Toward electron-beam sterilization of a pre-assembled Boston keratoprosthesis.

PURPOSE: To evaluate the effects of electron-beam (E-beam) irradiation on the human cornea and the potential for E-beam sterilization of Boston keratoprosthesis (BK) devices when pre-assembled with a donor cornea prior to sterilization. METHODS: Human donor corneas and corneas pre-assembled in BK devices were immersed in recombinant human serum albumin (rHSA) media and E-beam irradiated at 25 kGy. Mechanical (tensile strength and modulus, and compression modulus), chemical, optical, structural, and degradation properties of the corneal tissue after irradiation and after 6 months of preservation were evaluated. RESULTS: The mechanical evaluation showed that E-beam irradiation enhanced the tensile and compression moduli of human donor corneas, with no impact on their tensile strength. By chemical and mechanical analysis, E-beam irradiation caused a minor degree of crosslinking between collagen fibrils. No ultrastructural changes due to E-beam irradiation were observed. E-beam irradiation slightly increased the stability of the cornea against collagenase-induced degradation and had no impact on glucose diffusion. The optical evaluation showed transparency of the cornea was maintained. E-beam irradiated corneal tissues and BK-cornea pre-assembled devices were stable for 6 months after room-temperature preservation. CONCLUSIONS: E-beam irradiation generated no detrimental effects on the corneal tissues or BK-cornea pre-assembled devices and improved native properties of the corneal tissue, enabling prolonged preservation at room temperature. The pre-assembly of BK in a donor cornea, followed by E-beam irradiation, offers the potential for an off-the-shelf, ready to implant keratoprosthesis device.

Electron Beam Sterilization of Poly(Methyl Methacrylate)-Physicochemical and Biological Aspects.

Electron beam (E-beam) irradiation is an attractive and efficient method for sterilizing clinically implantable medical devices made of natural and/or synthetic materials such as poly(methyl methacrylate) (PMMA). As ionizing irradiation can affect the physicochemical properties of PMMA, understanding the consequences of E-beam sterilization on the intrinsic properties of PMMA is vital for clinical implementation. A detailed assessment of the chemical, optical, mechanical, morphological, and biological properties of medical-grade PMMA after E-beam sterilization at 25 and 50 kiloGray (kGy) is reported. Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry studies indicate that E-beam irradiation has minimal effect on the chemical properties of the PMMA at these doses. While 25 kGy irradiation does not alter the mechanical and optical properties of the PMMA, 50 kGy reduces the flexural strength and transparency by 10% and 2%, respectively. Atomic force microscopy demonstrates that E-beam irradiation reduces the surface roughness of PMMA in a dose dependent manner. Live-Dead, AlamarBlue, immunocytochemistry, and complement activation studies show that E-beam irradiation up to 50 kGy has no adverse effect on the biocompatibility of the PMMA. These findings suggest that E-beam irradiation at 25 kGy may be a safe and efficient alternative for PMMA sterilization.

Electron Beam Irradiated Corneal Versus Gamma-Irradiated Scleral Patch Graft Erosion Rates in Glaucoma Drainage Device Surgery.

INTRODUCTION: Patch graft erosion and implant exposure is a known complication of glaucoma drainage device (GDD) surgery. Recently, electron beam (e-beam) irradiated corneal tissue ha s become available; however, limited data exist on the rates of erosion for e-beam irradiated corneal grafts compared to traditional scleral grafts after GDD surgery. METHODS: This retrospective study examines the records of 253 eyes from 225 adult subjects who underwent GDD surgery with either e-beam irradiated corneal or scleral grafts at the Casey Eye Institute by five surgeons between April 22, 2014 and October 11, 2017. Surgical procedures and the occurrence of graft erosion were determined using billing codes and verified by manual review of electronic health records. RESULTS: The average age at the time of surgery was 61.3 ± 17.5 years (n = 200) and 60.8 ± 16.8 years (n = 53) for the e-beam irradiated cornea and sclera groups, respectively. The average follow-up time post-surgery was 416 ± 345 days and 495 ± 343 days for the e-beam irradiated cornea and sclera groups, respectively. There were no statistically significant differences in sex, age, follow-up time, and glaucoma diagnosis between the groups; however, the e-beam irradiated cornea group was statistically more likely to have an Ahmed implant as compared to the sclera group. No erosion events were noted in either group. CONCLUSION: e-Beam irradiated corneal grafts were used 3.8 times more frequently relative to scleral grafts, yet there were no cases of graft erosion in either group during the follow-up period.