XPS and surface-MALDI-MS characterisation of worn HEMA-based contact lenses

XPS and MALDI-MS were used to analyse initial adsorption events in the foul ing of HEMA-based contact lenses. All of the lenses tested accumulated tear film deposits within 10 min of wear. XPS indicated the presence of mainly proteinaceous deposits, with indications of some contributions by mucins or lipids on some lenses and the nature of the deposit being influenced by th e lens chemistry. MALDI-MS detected the presence of surface-adsorbed specie s with molecular weights <15 kDa. While lysozyme could be identified by com parison of MALDI-MS signals with known protein mass and assignments are sug gested for some other signals, several other species, with MWs less than th at of lysozyme, could not be identified as no ocular proteins with correspo nding MWs had been reported in previous biochemical tear film analyses. The se species, and others, were also detected in MALDI-MS analysis of reflex t ear film, suggesting that the adsorbed unidentified species were not simply products of surface-induced dissociation of adsorbing higher-MW proteins. This short-term wear study detected rapid interface conversion and demonstr ated the utility and surface sensitivity of XPS and MALDI-MS in characteris ing contact lens deposits at the initial stages when sub-monolayer adsorbed amounts are present on lenses. (C) 2001 Elsevier Science Ltd. All rights r eserved.