In vitro release of lysozyme from gelatin microspheres: effect of cross-linking agents and thermoreversible gel as suspending medium.

This study was aimed to characterize the microstructure and the performance of gelatin microspheres (GMs) cross-linked by two different cross-linkers viz. d-glucose and glutaraldehyde. New formulations were obtained, suspending the GMs in a thermoreversible Pluronic F127 (PF127) liquid-crystalline gel. Lysozyme was used as a model biomacromolecular drug to evaluate release features. Both types of cross-linked GMs were prepared by thermal gelation method. The lysozyme-loaded microspheres were characterized by scanning electron microscopy (SEM) for size distribution, shape, and surface texture. SEM revealed that both types of lysozyme-loaded GMs were spherical in shape and that the surface of glutaraldehyde cross-linked GMs was smoother than that of the glucose cross-linked GMs. The degree of cross-linking of microspheres was investigated using ATR-FTIR technique. The prepared GMs were suspended in 20% w/v aqueous PF127 gel for which the usual sol-gel transition temperature of 22 °C did not change in the presence of GMs, as indicated by rheological measurements. SAXS study of the PF127 gel confirmed the occurrence of a discrete cubic liquid-crystalline phase of the Fm3m type whose lattice parameter slightly decreased as a result of GMs addition. The in vitro release of lysozyme from both types of cross-linked GMs was successfully controlled when they were suspended in PF127 gel, thus suggesting the potential use of this new combined formulation as a drug-depot system.

Liposomes and niosomes as potential carriers for dermal delivery of minoxidil.

The aim of this work was to formulate minoxidil loaded liposome and niosome formulations to improve skin drug delivery. Multilamellar liposomes were prepared using soy phosphatidylcholine at different purity degrees (Phospholipon 90, 90% purity, soy lecithin (SL), 75% purity) and cholesterol (Chol), whereas niosomes were made with two different commercial mixtures of alkylpolyglucoside (APG) surfactants (Oramix NS10, Oramix CG110), Chol and dicetylphosphate. Minoxidil skin penetration and permeation experiments were performed in vitro using vertical diffusion Franz cells and human skin treated with either drug vesicular systems or propylene glycol-water-ethanol solution (control). Penetration of minoxidil in epidermal and dermal layers was greater with liposomes than with niosomal formulations and the control solution. These differences might be attributed to the smaller size and the greater potential targeting to skin and skin appendages of liposomal carriers, which enhanced globally the skin drug delivery. The greatest skin accumulation was always obtained with non-dialysed vesicular formulations. No permeation of minoxidil through the whole skin thickness was detected in the present study irrespective of the existence of hair follicles. Alcohol-free liposomal formulations would constitute a promising approach for the topical delivery of minoxidil in hair loss treatment.

Niosomes as carriers for tretinoin. III. A study into the in vitro cutaneous delivery of vesicle-incorporated tretinoin.

The influence of drug thermodynamic activity and niosome composition, size, lamellarity and charge on the (trans)dermal delivery of tretinoin (TRA) was studied. For this purpose, tretinoin was incorporated at saturated and unsaturated concentrations in both multilamellar (MLV) and unilamellar (UV) vesicular formulations using two different commercial mixtures of alkyl polyglucosides: octyl-decyl polyglucoside and decyl polyglucoside. Positively and negatively charged vesicular formulations were prepared using either stearylamine or dicetylphosphate as a charge inducer. Niosomes made with polyoxyethylene (4) lauryl ether and liposomes made with soy phosphatidylcholine were also prepared and studied. Vesicular formulations were characterised by transmission electron microscopy and optical and light polarized microscopy for vesicle formation and morphology, and by dynamic laser light scattering for size distribution. The effect of the vesicular incorporation of tretinoin on its (trans)dermal delivery through the newborn pig skin was also investigated in vitro using Franz cells, in comparison with a commercial formulation of the drug (RetinA). The amount of tretinoin delivered through and accumulated in the several skin layers was detected by HPLC. Overall, obtained results showed that tretinoin cutaneous delivery is strongly affected by vesicle composition and thermodynamic activity of the drug. In particular, small, negatively charged niosomal formulations, which are saturated with tretinoin, have shown to give higher cutaneous drug retention than both liposomes and commercial formulation. Moreover, interactions between skin and vesicles seem to depend on physico-chemical properties of the main component of the vesicular bilayer.

