Characterization Methods for Nanoparticle-Skin Interactions: An Overview.

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.

Microfluidic Fabricated Liposomes for Nutlin-3a Ocular Delivery as Potential Candidate for Proliferative Vitreoretinal Diseases Treatment.

Purpose: Proliferative vitreoretinal diseases (PVDs) represent a heterogeneous group of pathologies characterized by the presence of retinal proliferative membranes, in whose development retinal pigment epithelium (RPE) is deeply involved. As the only effective treatment for PVDs at present is surgery, we aimed to investigate the potential therapeutic activity of Nutlin-3a, a small non-genotoxic inhibitor of the MDM2/p53 interaction, on ARPE-19 cell line and on human RPE primary cells, as in vitro models of RPE and, more importantly, to formulate and evaluate Nutlin-3a loaded liposomes designed for ophthalmic administration. Methods: Liposomes were produced using an innovative approach by a microfluidic device under selection of different conditions. Liposome size distribution was evaluated by photon correlation spectroscopy and centrifugal field flow fractionation, while the liposome structure was studied by transmission electron microscopy and Fourier-transform infrared spectroscopy. The Nutlin-3a entrapment capacity was evaluated by ultrafiltration and HPLC. Nutlin-3a biological effectiveness as a solution or loaded in liposomes was evaluated by viability, proliferation, apoptosis and migration assays and by morphological analysis. Results: The microfluidic formulative study enabled the selection of liposomes composed of phosphatidylcholine (PC) 5.4 or 8.2 mg/mL and 10% ethanol, characterized by roundish vesicular structures with 150-250 nm mean diameters. Particularly, liposomes based on the lower PC concentration were characterized by higher stability. Nutlin-3a was effectively encapsulated in liposomes and was able to induce a significant reduction of viability and migration in RPE cell models. Conclusion: Our results lay the basis for a possible use of liposomes for the ocular delivery of Nutlin-3a.

Ethosomes for Curcumin and Piperine Cutaneous Delivery to Prevent Environmental-Stressor-Induced Skin Damage.

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.

Calcitermin-Loaded Smart Gels Activity against Candida albicans: A Preliminary In Vitro Study.

Calcitermin is an antimicrobial peptide of 15 amino acids found in human nasal fluid characterized by antifungal and antibacterial properties. Candida albicans is the most common human fungal pathogen affecting many tissues, such as vaginal mucosa. In this study a formulation suitable for calcitermin administration on vaginal mucosa was developed for the treatment of fungal infections. To favor topical application, mucosal adhesion, and permanence, gels based on poloxamer 407 and xanthan gum were designed and compared with regard to their rheological behavior, erosion, and leakage. The selected gel was loaded with calcitermin, whose release kinetic was evaluated in vitro by Franz cells. An antifungal activity assay was conducted to assess the calcitermin anticandidal potential and the effect of its inclusion in the selected gel. The rheological study revealed the elastic and viscous moduli behavior as a function of poloxamer 407 and xanthan gum concentration. Xanthan gum presence decreased the transition temperature of the gel, while prolonging its erosion and leakage. Particularly, poloxamer 407, 18% and xanthan gum 0.4% were chosen. The calcitermin loading in the selected gel resulted in a transparent and homogeneous formulation and in a 4-fold decrease of the release rate with respect to the calcitermin solution, as evidenced by Franz cell study. The anticandidal activity tests demonstrated that calcitermin-loaded gel was more active against Candida albicans with respect to the peptide solution.

Ethosomal Gel for Topical Administration of Dimethyl Fumarate in the Treatment of HSV-1 Infections.

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.

Dimethyl Fumarate-Loaded Transethosomes: A Formulative Study and Preliminary Ex Vivo and In Vivo Evaluation.

