene blue, a model hydrophilic drug. The niosomes were prepared by the film hydration method and characterized for drug entrapment efficiency (EE), vesicle size, zeta potential and thermal properties of niosomal membrane. It was found that niosomal vesicles possessed median diameter ranging from 0.35 to 1.85 μm. The niosomes that were formulated with lower molar ratios of cholesterol to Span 60 of 0.33 and 0.50 produced significantly higher EE with both stabilizers when compared to cholesterol to Span 60 molar ratios of 1.0 and above (p < 0.05). The EE of niosomes stabilized with DCP was significantly higher (p < 0.05) than those prepared with Solutol HS 15 except at a molar ratio of cholesterol to Span 60 of 0.33. In conclusion, with low molar ratios of cholesterol to Span 60, more drugs could be entrapped within the niosomes regardless of the type of stabilizers. Furthermore, EE and median diameter of niosomes containing DCP were higher than those stabilized with Solutol HS 15.     

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.     

Characterization of niosomes prepared with various nonionic surfactants for paclitaxel oral delivery

Nonionic surfactant based vesicles (niosomes) are novel drug delivery systems formed from the self‐assembly of nonionic amphiphiles in aqueous media. In the present study niosomal formulations of Paclitaxel (PCT), an antineoplastic agent, were prepared using different surfactants (Tween 20, 60, Span 20, 40, 60, Brij 76, 78, 72) by film hydration method. PCT was successfully entrapped in all of the formulations with encapsulation efficiencies ranging between 12.1 ± 1.36% and 96.6 ± 0.482%. Z‐average sizes of the niosomes were between 229.3 and 588.2 nm. Depending on the addition of the negatively charged dicetyl phosphate to the formulations negative zeta potential values were obtained. High surface charges showed that niosomes can be suspended in water well and this is beneficial for their storage and administration. PCT released from niosomes by a diffusion controlled mechanism. The slow release observed from these formulations might be beneficial for reducing the toxic side effects of PCT. The niosome preparation method was found to be repeatable in terms of size distribution, zeta potential and % drug loading values. The efficiency of niosomes to protect PCT against gastrointestinal enzymes (trypsin, chymotrypsin, and pepsin) was also evaluated for PCT oral delivery. Among all formulations, gastrointestinal stability of PCT was well preserved with Span 40 niosomes. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2049–2060, 2010     

Niosomes with sorbitan monoester as a carrier for vaginal delivery of insulin: studies in rats

To prepare and investigate the potential of the niosomes vaginal delivery system for systemic treatment of insulin is the goal of this study. Two kinds of vesicles with Span 40 and Span 60 were prepared by lipid phase evaporation methods with sonication. The niosomal entrapment efficiency was determined by column chromatography. The particle size and morphology of the vesicles also were evaluated. The results showed optimized niosomes prepared in this study had niosomal entrapment efficiency 26.68 +/- 1.41% for Span 40 and 28.82 +/- 1.35% for Span 60, respectively. The particle sizes of Span 40 niosomes and Span 60 niosomes were 242.5 +/- 20.5 nm and 259.7 +/- 33.8 nm, respectively. There were no significant differences in appearance between the two types of vesicles. The hypoglycemic effects, and insulin concentrations after vaginal administration of insulin vesicles to rats were investigated. Compared with subcutaneous administration of insulin solution, the relative pharmacological bioavailability and the relative bioavailability of vaginal administration of insulin vesicles were determined. Compared with subcutaneous administration of insulin solution, the relative pharmacological bioavailability and the relative bioavailability of insulin-Span 60 vesicles group were 8.43% and 9.61%, and insulin-Span 40 niosomes were 9.11% and 10.03% (p > 0.05). Span 60 and Span 40 niosomes were both higher than blank Span 40, Span 60 vesicles, and free insulin physical mixture groups (p < 0.05). The results indicates insulin-Span 60, Span 40 niosomes had an enhancing effect on vaginal delivery of insulin. Although the factors controlling the process for penetration of a portion of vaginally administrated niosomes into bloodstream from vaginal tract is still not fully understood, our results demonstrated that after encapsulation in niosomes of definite type, insulin became an active and efficiently therapeutic agent when administrated vaginally and might be a good carrier for vaginal delivery of protein drugs.     

