Maria Manconi

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.

Penetration enhancer-containing vesicles (PEVs) as carriers for cutaneous delivery of minoxidil

The aim of this work was to evaluate the ability of a few different penetration enhancers to produce elastic vesicles with soy lecithin and the influence of the obtained vesicles on in vitro (trans)dermal delivery of minoxidil. To this purpose, so-called Penetration Enhancer-containing Vesicles (PEVs) were prepared as dehydrated-rehydrated vesicles by using soy lecithin and different amounts of three penetration enhancers, 2-(2-ethoxyethoxy)ethanol (Transcutol), capryl-caproyl macrogol 8-glyceride (Labrasol), and cineole. Soy lecithin liposomes, without penetration enhancers, were used as control. Prepared formulations were characterized in terms of size distribution, morphology, zeta potential, and vesicle deformability. The influence of PEVs on (trans)dermal delivery of minoxidil was studied by in vitro diffusion experiments through newborn pig skin in comparison with traditional liposomes and ethanolic solutions of the drug also containing each penetration enhancer. A skin pre-treatment study using empty PEVs and conventional liposomes was also carried out. Results showed that all the used penetration enhancers were able to give more deformable vesicles than conventional liposomes with a good drug entrapment efficiency and stability. In vitro skin penetration data showed that PEVs were able to give a statistically significant improvement of minoxidil deposition in the skin in comparison with classic liposomes and penetration enhancer-containing drug ethanolic solutions without any transdermal delivery. Moreover, the most deformable PEVs, prepared with Labrasol and cineole, were also able to deliver to the skin a higher total amount of minoxidil than the PE alcoholic solutions thus suggesting that minoxidil delivery to the skin was strictly correlated to vesicle deformability, and therefore to vesicle composition.

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.

Nanocarriers for antioxidant resveratrol: formulation approach, vesicle self-assembly and stability evaluation.

In this work we studied various nanoformulations of resveratrol in phospholipid vesicles. Conventional phophatidylcholine liposomes were prepared and characterized in parallel with PEVs (Penetration Enhancer-containing Vesicles) obtained by adding one of eight selected amphiphilic penetration enhancers (PEs; 0.2% w/v; HLB range 1-16) to the composition. All vesicles were around 100 nm, negatively charged (∼-30 mV) and able to incorporate resveratrol in good yields (>74%). The structure and the lamellar self-organization of the vesicles were investigated by Transmission Electron Microscopy (TEM) and Small and Wide Angle X-ray Scattering (SWAXS). These analyses showed that the lamellarity of the vesicles depended on the formulation composition. This work also addressed the stability of our colloidal dispersions, which was measured by means of the analytical centrifuge LUMiSizer(®): this procedure disclosed the absence of any demixing phenomena and estimated a 3- to 6-month shelf-life. Moreover, the antioxidant activity of resveratrol was determined by assessing its ability to scavenge free radicals (DPPH assay), and showed that it was not affected by the vesicular formulation.

Fabrication of quercetin and curcumin bionanovesicles for the prevention and rapid regeneration of full-thickness skin defects on mice

In the present work biocompatible quercetin and curcumin nanovesicles were developed as a novel approach to prevent and restore skin tissue defects on chronic cutaneous pathologies. Stable and suitable quercetin- and curcumin-loaded phospholipid vesicles, namely liposomes and penetration enhancer-containing vesicles (PEVs), were prepared. Vesicles were made from a highly biocompatible mixture of phospholipids and alternatively a natural polyphenol, quercetin or curcumin. Liposomes were obtained by adding water, while PEVs by adding polyethylene glycol 400 and Oramix®CG110 to the water phase. Transmission electron microscopy, cryogenic-transmission electron microscopy and small- and wide-angle X-ray scattering showed that vesicles were spherical, oligo- or multilamellar and small in size (112-220 nm). In vitro and in vivo tests underlined a good effectiveness of quercetin and curcumin nanovesicles in counteracting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) induced lesions and inflammation. Myeloperoxydase activity, used to gauge inflammation, was markedly inhibited by quercetin liposomes (59%) and curcumin liposomes and polyethylene glycol (PEG)-PEVs (∼ 68%). Histology showed that PEG-PEVs provided an extensive re-epithelization of the TPA-damaged skin, with multiple layers of thick epidermis. In conclusion, nanoentrapped polyphenols prevented the formation of skin lesions abrogating the various biochemical processes that cause epithelial loss and skin damage.

