Studies on the skin penetration mechanisms of liposomal formulations

Liposomes have also been shown to enhance the penetration of a variety of drugs in the skin. When drug substances are applied on the skin in solution form, drug penetration mainly depends on the physicochemical properties of the drug however, incorporation of drugs in the liposomes results in a rather complex interaction between the stratum corneum, phospholipid membrane and drug. Studies in this thesis were designed to probe the interactions between the stratum corneum and invasomes in order to gain a better understanding of the mechanisms involved in the drug delivery to skin from invasomes. Confocal Raman microscopy was employed to study the co-diffusion of liposomally entrapped drugs and the phospholipids forming the liposomal bilayers. The study was based on a premise that if diffusion patterns of both, drug and phospholipid could be studied in the skin then it might allow us to comment on the underlying mechanism responsible for penetration of drug as each mechanism should give rise to a different diffusion profile. A method was developed to obtain non-invasive Raman depth profiles in ex vivo human skin. Optical biopsies of untreated skin were measured along with diffusion profiles of skin treated with beta-carotene and deuterated water. Tip-enhanced Raman scattering (TERS) was the tool of choice as TERS is not limited by the Abbe’s resolution limit and is an excellent tool for providing chemical and structural information. Conventional tape stripping technique was adopted to allow application of TERS. In vivo human skin was treated with deuterated invasomes and the stratum corneum was progressively removed. TERS and atomic force microscopy measurements revealed that intact invasome vesicles did penetrate the stratum corneum. For the first time spectroscopic evidence along with high resolution imaging confirmed that intact liposomes can penetrate the human stratum corneum

Comparing the delivery to the hair bulb of two fluorescent molecules of distinct hydrophilicities by different nanoparticles and a serum formulation

The follicular route is an important drug penetration pathway in any topical application, either concerning dermatological and cosmetic skin treatments or any transdermal administration regimen. Efficient transport into follicles will depend on drug inherent properties but also on the chosen vehicle. The main study goal was to compare several systems for the delivery to the hair bulb of two fluorescent molecules of different water affinities: the hydrophobic Nile Red and the quite similar but hydrophilic Nile Blue. Three common nanoparticle types were compared in terms of encapsulation efficiency and stability: liposomes, ethosomes and polymeric nanoparticles. A liquid serum-like formulation was also developed, adjusting the final ethanol amount to the type of dye to be solubilized. Then, this formulation and the nanoparticle systems that successfully passed characterization and stability stages were further studied on their ability to reach the bulb. The serum formulation was able to deliver, both drug models, to deeper follicular regions than nanoparticles. Attending to the envisioned zone target of the follicle, the simplest approach proved to be the best choice from all the systems tested in this work. Nonetheless, nanocarriers and the inherent complexity of their manufacturing processes may be justified under very specific requirements.The author Cristiana Costa would like to acknowledge his PhD scholarship funded by Portuguese Foundation for Science and Technology (FCT) (SFRH/BD/139522/2018). The author Bruno Fernandes would like to acknowledge his PhD scholarship funded by FCT (SFRH/BD/131824/2017). The author Diana Guimarães would like to acknowledge his PhD scholarship funded by FCT (SFRH/BD/140321/2018). This study was supported by the FCT under the scope of BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 – Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Stimulating brain recovery after stroke using theranostic albumin nanocarriers loaded with nerve growth factor in combination therapy

For many years, delivering drug molecules across the blood brain barrier has been a major challenge. The neuropeptide nerve growth factor is involved in the regulation of growth and differentiation of cholinergic neurons and holds great potential in the treatment of stroke. However, as with many other compounds, the biomolecule is not able to enter the central nervous system. In the present study, nerve growth factor and ultrasmall particles of iron oxide were co-encapsulated into a chemically crosslinked albumin nanocarrier matrix which was modified on the surface with apolipoprotein E. These biodegradable nanoparticles with a size of 212 ± 1 nm exhibited monodisperse size distribution and low toxicity. They delivered NGF through an artificial blood brain barrier and were able to induce neurite outgrowth in PC12 cells in vitro. In an animal model of stroke, the infarct size was significantly reduced compared to the vehicle control. The combination therapy of NGF and the small-molecular MEK inhibitor U0126 showed a slight but not significant difference compared to U0126 alone. However, further in vivo evidence suggests that successful delivery of the neuropeptide is possible as well as the synergism between those two treatments

