Modification Of Hydrophobic Acrylic Intraocular Lens With Poly(Ethylene Glycol) By Atmospheric Pressure Glow Discharge

PartⅠModification of hydrophobic acrylic intraocular lens with poly(ethylene glycol) by atmospheric pressure glow dischargeObjective:To improve the anterior surface biocompatibility of hydrophobic acrylic intraocular lens (IOL) in an efficient and continuous way, increase the anterior surface hydrophilicity while keeping the posterior surface hydrophobic, without change in the optical and mechanical properties of the bulk.Methods:Poly(ethylene glycol)s (PEGs) were immobilized by atmospheric pressure glow discharge (APGD) treatment using argon as the discharge gas. The hydrophilicity and chemical changes on the IOL surface were characterized by static water contact angle and X-ray photoelectron spectroscopy to confirm the covalent binding of PEG. The physic and optic properties were determined by national standards. The morphology of the IOL surface was observed under field emission scanning electron microscopy and atomic force microscopy. The surface biocompatibility was evaluated by adhesion experiments with platelets, macrophages and lens epithelial cells (LECs) in vitro.Results:The results revealed that the anterior surface of the PEG-grafted IOL displayed significantly and permanently improved hydrophilicity. The physic and optic properties of modified acrylic IOLs meet the national standards (including optical power, image quality, spectral transmittance and dynamic fatigue durability). Cell repellency was observed, especially in the PEG-modified IOL group, which resisted the attachment of platelets, macrophages and LECs. Moreover, the spread and growth of cells were suppressed, and may be attributed to the steric stabilization force and chain mobility effect of the modified PEG.Conclusion:All of these results indicated that hydrophobic acrylic IOLs can be hydrophilic modified by PEG through APGD treatment in a convenient and continuous manner and will provide advantages for further industrial applications. Part II The biocompatibility of anterior surface PEG-modified acrylic IOLs prepared via APGD treatment in vivoObjective:To detect the biocompatibility of anterior surface PEG-grafted IOLs (via APGD treatment) in rabbit eyes, including complications related to anterior chamber inflammatory reaction and capsule opacification.Methods:Anterior surfaces of hydrophobic acrylic IOLs were grafted with PEG by APGD treatment. The hydrophilicity of IOL surface was characterized by contact angle test. Thirty-six rabbit eyes were operated on with phacoemulsification and randomly implantation of one from the three types of foldable IOLs:anterior surface PEG-grafted acrylic IOL (PEG-grafted IOL) (n=12), original acrylic IOL (Acrylic IOL) (n=12) and hydrophilic IOL (Akreos IOL) (n=12). Postoperative follow-up was done on the 1st,3rd, 7th,14th,30th,60th and 90th days after surgery. On each visit, all rabbits were observed by slitlamp examination to evaluate aqueous flare, aqueous cell, posterior synechia and IOL dislocation. Standardized digital retroilluminated slitlamp images of posterior capsule opacification (PCO) were taken and the evaluation of PCO was done by EPCO 2000 software. The rabbits were killed three months postoperatively, the Miyake-Apple posterior photographic technique was used to evaluate the PCO formation. The IOLs were extracted from the rabbits eyes, and the cells attached on IOLs surface were observed by inverted phase contrast microscopy with hematoxylin and eosin (HE) staining; the samples were also prepared and observed by SEM. Histological sections of rabbits globe were prepared and stained with HE staining, periodic acid-schiff (PAS) and Masson's trichrome staining to document proliferation of LECs and extracellular matrix (ECM) in capsular bag. Immunohistochemistry (IHC) for collagenⅠ, collagenⅢandα-SMA was also done to evaluate mesenchymal transition in LECs. Both the anterior and posterior capsules were processed for transmission electron microscopy (TEM) to observe the microstructure of lens capsule.Results:The water contact angle of PEG IOL showed a stable significantly improved hydrophilicity of anterior surface, with a hydrophobic original posterior surface. The follow up observation with slitlamp examination showed that the anterior chamber inflammation was severer in Acrylic IOL group than in other two groups, two eyes in Acrylic IOL group and one eye in Akreos IOL group presented posterior synechia and IOL dislocation, no obvious inflammation was found in eyes with PEG IOLs. On the 7th and 14th day postoperatively, the aqueous flare results were statistically higher in Acrylic IOL group than in other two groups (p<0.05), the aqueous cell results showed that no statistically difference among the three groups was observed in the measured time point (p>0.05). The EPCO analysis and Miyake-Apple evaluation revealed that the eyes of Akreos IOLs had higher incidence of PCO compared to those of PEG IOLs and Acrylic IOLs (p<0.05), but there were no statistically significant difference between PEG IOLs and Acrylic IOL groups (p>0.05). The inverted phase contrast microscope observation showed that there were more cells adhered on Acrylic IOLs than PEG IOLs and Akreos IOLs (p<0.05). Histopathological, IHC and TEM analyses demonstrated the remnant LECs had some growth, and Soemmering's ring was observed in all groups. However, LECs were stopped at the optic periphery of the Acrylic IOLs and PEG IOLs, which keeping hydrophobic posterior surface. The central posterior capsule area of IOLs were clear in above both groups. In contrast, in Akreos IOL group, the LECs and ECM were observed apparently grew into the central field of the optic, thus leading to the PCO in visual axis area. Conclusion:The PEG IOLs via APGD treatment had stable hydrophilic anterior surface and original hydrophobic posterior surface. The PEG IOLs have both excellent uveal biocompatibility, characterized by minimal postoperative anterior chamber inflammation, and good capsular biocompatibility, characterized by low incidence of PCO.