Artemisia arborescens L essential oil-loaded solid lipid nanoparticles for potential agricultural application: preparation and characterization.

The aim of this study was to formulate a new delivery system for ecological pesticides by the incorporation of Artemisia arborescens L essential oil into solid lipid nanoparticles (SLN). Two different SLN formulations were prepared following the high-pressure homogenization technique using Compritol 888 ATO as lipid and Poloxamer 188 or Miranol Ultra C32 as surfactants. The SLN formulation particle size was determined using Photon correlation spectroscopy (PCS) and laser diffraction analysis (LD). The change of particle charge was studied by zeta potential (ZP) measurements, while the melting and recrystallization behavior was studied using differential scanning calorimetry (DSC). In vitro release studies of the essential oil were performed at 35 degrees C. Data showed a high physical stability for both formulations at various storage temperatures during 2 months of investigation. In particular, average diameter of Artemisia arborescens L essential oil-loaded SLN did not vary during storage and increased slightly after spraying the SLN dispersions. In vitro release experiments showed that SLN were able to reduce the rapid evaporation of essential oil if compared with the reference emulsions. Therefore, obtained results showed that the studied SLN formulations are suitable carriers in agriculture.

Artemisia arborescens L essential oil-loaded solid lipid nanoparticles for potential agricultural application: Preparation and characterization.

The aim of this study was to formulate a new delivery system for ecological pesticides by the incorporation of Artemisia arborescens L essential oil into solid lipid nanoparticles (SLN). Two different SLN formulations were prepared following the high-pressure homogenization technique using Compritol 888 ATO as lipid and Poloxamer 188 or Miranol Ultra C32 as surfactants. The SLN formulation particle size was determined using Photon correlation spectroscopy (PCS) and laser diffraction analysis (LD). The change of particle charge was studied by zeta potential (ZP) measurements, while the melting and recrystallization behavior was studied using differential scanning calorimetry (DSC). In vitro release studies of the essential oil were performed at 35°C. Data showed a high physical stability for both formulations at various storage temperatures during 2 months of investigation. In particular, average diameter of Artemisia arborescens L essential oil-loaded SLN did not vary during storage and increased slightly after spraying the SLN dispersions. In vitro release experiments showed that SLN were able to reduce the rapid evaporation of essential oil if compared with the reference emulsions. Therefore, obtained results showed that the studied SLN formulations are suitable carriers in agriculture.

Niosomes as carriers for tretinoin. I. Preparation and properties.

Tretinoin-loaded niosomes were prepared from polyoxyethylene (4) lauryl ether, sorbitan esters and a commercial mixture of octyl/decyl polyglucosides, in the presence of cholesterol and dicetyl phosphate. Liposomes made of hydrogenated and non-hydrogenated phosphatidylcholine were also prepared as a comparison reference. A study was made of the influence of vesicle composition and preparation method on the vesicle structure (MLV, LUV, SUV), size distribution, entrapment efficiency and in vitro release of incorporated tretinoin. Results showed that in the presence of cholesterol all the amphiphiles used were able to form stable vesicle dispersions with or without tretinoin. Vesicle sizes were dependent on the preparation method, bilayer composition and drug load. Multilamellar (MLV) vesicles were larger than extruded (LUV) and sonicated (SUV) vesicles while drug-loaded vesicles were generally smaller than empty ones. Entrapment efficiencies of tretinoin were always very high especially for multilamellar (91-99%) and extruded (88-98%) vesicles. The in vitro release of tretinoin from the prepared vesicular formulations was studied using the vertical Franz diffusion cells. The rate of drug release through a Silastic membrane from a liposomal and niosomal tretinoin dispersion was generally faster than from a tretinoin solution. Release data showed that tretinoin delivery is mainly affected by the vesicular structure and that tretinoin delivery increased from MLVs to LUVs to SUVs.

Niosomes as carriers for tretinoin. II. Influence of vesicular incorporation on tretinoin photostability.