Glycerosomes: A new tool for effective dermal and transdermal drug delivery

This work describes glycerosomes, vesicles composed of phospholipids, glycerol, and water, as novel vesicular carriers for (trans)dermal drug delivery. In this work, glycerosomes were prepared by hydrating dipalmitoylglycerophosphatidylcholine-cholesterol films with glycerol aqueous solutions (10-30%, v/v). The model drug was diclofenac sodium salt and conventional liposomes were used as control. Prepared formulations were characterized in terms of size distribution, morphology, zeta potential, and vesicle deformability. Glycerosomes and liposomes were oligo/multilamellar vesicles, spherical in shape with a mean diameter ranging between 81 and 97 nm and a fairly narrow distribution (P.I.=0.14-0.19), negative zeta potential values (from -35 to -48) and drug loading capacity between 64 and 73%. Deformability index of both conventional liposomes and glycerosomes showed that glycerol is able to act as edge activator for dipalmitoylglycerophosphatidylcholine bilayers when used in concentration higher than 10%. DSC studies suggested that glycerosomes are in a more fluid state than conventional liposomes. In vitro transdermal delivery experiments showed an improved skin deposition and permeation of diclofenac when 20 and 30% glycerosomes were used. MTT test demonstrated that glycerosomes were able to reduce the in vitro drug toxicity versus keratinocytes.

Chitosomes as drug delivery systems for C-phycocyanin: Preparation and characterization

The aim of this work was to investigate chitosomes, i.e. liposomes coated by a polyelectrolyte complex between chitosan (CH) and xantan gum (XG), as potential delivery system for oral administration of the protein C-phycocyanin. To this purpose several CH-XG-microcomplexes were prepared in aqueous lactic acid at different chitosan-xanthan gum percent ratios and rheological properties of the microcomplexes were studied to analyse the contribution of chitosan and xanthan gum in the reaction of microcomplexation. After establishing the best microcomplexes, chitosomes were prepared by coating C-phycocyanin loaded liposomes with the CH-XG hydrogels using spray-drying or freeze-drying. The chitosomes were characterized in terms of morphology, size distribution, zeta potential, swelling properties, drug release, and mucoadhesive properties. Rheological studies showed the influence of xanthan gum in the microcomplex properties. Moreover, obtained results demonstrated the effects of formulation and process variables on particle size, drug content, swelling, drug release, and especially on the mucoadhesiveness of C-PC chitosomes of CH-XG. In particular, chitosomes prepared by spray-drying technique using CH-XG in 0.5/8.0 (w/w) ratio showed a regular surface and a drug release characteristic for a Fickian diffusion of the active ingredient. The in vitro mucoadhesive study revealed that the spray-drying method is advantageous to prepare C-phycocyanin loaded chitosomes with excellent mucoadhesive properties for colonic drug delivery.

Nanodesign of olein vesicles for the topical delivery of the antioxidant resveratrol

The ex‐vivo percutaneous absorption of the natural antioxidant resveratrol in liposomes and niosomes was investigated. The influence of vesicle composition on their physicochemical properties and stability was evaluated. Liposomes containing resveratrol were formulated using soy phosphatidylcholine (Phospholipon90G). Innovative niosomes were formulated using mono‐ or diglycerides: glycerol monooleate (Peceol) and polyglyceryl‐3 dioleate (Plurol OleiqueCC), respectively, two suitable skin‐compatible oleins used in pharmaceutical formulations as penetration enhancers.

Inhibition of skin inflammation in mice by diclofenac in vesicular carriers: liposomes, ethosomes and PEVs.

Diclofenac-loaded phospholipid vesicles, namely conventional liposomes, ethosomes and PEVs (penetration enhancer-containing vesicles) were developed and their efficacy in TPA (phorbol ester) induced skin inflammation was examined. Vesicles were made from a cheap and unpurified mixture of phospholipids and diclofenac sodium; Transcutol P and propylene glycol were added to obtain PEVs, and ethanol to produce ethosomes. The structure and lamellar organization of the vesicle bilayer were investigated by transmission electron microscopy and small and wide angle X-ray scattering, as well as the main physico-chemical features. The formulations, along with a diclofenac solution and commercial Voltaren Emulgel, were tested in a comparative trial for anti-inflammatory efficacy on TPA-treated mice dorsal skin. Vesicles were around 100 nm, negatively charged, able to encapsulate diclofenac in good yields, and disclosed different lamellarity, as a function of the formulation composition. Vesicular formulations promoted drug accumulation and reduced the permeation. Administration of vesicular diclofenac on TPA-inflamed skin resulted in marked attenuation of oedema and leucocyte infiltration, especially using PEVs. Histology confirmed the effectiveness of vesicles, since they provided an amelioration of the tissual damage induced by TPA. The proposed approach based on vesicular nanocarriers may hold promising therapeutic value for treating a variety of inflammatory skin disorders.