In this study, transethosomes were investigated as potential delivery systems for dimethyl fumarate. A formulative study was performed investigating the effect of the composition of transethosomes on the morphology and size of vesicles, as well as drug entrapment capacity, using cryogenic transmission electron microscopy, photon correlation spectroscopy, and HPLC. The stability of vesicles was evaluated, both for size increase and capability to control the drug degradation. Drug release kinetics and permeability profiles were evaluated in vitro using Franz cells, associated with different synthetic membranes. The in vitro viability, as well as the capacity to improve wound healing, were evaluated in human keratinocytes. Transmission electron microscopy enabled the evaluation of transethosome uptake and intracellular fate. Based on the obtained results, a transethosome gel was further formulated for the cutaneous application of dimethyl fumarate, the safety of which was evaluated in vivo with a patch test. It was found that the phosphatidylcholine concentration affected vesicle size and lamellarity, influencing the capacity to control dimethyl fumarate's chemical stability and release kinetics. Indeed, phosphatidylcholine 2.7% w/w led to multivesicular vesicles with 344 nm mean size, controlling the drug's chemical stability for at least 90 days. Conversely, phosphatidylcholine 0.9% w/w resulted in 130 nm sized unilamellar vesicles, which maintained 55% of the drug over 3 months. These latest kinds of transethosomes were able to improve wound healing in vitro and were easily internalised by keratinocytes. The selected transethosome gel, loading 25 mg/mL dimethyl fumarate, was not irritant after cutaneous application under occlusion, suggesting its possible suitability in the treatment of wounds caused by diabetes mellitus or peripheral vascular diseases.

Synthetic and Nanotechnological Approaches for a Diagnostic Use of Manganese.

The development of multimodal imaging techniques such as positron emission tomography (PET) and magnetic resonance imaging (MRI) allows the contemporary obtaining of metabolic and morphological information. To fully exploit the complementarity of the two imaging modalities, the design of probes displaying radioactive and magnetic properties at the same time could be very beneficial. In this regard, transition metals offer appealing options, with manganese representing an ideal candidate. As nanosized imaging probes have demonstrated great value for designing advanced diagnostic/theranostic procedures, this work focuses on the potential of liposomal formulations loaded with a new synthesized paramagnetic Mn(II) chelates. Negatively charged liposomes were produced by thin-layer hydration method and extrusion. The obtained formulations were characterized in terms of size, surface charge, efficiency of encapsulation, stability over time, relaxivity, effective magnetic moment, and in vitro antiproliferative effect on human cells by means of the MTT assay. The negatively charged paramagnetic liposomes were monodisperse, with an average hydrodynamic diameter not exceeding 200 nm, and they displayed good stability and no cytotoxicity. As determined by optical emission spectroscopy, manganese complexes are loaded almost completely on liposomes maintaining their paramagnetic properties.

Manganese in Diagnostics: A Preformulatory Study.

This investigation aims to find lipid-based nanosystems to be used as tools to deliver manganese for diagnostic purposes in multimodal imaging techniques. In particular, the study describes the production and characterization of aqueous dispersions of anionic liposomes as delivery systems for two model manganese-based compounds, namely manganese chloride and manganese acetylacetonate. Negatively charged liposomes were obtained using four different anionic surfactants, namely sodium docusate (SD), N-lauroylsarcosine (NLS), Protelan AG8 (PAG) and sodium lauroyl lactylate (SLL). Liposomes were produced by the direct hydration method followed by extrusion and characterized in terms of size, polydispersity, surface charge and stability over time. After extrusion, liposomes are homogeneous and monodispersed with an average diameter not exceeding 200 nm and a negative surface charge as confirmed by ζ potential measurement. Moreover, as indicated by atomic absorption spectroscopy analyses, the loading of manganese-based compounds was almost quantitative. Liposomes containing NLS or SLL were the most stable over time and the presence of manganese-based compounds did not affect their size distribution. Liposomes containing PAG and SD were instable and therefore discarded. The in vitro cytotoxicity of the selected anionic liposomes was evaluated by MTT assay on human keratinocyte. The obtained results highlighted that the toxicity of the formulations is dose dependent.