Evaluation of skin absorption of drugs from topical and transdermal formulations

ABSTRACT The skin barrier function has been attributed to the stratum corneum and represents a major challenge in clinical practice pertaining to cutaneous administration of drugs. Despite this, a large number of bioactive compounds have been successfully administered via cutaneous administration because of advances in the design of topical and transdermal formulations. In vitro and in vivo evaluations of these novel drug delivery systems are necessary to characterize their quality and efficacy. This review covers the most well-known methods for assessing the cutaneous absorption of drugs as an auxiliary tool for pharmaceutical formulation scientists in the design of drug delivery systems. In vitro methods as skin permeation assays using Franz-type diffusion cells, cutaneous retention and tape-stripping methods to study the cutaneous penetration of drugs, and in vivo evaluations as pre-clinical pharmacokinetic studies in animal models are discussed. Alternative approaches to cutaneous microdialysis are also covered. Recent advances in research on skin absorption of drugs and the effect of skin absorption enhancers, as investigated using confocal laser scanning microscopy, Raman confocal microscopy, and attenuated total reflectance Fourier-transform infrared spectroscopy, are reviewed

Transdermal delivery from liposomal formulations - evolution of the technology over the last three decades

Strong barrier properties of stratum corneum often limits the efficiency of drug delivery through skin. Several strategies were tried to improve permeation of drug through skin for local as well as systemic drug delivery. Incorporation of the drug within flexible liposomal vesicles has been one of the popular and well-studied approaches for delivering drug to deeper layers of the skin or even systemic circulation. Flexible/deformable/elastic liposomal systems such as invasomes, Transfersomes®, ethosomes, niosomes, etc. have demonstrated encouraging results in delivering small molecules and large proteins to the skin. It is necessary to recognize the promising concepts and analyze their potential, since a clear understanding of the drawbacks and advantages of these approaches will lead towards future development. In the current review we have attempted to give an overview of different liposomal drug carriers for transdermal drug delivery and their efficiency as drug delivery system through different in vivo and in vitro studies. Also, an overview of the studies which investigated the interactions between skin and vesicles, which have lead us to our current understanding of the skin penetration mechanisms of liposomal formulations is presented

Nanomaterials - Tiny particles and big challenges

After decades of research, nanotechnology has been used in a broad array of biomedical products including medical devices, drug products, drug substances, and pharmaceutical-grade excipients. But like many great achievements in science, there is a fine balance between the risks and opportunities of this new technology. Some materials and surface structures in the nanosize range can exert unexpected toxicities and merit a more detailed safety assessment. Regulatory agencies such as the United States Food and Drug Administration or the European Medicines Agency have started dealing with the potential risks posed by nanomaterials. Considering that a thorough characterization is one of the key aspects of controlling such risks this review presents the regulatory background of nanosafety assessment and provides some practical advice on how to characterize nanomaterials and drug formulations. Further, the challenges of how to maintain and monitor pharmaceutical quality through a highly complex production processes will be discussed.JRC.F.2-Consumer Products Safet

Stability of Biorelevant Media Under Various Storage Conditions

The physical and chemical stability of various biorelevant media (FaSSGF, FaSSIF V1, FaSSIF V2, FaSSIF V3, and FeSSIF) were investigated over periods after preparation of up to 120 h at room temperature (RT) (22 degrees C) and 37 degrees C. It was shown that biorelevant instant powders are not a source of microbiological contamination. It was also established that the physical characteristics of FaSSGF and FeSSIF are invariant with time, so they can be used immediately after preparation, i.e., without any equilibration time. Alternatively, they can be stored for up to 96 h at RT before use. By contrast, FaSSIF V1 requires an equilibration time of 2 h, and FaSSIF V2 requires an equilibration time of 24 h to enable the media characteristics to stabilize. After this equilibration time, both FaSSIF V1 and V2 can also be stored for at least up to 96 h at RT prior to use; longer storage times have not yet been tested. The particle size of FaSSIF V3 appears to continually evolve over time. For FaSSIF V3, it is thus recommended that the waiting period between preparation and use be standardized among experiments. Additionally, the colloidal particle structures present in the various FaSSIF versions were analyzed by cryogenic transmission electron microscopy (Cryo-TEM). Various kinds of micelles (globular, disc, multilayer disc, and thread-like micelles) were observed in all samples, and some samples also contained unilamellar vesicles. Differences in solubility of drugs among the various FaSSIF versions can be partly explained by the results from Cryo-TEM

Nanomedicines - Tiny particles and big challenges

After decades of research, nanotechnology has been used in a broad array of biomedical products including medical devices, drug products, drug substances, and pharmaceutical-grade excipients. But like many great achievements in science, there is a fine balance between the risks and opportunities of this new technology. Some materials and surface structures in the nanosize range can exert unexpected toxicities and merit a more detailed safety assessment. Regulatory agencies such as the United States Food and Drug Administration or the European Medicines Agency have started dealing with the potential risks posed by nanomaterials. Considering that a thorough characterization is one of the key aspects of controlling such risks this review presents the regulatory background of nanosafety assessment and provides some practical advice on how to characterize nanomaterials and drug formulations. Further, the challenges of how to maintain and monitor pharmaceutical quality through a highly complex production processes will be discussed