Effect of some formulation parameters on flurbiprofen encapsulation and release rates of niosomes prepared from proniosomes

Proniosomal gels or solutions of flurbiprofen were developed based on span 20 (Sp 20), span 40 (Sp 40), span 60 (Sp 60), and span 80 (Sp 80) without and with cholesterol. Nonionic surfactant vesicles (niosomes) formed immediately upon hydrating proniosomal formulae. The entrapment efficiency (EE%) of flurbiprofen (a poorly soluble drug) was either determined by exhaustive dialysis of freshly prepared niosomes or centrifugation of freeze-thawed vesicles. The influence of different processing and formulation variables such as surfactant chain length, cholesterol content, drug concentration, total lipid concentration, negatively or positively charging lipids, and the pH of the dispersion medium on flurbiprofen EE% was demonstrated. Also, the release of the prepared niosomes in phosphate buffer (pH 7.4) was illustrated. Results indicated that the EE% followed the trend Sp 60 (C(18))>Sp 40 (C(16))>Sp 20 (C(12))>Sp 80 (C(18)). Cholesterol increased or decreased the EE% depending on either the type of the surfactant or its concentration within the formulae. The maximum loading efficiency was 94.61% when the hydrating medium was adjusted to pH 5.5. Increasing total lipid or drug concentration also increased the EE% of flurbiprofen into niosomes. However, incorporation of either dicetyl phosphate (DCP) which induces negative charge or stearyl amine (SA) which induces positive charge decreased the EE% of flurbiprofen into niosomal vesicles. Finally, in vitro release data for niosomes of Sp 40 and Sp 60 showed that the release profiles of flurbiprofen from niosomes of different cholesterol contents is an apparently biphasic release process. As a result, this study suggested the potential of proniosomes as stable precursors for the immediate preparation of niosomal carrier systems.     

Niosomes with Sorbitan Monoester as a Carrier for Vaginal Delivery of Insulin: Studies in Rats

To prepare and investigate the potential of the niosomes vaginal delivery system for systemic treatment of insulin is the goal of this study. Two kinds of vesicles with Span 40 and Span 60 were prepared by lipid phase evaporation methods with sonication. The niosomal entrapment efficiency was determined by column chromatography. The particle size and morphology of the vesicles also were evaluated. The results showed optimized niosomes prepared in this study had niosomal entrapment efficiency 26.68 ± 1.41% for Span 40 and 28.82 ± 1.35% for Span 60, respectively. The particle sizes of Span 40 niosomes and Span 60 niosomes were 242.5 ± 20.5 nm and 259.7 ± 33.8 nm, respectively. There were no significant differences in appearance between the two types of vesicles. The hypoglycemic effects, and insulin concentrations after vaginal administration of insulin vesicles to rats were investigated. Compared with subcutaneous administration of insulin solution, the relative pharmacological bioavailability and the relative bioavailability of vaginal administration of insulin vesicles were determined. Compared with subcutaneous administration of insulin solution, the relative pharmacological bioavailability and the relative bioavailability of insulin-Span 60 vesicles group were 8.43% and 9.61%, and insulin-Span 40 niosomes were 9.11% and 10.03% (p > 0.05). Span 60 and Span 40 niosomes were both higher than blank Span 40, Span 60 vesicles, and free insulin physical mixture groups (p < 0.05). The results indicates insulin-Span 60, Span 40 niosomes had an enhancing effect on vaginal delivery of insulin. Although the factors controlling the process for penetration of a portion of vaginally administrated niosomes into bloodstream from vaginal tract is still not fully understood, our results demonstrated that after encapsulation in niosomes of definite type, insulin became an active and efficiently therapeutic agent when administrated vaginally and might be a good carrier for vaginal delivery of protein drugs.     

Effect of ciprofloxacin and chloramphenicol on humoral immune response elicited by bovine albumin encapsulated in niosomes

The aim is to evaluate the effect of ciprofloxacin and chloramphenicol on anti-BSA antibodyproduction triggered by bovine albumin encapsulated in non-ionic surfactant vesicle, niosomes. Reversephase evaporation method was adopted to entrap the antigen in colloidal carrier composed of Span 80 andSpan 85 followed by simultaneous characterization for particle size, entrapment efficiency and in vitrorelease. The protein content was determined by Bradford method using UV Visible Spectrophotometer at595 nm. Humoral immune response was measured in terms of systemic IgG antibody titre by ELISAmethod. Experimental data indicated that 7：3 molar ratio of Span 80 and cholesterol based niosomalformulation possessed maximum （39. 8 - 2.9） % of soluble protein. Ciprofloxacin markedly （ P 〈 0. 05 ）decreased the antibody titre. In contrast, chloramphenicol did not reduce the antibody titre significantly incomparison to control group （P 〉 0. 05）. It is necessary to explore the effect of a vaccine antigen when acandidate is medicated with a therapeutic agent, which might help in programming a new drug managementand vaccination programme.[编者按]     

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.     

