{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,12]],"date-time":"2026-05-12T00:21:06Z","timestamp":1778545266461,"version":"3.51.4"},"reference-count":31,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2020,9,14]],"date-time":"2020-09-14T00:00:00Z","timestamp":1600041600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"German Research Foundation","award":["Nanocarriers: Architecture, Transport, and Topical Application of Drugs for Therapeutic Use"],"award-info":[{"award-number":["Nanocarriers: Architecture, Transport, and Topical Application of Drugs for Therapeutic Use"]}]},{"DOI":"10.13039\/501100002347","name":"Bundesministerium f\u00fcr Bildung und Forschung","doi-asserted-by":"publisher","award":["ParOptiSense\u201dFKZ 031B0763A"],"award-info":[{"award-number":["ParOptiSense\u201dFKZ 031B0763A"]}],"id":[{"id":"10.13039\/501100002347","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Nanoparticles can be applied to the hair follicles, which can serve as reservoirs for triggered drug release. A valid measurement method for the determination of the pH within the hair follicle in vivo has not been shown yet. Here, melamine formaldehyde particles up to 9 \u00b5m in size were applied on 40 freshly plucked scalp hairs of eight individuals to determine the pH along the hair shaft down to the root area of the hair. For fluorescent pH indicators, pyranine and Nile blue were incorporated into the particles. Measurements were conducted using confocal laser scanning microscopy. A pH decay gradient could be found from the hair sheath towards the external hair shaft (p = 0.012) with pH values at the hair sheath of 6.63 \u00b1 0.09, at the hair sheath end at 6.33 \u00b1 0.11, and at the external hair shaft at 6.17 \u00b1 0.09 (mean \u00b1 SE). The pH difference between the hair sheath end and the external hair shaft was found to be significant (p = 0.036). The results might be comparable with the pH within the hair follicle in vivo indicating a pH increase towards the hair root.<\/jats:p>","DOI":"10.3390\/s20185243","type":"journal-article","created":{"date-parts":[[2020,9,14]],"date-time":"2020-09-14T09:04:53Z","timestamp":1600074293000},"page":"5243","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Determination of the pH Gradient in Hair Follicles of Human Volunteers Using pH-Sensitive Melamine Formaldehyde-Pyranine Nile Blue Microparticles"],"prefix":"10.3390","volume":"20","author":[{"given":"Dennis","family":"Kaden","sequence":"first","affiliation":[{"name":"Surflay Nanotec GmbH, 12489 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lars","family":"D\u00e4hne","sequence":"additional","affiliation":[{"name":"Surflay Nanotec GmbH, 12489 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fanny","family":"Knorr","sequence":"additional","affiliation":[{"name":"Charit\u00e9\u2013Universit\u00e4tsmedizin Berlin, Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology (CCP), 10117 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Heike","family":"Richter","sequence":"additional","affiliation":[{"name":"Charit\u00e9\u2013Universit\u00e4tsmedizin Berlin, Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology (CCP), 10117 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1828-7460","authenticated-orcid":false,"given":"J\u00fcrgen","family":"Lademann","sequence":"additional","affiliation":[{"name":"Charit\u00e9\u2013Universit\u00e4tsmedizin Berlin, Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology (CCP), 10117 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Martina C.","family":"Meinke","sequence":"additional","affiliation":[{"name":"Charit\u00e9\u2013Universit\u00e4tsmedizin Berlin, Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology (CCP), 10117 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alexa","family":"Patzelt","sequence":"additional","affiliation":[{"name":"Charit\u00e9\u2013Universit\u00e4tsmedizin Berlin, Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology (CCP), 10117 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1075-1994","authenticated-orcid":false,"given":"Maxim E.","family":"Darvin","sequence":"additional","affiliation":[{"name":"Charit\u00e9\u2013Universit\u00e4tsmedizin Berlin, Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology (CCP), 10117 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sora","family":"Jung","sequence":"additional","affiliation":[{"name":"Charit\u00e9\u2013Universit\u00e4tsmedizin Berlin, Department of Dermatology, Venerology and Allergology, Center of Experimental and Applied Cutaneous Physiology (CCP), 10117 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,9,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"256-e60","DOI":"10.1111\/vde.12325","article-title":"Penetration of topically applied nanocarriers into the hair follicles of dog and rat dorsal skin and porcine ear skin","volume":"27","author":"Knorr","year":"2016","journal-title":"Vet. 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