Matrix-assisted laser desorption ionization mass spectrometry detection of proteins adsorbedin vivo onto contact lenses

Abstract

Identification of the biomolecules that form the first adsorbed monolayer, which thus effect "interface conversion", in competitive adsorption from multicomponent biological solutions can be challenging because of limitations in mass resolution and sensitivity of established techniques. In this study matrix-assisted laser desorption ionization (MALDI) time of flight mass spectrometry is developed and applied as a novel surface analytical method to enable analysis of adsorbed multicomponent biomolecule layers directly on the biomaterial surfaces. We show that proteins adsorbed in vivo (on human eyes) on contact lenses can be detected rapidly and conveniently by the diagnostic highly resolved mass signals recorded by MALDI mass spectrometry. This new approach allows detection of minor (and major) proteinaceous constituents of biofouled layers at levels substantially below monolayer coverage. Identification is done by comparison with molecular masses of known proteins. Specifically, it is shown that in addition to lysozyme, other low molecular weight proteins adsorb from human tear fluid onto contact lenses; these proteins had not been detected in earlier studies using other techniques.

Characterization of lysozyme films produced by matrix assisted pulsed laser evaporation (MAPLE)

“…Lysozyme is an enzyme with bacteriocidal action and is found in milk [7] and tears as well as other human secretions [8]. It has also been shown to adsorb to contact lenses that are worn by human patients as the first interface between the lens and the biological environment in the eye [9].…”

Quantitative and conformational characterization of lysozyme deposited on balafilcon and etafilcon contact lens materials

“…For direct quantification of proteins adhered to a surface, the method employed must be able to detect all proteins of interest absorbed to the surface. While in-situ surface analytical techniques such as atomic force microscopy, matrix-assisted laser desorption/ionization and surface plasmon resonance are highly sensitive to detecting deposits, [37][38][39][40][41][42] they are unable to determine the composition of multi-layered, multi-species deposits. Thus, protein elution from a surface followed by separation and immunological characterisation remains the best option, to date, to quantify individual proteins deposited on the surface of contact lenses.…”

Tear film proteins deposited on high water content contact lenses identified with two‐dimensional gel electrophoresis and mass spectrometry

“…Already within 10 min of wearing, proteins are detectable (Kingshott et al. ). Deposited proteins are the agent for irritation.…”