Abstract
Purpose :
Core-skirt configuration of a keratoprosthesis (KPro), such as that of the Boston KPro, is favored due to the PMMA optic that acts as the core that provides clear window for patients’ vision and also resistance to biodegradability. The surrounding skirt (the corneal graft) allows for host tissue integration. However, due to poor biointegration between the dissimilar core and skirt materials, it often results in poor tissue adhesion and complications, such as bacterial infection in the tissue-PMMA gap and device extrusion. In this study, we set out to improve the tissue adhesion and biointegration by modifying the PMMA surface with nano-hydroxyapatite (nHAp) via a dipcoating technique.
Methods :
Nanoparticles of 60 nm in size were used. The nHAp-coated 3-mm-diameter PMMA discs were implanted in the rabbit corneas (n=4) intrastromally for 5 weeks. Non-coated discs were used as controls (n=4). Post-operative examination consisting of in vivo confocal microscopy, slit lamp, and AS-OCT was performed weekly. Following animal euthanization, the corneas were stained with hematoxylin and eosin, fibronectin, tenascin-C, CD18, CD58, collagen types I and III, Thy-1, and α-smooth muscle actin (α-SMA). In a separate experiment, tissue adhesion between nHAp-coated PMMA cylinder and porcine cornea was determined by a mechanical pull-out test. The PMMA-cornea construct had been maintained in the organ culture for 2 weeks.
Results :
It appeared that wound healing (fibronectin and tenasin-C) and inflammatory (CD18 and CD58) responses to nHAp-coated PMMA were substantially milder than to the non-coated PMMA, thus, attenuating the fibroblast (Thy-1) and myofibroblast (α-SMA) formation. A more mature collagen (type I), similar to pre-operated cornea, was maintained in the tissue adjacent to the nHAp-coated implant edge. On the contrary, abundant new collagen (type III) was formed around the non-coated cylinder. On histology, this new connective tissue appeared as layers of loose and non-adhesive fibrous tissue around the implant edge. As a result of superior biointegration, tissue adhesion with nHAp-coated cylinder was also enhanced significantly (65x more work was needed to detach porcine stromal tissue from the coated PMMA compared to the non-coated PMMA; p=0.005).
Conclusions :
The immobilized nHAp on the surface of PMMA optic led to a superior biointegration and adhesion with the corneal stromal tissue.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.