Effect of β-sitosterol on the characteristics of vesicular gels containing chlorhexidine

Effects of Phytosterol Butyrate Ester on the Characteristics of Soybean Phosphatidylcholine Liposomes

The nutritional and structural properties of phytosterols (PS)/phytosterol esters (PEs) facilitate their use as substitutes for cholesterol in liposome encapsulation systems designed for oral drugs and health products. The purpose of this study was to determine the effect of phytosterol butyrate ester (PBE) on the properties of liposomes. PBE was encapsulated within liposomes (approximately 60 nm) prepared using soybean phosphatidylcholine using the thin-film hydration method. There was no significant change in the average particle diameter and zeta potential of these liposomal vesicles corresponding to the increasing amounts of encapsulated PBE. The incorporation of PBE increased the polydispersity index (PDI) independent of concentration. Additionally, we observed that the storage stability of PBE liposomes with uniform particle size and approximately spherical shape vesicle was better at low concentration. The results of Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy showed that PBE was positioned at the water interface, which increased the order of hydrophobic alkyl chains in the lipid membranes. The incorporation of PBE led to an increase in the trans conformation of hydrophobic alkyl chain and consequently, the thermal stability of liposomes, which was confirmed by differential scanning calorimetry (DSC). The results of powder X-ray diffraction (XRD) analysis confirmed that PBE was present in an amorphous form in the liposomes. Additionally, the incorporation of PBE reduced the micropolarity of the lipid membrane. Thus, when preparing liposomes using thin-film hydration, the presence of PBE affected the characteristics of liposomes.

Phase Behavior of the Bilayers Containing Hydrogenated Soy Lecithin and β-Sitosteryl Sulfate

The phase behaviors of systems containing saturated phosphatidylcholine (PC) and plant steroids can be important for designing new alternative delivery methods. In our previous studies, we found that even a small amount of β-sitosteryl sulfate (PSO₄) significantly affects the phase behavior, hydration properties, and liposomal properties of pure saturated phosphatidylcholines [Kafle, A.; Colloids Surf., B 2018, 161, 59-66; Kafle, A.; J. Oleo Sci. 2018, 67 (12), 1511-1519]. In the current paper, we are reporting the phase behavior of a more complex system consisting of hydrogenated soy lecithin (HLC), which is useful as a carrier in drug delivery systems or in cosmetics, and PSO₄. HLC, which is composed of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidic acid (PA), and lysophosphatidylcholine (LPC), demonstrated a versatile phase behavior. The PC component of HLC was found to separate from the PE and PA components as a result of nonideal mixing. At room temperature, these two domains represented two distinct gel phases denoted L_β1 and L_β2. The L_β1 phase selectively underwent transition into the liquid crystalline phase (L_α) at a lower temperature than L_β2. Upon addition of PSO₄, at room temperature, the PC fraction gradually converted into the liquid-ordered (L_o) phase, while the (PE + PA) fraction remained unaffected. When heated above 60 °C, the whole material converted into the liquid crystalline phase. The observed fluidizing effect of PSO₄ on HLC can find applications in preparing vehicles for moisture or drugs in cosmetic and pharmaceutical formulations.

Effect of gentisic acid on the structural-functional properties of liposomes incorporating β-sitosterol

Multifunctional liposomes incorporating β-sitosterol were developed for delivery of gentisic acid (GA). The interactions of both compounds with phospholipid bilayer were interpreted viaeffects of different β-sitosterol content (0, 20 and 50 mol %) and different gentisic acid to lipid ratio (n_GA/n_lip from 10^-5 to 1) on membrane fluidity and thermotropic properties. Multilamellar vesicles of phosphatidylcholines (with size range between 1350 and 1900 nm) effectively encapsulated GA (54%) when n_GA/n_lip was higher than 0.01. Suppression of lipid peroxidation was directly related to concentration of GA. The resistance to diffusion of gentisic acid from liposomes increased for ˜50% in samples incorporating 50 mol % β-sitosterol compared to sterol-free liposomes. Finally, simulated in vitro gastrointestinal conditions showed that the release was mainly affected by low pH of simulated gastric fluid and the presence of cholates in simulated intestinal fluid, rather than by enzymes activity.

Effects of β-Sitosteryl Sulfate on the Properties of DPPC Liposomes

The effect of β-sitosteryl sulfate (PSO₄) on the liposomal size, stability, fluidity, and dispersibility of DPPC liposomes prepared by vortex mixing, bath-sonication, and probe-sonication has been studied. PSO₄ significantly decreases the particle size of the multilamellar liposomes (MLVs). The sizes of the vortexmixed and the bath-sonicated liposomes vary as a function of PSO₄ concentration. On the other hand, PSO₄ has only little effect on the particle sizes of probe sonicated liposomes. In some cases, the liposomal stability at higher PSO₄ concentrations depends on the preparation method. PSO₄ improves the dispersibility of the DPPC liposomes and enhances their hydration. It also increases the fluidity of the liposomes prepared by each method. Our results suggest that liposomes consisting of DPPC and PSO₄ can be suitable as a cosmetic or pharmaceutical ingredient for the effective delivery of the active components into the body.

