Drug Delivery and Translational Research

, Volume 6, Issue 6, pp 755–762 | Cite as

Simulation of the hydrodynamic conditions of the eye to better reproduce the drug release from hydrogel contact lenses: experiments and modeling

  • A. F. R. Pimenta
  • A. Valente
  • J. M. C Pereira
  • J. C. F Pereira
  • H. P. Filipe
  • J. L. G. Mata
  • R. Colaço
  • B. Saramago
  • A. P. Serro
Original Article


Currently, most in vitro drug release studies for ophthalmic applications are carried out in static sink conditions. Although this procedure is simple and useful to make comparative studies, it does not describe adequately the drug release kinetics in the eye, considering the small tear volume and flow rates found in vivo. In this work, a microfluidic cell was designed and used to mimic the continuous, volumetric flow rate of tear fluid and its low volume. The suitable operation of the cell, in terms of uniformity and symmetry of flux, was proved using a numerical model based in the Navier-Stokes and continuity equations. The release profile of a model system (a hydroxyethyl methacrylate-based hydrogel (HEMA/PVP) for soft contact lenses (SCLs) loaded with diclofenac) obtained with the microfluidic cell was compared with that obtained in static conditions, showing that the kinetics of release in dynamic conditions is slower. The application of the numerical model demonstrated that the designed cell can be used to simulate the drug release in the whole range of the human eye tear film volume and allowed to estimate the drug concentration in the volume of liquid in direct contact with the hydrogel. The knowledge of this concentration, which is significantly different from that measured in the experimental tests during the first hours of release, is critical to predict the toxicity of the drug release system and its in vivo efficacy. In conclusion, the use of the microfluidic cell in conjunction with the numerical model shall be a valuable tool to design and optimize new therapeutic drug-loaded SCLs.


Controlled drug release Hydrogels Contact lenses Microfluidics Numerical simulation 



Acknowledgements are due to Fundação para a Ciência e a Tecnologia for funding through the projects PEst-OE/QUI/UI0100/2013 and M-ERA.NET/0005/2012 and support, through IDMEC, under LAETA, of project UID/EMS/50022/2013. A.F.R. Pimenta acknowledges Fundação para a Ciência e a Tecnologia for the PhD Grant SFRH/BD/52334/2013. The authors also thank Professor J.R. Ascenso (CQE-IST, University of Lisbon) for the NMR measurement.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflicts of interest.


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Copyright information

© Controlled Release Society 2016

Authors and Affiliations

  • A. F. R. Pimenta
    • 1
    • 2
  • A. Valente
    • 1
  • J. M. C Pereira
    • 2
  • J. C. F Pereira
    • 2
  • H. P. Filipe
    • 3
    • 4
  • J. L. G. Mata
    • 1
  • R. Colaço
    • 2
  • B. Saramago
    • 1
  • A. P. Serro
    • 1
    • 5
  1. 1.Centro de Química Estrutural, Complexo I, Instituto Superior TécnicoUniversity of LisbonLisbonPortugal
  2. 2.IDMEC, Mechanical Engineering Department, Instituto Superior TécnicoUniversity of LisbonLisbonPortugal
  3. 3.Hospital das Forças Armadas - Polo de LisboaLisbonPortugal
  4. 4.Hospital dos SAMSLisbonPortugal
  5. 5.Centro de Investigação Interdisciplinar Egas MonizInstituto Superior de Ciências da Saúde Egas MonizMonte de CaparicaPortugal

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