Biomaterials 24 (2003) 4729–4739 A model for the preliminary biological screening of potential keratoprosthetic biomaterials S.R. Sandeman a , A.W. Lloyd a, *, B.J. Tighe b , V. Franklin b , J. Li b , F. Lydon b , C.S.C. Liu c , D.J. Mann d , S.E. James d , R. Martin d a Biomedical Materials Research Group, School of Pharmacy and Biomolecular Sciences, University of Brighton, Moulsecoomb Brighton BN2 4GJ, UK b Biomaterials Research Group, Aston University, Birmingham, UK c Sussex Eye Hospital, Brighton, UK d Blond McIndoe Research Centre, Queen Victoria Hospital, East Grinstead, UK Received 7 August 2002; accepted 13 May 2003 Abstract A series of in vitro screening assays for the preliminary selection of biomaterials for use in the fabrication of artificial corneas (keratoprostheses) (KPros) have been investigated. These screening assays assessed the initial binding of inflammatory and cell adhesive proteins, activation of inflammatory proteins, adhesion of keratocytes, epithelial cells and macrophages and the production of inflammatory cytokines by keratocytes contacting biomaterials. Central optic biomaterials were selected on the basis of low- inflammatory and cell adhesion potential. Peripheral skirt materials were selected on the basis of low-inflammatory potential but good cell adhesion to anchor the implant within the host cornea. Green fluorescent protein (GFP) gene transfer was used in a novel context to investigate cell invasion in the absence of external staining techniques. Confocal laser scanning microscopy and scanning electron microscopy were used to investigate GFP positive keratocyte invasion of porous materials. The results of in vitro assays were compared to a corneal organ culture system in which the biomaterials were assessed within a stromal environment. A range of polyurethane-based interpenetrating polymers with a range of water contents were screened. All materials showed low-inflammatory potential. A reduction in biomaterial water content induced an increase in complement C3 and fibronectin binding and in cell adhesion to materials, whilst differences in co-monomer formulation had little impact. The screening methods used in the current study provide a suitable preliminary assessment regime for the in vitro evaluation of potential KPro materials. r 2003 Elsevier Ltd. All rights reserved. Keywords: Keratoprosthesis; Cornea; Preliminary screening model; GFP 1. Introduction The successful integration of keratoprostheses (KPros) is dependent on many interrelated factors including the physicochemical properties of the bioma- terial itself and the response of the host tissue to implantation. A KPro suitable for retention by patients unable to retain donor corneal transplants will ideally invoke a limited inflammatory response, allow periph- eral host keratocyte adhesion to encourage tissue integration and retain a clear central optic for vision. Early KPro designs were poly(methyl methacrylate) (PMMA) based. Some clinical successes have been reported but are overshadowed by complications including epithelial downgrowth, glaucoma and tissue necrosis leading to implant extrusion [1]. Initial clinical results using poly(2-hydroxyethyl methacrylate) (p(HEMA)) KPros have been promising but problems with mechanical weakness and calcium deposition have yet to be resolved [2]. Current research has begun to focus on the tissue–implant interface and recognises the need to understand tissue–material interactions at the cellular level in order to control this interaction for a positive outcome. In addition, the spectrum of available analytical tools has been broadened to encompass more intricate cell and molecular biology-based techniques in the investigation of cell–material interactions. Corneal inflammation following KPro implantation is governed by the complex, interrelated facets of the biomaterial-induced foreign body host response and the ARTICLE IN PRESS *Corresponding author. Tel.: +44-1273-642-049; fax: +44-1273- 679-333. E-mail address: a.w.lloyd@brighton.ac.uk (A.W. Lloyd). 0142-9612/03/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0142-9612(03)00370-3