Research progresses have led to the development of different kinds of nanoplatforms to deliver drugs through different biological membranes. Particularly, nanocarriers represent a precious means to treat skin pathologies, due to their capability to solubilize lipophilic and hydrophilic drugs, to control their release, and to promote their permeation through the stratum corneum barrier. A crucial point in the development of nano-delivery systems relies on their characterization, as well as in the assessment of their interaction with tissues, in order to predict their fate under in vivo administration. The size of nanoparticles, their shape, and the type of matrix can influence their biodistribution inside the skin strata and their cellular uptake. In this respect, an overview of some characterization methods employed to investigate nanoparticles intended for topical administration is presented here, namely dynamic light scattering, zeta potential, scanning and transmission electron microscopy, X-ray diffraction, atomic force microscopy, Fourier transform infrared and Raman spectroscopy. In addition, the main fluorescence methods employed to detect the in vitro nanoparticles interaction with skin cell lines, such as fluorescence-activated cell sorting or confocal imaging, are described, considering different examples of applications. Finally, recent studies on the techniques employed to determine the nanoparticle presence in the skin by ex vivo and in vivo models are reported.

Diesel particulate matter is one of the most dangerous environmental stressors affecting human health. Many plant-derived compounds with antioxidant and anti-inflammatory properties have been proposed to protect the skin from pollution damage. Curcumin (CUR) has a plethora of pharmacological activities, including anticancer, antimicrobial, anti-inflammatory and antioxidant. However, it has low bioavailability due to its difficult absorption and rapid metabolism and elimination. CUR encapsulation in nanotechnological systems and its combination with biopotentiators such as piperine (PIP) can improve its pharmacokinetics, stability and activity. In this study, ethosomes (ETs) were investigated for CUR and PIP delivery to protect the skin from damage induced by diesel particulate matter. ETs were produced by different strategies and characterized for their size distribution by photon correlation spectroscopy, for their morphology by transmission electron microscopy, and for their drug encapsulation efficiency by high-performance liquid chromatography. Franz cells enabled us to evaluate in vitro the drug diffusion from ETs. The results highlighted that ETs can promote the skin permeation of curcumin. The studies carried out on their antioxidant activity demonstrated an increase in the antioxidant power of CUR using a combination of CUR and PIP separately loaded in ETs, suggesting their possible application for the prevention of skin damage due to exogenous stressors. Ex vivo studies on human skin explants have shown the suitability of drug-loaded ETs to prevent the structural damage to the skin induced by diesel engine exhaust exposure.

The infections caused by the HSV-1 virus induce lesions on the lips, mouth, face, and eye. In this study, an ethosome gel loaded with dimethyl fumarate was investigated as a possible approach to treat HSV-1 infections. A formulative study was conducted, evaluating the effect of drug concentration on size distribution and dimensional stability of ethosomes by photon correlation spectroscopy. Ethosome morphology was investigated by cryogenic transmission electron microscopy, while the interaction between dimethyl fumarate and vesicles, and the drug entrapment capacity were respectively evaluated by FTIR and HPLC. To favor the topical application of ethosomes on mucosa and skin, different semisolid forms, based on xanthan gum or poloxamer 407, were designed and compared for spreadability and leakage. Dimethyl fumarate release and diffusion kinetics were evaluated in vitro by Franz cells. The antiviral activity against HSV-1 was tested by plaque reduction assay in Vero and HRPE monolayer cells, while skin irritation effect was evaluated by patch test on 20 healthy volunteers. The lower drug concentration was selected, resulting in smaller and longer stable vesicles, mainly characterized by a multilamellar organization. Dimethyl fumarate entrapment in ethosome was 91% w/w, suggesting an almost total recovery of the drug in the lipid phase. Xanthan gum 0.5%, selected to thicken the ethosome dispersion, allowed to control drug release and diffusion. The antiviral effect of dimethyl fumarate loaded in ethosome gel was demonstrated by a reduction in viral growth both 1 h and 4 h post-infection. Moreover, the patch test demonstrated the safety of the ethosomal gel applied on the skin.

