{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,2]],"date-time":"2026-05-02T06:16:22Z","timestamp":1777702582351,"version":"3.51.4"},"reference-count":43,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2021,4,30]],"date-time":"2021-04-30T00:00:00Z","timestamp":1619740800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001807","name":"Funda\u00e7\u00e3o de Amparo \u00e0 Pesquisa do Estado de S\u00e3o Paulo","doi-asserted-by":"publisher","award":["2012\/06974-4"],"award-info":[{"award-number":["2012\/06974-4"]}],"id":[{"id":"10.13039\/501100001807","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002322","name":"Coordena\u00e7\u00e3o de Aperfei\u00e7oamento de Pessoal de N\u00edvel Superior","doi-asserted-by":"publisher","award":["Finance Code 001"],"award-info":[{"award-number":["Finance Code 001"]}],"id":[{"id":"10.13039\/501100002322","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pharmaceutics"],"abstract":"<jats:p>Permeation assays are important for the development of topical formulations applied on buccal mucosa. Swine buccal and esophageal epithelia are usually used as barriers for these assays, while frozen epithelia have been used to optimize the experimental setup. However, there is no consensus on these methods. In transdermal studies, barrier integrity has been evaluated by measuring electrical resistance (ER) across the skin, which has been demonstrated to be a simple, fast, safe, and cost-effective method. Therefore, the aims here were to investigate whether ER might also be an effective method to evaluate buccal and esophageal epithelium mucosa integrity for in vitro permeation studies, and to establish a cut-off ER value for each epithelium mucosa model. We further investigated whether buccal epithelium could be substituted by esophageal epithelium in transbuccal permeation studies, and whether their permeability and integrity were affected by freezing at \u221220 \u00b0C for 3 weeks. Fresh and frozen swine buccal and esophageal epithelia were mounted in Franz diffusion cells and were then submitted to ER measurement. Permeation assays were performed using lidocaine hydrochloride as a hydrophilic drug model. ER was shown to be a reliable method for evaluating esophageal and buccal epithelia. The esophageal epithelium presented higher permeability compared to the buccal epithelium. For both epithelia, freezing and storage led to decreased electrical resistivity and increased permeability. We conclude that ER may be safely used to confirm tissue integrity when it is equal to or above 3 k\u03a9 for fresh esophageal mucosa, but not for buccal epithelium mucosa. However, the use of esophageal epithelium in in vitro transmucosal studies could overestimate the absorption of hydrophilic drugs. In addition, fresh samples are recommended for these experiments, especially when hydrophilic drugs are involved.<\/jats:p>","DOI":"10.3390\/pharmaceutics13050643","type":"journal-article","created":{"date-parts":[[2021,5,1]],"date-time":"2021-05-01T21:35:39Z","timestamp":1619904939000},"page":"643","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":15,"title":["Resistivity Technique for the Evaluation of the Integrity of Buccal and Esophageal Epithelium Mucosa for In Vitro Permeation Studies: Swine Buccal and Esophageal Mucosa Barrier Models"],"prefix":"10.3390","volume":"13","author":[{"given":"Jaiza Samara Macena","family":"de Ara\u00fajo","sequence":"first","affiliation":[{"name":"Department of Biosciences, Piracicaba Dental School, University of Campinas-UNICAMP, Piracicaba 13414-903, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Maria Cristina","family":"Volpato","sequence":"additional","affiliation":[{"name":"Department of Biosciences, Piracicaba Dental School, University of Campinas-UNICAMP, Piracicaba 13414-903, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bruno Vilela","family":"Muniz","sequence":"additional","affiliation":[{"name":"Department of Biosciences, Piracicaba Dental School, University of Campinas-UNICAMP, Piracicaba 13414-903, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Gabriela Gama Augusto","family":"Xavier","sequence":"additional","affiliation":[{"name":"Department of Biosciences, Piracicaba Dental School, University of Campinas-UNICAMP, Piracicaba 13414-903, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Claudia Cristina Maia","family":"Martinelli","sequence":"additional","affiliation":[{"name":"Department