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    Reversible thermosensitive glue for retinal implants
    (Lippincott Williams & Wilkins, 2007) Tunç, Murat; Cheng, Xuanhong; Ratner, Buddy D.; Meng, Ellis; Humayun, Mark
    Purpose: To determine in vitro effects of a plasma polymerized N-isopropyl acrylamide (pNIPAM) coating for thermally controllable adhesion to retinal tissue. Methods: Polyimide (50 mu m), parylene C [poly(monochloro-p-xylylene)] (20 mu m), and poly(dimethyl siloxane) (PDMS) (200 mu m) coated with pNIPAM were used as implant materials to test retinal adhesion in enucleated pig eyes. Following preparation of the implant materials (n = 5) and retina, the authors held the implants over the retinal tissue at 22 degrees C and gradually increased the temperature of the water bath within 15 minutes. While increasing the temperature the authors monitored the adhesion with the retina and pNlPAM coated implant. The authors measured the adhesive force by a traction test using a suture attached to the implant and a strain gauge. Then the authors checked the reversibility of the adhesion by lowering the temperature of the water bath. Results: There was no retinal adhesion at room temperature (22 degrees C). The adhesion developed strongly within 60 seconds after reaching the critical temperature ( >= 32 degrees C). This adhesion was persistent when the authors applied tractional forces of 98 mN and 148 mN between 32 and 38 degrees C. When the authors lowered the temperature back to 22 degrees C by irrigation with cold BSS, the implants detached from the retinal surface without using any tractional force. Conclusion: pNIPAM provides effective in vitro retinal adhesion between 32 and 38 degrees C and this adhesion is completely reversible by lowering the temperature of the physiologic medium.