Preparation of niosomes as an ocular delivery system for naltrexone hydrochloride: physicochemical characterization

Recent reports have demonstrated that topical and systemic application of naltrexone markedly improves the characteristic signs of diabetic keratopathy; most notably, impaired corneal sensation and delayed wound repair. The aim of this study was to prepare and characterise non-ionic surfactant vesicles (niosomes) for the ocular drug delivery of naltrexone hydrochloride. The niosomes were prepared using the thin film hydration method and characterised using polarized light microscopy, cryo-scanning electron microscopy (Cryo-SEM), percent drug entrapment efficiency (EE %), laser light diffraction and differential scanning calorimetry (DSC). Two classes of non-ionic surfactants (sorbitan esters and polyoxyethylene alkyl ethers) were investigated. The results revealed that tuning of cholesterol concentrations can significantly alter the niosome's physical properties including sizes, EE% and membrane fluidity (thermo-responsiveness). The prepared vesicles were in the range of 7.0 +/- 1.0 to 14.6 +/- 0.8 microm in size. The prepared niosomes showed different abilities to accommodate cholesterol. This was highly dependent on the structure and continuity of the hydrophobic chains of the used surfactants. Span 60-based vesicles containing 30% mol/mol of cholesterol showed the highest EE%. The microstructure and lamellarity of the niosomes were studied using Cryo-SEM. Typical concentric multilayered structures (onion or rose-like) were seen suggesting the formation of multilamellar vesicles. DSC-studies conducted on Span 60-based niosomes containing 30% mol/mol cholesterol revealed liquid-gel transition (T(m) and entropy of 43.5 degrees C and 0.82 kcal/mol, respectively). Such transition reflects potential thermo-responsive properties, which is desirable for ocular delivery.     

Oil based nanocarrier for improved oral delivery of silymarin: In vitro and in vivo studies

In this study the influence of hydrogen bonding interaction between niosomal membrane and solutes on the drug loading and release was investigated. Salicylic acid (SA) and p-hydroxyl benzoic acid (p-BA) were selected as models. Niosomes were prepared with 1:1 molar ratios of various surfactants and cholesterol by film hydration technique, and the corresponding formulation variables were optimized to achieve the maximum entrapment efficiencies (EE%). The EE% of different formulations followed the trend Span 60>Span 40>Span 20>Span 80. Additionally, it was also found that the EE% of p-BA was much higher than that of SA. This difference may be due to the formation of hydrogen bond between p-BA and niosomal membrane, and the corresponding interaction diagram has been proposed and confirmed indirectly by UV spectroscopy method. The quantitative analysis of hydrogen binding interaction between solutes and niosome has been finished firstly, and the corresponding entrapment equilibrium constant K has been calculated as well. Moreover, in vitro the release of both drugs from niosomes was examined in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF), respectively. The results indicated that the release of p-BA in SIF was much slower than that in SGF, and the release rate of SA in SGF is apparently slower than that in SIF. The possible mechanism was given as well.     

Design and in vitro characterization of small unilamellar niosomes as ophthalmic carrier of dorzolamide hydrochloride

Abstract

The objective of this work was to formulate and characterize non-ionic surfactant vesicles (niosomes) as an ocular carrier of dorzolamide hydrochloride (Dorzo); one of the antiglaucoma drugs. Niosomes were prepared of Cholesterol (Chol) with sorbitan monoesters (Span 20, 40, 60) or sorbitan trioleate (Span 85) in a molar ratio of 40:150. Those prepared from Span 40 were selected for further investigation on the effect of addition of dicetylphosphate (DCP) and polyoxyethylene fatty acid esters (either Tween 20, 40 or 80). All The batches were prepared using mechanical shaking technique, followed by sonication and then characterized using Zetasizer, transmission electron microscopy (TEM), calculating percent drug entrapment efficiency and cumulative percent released. Z-average sizes of the niosomes were between 25.9 and 165.5?nm. All niosomal formulations showed negative zeta potential charge. Dorzo was successfully entrapped in all of the formulations with entrapment efficiencies ranging between 34.81% and 97.66%. With reference to release profiles, Dorzo-loaded niosomal formulations showed significant reduction in cumulative percent drug released than Dorzo solution. High entrapment efficiencies, biphasic prolonged release rate and small particles size highlight Dorzo-loaded niosomal preparations as a promising ophthalmic carrier to prolong the drug lowering effect on the intraocular pressure.     

Essential oils in niosomes for enhanced transdermal delivery of felodipine

The fluidity of vesicular membrane affects vesicular transdermal drug delivery. Essential oils can be located in vesicular membrane imparting flexibility and influencing transdermal delivery. Accordingly, the objective was to investigate the effect of incorporation of essential oils in niosomes on felodipine transdermal delivery. Rigid niosomes comprising Span 60 with cholesterol (2:1, w/w) were used with clove, eucalyptus or lemon oils being incorporated in the vesicles at increasing concentrations. The vesicle size and shape was monitored using scanning electron microscopy. Thermal analysis was used to monitor the thermal behavior. Drug entrapment efficiency, release and skin permeation were monitored. Niosomes were spherical with size ranging from 279 to 345?nm. The drug entrapment ranged from 97.9 to 98.8%. Thermal analysis confirmed the existence of oils within vesicular membrane and highlighted the membrane fluidizing effect. Drug release depended on the oil with clove oil or eucalyptus oil showing a trend of increased drug release compared with plain niosomes. In contrast, lemon oil reduced drug release rate. Skin permeation study reflected the superiority of oil containing niosomes. The results correlated with the fluidizing and penetration enhancing effects of oils. The study introduced essential oils as potential niosomes fluidizing agents for enhanced transdermal drug delivery.