of Biosciences, Piracicaba Dental School, University of Campinas-UNICAMP, Piracicaba 13414-903, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6448-6711","authenticated-orcid":false,"given":"Renata Fonseca Vianna","family":"Lopez","sequence":"additional","affiliation":[{"name":"School of Pharmaceutical Sciences of Ribeir\u00e3o Preto, University of S\u00e3o Paulo-USP, Ribeir\u00e3o Preto 14040-903, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8513-773X","authenticated-orcid":false,"given":"Francisco Carlos","family":"Groppo","sequence":"additional","affiliation":[{"name":"Department of Biosciences, Piracicaba Dental School, University of Campinas-UNICAMP, Piracicaba 13414-903, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0760-1389","authenticated-orcid":false,"given":"Michelle","family":"Franz-Montan","sequence":"additional","affiliation":[{"name":"Department of Biosciences, Piracicaba Dental School, University of Campinas-UNICAMP, Piracicaba 13414-903, S\u00e3o Paulo, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,4,30]]},"reference":[{"key":"ref_1","first-page":"15","article-title":"Buccal mucosa as a route for systemic drug delivery: A review","volume":"1","author":"Shojaei","year":"1998","journal-title":"J. Pharm. Pharm. Sci."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"579","DOI":"10.3109\/03639045.2014.892960","article-title":"Novel strategies for the buccal delivery of macromolecules","volume":"40","author":"Morales","year":"2014","journal-title":"Drug Dev. Ind. Pharm."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"720","DOI":"10.1016\/j.tips.2019.07.010","article-title":"Striving Towards the Perfect In Vitro Oral Drug Absorption Model","volume":"40","author":"Gleeson","year":"2019","journal-title":"Trends Pharmacol. Sci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1300","DOI":"10.1177\/00220345870660080201","article-title":"The surface area of the adult human mouth and thickness of the salivary film covering the teeth and oral mucosa","volume":"66","author":"Collins","year":"1987","journal-title":"J. Dent. Res."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1186\/1746-160X-9-8","article-title":"The oral mucosal surface and blood vessels","volume":"9","author":"Naumova","year":"2013","journal-title":"Head Face Med."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1093\/oxfordjournals.jncimonographs.a003443","article-title":"Biology of oral mucosa and esophagus","volume":"29","author":"Squier","year":"2001","journal-title":"J. Natl. Cancer Inst. Monogr."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1016\/S0168-3659(01)00269-3","article-title":"Drug permeation enhancement via buccal route: Possibilities and limitations","volume":"72","author":"Senel","year":"2001","journal-title":"J. Control Release"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1517\/17425240903338758","article-title":"Chemical permeation enhancers for transbuccal drug delivery","volume":"7","author":"Hassan","year":"2010","journal-title":"Expert Opin. Drug Deliv."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1038\/nrd.2018.183","article-title":"Non-invasive delivery strategies for biologics","volume":"18","author":"Anselmo","year":"2019","journal-title":"Nat. Rev. Drug Discov."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Padula, C., Pescina, S., Nicoli, S., and Santi, P. (2018). New Insights on the Mechanism of Fatty Acids as Buccal Permeation Enhancers. Pharmaceutics, 10.","DOI":"10.3390\/pharmaceutics10040201"},{"key":"ref_11","unstructured":"Food & Drug Administration (2019). Transdermal and Topical Delivery Systems Product Development and Quality Considerations, U.S. Food & Drug Administration."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"54","DOI":"10.3109\/08982104.2012.742536","article-title":"Liposomal-benzocaine gel formulation: Correlation between in vitro assays and in vivo topical anesthesia in volunteers","volume":"23","author":"Cereda","year":"2013","journal-title":"J. Liposome Res."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2777","DOI":"10.1002\/jps.20409","article-title":"Evaluation of pig esophageal mucosa as a permeability barrier model for buccal tissue","volume":"94","author":"Pizzolato","year":"2005","journal-title":"J. Pharm. Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"981","DOI":"10.1016\/j.archoralbio.2005.04.008","article-title":"Comparison of the lipid composition of porcine buccal and esophageal permeability barriers","volume":"50","author":"Jacques","year":"2005","journal-title":"Arch. Oral. Biol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1265","DOI":"10.1002\/jps.21907","article-title":"Porcine buccal mucosa as in vitro model: Effect of biological and experimental variables","volume":"99","author":"Kulkarni","year":"2010","journal-title":"J. Pharm. Sci."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1345","DOI":"10.1177\/00220345890680091101","article-title":"The permeability of human oral mucosa and skin to water","volume":"68","author":"Lesch","year":"1989","journal-title":"J. Dent. Res."},{"key":"ref_17","first-page":"271","article-title":"Developments in buccal drug delivery","volume":"8","author":"Verhoef","year":"1991","journal-title":"Crit. Rev. Ther. Drug Carrier Syst."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1016\/j.ejps.2014.04.017","article-title":"An improved cryopreservation method for porcine buccal mucosa in ex vivo drug permeation studies using Franz diffusion cells","volume":"60","author":"Amores","year":"2014","journal-title":"Eur. J. Pharm. Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"587","DOI":"10.1208\/s12249-011-9621-2","article-title":"Effect of freezing and type of mucosa on ex vivo drug permeability parameters","volume":"12","author":"Caon","year":"2011","journal-title":"AAPS PharmSciTech"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"471","DOI":"10.1002\/jps.21436","article-title":"Porcine buccal mucosa as an in vitro model: Relative contribution of epithelium and connective tissue as permeability barriers","volume":"98","author":"Kulkarni","year":"2009","journal-title":"J. Pharm. Sci."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1016\/j.ejps.2015.09.021","article-title":"Evaluation of different pig oral mucosa sites as permeability barrier models for drug permeation studies","volume":"81","author":"Serpe","year":"2016","journal-title":"Eur. J. Pharm. Sci."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1141","DOI":"10.1023\/A:1015928225089","article-title":"Electrical analysis of fresh, excised human skin: A comparison with frozen skin","volume":"7","author":"Kasting","year":"1990","journal-title":"Pharm. Res."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"134","DOI":"10.1023\/A:1015820600672","article-title":"DC electrical properties of frozen, excised human skin","volume":"7","author":"Kasting","year":"1990","journal-title":"Pharm. Res."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1016\/j.tiv.2003.10.004","article-title":"Multi-species assessment of electrical resistance as a skin integrity marker for in vitro percutaneous absorption studies","volume":"18","author":"Davies","year":"2004","journal-title":"Toxicol. In Vitro"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"129","DOI":"10.1016\/j.tiv.2018.04.009","article-title":"Transepidermal water loss and skin conductance as barrier integrity tests","volume":"51","author":"Zhang","year":"2018","journal-title":"Toxicol. In Vitro"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"731","DOI":"10.1016\/S0887-2333(02)00084-X","article-title":"Rapid integrity assessment of rat and human epidermal membranes for in vitro dermal regulatory testing: Correlation of electrical resistance with tritiated water permeability","volume":"16","author":"Fasano","year":"2002","journal-title":"Toxicol. In Vitro"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1016\/0378-5173(91)90340-T","article-title":"Localization of the permeability barrier inside porcine buccal mucosa: A combined in vitro study of drug permeability, electrical resistance and tissue morphology","volume":"76","author":"Boddk","year":"1991","journal-title":"Int. J. Pharm."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1193","DOI":"10.1016\/j.colsurfb.2015.11.005","article-title":"Needle-free buccal anesthesia using iontophoresis and amino amide salts combined in a mucoadhesive formulation","volume":"136","author":"Cubayachi","year":"2015","journal-title":"Colloids Surf. B Biointerfaces"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"8709","DOI":"10.1021\/acs.langmuir.9b00726","article-title":"Effect of Temperature on the Structure, Electrical Resistivity, and Charge Capacitance of Supported Lipid Bilayers","volume":"35","author":"Abraham","year":"2019","journal-title":"Langmuir"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1525","DOI":"10.1007\/s11095-005-6020-y","article-title":"Transport of fentanyl through pig buccal and esophageal epithelia in vitro: Influence of concentration and vehicle pH","volume":"22","author":"Falson","year":"2005","journal-title":"Pharm. Res."