In this work, we compared the chemical stability of tretinoin (TRA) in methanol and in vesicular suspensions exposed both to UV and artificial daylight conditions with the aim of evaluating the potential of niosomes as topical carriers capable of improving the stability of photosensitive drugs. Tretinoin-loaded niosomes were prepared from polyoxyethylene (4) lauryl ether (Brij 30), sorbitan esters (Span 40 and Span 60) and a commercial mixture of octyl/decyl polyglucosides (Triton CG110). Liposomes made from hydrogenated (P90H) and non-hydrogenated (P90) soy phosphatidylcholines were also prepared and studied. In order to evaluate the influence of vesicle structure on the photostability of tretinoin, TRA-loaded vesicles were prepared by the film hydration method, extrusion technique and sonication. After UV irradiation, TRA dissolved in methanol degraded very quickly while the incorporation in vesicles always led to a reduction of the photodegradation process. The photoprotection offered by vesicles varied depending on the vesicle structure and composition. After fluorescent light irradiation for 21 days, not all the studied vesicular formulations improved TRA stability when compared with the free drug in methanol. Tretinoin incorporated in P90 or Span vesicles presented a half-life shorter or very close to that of the free drug. However, the inclusion of TRA in P90H liposomes and Brij 30 or Triton CG110 niosomes retarded the drug photodegradation.

Isoniazid-gelatin conjugate microparticles containing rifampicin for the treatment of tuberculosis.

OBJECTIVES: In this work, a new polymeric microparticle system based on gelatin covalently bound to isoniazid (ISN) and containing rifampicin (RFP) was prepared by spray-drying technique. Microparticle aptitude to nebulisation and their capability of interacting with A549, alveolar basal epithelial cells, were evaluated in vitro. METHODS: Microparticles were obtained by spray drying, and their morphology, size, zeta potential, thermotropic behaviour and nebulisation ability were evaluated. KEY FINDINGS: Microparticles were positively charged with a mean size of 4.88 ± 0.3 µm. Microspheres were able to incorporate both RFP and ISN: encapsulation efficiency was 51 ± 6% and 22 ± 1%, respectively. X-ray diffraction study showed a new extensive and flattened diffraction peak providing evidence that the drugs were dispersed into the microparticles. Differential scanning calorimetry analysis confirmed effective interactions between gelatin and drug molecules by the presence of new transition peaks. Fifty-nine per cent of used microparticles were aerosolised. In-vitro toxicity studies on A549 alveolar basal epithelial cells showed that microparticles decreased cytotoxicity in comparison with the RFP solution. Laser scanning confocal microscopy observation confirmed that fluorescent probes delivered by microparticles are efficiently internalised in A549 cells. CONCLUSIONS: Overall, microparticles based on gelatin covalently bound to ISN and containing RFP showed a promising behaviour for pulmonary drug delivery.

SLN as a topical delivery system for Artemisia arborescens essential oil: in vitro antiviral activity and skin permeation study.

The effect of SLN incorporation on transdermal delivery and in vitro antiherpetic activity of Artemisia arborescens essential oil was investigated. Two different SLN formulations were prepared using the hot-pressure homogenization technique, Compritol 888 ATO as lipid, and Poloxamer 188 and Miranol Ultra C32 as surfactants. Formulations were examined for their stability for two years by monitoring average size distribution and zeta potential values. The antiviral activity of free and SLN incorporated essential oil was tested in vitro against Herpes Simplex Virus-1 (HSV-1) by a quantitative tetrazolium-based colorimetric method (MTT), while the effects of essential oil incorporation into SLN on both the permeation through and the accumulation into the skin strata was investigated by using in vitro diffusion experiments through newborn pig skin and an almond oil Artemisia essential oil solution as a control. Results showed that both SLN formulations were able to entrap the essential oil in high yields and that the mean particle size increased only slightly after two years of storage, indicating a high physical stability. In vitro antiviral assays showed that SLN incorporation did not affect the essential oil antiherpetic activity. The in vitro skin permeation experiments demonstrated the capability of SLN of greatly improving the oil accumulation into the skin, while oil permeation occurred only when the oil was delivered from the control solution.