The synergistic effect of ultrasound and chemical penetration enhancers on chorioamnion mass transport Aharon Azagury a , Luai Khoury b , Yair Adato c , Lior Wolloch b , Ilana Ariel d , Mordechai Hallak e , Joseph Kost a, ⁎ a Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel b Department of Biomedical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel c Department of Computer science, Ben-Gurion University of the Negev, Beer-Sheva, Israel d Department of Pathology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel e Departments of Obstetrics and Gynecology, Hillel Yaffe Medical Center, Hadera, Israel abstract article info Article history: Received 27 August 2014 Received in revised form 12 December 2014 Accepted 13 December 2014 Available online 22 December 2014 Keywords: Ultrasound Chemical penetration enhancers Chorioamnion membrane Image analysis In our previous study we proposed the use of chemical penetration enhancers for noninvasive detection of fetus abnormalities that can also be utilized for direct fetal drug delivery. In an attempt to further increase the mass transport rate across the amniotic membrane, thus shortening the procedure and improving the applicability of the proposed procedure, the effect and mechanism of combining ultrasound exposure with chemical penetra- tion enhancers' application were assessed. The combined effect was evaluated in vitro on post-delivery human amniotic membrane and ex vivo on rat's whole amniotic sac. Ultrasound effect has been assessed by dye exper- iments using a customized image analysis program. Additional insights of ultrasound effect's mechanism on bi- ological membranes are presented. Previously we have determined that chemical penetration enhancers affect the fetal membranes via two mechanisms termed as ‘extractors’ and ‘fluidizers’. In this study, we found that com- bining ultrasound with a ‘fluidizer’ CPE (e.g. bupivacaine) results in a synergistic enhancement (90-fold) of fetal membrane's mass transport, while combining ultrasound with ‘extractors’ (e.g. ethanol and NMP) results in an antagonistic effect. The combined procedure is faster and gain greater accuracy than the applications of sole chemical penetration enhancers. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Low frequency ultrasound (LFU) is known to increase mass trans- port across skin and to induce a synergistic effect when combined with other enhancing methods such as chemical penetration enhancers (CPEs) [1–3]. Sonophoresis is the term used to describe the enhance- ment effect (EE) on skin permeability induced by LFU. Most would agree that sonophoresis occurs mainly due to cavitational effects (when using intensities above the cavitational threshold) [4,5]. Cavita- tion is an effect in which gas bubbles coalescence in insonated medium. These bubbles then oscillate with the sound wave (noninertial cavita- tion) and may collapse and explode (inertial cavitation) due to a process termed rectified diffusion [6]. These explosions result in temperature el- evation and pressure amplitude in the vicinity of the bubble collapse, thus creating microjets, acoustic streaming, and additional thermal ef- fect. LFUs can also generate acoustic streaming/jets and thermal effects below cavitational intensity threshold [7–9]. LFU effect on mass trans- port was also assessed for other biological membranes such as the nasal membrane [10], the tympanic membrane [11], and recently the chorioamnion (CA) membrane [12]. The fetal membranes (CA membrane) constitute the sac enveloping the fetus: The membrane facing the maternal side is called the chorion membrane, and the membrane that faces the fetal side is called the am- nion. These membranes are loosely attached to each other and incom- pletely fused by pressure exerted by the amniotic fluid in the inner amniotic sac. The definitive sac develops in stages, similar to two bal- loons gradually being inflated inside of a sphere. The final arrangement of membranes is present for at least the last half of the pregnancy. The amnion is composed of an inner layer of epithelial cells lying on a base- ment membrane which is planted on a layer of connective tissue. Unlike the epidermis which is a multilayered stratified epithelium, the amnion is simple epithelium, and, as such, it is composed of one layer of flat-to- columnar cells. The amniotic epithelium is not continuous and exhibits many defects due to cell degeneration [13] and therefore it is not sur- prising that, as we have demonstrated in our previous studies [12,14], it is much more permeable than the chorion. The amnion is loosely at- tached to the outer layer of the chorion, which is smooth (chorion laeve) and devoid of blood vessels in the membranous part of the sac. The chorion is composed of a dense connective tissue, similar to the fi- brous layer of amnion, lined on the external surface by basal lamina followed by a variable layer of trophoblastic cells. These trophoblastic Journal of Controlled Release 200 (2015) 35–41 ⁎ Corresponding author at: Ben-Gurion University of the Negev, Faculty of Engineering Sciences, POB 653, Beer-Sheva 8410501, Israel. E-mail address: kost@bgu.ac.il (J. Kost). http://dx.doi.org/10.1016/j.jconrel.2014.12.025 0168-3659/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Controlled Release journal homepage: www.elsevier.com/locate/jconrel