Chirila, T. V.

Nann, T.

Toimil-Molares, M. E.

Trautmann, C.

GSI Repository

Nanopores in Track-Etched Polymer Membranes as Substitutes for the Tight Junctions in a Novel Concept of an Artificial Corneal Endothelium * T. V. Chirila1,#, T. Nann 2, M. E. Toimil-Molares3 and C. Trautmann3,41Queensland Eye Institute, Brisbane, Australia; 2 Ian Wark Research Institute, University of South Australia, Adelaide,Australia; 3GSI Helmholtz Centre, Darmstadt, Germany; 4Technische Universität Darmstadt, GermanyThis collaborative project is aimed at creating an artifi-cial substitute for the eye’s corneal endothelium. Theavailability of an artificial endothelium able to duplicatethe transendothelial ion-and-fluid transport function of thenatural endothelium will remove the need for donor tissueor cell-based constructs in the treatment of corneal blind-ness. To date, no attempts were successful to substitute a dysfunctional corneal endothelium with an artificialmembrane.The natural endothelium consists of a monolayer ofspecialized cells, and has an essential role in maintainingthe transparency of our cornea by performing a processcalled “pump-barrier function”, which assures a constanthydration of the corneal stroma. The loss of this functionleads eventually to blindness.The mechanism of the pump-barrier function is stilldisputed. Based on Fischbarg’s hypothesis [1] that thefluid transport through the endothelium is achieved byelectroosmosis through the leaky tight junctions betweencells, we proposed [2] that the nanopores in track-etchedmembranes can mimic the natural tight junctions. An es-sential condition for the electoosmosis is fulfilled by thefact that the internal pore walls are electrically charged.Poly(ethylene terephthalate) (PET) membranes (12-μmthick) were irradiated at the UNILAC using Au ions (11.1MeV/u) and a fluence of either 106 or 107 ions/cm2. Sub-sequent track etching was performed at 50 ºC in 2MNaOH for various times (5, 25, 125 and 250 min) yieldingcylindrical, parallel oriented pores of diameter 20, 100, 500 and 1000 nm, respectively.Preliminary experiments have been performed to quan-tify the electroosmotic flow (EOF) through track-etchedpolymer membranes. Wang and co-workers did performsimilar experiments earlier, where they recorded a massflow by direct displacement of the electrolyte [3, 4]. In our work, we used a fluorophore to monitor the masstransport through the membrane, with the view that thefluorophore will also allow to account for other effectssuch as diffusion and electrophoresis. In our experiment, two compartments were separatedby a track-etched polymer membrane where the averagepore diameter was 100 nm. One compartment was loadedwith an electrolyte containing 100 mM KCl and 1 mg/mlEosin Y, and the other was filled with exactly 1 ml ofelectrolyte without the dye. Then, gold electrodes wereplaced in each compartment and a potential of 500 mVwas applied for two hours.Figure 1 shows photoluminescence spectra of a dilutedaliquot of the electrolyte-only compartment after twohours of application of the potential. The red spectrumshows the results when the anode was placed in the elec-trolyte-only compartment, the black spectrum corre-sponds to the reverse polarisation. The arrows indicate thedirection of the respective flow components. By compar-ing these two spectra, it is evident that EOF is the domi-nating contribution, however, diffusion plays a significantrole as well. Further studies will be necessary to quantifyall transport mechanisms systematically. Figure 1: Photoluminescence spectra from electrolyte-only compartment after two hours of voltage applicationindicating the electroosmotic transport of Eosin Y. For thered (black) spectrum the anode (cathode) was placed inthe electrolyte-only compartment. EOF is the direction ofthe electroosmotic flow, Diff denotes diffusion, and EMmeans electrophoretic flow. References[1] J. Fischbarg, Physiol. Rev. 90 (2010) 1271[2] T.V. Chirila et al., J. Biomim. Biomater. Tissue Eng.5 (2010) 13[3] C. Wang et al., Nucl. Instr. Meth. B 286 (2012) 223[4] C. Wang et al., Lab Chip 12 (2012) 1710* This work has been supported in part by the PreventBlindness Foundation (Queensland), Australia# Traian.Chirila@qei.org.auGSITemplate2007PNI-INHOUSE-EXP-43 GSI SCIENTIFIC REPORT 2012412

Nanopores in Track-Etched Polymer Membranes as Substitutes for the Tight Junctions in a Novel Concept of an Artificial Corneal Endothelium

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Nanopores in Track-Etched Polymer Membranes as Substitutes for the Tight Junctions in a Novel Concept of an Artificial Corneal Endothelium

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