In vitrohuman topical bioactive drug transdermal absorption: estradiol

A novel concept of overcoming the skin barrier using augmented liquid nanocrystals: Box-Behnken optimization, ex vivo and in vivo evaluation

Agomelatine suffers from extensive inactivation through 1^st pass effect with a limited oral bioavailability (5%). The aim of this study was to formulate and optimize liquid nanocrystals (LNC) containing agomelatine to enhance the transdermal permeation of the drug. The independent factors of the employed Box-Behnken design were the Pluronic F127, deoxycholic acid sodium salt and propylene glycol percentages. On the other hand, particle size, polydispersity index, zeta potential, entrapment efficiency, cumulative amount permeated at certain time intervals and permeation enhancement ratio were considered as dependent responses. The optimized formulation was composed of 1.5% Pluronic F127 and 1.5% deoxycholic acid sodium salt and it was found to have significantly higher AUC_0-24h, AUC_0-∞ and elimination t_1/2 than that of the employed reference indicating the enhancement of the drug permeation. The obtained findings indicated the ability of the optimized LNC formulation to improve the drug bioavailability after its transdermal application.

Transdermal agomelatine microemulsion gel: pyramidal screening, statistical optimization and in vivo bioavailability

Agomelatine is a new antidepressant having very low oral drug bioavailability less than 5% due to being liable to extensive hepatic 1st pass effect. This study aimed to deliver agomelatine by transdermal route through formulation and optimization of microemulsion gel. Pyramidal screening was performed to select the most suitable ingredients combinations and then, the design expert software was utilized to optimize the microemulsion formulations. The independent variables of the employed mixture design were the percentages of capryol 90 as an oily phase (X1), Cremophor RH40 and Transcutol HP in a ratio of (1:2) as surfactant/cosurfactant mixture 'Smix' (X2) and water (X3). The dependent variables were globule size, optical clarity, cumulative amount permeated after 1 and 24 h, respectively (Q1 and Q24) and enhancement ratio (ER). The optimized formula was composed of 5% oil, 45% Smix and 50% water. The optimized microemulsion formula was converted into carbopol-based gel to improve its retention on the skin. It enhanced the drug permeation through rat skin with an enhancement ratio of 37.30 when compared to the drug hydrogel. The optimum ME gel formula was found to have significantly higher Cmax, AUC 0-24 h and AUC0-∞ than that of the reference agomelatine hydrogel and oral solution. This could reveal the prosperity of the optimized microemulsion gel formula to augment the transdermal bioavailability of agomelatine.

Skin aging and oxidative stress: Equol's anti-aging effects via biochemical and molecular mechanisms

Oxygen in biology is essential for life. It comes at a cost during normal cellular function, where reactive oxygen species (ROS) are generated by oxidative metabolism. Human skin exposed to solar ultra-violet radiation (UVR) dramatically increases ROS production/oxidative stress. It is important to understand the characteristics of human skin and how chronological (intrinsic) aging and photo-aging (extrinsic aging) occur via the impact of ROS production by cascade signaling pathways. The goal is to oppose or neutralize ROS insults to maintain good dermal health. Botanicals, as active ingredients, represent one of the largest categories used in dermatology and cosmeceuticals to combat skin aging. An emerging botanical is equol, a polyphenolic/isoflavonoid molecule found in plants and food products and via gastrointestinal metabolism from precursor compounds. Introductory sections cover oxygen, free radicals (ROS), oxidative stress, antioxidants, human skin aging, cellular/molecular ROS events in skin, steroid enzymes/receptors/hormonal actions and genetic factors in aging skin. The main focus of this review covers the characteristics of equol (phytoestrogenic, antioxidant and enhancement of extracellular matrix properties) to reduce skin aging along with its anti-aging skin influences via reducing oxidative stress cascade events by a variety of biochemical/molecular actions and mechanisms to enhance human dermal health.

Diffusion profile of macromolecules within and between human skin layers for (trans)dermal drug delivery

Delivering a drug into and through the skin is of interest as the skin can act as an alternative drug administration route for oral delivery. The development of new delivery methods, such as microneedles, makes it possible to not only deliver small molecules into the skin, which are able to pass the outer layer of the skin in therapeutic amounts, but also macromolecules. To provide insight into the administration of these molecules into the skin, the aim of this study was to assess the transport of macromolecules within and between its various layers. The diffusion coefficients in the epidermis and several locations in the papillary and reticular dermis were determined for fluorescein dextran of 40 and 500 kDa using a combination of fluorescent recovery after photobleaching experiments and finite element analysis. The diffusion coefficient was significantly higher for 40 kDa than 500 kDa dextran, with median values of 23 and 9 µm(2)/s in the dermis, respectively. The values only marginally varied within and between papillary and reticular dermis. For the 40 kDa dextran, the diffusion coefficient in the epidermis was twice as low as in the dermis layers. The adopted method may be used for other macromolecules, which are of interest for dermal and transdermal drug delivery. The knowledge about diffusion in the skin is useful to optimize (trans)dermal drug delivery systems to target specific layers or cells in the human skin.

Protective effects of equol and their polyphenolic isomers against dermal aging: microarray/protein evidence with clinical implications and unique delivery into human skin

CONTEXT

Equol is a polyphenolic/isoflavonoid molecule that can be expressed as isomers. However, the characteristics of the equol isomers on dermal gene/protein expression and human skin percutaneous absorption remain unknown.

OBJECTIVE

Perform a comprehensive investigation on equol as: R-equol, racemic equol or S-equol to determine their differential expression of skin-related genes, quantify collagen expression and determine percutaneous absorption in human skin.

METHODS

Quantified: (i) gene expression/mRNA levels via gene array technology using human skin equivalents with equol exposure at 1.2% in qPCR experiments, (ii) in vitro collagen expression in human fibroblasts, and (iii) percutaneous absorption by Franz cell techniques.

RESULTS

In the qPCR studies, only three genes displayed the greatest significant expression by S-equol, whereas 16 genes displayed the greatest significant levels (either stimulation or inhibition) by R-equol and/or racemic equol, such as extracellular matrix proteins (i.e., collagen and elastin), nerve growth factor, aging genes [FOS, 100 A8 and A9 calcium-binding proteins, 5α-reductase type 1, and matrix metalloproteinases (1, 3, and 9)], and inflammatory genes (e.g., interleukin-1 alpha, interleukin-6, and cyclooxygenase-1). Collagen type I expression in fibroblasts was greater with racemic versus S-equol treatment at 1 and 10 nM. Percutaneous absorption demonstrated high sequestering in keratinocytes with subsequent accumulation/release over time.

DISCUSSION AND CONCLUSION

Overall, these results illustrate the significant differences in mirror-image molecules or isomers of equol where R-equol and/or racemic equol are better molecules for skin gene expression compared to S-equol and the percutaneous absorption of equol represents a unique epidermal reservoir delivery mechanism.