The role of surface quality of keratoprostheses in microbial adherence and biofilm formation

Abstract

 

Purpose

 

To investigate the relationship between surface roughness of keratoprostheses to microbial adherence and biofilm formation using bright field confocal microscopy.

 

Methods

 

Unused keratoprosthesis mesoplants (n=9) obtained from various manufacturers were examined under bright field confocal microscopy. The keratoprostheses were carefully immersed in high purity water and imaged with a Leica TCS SP5 laser scanning confocal microscope in bright field mode. 5x, 20x, and 63x objective lenses (NA=0.15, 0.5, 0.9, respectively) were used and the images were processed with Leica’s Advanced Fluorescence Lite software. As a preliminary study, custom poly(methyl methacrylate) (PMMA) optical cylinders (n=3) were fabricated to mock keratoprosthesis optical cylinders of three different polish states (i.e. unpolished, semi-polished, polished). The imitation keratoprosthesis optical cylinders were imaged with bright field illumination on the confocal microscope to visualize the initial surface quality. After imaging, the custom optical cylinders were placed in a CDC (Center for Disease Control and Prevention) biofilm reactor with Staphylococcus epidermidis and thioglycollate dextrose media for 96 hours after the initiation of the magnetic stirrer in the reactor. The optical cylinders were then stained with a fluorescent live/dead staining kit (L13152, Invitrogen) and imaged with the laser scanning confocal microscope to observe any microbial adherence or biofilm formation.

 

Results

 

The images of the surfaces of various mesoplants show several inadequate surface characteristics for intraocular implantation including but not limited to scratches, machine marks, crevices, and indentations. Imaging of custom optical cylinders after incubation in the CDC biofilm reactor showed increased microbial adherence and biofilm formation on the less polished surfaces.

 

Conclusions

 

Irregular surface characteristics of keratoprostheses have been observed using bright field confocal microscopy and these mesoplants are not currently suitable for orbital implantation. This poor surface quality of the mesoplants may provide an environment within the eye that allows microbes to flourish, which may lead to post-operative complications, such as endophthalmitis.

 

 

Confocal microscopy images of unused keratoprostheses.

 

 

Confocal microscopy images of optical cylinders after biofilm reactor incubation. Green = live bacteria, red = dead bacteria.

 

Keywords: 575 keratoprostheses