This study evaluated ethosomes as a novel nanodelivery system for nutlin-3a, a known MDM2 inhibitor and activator of the p53 pathway, to improve nutlin-3a’s poor solubility, limiting its bio-distribution and therapeutic efficacy. The potential of nutlin-3a-loaded ethosomes was investigated on two in vitro models of melanoma: the HT144 cell line p53^wild-type and the SK-MEL-28 cell line p53^mutated. Nutlin-3a-loaded ethosomes were characterized for their physicochemical properties and used to treat melanoma cells at different concentrations, considering nutlin-3a solution and empty ethosomes as controls. The biological effects on cells were evaluated 24 and 48 h after treatment by analyzing the cell morphology and viability, cell cycle, and apoptosis rate using flow cytometry and the p53 pathway’s activation via Western blotting. The results indicate that ethosomes are delivery systems able to maintain nutlin-3a’s functionality and specific biological action, as evidenced by the molecular activation of the p53 pathway and the biological events leading to cell cycle block and apoptosis in p53^wild-type cells. Nutlin-3a-loaded ethosomes induced morphological changes in the HT144 cell line, with evident apoptotic cells and a reduction in the number of viable cells of over 80%. Furthermore, nutlin-3a-loaded ethosomes successfully modulated two p53-regulated proteins involved in survival/apoptosis, with up to a 2.5-fold increase in membrane TRAIL-R2 and up to an 8.2-fold decrease in Notch-1 (Notch intracellular domain, NICD) protein expression. The expression of these molecules is known to be altered or dysfunctional in a large percentage of melanoma tumors. Notably, ethosomes, regardless of their nutlin-3a loading, exhibited the ability to reduce HT144 melanoma cellular migration, as assessed in real time using xCELLigence, likely due to the modification of lipid rafts, suggesting their potential antimetastatic properties. Overall, nutlin-3a delivery using ethosomes appears to be a significantly effective means for upregulating the p53 pathway and downregulating active Notch-1, while also taking advantage of their unexpected ability to reduce cellular migration. The findings of this study could pave the way for the development of specific nutlin-3a-loaded ethosome-based medicinal products for cutaneous use.

A preformulative study was conducted to produce and characterize ethosomes for the transdermal delivery of gossypin. This plant-derived compound possesses many pharmacological properties, including antitumoral potential. Ethosome dispersions were designed as transdermal delivery systems for gossypin, employing two different production procedures. The evaluation of vesicle size distribution by photon correlation spectroscopy, morphology by cryogenic transmission electron microscopy, and gossypin entrapment capacity, as well as in vitro release and permeation by vertical diffusion cells, enabled us to select a production strategy based on the injection of a phosphatidylcholine ethanolic solution in water. Indeed, vesicles prepared by this method were almost unilamellar and measured roughly 150 nm mean diameter while displaying an entrapment capacity higher than 94%. Moreover, vesicles prepared by the ethanol injection method enabled us to control gossypin release and to improve its permeation with respect to the solution of the drug. To obtain semi-solid forms suitable for cutaneous gossypin administration, ethosome dispersions were thickened with 0.5% w/w xanthan gum, selected by a spreadability test. These ethosome gels were then further characterized by small- and wide-angle X-ray scattering, while their antioxidant activity was demonstrated in vitro by a radical scavenging assay. Finally, in vitro biological studies were conducted on A375 melanoma cell lines. Namely, wound healing and cell migration assays confirmed the potential antitumoral effect of gossypin, especially when loaded in the selected ethosomal gel. The promising results suggest further investigation of the potential of gossypin-loaded ethosomal gel in the treatment of melanoma.

In this study, bile acid-based vesicles and nanoparticles (i.e., bilosomes and biloparticles) are studied to improve the water solubility of lipophilic drugs. Ursodeoxycholic acid, sodium cholate, sodium taurocholate and budesonide were used as bile acids and model drugs, respectively. Bilosomes and biloparticles were prepared following standard protocols with minor changes, after a preformulation study. The obtained systems showed good encapsulation efficiency and dimensional stability. Particularly, for biloparticles, the increase in encapsulation efficiency followed the order ursodeoxycholic acid < sodium cholate < sodium taurocholate. The in vitro release of budesonide from both bilosytems was performed by means of dialysis using either a nylon membrane or a portion of Wistar rat small intestine and two receiving solutions (i.e., simulated gastric and intestinal fluids). Both in gastric and intestinal fluid, budesonide was released from bilosystems more slowly than the reference solution, while biloparticles showed a significant improvement in the passage of budesonide into aqueous solution. Immunofluorescence experiments indicated that ursodeoxycholic acid bilosomes containing budesonide are effective in reducing the inflammatory response induced by glucose oxidase stimuli and counteract ox-inflammatory damage within intestinal cells.