In vitro and in vivo sustained release of exenatide from vesicular phospholipid gels for type II diabetes

Diabetes is a chronic disease that requires daily treatment to maintain a stable blood glucose level. Sustained-release formulations can thus benefit the treatment of diabetes by reducing the repeated administration of therapeutics. Our study aimed to develop a sustained-release platform for exenatide that is biocompatible and capable of mass production. Vesicular phospholipid gels (VPGs) are semisolid phospholipid dispersions with controlled release profiles. Exenatide-VPGs prepared via simple magnetic stirring showed excellent biocompatibility with an average particle size of about 15 μm after redispersion. VPGs were shown to achieve sustained release for up to 21 days in vitro with no obvious burst effect. The in vivo release study showed that VPGs sustained the release of the exenatide for up to 11 days. Moreover, after subcutaneous injection of the exenatide-VPGs in the diabetic rats, the hypoglycemic effect lasted for 10 days compared with exenatide solution. In sum, the exenatide-VPGs system represents a promising sustained-release formulation for exenatide with a long-acting therapeutic efficacy in vivo.

Development of a novel niosomal system for oral delivery of Ginkgo biloba extract

Background

The aim of this study was to develop an optimal niosomal system to deliver Ginkgo biloba extract (GbE) with improved oral bioavailability and to replace the conventional GbE tablets.

Methods

In this study, the film dispersion-homogenization method was used to prepare GbE niosomes. The resulting GbE niosome suspension was freeze-dried or spray-dried to improve the stability of the niosomes. GbE-loaded niosomes were formulated and characterized in terms of their morphology, particle size, zeta potential, entrapment efficiency, and angle of repose, and differential scanning calorimetry analysis was performed. In vitro release and in vivo distribution studies were also carried out.

Results

The particle size of the optimal delivery system prepared with Tween 80, Span 80, and cholesterol was about 141 nm. There was a significant difference (P < 0.05) in drug entrapment efficiency between the spray-drying method (about 77.5%) and the freeze-drying method (about 50.1%). The stability study revealed no significant change in drug entrapment efficiency for the GbE niosomes at 4°C and 25°C after 3 months. The in vitro release study suggested that GbE niosomes can prolong the release of flavonoid glycosides in phosphate-buffered solution (pH 6.8) for up to 48 hours. The in vivo distribution study showed that the flavonoid glycoside content in the heart, lung, kidney, brain, and blood of rats treated with the GbE niosome carrier system was greater than in the rats treated with the oral GbE tablet (P < 0.01). No flavonoid glycosides were detected in the brain tissue of rats given the oral GbE tablets, but they were detected in the brain tissue of rats given the GbE niosomes.

Conclusion

Niosomes are a promising oral system for delivery of GbE to the brain.

Niosomes: novel sustained release nonionic stable vesicular systems--an overview

Vesicular systems are novel means of delivering drug in controlled manner to enhance bioavailability and get therapeutic effect over a longer period of time. Niosomes are such hydrated vesicular systems containing nonionic surfactants along with cholesterol or other lipids delivering drug to targeted site which are non toxic, requiring less production cost, stable over a longer period of time in different conditions, so overcomes drawbacks of liposome. Present review describes history, all factors affecting niosome formulation, manufacturing conditions, characterization, stability, administration routes and also their comparison with liposome. This review also gives relevant information regarding various applications of niosomes in gene delivery, vaccine delivery, anticancer drug delivery, etc.

Competitive molecular interaction among paeonol-loaded liposomes: differential scanning calorimetry and synchrotron X-ray diffraction studies

Thermotropic phase behavior of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes containing 5 mol% cholesterol, or 5 mol% stigmasterol, or 5 mol% paeonol have been investigated by differential scanning calorimetry (DSC) and synchrotron X-ray diffraction (XRD) techniques, to investigate the competitive molecular interaction among paeonol-loaded liposomes. The results show that both sterol and paeonol can incorporate into hydrophobic region and interact with acyl chains of DPPC. Both 5 mol% sterols and 5 mol% paeonol can promote the formation of rippled gel phase of DPPC liposomes at room temperature. 5 mol% paeonol can induce the occurrence of phase separation in DPPC liposomes, but 5 mol% cholesterol or 5 mol% stigmasterol cannot induce this phenomenon. Both the repeat distance and the correlation length of paeonol-poor domain are larger than those of coexisted paeonol-rich domain. Both calorimetric data and SAXS patterns show that sterols have more favorable, stabilizing interactions with DPPC than paeonol, implying that high concentrations of sterols will have a negative effect on the loading of paeonol. In addition, calorimetric data show that cholesterol have a little more favorable, stabilizing interactions with DPPC than stigmasterol. The results of this study will play an important role in optimizing the formulation of paeonol-loaded liposomes.

