The effects of pH and ionic strength on topical delivery of a negatively charged porphyrin (TPPS4) |
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| Authors: | Gelfuso Guilherme Martins Figueiredo Fábio Vasconcelos Gratieri Taís Lopez Renata Fonseca Vianna |
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| Institution: | 1. Department of Applied Chemistry, University of Johannesburg, Doornfontein Campus, P.O. Box 17011, Doornfontein 2028, Johannesburg, South Africa;2. Centre for Nanomaterials Science Research, University of Johannesburg, Johannesburg, South Africa;3. Department of Chemistry, University of Zululand, Private Bag X1001, Kwadlangezwa 3886, South Africa;4. Graduate School Of Biomedical Engineering, Tohoku University, 4-1 Seiryo, Aoba Sendai 980-8575, Japan;1. Florida State University, Department of Physics, Tallahassee, Fl 32306, USA;2. University of North Florida, Department of Physics, Jacksonville, Fl 32224, USA;1. China Academy of Engineering Physics, Institute of Fluid Physics, Mianyang, Sichuan, 621999, China;2. University of Science and Technology of China, National Synchrotron Radiation Laboratory, Hefei, Anhui, 230029, China;3. Soochow University, Institute of Functional Nano & Soft Materials, Suzhou, Jiangsu 215123, China;1. Ataturk University, Faculty of Science, Department of Physics, 25240 Erzurum, Turkey;2. Georgia Institute of Technology, Atlanta, GA 30332-0245, USA;3. PhosphorTech Corporation, 3645 Kennesaw North Industrial Parkway, GA 30144, USA |
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| Abstract: | Meso-tetra-4-sulfonatophenyl]-porphyrin (TPPS(4)) is a charged porphyrin derivate used in photodynamic therapy (PDT) by parenteral administration. This study means to investigate potential enhancement for its topical delivery by determining the TPPS(4) dependence on the environmental characteristics and applying iontophoresis. In order to accomplish this task, cathodal and anodal iontophoresis as well as passive delivery of the drug were studied in vitro and in vivo in function of its concentration, pH and ionic strength. A reduction in drug concentration as well as the NaCl elimination from donor formulation at pH 2.0 increased TPPS(4) passive permeation through the skin in vitro. Iontophoresis improved TPPS(4) delivery across the skin when applied in solutions containing NaCl at pH 2.0, regardless electrode polarity. However, at pH 7.4, the amount of TPPS(4) permeated by iontophoresis was not different from that one permeated after passive experiments from a solution containing NaCl. Despite the fact that iontophoresis did not improve TPPS(4) transdermal delivery at this specific condition, in vivo experiments showed that 10 min of iontophoresis quickly and homogeneously delivered TPPS(4) to deeper skin layers when compared to passive administration, which is an important condition for topical treatment of skin tumors with PDT. |
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