Evaluation of the combination of dendrimers and iontophoresis for ocular drug administration

Author(s)

Joel Gonçalves de Souza

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC)
• Defense date: 2014-09-22

Examining board members

Renata Fonseca Vianna Lopez; André Augusto Gomes Faraco; Simone Odília Antunes Fernandes; Vanessa Carla Furtado Mosqueira

• Advisor: Renata Fonseca Vianna Lopez

Abstract

Topical administration of eye drops is the most convenient way for treatment of eye diseases. The challenge for the pharmaceutical technology is to ensure that the drug administered in the eye drops reaches the site of action in appropriate concentrations with reduced side effects, prolonged effect and single dose. Therefore, the development of drug delivery systems and appropriate strategies become necessary. The objective of this work was to evaluate the influence of iontophoresis in the ocular penetration of generation 4 polyamidoamine dendrimers (PAMAM) with different surface groups (PAMAM G4, cationic, and PAMAM G3.5, anionic), prepare complexes of these dendrimers with an anti-inflammatory drug model, dexamethasone (Dexa), and evaluate the influence of dendrimers and iontophoresis association on Dexa cornea penetration using ex vivo and in vivo models. Dexa-PAMAM complexes were obtained and characterized by infrared spectroscopy, nuclear magnetic resonance (H1-NMR, 13C-NMR and DOSY), dynamic light scattering and UV/VIS spectroscopy to evaluate the formation of the complexes, their size and zeta potential, as well as changes in drug solubility. Dexa release rate from complexes was determined from the in vitro release studies using synthetic membrane. The penetration and distribution of PAMAMs into the cornea and their influence in the ex vivo Dexa penetration was assessed using pig\'s cornea, confocal scanning laser microscopy (CSLM) and ultra performance chromatography coupled to a mass spectrometer for quantification of the drug permeated. PAMAMs cytotoxicity was assessed in culture of retina epithelial cells and cornea epithelial cells. Finally, the influence of iontophoresis and PAMAMs on Dexa concentration in the aqueous humor of rabbit eyes was evaluated in vivo. The characterization results showed that Dexa was incorporated to PAMAMs and that these complexes had an average size of approximately 50 nm using the NTA technique, with the distribution of small particles and aggregates when dispersed in physiological medium. The zeta potential of Dexa-PAMAM G4 and Dexa PAMAM G3.5 complexes were +6.4 mV and -18.5 mV, respectively. PAMAM G4 and G3.5 PAMAM enhanced Dexa solubility by 3.9 and 10.3-fold, respectively. PAMAM G3.5 and PAMAM G4 decreased by 82 and 1.7-fold Dexa diffusion coefficient. The ex vivo studies indicated that iontophoresis directed dendrimers into the cornea, increasing the amount of Dexa permeated by 2.9, 5.6 and 3.0-fold for the formulations containing free Dexa, Dexa-PAMAM G4 and Dexa-PAMAM G3.5, respectively. Iontophoresis also increased approximately 2-fold the amount of drug retained into the cornea for all formulations. The cytotoxicity experiments revealed that PAMAM G4 toxicity was dependent on the concentration and incubation time. Finally, the in vivo experiments showed that iontophoresis increased Dexa concentration in the aqueous humor by 2, 2.5 and 6.6-fold for free Dexa, Dexa-PAMAM G4 and Dexa-PAMAM-G3.5, respectively. Therefore, the combination of iontophoresis with PAMAM dendrimers represents a promising strategy for targeted and sustained topical drug delivery to the cornea. (AU)

• FAPESP's process: 10/19210-7 - Potential evaluation of dendrimer and iontophoresis association for ocular drugs administration
• Grantee: Joel Gonçalves de Souza
• Support Opportunities: Scholarships in Brazil - Doctorate