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"113769","DOI":"10.1016\/j.jpba.2020.113769","article-title":"Development, validation and standardization of oromucosal ex-vivo permeation studies for implementation in quality-controlled environments","volume":"194","author":"Majid","year":"2021","journal-title":"J. Pharm. Biomed. Anal"},{"key":"ref_32","unstructured":"European Food Safety Authority (2012). Guidance on Dermal Absorption. EFSA J., 15, e04873."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"11","DOI":"10.3109\/08982104.2014.911315","article-title":"Liposomal lidocaine gel for topical use at the oral mucosa: Characterization, in vitro assays and in vivo anesthetic efficacy in humans","volume":"25","author":"Baroni","year":"2015","journal-title":"J. Liposome Res."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2036","DOI":"10.1007\/s11095-013-1052-1","article-title":"Characterization of damaged skin by impedance spectroscopy: Mechanical damage","volume":"30","author":"White","year":"2013","journal-title":"Pharm. Res."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"121","DOI":"10.1016\/j.ejps.2017.09.034","article-title":"Evaluation of critical parameters for in vitro skin permeation and penetration studies using animal skin models","volume":"111","author":"Medina","year":"2018","journal-title":"Eur. J. Pharm. Sci."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1016\/S0168-3659(99)00026-7","article-title":"Mechanistic aspects of iontophoresis in human epidermal membrane","volume":"62","author":"Higuchi","year":"1999","journal-title":"J. Control Release"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"419","DOI":"10.1021\/js980331y","article-title":"Pore induction in human epidermal membrane during low to moderate voltage iontophoresis: A study using AC iontophoresis","volume":"88","author":"Li","year":"1999","journal-title":"J. Pharm. Sci."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"243","DOI":"10.1159\/000351926","article-title":"Passive and iontophoretic transport through the skin polar pathway","volume":"26","author":"Li","year":"2013","journal-title":"Skin Pharmacol. Physiol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"327","DOI":"10.12968\/denu.2009.36.6.327","article-title":"Mastication and swallowing: 1. Functions, performance and mechanisms","volume":"36","author":"Orchardson","year":"2009","journal-title":"Dent. Update"},{"key":"ref_40","first-page":"200","article-title":"Comparative permeability of fresh and frozen\/thawed porcine buccal mucosa towards various chemical markers","volume":"61","year":"2006","journal-title":"SADJ"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"579","DOI":"10.1208\/s12249-011-9624-z","article-title":"Effect of experimental temperature on the permeation of model diffusants across porcine buccal mucosa","volume":"12","author":"Kulkarni","year":"2011","journal-title":"AAPS Pharm. Sci. Tech."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1016\/j.jconrel.2017.09.039","article-title":"Combining amino amide salts in mucoadhesive films enhances needle-free buccal anesthesia in adults","volume":"266","author":"Cubayachi","year":"2017","journal-title":"J. Control Release"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1016\/j.ejps.2016.08.023","article-title":"Influence of salivary washout on drug delivery to the oral cavity using coated microneedles: An in vitro evaluation","volume":"93","author":"Serpe","year":"2016","journal-title":"Eur. J. Pharm. Sci."}],"container-title":["Pharmaceutics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4923\/13\/5\/643\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:56:22Z","timestamp":1760162182000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4923\/13\/5\/643"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,4,30]]},"references-count":43,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2021,5]]}},"alternative-id":["pharmaceutics13050643"],"URL":"https:\/\/doi.org\/10.3390\/pharmaceutics13050643","relation":{},"ISSN":["1999-4923"],"issn-type":[{"value":"1999-4923","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,4,30]]}}}