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    Conjunctival impression cytology by using a thermosensitive adhesive: polymerized N-isopropyl acrylamide.
    (2009) Tunç, Murat; Yıldırım, Ümran; Yüksel, Harun; Cheng, Xuanhong; Humayun, Mark; Ratner, Buddy D.
    We aimed to evaluate a new technique using a thermosensitive glue coating for impression cytology of the ocular surface. We prepared plasma polymerized N-isopropyl acrylamide (pNIPAM)-coated parylene C (poly(monochloro-p-xylylene)) films to obtain cytological samples from the conjunctival surface. We compared this new technique with the conventional nitrocellulose paper method in regards to the quality of impression cytology and quantity of the cells in 30 postmenauposal women with dry eye complaints. The cellular material was adequate for evaluation in 28 (93%) of 30 eyes in pNIPAM-coated parylene group and in 18 (60%) of 30 eyes in the nitrocellulose group (P = 0.0002). pNIPAM-coated parylene technique was superior to the nitrocellulose technique regarding the mean number of cells per microscopic field (P = 0.00003), integrity of the cells (P = 0.00001), and cellular preservation (P = 0.0002). The number of cells and the quality scores were significantly higher in the pNIPAM-coated impression cytology technique than the nitrocellulose method.
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    Plasma deposited poly(N-isopropylacrylamide) surfaces: Powerful tools for biology and medical devices
    (Amer Chemical Soc, 2007) Ratner, Buddy D.; Canavan, Heather; Cheng, Xuanhong; Tunç, Murat; Humayun, Mark
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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.
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    A REVERSIBLE THERMOSENSTTIVE ADHESIVE FOR RETINAL IMPLANTS In Vivo Experience with Plasma-deposited Poly(N-Isopropyl Acrylamide)
    (Lippincott Williams & Wilkins, 2008) Tunç, Murat; Humayun, Mark; Cheng, Xuanhong; Ratner, Buddy D.
    Purpose: To study the in vivo effects of a thermosensitive retinal adhesive, plasma-polymerized N-isopropyl acrylamide (ppNIPAM), in rabbit eyes. Methods: Parylene C(poly(monochloro-p-xylylene)) (20 mu m) and poly(dimethyl siloxane) (PDMS) (>= 200 mu m) coated with ppNIPAM were used as implant materials. Following pars plana vitrectomy (PPV), ppNIPAM coated parylene (n = 3) and PDMS (n = 3) implants were inserted over the retina in six rabbits. Baseline and follow-up imaging (color fundus photographs, fluorescein angiography, and optic coherence tomography [OCT]) and electroretinogram recordings were performed. Histologic evaluation was performed following enucleation at 6 weeks. Results: Intraoperative retinal adhesion occurred in all eyes with ppNIPAM coated parylene and PDMS implants. Two eyes developed retinal tears during the implantation procedure and the ppNIPAM coated implants closed the retinal tears successfully preventing retinal detachment. OCT findings confirmed the retinal adhesion in all eyes. Four weeks after implantation one parylene and one PDMS implant detached partly from the retinal surface. Histology showed mild changes at the outer retinal segments. There was no evidence of ocular toxicity and inflammation. None of the eyes that had an implant covering the retinal tear developed a retinal detachment but had some inflammatory changes around the implants. Conclusions: ppNIPAM coated implants may provide retinal adhesion in vivo without measurable ocular toxicity in the short term. Covering a retinal tear, the ppNIPAM coated implants may prevent retinal detachment. RETINA 28:1338-1343, 2008