-mechanism of action . – Med. Inflam., vol.7, pp.183-193.
 Higuchi T. (1960): Physical chemical analysis of percutaneous absorption process from creams and ointments . – J. Soc. Cosmet. Chem., vol.11, pp.85-97.
 Higuchi T. (1961): Rate of release of medicaments from ointment basis containing drugs in suspension . – J. Pharm. Sci., vol.50, pp.874-875.
 Michaels A.S., Chandraskeran S.K. and Shaw J.E. (1975): Drug permeation through humanskin: theory and in vitro experimental measurement. – Amer. Inst. Chem. Eng., vol.21, No.5, pp.985
This paper focuses on a 4-memristor bridge circuit (similar to a Wheatstone bridge but based on transversal memristor models instead of resistors, see Fig. 1a ) that was used for synaptic weight programming in [ 15 ]. The same circuit was used for the generation of nth-order harmonics and frequency doubling in [ 16 ] and as full-wave rectifier in [ 17 ]. Here this circuit (in a two memristor configuration, see [ 17 ] and Fig. 1b ) is realized with humanskin (see Fig. 1c .) Humanskin exhibits non-linear electrical properties if the applied stimulus is
Ada Stelmakienė, Kristina Ramanauskienė and Vitalis Briedis
the humanskin in vitro, Evid. Based Compl. Altern. Med. (2013) Article ID 958717; DOI: 10.1155/2013/958717.
10. T. Kezutyte, T. Drevinskas, A. Maruska, R. Rimdeika and V. Briedis, Study of tolnaftate release from fatty acids containing ointment and penetration into humanskin ex vivo, Acta Pol. Pharm. 68 (2011) 965-973.
11. R.-K. Chang, A. Raw, R. Lionberger and L. Yu, Generic development of topical dermatologic products: Formulation development, process development, and testing of topical dermatologic products, AAPS J. 15 (2013) 41
Zorica Gajinov, Milan Matić, Sonja Prćić and Verica Đuran
1. Kollias N. The interaction of light with the skin. In: Wilhelm K, Elsner P, Berardesca E, Maibach H, editors, Bioengineering of the skin: skin imaging and analysis. 2nd ed. New York: Informa Healthcare; 2007. p. 222-8.
2. Anderson R, Parrish JA. The optics of humanskin. J Invest Dermatol 1981;77:13-9
3. Igarashi T, Nishino K, Nayar SK. The appearance of humanskin. Technical Report: CUCS-024-05 [cited 21.01.2011.] Available at http://citeseerx.ist.psu.edu/viewdoc/download?doi=10
the humanskin. – Int. J. of App. Mech. Eng., vol.23, No.4, pp.977-988.
 Mikari B.V. and Machadik K.R. (2010): Formulation and evaluation of typical liposomal gel for fluconozole . – Ind. J. Pharm Sci., vol.44, No.4, pp.324-325.
 Scheuplein R.J. (2013): A personal view of skin permeation . – Skin Pharm. Physiol., vol.26, No.1, pp.199-212.
 Siegel R.A. (1990): PH-sensitive gels: Swelling equilibria, kinetics and applications for drug delivery . – In: Pulsed and Self-Regulated Drug Delivery (Kost J. Ed.), CRC Press, New York, pp.129
. Der Marderosian, G. Hanson, T. Medwick, N. Popovich, R. Schnaare, J. Schwartz and H. White), Lippincott Williams & Wilkins, Baltimore 2000, pp. 836-848.
8. S. E. Belo, L. R. Gaspar, P. M. B. G. Maia Campos and J.-P. Marty, Skin penetration of epigallocathechin-3-gallate and quercetin from green tea and ginkgo biloba extracts vehiculated in cosmetic formulations, Skin Pharmacol. Physiol. 22 (2009) 299-304; DOI: 10.1159/000241299.
9. W. Wisuitiprot, A. Somsiri, K. Ingkaninan and N. Waranuch, In vitro humanskin penetration and cutaneous
Skin, separating the vital organs of a human body, is a desirable route for drug delivery. However, the intact skin is normally permeable only for drug molecules with a low molecular weight. The stratum corneum (SC), being the outermost layer of the skin and the epidermis being the second – more permeable – layer of the skin, play an essential function in transdermal drug delivery. Physical and chemical methods of skin poration are used to enhance transdermal drug delivery. Each poration leads to an irregular system of pores which are connected with a system of micro-capillaries passing through the epidermis. Both the systems by their irregularity form a fractal porous matrix. Drugs administrated by this matrix can be either suspensions and solutions or creams and gels, therefore they have to be modelled as non-Newtonian fluids.
To analyse the fluid flow through the porous matrix the model of the epidermis is assumed as gobbet-andmortar with the tortuous mortar of variable thickness and after transition from the mortar to the tube one considered classical and fractal capillary flows of selected non-Newtonian fluids.
Fractal expressions for the flow rate, velocity and permeability of fluids flow in a porous matrix are derived based on the fractal properties of the epidermis and capillary model. Each parameter in the proposed expressions does not contain any empirical constant and has a clear physical meaning and the proposed fractal models relate the flow properties of considered fluids with the structural parameters of the epidermis as a porous medium. The presented analytical expressions will help understand some of the physical principles of transdermal drug delivery.
B. Tsai, H. Xue, E. Birgersson, S. Ollmar and U. Birgersson
A promising noninvasive method to quantitatively study tissue alterations of humanskin is electrical impedance spectroscopy (EIS). During an EIS measurement, an alternating current at varying frequencies is passed between electrodes and through the various layers of the skin. The resulting spectrum provides the skin tissue's overall resistance and reactance.
To aid in the interpretation of EIS spectra and to elucidate the mechanisms involved in EIS of humanskin, mathematical models have been developed. Out of these models, equivalent
on drug release from controlled drug delivery systems. Act Pol Pharm-Dru Res 2010;67(3):217-33.
18. Williams AC. Expert opinion: Rat or mouse skin model for humanskin. In: Ashara KC, editor. 2016:1-3. DOI:10.13140/RG.2.2.27085.23522.
19. Berry BW, Rigg PC. Shed snake skin and hairless mouse skin as model membrane for humanskin during permeation study. J Inv Dermat 1990;94(2):235-40.
20. Berry BW, Bond JR. Hairless mouse skin is limited as a model for assessing the effect of penetration enhancers in humanskin. J Inv Dermat 1987;90(6):810-13.
B. Tsai, H. Xue, E. Birgersson, S. Ollmar and U. Birgersson
The humanskin comprises several layers—stratum corneum (SC), living epidermis (LE), dermis (DE) and hypodermis— with different dielectric properties that are functions of not only the frequency of the applied voltage but also other factors such as age [ 1 ] and health condition [ 2 ] during electrical impedance spectroscopy (EIS) measurements.
The dielectric properties of humanskin have been studied experimentally for different locations and frequencies. A database treating the skin as a one-layer entity for both wet and dry skin has been