Optimization of gatifloxacin liposomal hydrogel for enhanced transcorneal permeation

The aim of this study was to prepare and characterize a topically effective prolonged-release ophthalmic gatifloxacin liposomal hydrogel formulation. Reverse-phase evaporation was used for the preparation of liposomes consisting of phosphatidylcholine (PC) and cholesterol (CH). The effect of PC:CH molar ratio on the percentage of drug encapsulated was investigated. The effect of additives, such as stearylamine (SA) or dicetyl phosphate (DP), as positive and negative charge inducers, respectively, was studied. Morphology, mean size, encapsulation efficiency, and in vitro release of gatifloxacin from liposomes were evaluated. For hydrogel preparation, carbopol 940 was applied. In vitro transcorneal permeation through excised albino rabbit cornea was also determined. Optimal encapsulation efficiency was found at the 5:3 PC:CH molar ratio; by increasing CH content above this limit, the encapsulation efficiency decreased. Positively charged liposomes showed superior entrapment efficiency over other liposomes. Hydrogel-containing liposomes with lipid content PC, CH, and SA in a molar ratio of 5:3:1, respectively, showed best release and transcorneal permeation. These results suggest that the encapsulation of gatifloxacin into liposomes prolonged the in vitro release, depending on composition of the vesicles. In addition, the polymer hydrogel used in the preparation ensured steady, prolonged transcorneal permeation. In conclusion, gatifloxacin liposomal hydrogel is a suitable delivery system for the improvement of the ocular bioavailability of gatifloxacin.

Ciprofloxacin as ocular liposomal hydrogel

The purpose of this study was to prepare and characterize an ocular effective prolonged-release liposomal hydrogel formulation containing ciprofloxacin. Reverse-phase evaporation was used for preparation of liposomes consisting of soybean phosphatidylcholine (PC) and cholesterol (CH). The effect of PC/CH molar ratio on the percentage drug encapsulation was investigated. The effect of additives such as stearylamine (SA) or dicetyl phosphate (DP) as positive and negative charge inducers, respectively, were studied. Morphology, mean size, encapsulation efficiency, and in vitro release of ciprofloxacin from liposomes were evaluated. For hydrogel preparation, Carbopol 940 was applied. In vitro transcorneal permeation through excised albino rabbit cornea was also determined. Optimal encapsulation efficiency of 73.04 +/- 3.06% was obtained from liposomes formulated with PC/CH at molar ratio of 5:3 and by increasing CH content above this limit, the encapsulation decreased. Positively charged liposomes showed superior entrapment efficiency (82.01 +/- 0.52) over the negatively charged and the neutral liposomes. Hydrogel containing liposomes with lipid content PC, CH, and SA in molar ratio 5:3:1, respectively, showed the best release and transcorneal permeation with the percentage permeation of 30.6%. These results suggest that the degree of encapsulation of ciprofloxacin into liposomes and prolonged in vitro release depend on composition of the vesicles. In addition, the polymer hydrogel used in preparation ensure steady and prolonged transcorneal permeation. In conclusion, ciprofloxacin liposomal hydrogel is a suitable delivery system for improving the ocular bioavailability of ciprofloxacin.

Preparation and evaluation of thermosensitive liposomal hydrogel for enhanced transcorneal permeation of ofloxacin

Ofloxacin, available as ophthalmic solution, has two major problems: first, it needs frequent administration every 4 hours or even every 1 hour to treat severe eye infection; second, there is formation of white crystalline deposit on cornea due to its pH-dependent solubility, which is very low at pH of corneal fluid. In order to provide a solution to previous problems, ofloxacin in this study is prepared as topically effective in situ thermosensitive prolonged release liposomal hydrogel. Two preparation procedures were carried out, leading to the formation of multilamellar vesicles (MLVs) and reverse-phase evaporation vesicles (REVs) at pH 7.4. Effects of method of preparation, lipid content, and charge inducers on encapsulation efficiency were studied. For the preparation of in situ thermosensitive hydrogel, chitosan/beta-glycerophosphate system was synthesized and used as carrier for ofloxacin liposomes. The effect of addition of liposomes on gelation temperature, gelation time, and rheological behaviors of the hydrogel were evaluated. In vitro transcorneal permeation was also determined. MLVs entrapped greater amount of ofloxacin than REVs liposomes at pH 7.4; drug loading was increased by including charge-inducing agent and by increasing cholesterol content until a certain limit. The gelation time was decreased by the addition of liposomes into the hydrogel. The prepared liposomal hydrogel enhances the transcorneal permeation sevenfold more than the aqueous solution. These results suggested that the in situ thermosensitive ofloxacin liposomal hydrogel ensures steady and prolonged transcorneal permeation, which improves the ocular bioavailability, minimizes the need for frequent administration, and decreases the ocular side effect of ofloxacin.